MC LCChng 1 : Kho st h thng monitor ti ging bnh trong y t31.1.Gii thiu v h thng gim st bnh nhn31.2.Gii thiu v h thng monitor n thng s ti ging bnh51.3.Gii thiu h thng monitor a thng s ti ging bnh51.4.Chc nng ca monitor a thng s71.4.1.Hin th tn hiu in tim71.4.2.Hin th tn hiu SPO2111.4.3.Hin th tn hiu huyt p141.4.4.Hin th nhp th161.4.5.Hin th nhit 171.4.6.Hin th nhp tim181.5.C s l thuyt ca h thng monitor a thng s ti ging bnh191.5.1.Phng php o nhp tim191.5.2.Phng php o nhp mch231.5.3.Phng php o huyt p231.5.4.Phng php o nhit 301.5.5.Phng php o nhp th321.5.6.Phng php o nng CO2331.5.7.Ghi tn hiu in tim ECG361.5.8. bo ha oxi trong mu SpO2401.5.9.o cung lng tim CO411.6.H thng monitor trung tm491.6.1.Gii thiu v h thng monitor trung tm491.6.2.Xu hng pht trin h thng monitor trung tm hin nay511.6.3.S cn thit ca h thng monitor trung tm52CHNG 2: GII PHP MNG CHO H THNG MONITOR TRUNG TM542.1.Tip cn cu trc m trong h thng gim st bnh nhn542.1.1.Nhng ng dng mi ca bus trong ngnh cng nghip hin nay542.1.2.GPIB iu khin bn phn cng552.1.3.T b iu khin Ethernet ti GPIP iu khin tc cao552.1.4.T USB tc cao ti GPIB iu khin562.1.5.Tip cn phn mm linh hot trong h thng cu trc m562.1.6.Tng quan v kt ni mng trong h thng trung tm gim st bnh nhn572.1.7.H thng gim st bnh nhn s dng mt my ch582.1.8.Mng ng ng vi h thng gim st bnh nhn592.2.B iu khin mng chun Ethernet612.2.1.Tng quan v mng Ethernet612.2.2.Chun IEEE 802632.2.3.Giao thc CSMA/CD642.3.Mng khng dy702.3.1.Gii thiu v WLAN702.3.2.Cch lm vic ca mng WLAN712.3.3.Cc ty chn cng ngh722.3.4.Giao thc truy cp752.4.Cu hnh mng LAN782.4.1.Thit b Ethernet782.4.2.Cu hnh mng WLAN83CHNG 3: THIT K PHN MM V CU HNH873.1.Yu cu thit k873.1.1. Yu cu chc nng:873.1.2. Yu cu phi chc nng883.2.C s l thuyt883.2.1.nh dng khung d liu truyn ln893.2.2. nh dng khung lnh truyn xung963.3.Port cng giao tip973.3.1. Cc tr s port thng gp (Well Known Port 0-1023)993.3.2. Cc port ng k (registered port: 1024-49151)1013.3.3. Dynamic port / Private port (49152-65535)1013.4.Thut ton1023.4.1. Cu trc phn mm1023.4.2. Module x l tn hiu gi tr v dng sng in tim1023.4.3. Module x l gi tr NIBP1043.4.4. Module x l tn hiu gi tr v dng sng in RESP1053.4.5. Module x l gi tr nhit 1053.4.6. Module x l tn hiu gi tr v dng sng in SPO21073.5.Cu hnh108CHNG 4: XY DNG PHN MM1144.1La chn cng c lp trnh1144.1.1. Gii thiu v LabVIEW1154.1.2. Cc kiu d liu1184.2Xy dng cc khi c bn1224.2.1 Khi thu nhn d liu1224.2.2 Khi lu tr tn hiu1274.2.3. Khi phn tch v hin th d liu129CHNG 5: KT LUN131

Chng 1 : Kho st h thng monitor ti ging bnh trong y t1.1. Gii thiu v h thng gim st bnh nhnTrong y t, monitor l mt thit b dng gim st mt cn bnh, mt tnh trang hoc mt vi thng s y t ca bnh nhn theo thi gian thc.

Hnh 1.1:Thit b monitorH thng gim st bnh nhn (PMS) l mt h thng theo di rt quan trng, n c s dng cho gim st tn hiu sinh l bao gm in tm (ECG), h hp, huyt p xm ln v huyt p khng xm ln, bo ha oxy trong mu (SpO2 ), nhit c th v nng cc kh gy m, Trong PMS, nhiu cm bin v cc in cc c s dng cho vic nhn tn hiu sinh l nh l in cc ECG, cm bin ngn tay SpO2, bng qun o huyt p v que d nhit o cc tn hiu sinh l. Vic gim st ca monitor y t c thc hin bng cch o c lin tc cc thng s nht nh thng qua mt mn hnh y t, v d nh o lin tc mt tn hiu s sng bng mn hnh theo di ti ging bnh nhn hay vic thc thin lp i lp li cc xt nghim y t, chng hn nh theo di lng ng huyt vi my o lng ng nhng ngi mc bnh i tho ng.Trong khi iu tr, theo di lin tc cc du hiu sinh l quan trng ca bnh nhn l iu ht sc cn thit. V vy PMS lun c vai tr ht sc quan trng trong lnh vc thit b y t. Cc ci tin lin tc v cng ngh khng ch gip chng ta truyn ti nhng tn hiu sinh l quan trng ca bnh nhn ti cc nhn vin y t m cn n gin ha vic o lng, t lm tng hiu qu gim st bnh nhn.Trong nhng nm gn y, nhng ci tin cng ngh lin quan n o lng v thng tin truyn thng dn n vic theo di bnh nhn c hiu sut ton din hn v cht lng n nh. Trong qu kh, cc sn phm ca cc nh sn xut thit b y t ch o c mt thng s duy nht. Tuy nhin hin nay, cng ngh theo di bnh nhn a thng s mi c s dng ph bin. Ngy nay trong cng nghip, h thng gim st bnh nhn gm 2 loi:h thng monitor n thng s v h thng monitor a thng s.1.2. Gii thiu v h thng monitor n thng s ti ging bnhH thng gim st n thng s ch c kh nng o lng 1 tn hiu sinh l duy nht. Ngy nay, y l cng ngh c, nhng n vn c s dng cc nc ang pht trin nh n , Pa-ki-xtan, Bng-la-t, Cc h thng gim st n thng s c chi ph rt thp nn rt d sn xut v duy tr. H thng gim st n thng s c th dng o huyt p c th, ECG (in tm ), SpO2 ( bo ha oxy trong mu),Mn hnh hin th bnh nhn theo kiu tng t c da trn nguyn l b to dao ng v ch c duy nht mt knh, thng dnh ring cho in tim (ECG). Mt monitor phi theo di huyt p ca bnh nhn, mt ci khc th phi theo di lng SPO2, mt ci khc na l ECG. Cc mu my tng t sau ny c thm 2 hoc 3 knh o v hin th trn cng mt mn hnh, thng thng theo di huyt p v s hot ng ca h hp. cc loi my ny thng c s dng rng ri v cu sng nhiu sinh mang, nhng chng c mt vi hn ch, bao gm s nhy cm vi nhiu in, s ln xung tht thng ca mc c s v thiu s cnh bo.1.3. Gii thiu h thng monitor a thng s ti ging bnhH thng gim st bnh nhn a thng s (PMS) c dng o nhiu du hiu sinh l quan trng ca bnh nhn truyn ti cc thng tin quan trng nh in tm , nhp h hp, huyt p, V vy, PMS lun c vai tr rt quan trng trong lnh vc thit b y t. S ci tin lin tc v cng ngh trong PMS gip my o c nhiu du hiu sinh l quan trng cho nhn vin y t. Cc thit b theo di ti ging c cc cu hnh khc nhau ph thuc vo cc nh sn xut. Chng c thit k theo di cc thng s khc nhau nhng c tnh chung gia tt c cc my l kh nng theo di lin tc v cung cp s hin th r nt ng sng ECG v nhp tim. Mt s thit b cn bao gm kh nng theo di p sut, nhit , nhp th, nng oxi bo ha SpO2,

Hnh 1. 2 S khi thit b theo di bnh nhnPMS mi nht gip n gin ho cc php o du hiu sinh l v tng hiu qu theo di. V vy, ngy nay PMS rt linh hot v n c th theo di nhiu tn hiu sinh l trong cng mt h thng duy nht.S xut hin ca cc my vi tnh nh du s m u ca mt hng pht trin c bn mi trong cc h thng theo di bnh nhn. Nhng h thng nh vy c mt khi CPU chnh c kh nng tng hp, ghi nhn bn cht ca ngun tn hiu v x l chng mt cch thch hp. Phn cng chu trch nhim cho vic phn tch tn hiu sinh l, hin th thng tin v tng tc vi ngi s dng trn thc t l mt tp hp cc khi phn sn c thc hin di chng trnh vi tnh. Phn sn em li cho h thng tnh cht ca n cc cng tc, nt, nm xoay,v ng h o c thay th bng mn hnh s ( cm ng). Trong :ECG: Electrocardiogram in tm RESP: Respiration h hpSpO2: Nng Oxi trong mu BP: Blood Pressure huyt pTEMP: Temperature nhit NIBP: Non-Invasive Blood Pressure huyt p gin tipKhi u vo gm c ba khi chnh l khi ECG/RESP, SpO2/BP/TEMP, NIBP.1.4. Chc nng ca monitor a thng s1.4.1. Hin th tn hiu in tim Qu trnh hnh thnh tn hiu in timin tim ECG (Electrocadiography) l cc hot ng in ca tim c to ra bi qu trnh co bp ca c tim. Tim hot ng c l nh mt xung ng truyn qua h thng thn kinh t kch ca tim. u tin xung ng i t nt xoang ta ra c nh lm cho tm nh kh cc, tm nh co lm y mu xung tm tht, tip nt nh tht AV tip nhn xung ng ri truyn qua b His xung tm tht lm tm tht kh cc, lc ny tm tht y mu co mnh s y mu ra ngoi bin. Hin tng tm nh v tht kh cc ln lt trc sau nh vy chnh l duy tr qu trnh huyt ng bnh thng ca h thng tun hon. V th in tim gm hai phn, phn nh i trc ghi li hot ng in ca tm nh v tht i sau ghi li hot ng in ca tm tht.Vi qui c t in cc dng bn tri qu tim v in cc m bn phi qu tim ta thu c cc dng sng in tim.

Hnh 1.4: Dng tn hiu in tim chunDng sng in tim bao gm mt chui cc sng lp li theo mi chu k tim. Nhng sng thnh phn ny c k hiu bng cc k t P, Q, R, S, T theo quy c thng dng trong lm sng. Cc sng thnh phn ny tng ng vi cc hot ng ca mt chu k tim. Tng thi gian cho mt chu k tn hiu in tim l khong 800ms, tng ng vi khong 75 nhp/pht. Dng sng P: L qu trnh kh cc tm nh, xung ng i t nt xoang ti nh phi s ta ra lm kh cc c tm nh, hnh thnh mt in th dng hng t trn xung, t phi sang tri ca tim. Thi gian kh cc ny khong 80 ms. Khi tm nh ti cc, n cng to ra mt in th cc tnh m nh hn nhiu so vi in th kh cc tm tht cng lc , nn ta khng nhn thy trn in tim . Nh vy, hot ng ca tm nh trn in tim ch tn ti mt sng n - sng p. Sng phc hp QRS: L qu trnh kh cc tm tht, bt u t lc tm nh vn cn ang kh cc. Vic kh cc bt u t phn gia mt tri vch lin tht i xuyn sang mt phi vch ny to nn mt vect in th kh cc u tin hng t tri sang phi to nn mt sng m nh nhn trn in tim gi l sng Q. Tip , xung ng c truyn hng xung v bt u kh cc c hai tm tht theo hng xuyn qua b dy c tim. Lc ny, qu trnh kh cc hng nhiu v pha bn tri hn v tht tri dy hom v tim nm nghing hng trc gii phu sang bn tri. V th vect in th kh cc lc ny hng t phi sang tri hnh thnh mt sng dng rt cao v nhn gi l sng R. Sau cng l vng y tht c kh cc to nn mt vect in th hng t tri sang phi to nn mt sng m nh nhn gi l sng s. Nh vy, trong qu trnh kh cc tm tht sinh ra mt sng phc hp QRS c bin tng i ln, bin thin nhanh ch trong mt khong thi gian ngn khong 70ms. Sng T v U: Khi tm tht kh cc xong s qua mt thi gian ti cc chm khng th hin trn in tm bng mt sng no ht m ch l mt ng thng, on S-T sau l n mt thi k ti cc nhanh v xut hin sng T. Ti cc tin hnh t vng in dng n vng in m v c vect ti cc hng t trn xung di v t phi sang tri lm pht sinh mt ln sng dng thp. Sng T thng c dng khng i xng, sn ln thoai thoi v sn xung dc ng hn. Ngi ta khng o khong thi gian ca sng T v n thay i theo tng ngi v im bt u ca sn ln l khng r rng. Ngay sau khi sng T kt thc, ta cn c th thy mt sng chm nh gi l sng U. Sng U l giai on mun ca qu trnh ti cc. Sng T thng c rng khong 0,2s v sng u c rng khong 0,08s. S khi qu trnh x l tn hiu in timThc hin o mt knh tn hiu ECG v ng sng h hp (RESP) hnh (3.2). Cc mch tr khng cao v cc b hm kh bo v cc b khuch i u vo khi sc tim v cc tn hiu nhiu tn s cao t cc in cc gn trn ngi bnh nhn. Cc mch u vo ca khi ny c cch ly vi cc mch cn li bng cc b ni quang v my bin th. Khi ny nhn mt knh tn hiu ECG t cc o trnh 3 in cc hoc 5 in cc. Ph thuc vo ci t phn mm m b chn o trnh khi ny chn o trnh ph hp t 3 n 5 in cc t trn ngi bnh nhn. Mch x l ng sng h hp c kh nng o tr khng ca cc tn hiu u vo. S thay i tr khng ca cc tn hiu u vo gy ra s thay i in p ca tn hiu u ra v da vo s thay i in p ny my tnh ra s nhp th ca bnh nhn.

Bng1.3 S mch khi ECG/RESP c im ca tnh hiu in tim u raTn hiu in tim l tn hiu sinh hc ly t c th ngi thng qua cc in cc, do vy n c mt s c im sau: Bin ca tn hiu in tim tng i nh, khong lmV. Tn s nm trong khong t: 0.1Hz n 250Hz. D b can nhiu, ngun nhiu ny sinh ra do mt s nguyn nhn c bn nh: Nhiu 50Hz (nhiu ca ngun in p xoay chiu cung cp cho thit b), nhiu do tip xc ca cc in cc, do s chuyn ng ca bnh nhn, do s co c....1.4.2. Hin th tn hiu SPO2 bo ha Oxy trong muMu trong c th ngi mang oxy theo hai cch: Ha tan di dng cht dch trong mu hay gi l huyt tng v kt hp vi hemoglobin. Lng oxy dng cht dch chim khong 3% ton b oxy. Gi tr ny o c di dng cc kh trong mu (blood gases). Do hu ht oxy u kt hp vi hemoglobin, nn c ba yu t nh hng n lng oxy cung cp cho c th: Dch truyn m Lng hemoglobin S bo ha hemoglobin bi oxy.Nu mi phn t hemoglobin kt hp vi mt phn t oxy th ton b hemoglobin trong c th bo ha hon ton (100% bo ha). Khi ht th khng kh (21% oxy), lng oxy ny l rt t hemoglobin c bo ha hon ton. Nhng i lc ca hemoglobin vi oxy l rt cao nn gy ra s bo ha gn nh l hon ton trong mu (khong 97%).Khi hemoglobin khng mang oxy ti cc m (mc mao dn), s bo ha hemoglobin trong mao dn tng dn. Thng thng s bo ha trong tnh mch vo khong 75%. i lc ca hemoglobin i vi oxy cao hn ch oxy khi bo ha mc thp, bi vy mc chnh lch gia mc bo ha trng thi khe t 95 - 98% v mc th km (85-90%) l rt thp. Nu oxyhemoglobin thp (di 90%) th khng lng oxy cung cp cho c th. S khi o tn hiu SPO2Khi ny c dng o mt knh ng sng huyt p, mt knh ng sng nhit v gi tr ca SpO2. Cc mch u vo trn bng ny c cch ly khi cc mch cn li bng cc b ni quang v my bin th. Thng trn khi ny c mt cng tc ngm dng ci t cc thng s cn o trong khi. Trong mch x l nhit , tn hiu u vo t cc thermistor c lc qua b lc thng thp loi b nhiu tn s cao. B ghp knh sau s dng ng thi in p tham chiu 270C, in p nh c cho 370C v tn hiu nhit c th t cc thermistor. Trong mch x l huyt p(hnh 3.4) b kch thch iu khin hot ng ca u o huyt p. Nhng tn hiu u vo t transducer c khuch i v sau c lc qua b lc thng thp. Mch x l SpO2 (hnh 3.3) bao gm 3 mch nh: mch iu khin LED, mch pht in ID u o, v mch x l tn hiu u vo. Mch iu khin LED iu khin hot ng ca LED trong u o. Mch pht hin ID u o tm dng v s hin din ca u o. Trong mch x l tn hiu u vo, tn hiu u vo t photodiode c khuch i v c lc qua b lc thng thp. Trong qu trnh ny, mt phn tn hiu khi khng d c nh sng cgi li nh ng gc ca tn hiu.

Hnh 1.5. S nguyn l ca khi SpO2

Hnh 1.6 . S nguyn l hot ng ca khi IBPDng sng Pleth c to ra t tn hiu thu c ca cm bin o SpO2 nhng dng sng Pleth khng phi l s dao ng ca gi tr SpO2. Gi tr SpO2 thng c th hin bng dng s trn cc monitor theo di bnh nhn.Pleth c vit tt t Plethysmography c ngha l biu o th tch. N th hin s thay i th tch trong mt c quan hay trong ton b c th (thng l th tch mu hoc kh). Cc cm bin SpO2 da trn hin tng hp th nh sng tnh ton lng mu lu thng trong phn m gia u pht v u thu nh sng, do th to ra cng c gi l Plethysmography hay c th hn l Photopethysmography (PPG).

Hnh1.7: dng sng PlethMi chu k trn dng sng ny ng vi mt nhp p ca tim. ng i ln ng vi qu trnh tm thu, mu t ng mch ch c bm n ngn tay. ng i xung ng vi qu trnh tm trng. Trn ng i xung c mt gai nh, gai ny c to ra do mu t ng mch ch khi c bm n cc phn di c th to s p lc ln trn v truyn n ngn tay. cao ca sng cho bit dung lng mu lu thng trong ng mch, chiu di bc sng cho bit nhp tim. Cc dng sng Pleth khng bnh thng s cho bc s mt s thng tin v tnh trng ca bnh nhn.Mt s monitor khng v sng Pleth m biu din s thay i th tch mu lu thng trong ng mch din bng s dao ng ca mt chui vch. Ngy nay, nh s pht trin ca cng ngh, thit b o SpO2 ngy cng n gin v r, do gi tr SpO2 cng sng Pleth v ang tr thnh mt thng tin quan trng phc v cho cng tc chn on ca bc s.1.4.3. Hin th tn hiu huyt p S hnh thnh huyt pHuyt p l p lc gy ra cho thnh mch mu khi mu lu thng trong mch mu. S hnh thnh ca huyt p ng mch l kt qu ca tc dng tng quan gia tim bom mu v lc cn bn ngoi.Khi tim co li, tm tht s y mu vo mch mu. C tm tht phng thch ra nng lng, mt phn dng y mu di chuyn, mt phn s chuyn ha thnh p lc ln thnh mch mu. Tr s huyt p v lng mu do tim y ra c lin quan mt thit vi nhau. Lng mu y ra l tch s ca lng mu c y ra sau mi ln tim p v nhp tim. V vy, nhp tim nhanh hay chm u nh hng n tr s huyt p.Sc cn ngoi vi c hnh thnh ch yu do lc cn huyt qun, l mt nhn t quan trng hnh thnh nn huyt p. Neu khng c sc cn ngoi vi th lng mu t tim bm ra s chy nhanh ra ngoi. Ch khi phi hp vi sc cn ngoi vi, lng mu do tim bm ra s khng chy qu nhanh m lu li mch mu. Nh th, nng lng phng thch ra khi tm tht co li mi c th biu hin di dng p lc, hnh thnh nn huyt p tng i cao. p lc ngoi vi tng cao ch yu l do s thay i ca ng knh mch mu v lin quan mt thit n hot ng co, gin ca thnh mch mu. n hi ca ng mch v dnh ca mu cng s nh hng n tr s huyt p. Khi n hi ca ng mch tng c tc dng lm gim bin dao ng ca huyt p, ngn nga hin tng p sut tm thu qu cao v p sut tm trng qu thp. dnh ca mu tng cao, sc cn ngoi vi ln cng s lm cho huyt p tng cao. S khi o huyt pSau khi tn hiu nhn t u o huyt p, khi ny khuch i cc tn hiu u vo ri sau cho qua cc b lc v au vo b ghp knh. Cc tn hiu t b ghp knh sau c a vo bng mch m x l tip. Trong khi ny c mt b iu khin van an ton kim tra trng thi ca van an ton. Van an ton c thit k sao cho n t ng lm gim bt p sut ca Cuff khi p sut ny vt qu 300mmHg. Van ny gip bo v bnh nhn trong trng hp mch an ton khng dng tng p sut ca cuff khi p sut t n 300mmHg.

Hnh1.8: S nguyn l hot ng ca khi NIBP theo di huyt p lin tc v v th, cc bc s phi s dng phng php o huyt p xm ln (Invasive Blood Pressure hay IBP). Ngi ta c th o IBP ti nhiu v tr trn c th nhng thng thng nht l o ng mch quay, i,Dng sng huyt p c hnh dng gn ging vi hnh dng sng Pleth do c hai u lin quan n mc bm mu n ng mch.

Hnh1.9: dng sng huyt p1.4.4. Hin th nhp th Tng quan v h h hp ca ngiPhi thc hin chc nng thng kh vo trao i O2, CO2 vi mu. v mt trao i kh, mu s nhn O2 t khng kh ht vo v thi CO2 ra ngoi theo ng th ra. v mt thng kh, khi phi co li s to nn mt p lc m so vi p lc kh quyn v khng kh s i vo qua ng dn kh (mm, mi- kh qun, ph qun-phi). y l qu trnh ht vo ca con ngi. Khi phi dn ra, lng kh trong phi b y ra ngoi do p lc phi cao hon p lc kh quyn. y l qu trnh th ra ca con ngui. Hot ng ca h h hp uc theo di qua cc thng s kh c trong kh th ca con ngui nh C02, lng 02 tiu th cng nh s co bp ca phi v s ln ht vo, th ra (nhp th). S khiCc in cc c t trc ngc bnh nhn (ty theo v tr ca in cc th ta c Z) o tn hiu th, b to dao ng s to ra tn hiu dng in xoay chiu c tn s t 20KHz n 100KHz, cng t 25pA n 500pA tc ng vo in cc mc ch thu c gi tr in p a vo b khuch i. Tn hiu ra ca b khuch i s c lc, x l v tnh ton bi b vi x l. Trn mn hnh s hin th dng tn hiu th v nhp th/pht, tt c qu trnh ny uc th hin hnh 1.12.

Hnh 1.10: s khi qu trnh x l tn hiu th trong thit b theo di bnh nhn1.4.5. Hin th nhit Gii thiu chungNhit (temperature) c o ti mt s v tr khc nhau trn c th chn on v theo di bnh nhn. ngi, nhit phn gia c th l n nh nh chc nng iu ha nhit (thermoregulatory) sinh l. Nhit ca cc m nm su trong phn gia c th c gi l nhit li hay nhit c th su (deep body). Thut ng nhit c th thng dng cho nhit li mc d nhit ca c th l khng ng u m thay i t im ny ti im khc. Nhit li lun nm trong khong 35 - 40c. Hu ht cc thay i nhit sinh l hay bnh l u nm trong di ny, t thp nht vo sng sm hay trong thi tit lnh ti cao nht do st hay do vn ng mnh. S khi phn x l v hin thin tr nhit trong u o nhit c kt ni vi b so snh. B so snh ny s lin tc so snh u vo vi cc in tr chun lin tc hiu chun php o. in p c to ra sau s c khuch i, lc v c s ha ri a n b vi x l. Vic hiu chnh lin tc, tuyn tnh ha, iu khin, bin i sang c v hin trn mn hnh u c thc hin bi b vi x l.

Hnh 1.11: S khi phn x l tn hiu nhit

1.4.6. Hin th nhp timNhp tim (Heart Rate) c xc nh l s ln tim p trong mt pht. Vic theo di nhp tim l xc nh xem l tim p nhanh hay chm. Nhp tim c ly t qu trnh thu nhn v x l tn hiu in tim ECG v o bng cch ly trung bnh hay khong thi gian tc thi gia hai nh R lin nhau. Nhp tim c khong gi tr t 0-250 nhp/pht.Do nhp tim c ly t qu trnh thu nhn v x l tn hiu in tim ECG nn s khi ca qu trnh x l nhp tim cng l s khi hnh 1.6. B vi x l s thc hin vic tnh ton v hin th gi tr nhp tim khi tn hiu in tim c x l. hiu r hn v cch hot ng ca cc khi o, ta cn tm hiu l thuyt v phng php o cc thng s. Ni dung v cc phng php o c trnh by di y.1.5. C s l thuyt ca h thng monitor a thng s ti ging bnh1.5.1. Phng php o nhp timNhp tim c xc nh l s ln tim p trong mt pht. Vic theo di nhp tim l xc nh xem l tim p nhanh hay chm. nhp tim ly c t s khuch i xung ECG v o bng cch ly trung bnh hay khong thi gian tc th gia 2 nh R lin nhau. Di o t 0-300 nhp/pht. Cc in cc ECG ngc hay chi c s dng l cc cm bin. o nhp tim gm c php o trung bnh, php o tc th.Php o trung bnh:Da trn c s chuyn i mi nh sng R ca ECG thnh mt xung c bin v thi gian c nh v sau xc nh dng trung bnh t nhng xung . Chng kt hp mch c thit k mt cch c bit chuyn i tn s sang in p hin th nhp tim trung bnh theo n v nhp/ pht. Mch trung bnh thng thng c s dng chuyn i tn s sang in p hin th hp tim trung bnh l mch bm iot:

Hnh1.12: Mch bm Diot

Nu mt t C c np y bng mt xung c bin in p V, th in tch c gi trong n vi mt xung l: q = CVNu c N xung trong mt khong thi gian t, sao cho mi xung np mt lng in tch q ln t, sau tng in tch l: Q = Nq = NCVDo dng trung bnh trong chu k t l:

Khi mt xung dng c bin V c a vo u vo ca mch, t C1 s c np n C1V thng qua diot D1, diot ny s dn v to ra mt in tr khng ng k. Do , s np t s do hng s thi gian R1C1 khng ch, v hng s ny nh hn rt nhiu chiu rng ca xung u vo.Khi xung u vo chuyn thnh 0, cathode ca D2 l m V vn so vi anode, do iot D2 phn cc thun v bt u dn in. T C1 sau phng in qua diot D2, ng h o v cc in tr R1, R2. T C2 c s dng trung bnh ha dng qua ng h o v do n phi ln hn nhiu so vi t C1. Mch c sp xp sao cho t C1 phng in hon ton trc khi xung tip theo xut hin ti u vo. Mt xung khc c ln V li mt ln na np mt in tch q, sau li c bm qua ng h o khi xung u vo quay li bng 0.Nu dng trung bnh itb chy qua mt in tr R2 (in tr ng h o ch th), th in p ca t l: e = C.V.f.R2Mi lin h ny l ng ch khi e c mt t l nh so vi V. Tnh tuyn tnh 0.1% c th t c bng cch s dng V = 150V v e = 1V. Nhng cch ny khng thc t i vi hu ht cc mch. Do mt s dng bin i c thc hin c c mt in p u ra c mi quan h tuyn tnh vi tn s.

S khi ca mt dng c o nhp tim trung bnh c trc tip c m t trong hnh 1.8. Xung ECG nhn c t cc in cc c khuch i ti mt b tin khuch i ti mc c th vn hnh mch kch hot Schmidt. B kch hot Schmidt chuyn i mi sng R thnh mt xung hnh ch nht, sau c ly vi phn trong mt b vi phn RC mng li cc xung nh nhn cho vic kch hot Monostable Multivibrator. u ra ca b Multivibrator ny bao gm cc xung ng dng c cng mt bin v thi gian i ti b tch phn (mch bm diot), mch ny to ra mt dng t l thun vi tn s u vo.

Hnh 1.13: S khi mt my theo di nhp tim trung bnhPhp o tc th:Nhp tim tc th gip cho vic pht hin ra s ri lon nhp v cho php theo di kp thi cc trng hp tim mch khn cp khi chng mi chm xut hin. Hnh 3.9 cho thy nguyn l ca mt dng dng c o nhp tim tc th. N cung cp u ra n nh gia cc xung, biu din tn s tc th gia hai xung trc. in p u ra gia R2 v R3 t l vi tn s xung ca R1 v R2 tc l t l vi 1/T1.u ra gia R3 v R4 t l vi 1/T2, nu nhp tim tr nn thp hn ( vi T4>T3) v xung khng xut hin ti thi im thi gian bng T3 sau R4, u ra bt u gim v hiu chnh thnh gi tr mi. K thut ny c u im l thit k n gin nhng n khng cho ra u ra tuyn tnh cho mt di tn s rng.Mt k thut khc c dng rng ri cho vic o nhp tim tc th bao gm 2 t, mt c s dng nh t o thi gian v t kia c s dng nh mt t b nh. Hot ng ph thuc vo vic np t o theo chu k thi gian gia hai qung thi gian cui, trong khi t b nh hin th gi tr c lu tr tng ngvi qung thi gian gia hai qung thi gian cui. y u ra khng tuyn tnh. Cisek (1972) a ra mt thit k cho mt Cardiotachometer xung xung tuyn tnh s dng k thut ny. Trong mch ca ng mch o thi gian c np theo hm hypecbol gi hai xung lin tc to ra gi tr in p cui, c quan h tuyn tnh vi tn s xung tc thi.

Hnh 1.14: Nguyn l chuyn i tn s sang in p theo di nhp tim tc thHnh trn l s khi ca mt Cardiotachometer. ECG c ly mu trong mi bc 2ms. S chuyn tip nhanh ca cc thnh phn bin cao c lm suy yu i bng mt b hn ch t l xoay, b ny lm gim bin nhiu do my to nhp tim gy ra v lm gim kh nng tnh nhng nhiu ny thnh cc nhp p ca tim.Hai mu 2ms gn nhau c ly trung bnh v kt qu l mt chui mu 4ms c to ra. loi b nhng thnh phn tn s cao khng cn thit ca tn hiu, ngi ta dng mt b lc Butterworth xung phn hi khng gii hn tn s 30Hz. B lc ny cho ra cc mu 8ms trong qu trnh hot ng. Bt k mt sng DC no cui cng cng phi qua mt b lc so snh QRS, b d nhp p nhn bit cc t hp QRS trong cc gi tr ca ng in tim ang c ghi. Nu gi tr ny vt qu gi tr ngng th mt nhp tim c m. Ngng ny c hiu chnh t ng ph thuc vo gi tr ca bin sng QRS v khong thi gian gia cc t hp QRS. Tip theo mi nhp p l chu k c ch 200ms c a vo, trong qua trnh d khng c nhp tim no c nhn ra. iu ny lm gim kh nng sng T c tnh nhm. Chu k c ch cng c duy tr bin i nh mt phng trnh nghch o gii hn nhp tim trn vi cc gii hn nhp tim cao thp hn thi chu k c ch di hn.

Hnh 1. 15: S khi mt my Cardiotachometer da trn b lc so snh1.5.2. Phng php o nhp mchNhp mch c xc nh l s ln mu c y vo trong ng mch. Theo di thng s nhp mch l bit xem tim c y c mu i ln ng mch hay khng. o nhp mch ngi ta s dng mt transducer in quang thch hp t ln ngn tay hay di tai. Tn hiu t t bo quang hc c khuch i v c lc v khong thi gian c o gia hai xung lin tc. Di o t 0-250bpm.Theo di xung ngoi vi c ch hn v c lp hn so vi vic tnh nhp tim t ng in tim trong trng hp tc tim bi v n c th ngay lp tc ch ra s ngng lu thng mu trong cc chi. Thm vo cc Transducer in quang rt d dng so vi ba in cc in tim. Bin ca tn hiu thu c bng phng php ny cng ln so snh vi tn hiu in tim v do n cho ra t l tn hiu nhiu tt hn. Tuy nhin, k thut ny chu nh hng kh ln ca cc tc nhn nhiu do chuyn ng.1.5.3. Phng php o huyt pHuyt p l mt thng s ph bin v hiu qu nht trong y t thc hnh sinh l. Thc hin xc nh gi tr ln nht v gi tr nh nht ca p sut mu trong mi chu k nhp tim, b xung thm thng tin v cc thng s sinh l, h tr cho vic chn on nh gi iu kin c mch mu v mt vi kha cnh v hot ng ca tim. C nhiu phng phng php o huyt p khc nhau, nhng phn ra lm 2 loi: o huyt p theo phng php trc tip v o huyt p theo phng php gin tip.Cc gi tr p sut trong h thng chc nng c ch ra: H thng ng mch 30 300mmHg H thng tnh mch 5 15mmHg H thng phi 6 25mmHgo huyt p theo phng php trc tip IBP:L phng php o chnh xc nht v cm bin c cy trc tip vo ng mch ca c th. Phng php ny ch p dng khi cn chnh xc cao p ng cho yu cu theo di lin tc ca h thng monitor. Phng php ny cho php o huyt p trong cc vng su m phng php o gin tip khng o c. Trong phng php o trc tip ngi ta s dng cc loi ng thng c gn cm bin a vo trong ng mch hoc tnh mch vng quan tm. C hai loi ng thng c s dng, mt loi c cm bin c gn u ng v thc hin chuyn i p lc ca mu thnh tn hiu in. Mt loi khc l ng cha y cht lng, p lc mu s c truyn n u d thng qua cht lng trong ng. Sau u d s chuyn i sang cc tn hiu in tng ng. Cc tn hiu in ny sau c khuch i v hin th hoc l ghi li xem xt. Trong phng php o ny trc khi a cc ng thng vo trong mch mu phi c tit trng trc.

Hnh 1. 16: nh cy cm bin trc tip vo ng mchVic o p sut tnh mch chnh CVP (central Venous Pressure) c thc hin vi k thut ng dn c bit. Cc u d vi nhy cao c a vo trong tnh mch o p sut mu. Tuy nhin cc u d khng th gn trc tip ln u ca ng v khng th thay i v tr ca ng trong khi o. Vic o p sut tnh mch chnh thng c o t mt ng dn nh v cao cp, cc ng dn ny thng di t 25 30cm.S dng phng php gin tip NIBP:K thut ny dng xc nh p sut ca mu ti tm thu v tm trng bng cch cun quanh cnh tay ly p lc ca ng mch. Phng php ny c thc hin bng cch cun quanh cnh tay mt ti chu p lc, sau dng bng hi bm hi vo ti n mt gi tr nht inh. Cho gim dn p sut trong ti mt cch u n, ti khi no c mu chy trong ng mch th l gi tr p sut tm thu, tip tc gim dn p sut trong ti n khi mu chy bnh thng th gi tr l p sut tm trng. Nhng vn xc nh ngng ca hai p sut trn l rt kh, m theo cch trn l rt th cng thc hin bng tay, kt qu ph thuc nhiu vo kh nng ca y t. Nn t tm ra cc phng php o hon ton t ng c th thc hin trn my: T ng o huyt p s dng phng php KorotKoff:Phng php ny thc hin ging nh khi lm bng tay nhng c thm cm bin m c t vo ti kh thu cc m thanh Korokoff. Cc m thanh ny qua cht p in s c chuyn i thnh cc tn hiu in tng ng. Sau cc tn hiu ny c khuch i v truyn i qua cc b lc thng di loi b nhiu. T cc tn hiu thu c ngi ta xc nh c p sut tm thu v tm trng tng ng. Qu trnh din ra trong khong thi gian t 2-5s.

Hnh 1.17: Dng sng tn hiu thu c o theo phng php Korotkoff v daong k. T ng o huyt p s dng phng php dch phaDa vo s xut hin mch ti thi im tm thu v bin mt ti thi im tm trng. Xc nh tc th cc gi tr p sut tm trng v tm thu. thc hin c iu , ngi ta sp xp trn ti kh gm 3 ti con hoc l 3 ngng con c bm cao hn p sut sut tm thu khong 30 mmHg. Mt trong cc tui c gi l ti tm thu, hai ti cn li c gi l ti tm trng. Ga tr p sut tm thu c xc nh bng cch cm nhn mch mu u tin i qua cc ti tm trng. Cn gi tr p sut tm trng c xc nh bng cch pht hin ra khi tn hiu t cc ti tm trng khng cn b dch pha so vi nhau na T ng o huyt p s dng phng php Rheographic:Da vo s thay i tr khng ti 2 im di sc p ca ti kh xc nh p sut tm trng thay cho vic da vo s dch pha mch mu phng php trn.Hnh 1.10 m t cch t in cc o huyt p trong phng php ny. Ba in cc gn trn ti kh c t p st vo da trn cnh tay ca bnh nhn. Vic tip xc tt s lm gim tr khng tip xc gia in cc v da. ic cc B hot ng nh l mt in cc chnh c t gia ti kh, cc in cc A v C c gn hai bn in cc B. Mt ngun xoay chiu tn s cao c 100KHz c a vo cc A v C, khi thc hin o tr khng gia in cc bt k di p lc ca ti kh th n s a ra gi tr tng ng ca cc nhp p trong mch. Do cc xung mch c th c nhn bit v a i khuch i.Khi ti kh c bm ln ti khong gi tr ca p sut tm thu th khng c mt xung mch no c nhn bit bi in cc A. Xung mch s xut hin khi p sut ca ti kh gim xung di mc p sut tm thu. S xut hin cu xung th nht s to ra mt tn hiu in nh du gi tr ca p sut tm thu trn p k. Khi p sutti kh gim v nm trong khong gia p sut tm thu v p sut tm trng th cc tn hiu ny s khng c in cc A v C nhn bit, do dng mu b ngn cn bi ti kh lm cho cc xung xut hin ti A tr hn s vi xung xut hin ti C. Khi p sut ti kh gim xung gi tr p sut tm trng th dng mu khng cn b cn tr v cc tn hiu ny s bin mt. Mt tn hiu chnh xut hin v p sut ca tm trng c hin th trn p k.

Hnh 1. 18 Phng php o huyt p gin tip theo Rheographic

T ng o huyt p theo phng php dao ng k:Da trn phng php dao ng k hoc l khng thm nhp t ng xc nh huyt p ca ng mch. Thit b ny cng thc hin theo li truyn thng l dng ti kh bm cng v cho gim dn p lc. Khi cho p lc ca ti kh gim i th p sut ca ng mch c xc nh tai thi im p lc ca ti kh l thp nht, ti bin ca dao ng k l ln nht. Ti kh c tng p lc bi mt ng c cht v p sut c theo di bng mt ng khc c gn cm bin p lc t trong . Hot ng ca thit b c iu khin bi vi x l h 4040. Vic pht hin p lc ng mch c da vo hai dao ng k. Thit b ny c th t c h s tng quan l 0.98 trong vic xc nh p sut ca ng mch. T ng o huyt p s dng phng php hiu ng siu m Doppler:Cc Monitor t ng o huyt p cng c thit k da vo siu m v s vn ng ca thnh mch. Cc b logic iu khin c t hp trong thit b thc hin phn tch cc tn hiu thu c t s vn ng ca thnh mch xc nh p sut tm thu v tm trng v cho hin th gi tr tng ng.Hiu ng dch tn Doppler c xc nh nh sau: Trong : - tn s Doppler(Hz) - tc truyn m(m/s)- bc sng(m)i vi thit b o huyt p th ng mch cnh tay c s dng v sng siu m s phn x tt. S vn ng ca mch s to ra dch chuyn tn s Doppler:

Trong : - bc sng siu m trong mi trng(m)- vn tc sng truyn m trong mi trng(m/s c 1480m/s)- tn s ca sng siu m trong mi trng (2MHz)T ta c: V tn s Doppler l: Do o ta thy tn s Doppler f ph thuc vo vn tc ca sng siu m trong mi trng. xc nh tn s Doppler phi xc nh theo s vn ng ca thnh mch. S vn ng ca thnh mch c xc nh vo c 5. m v lp li trong khong thi gian t = 0.1s. T tc ca thnh mch c xc nh l:

Thay vo biu thc tnh tn s Doppler ta c:

Cc thit b s dng nguyn l dch tn siu m Doppler o huyt p u da vo vic xc nh tn s dch chuyn ca cc sng phn hi li t s vn ng ca thnh mch. Mt khc cc thit b o huyt p loi ny phi lc b i cc tn s cao v cc tn thp t cc tn hiu phn hi li khi gp s vn ng ca thnh mch.S khi ca cc thit b loi ny c m t trong hnh 3.15. gm 4 khi chnh. Ti cng mt thi im cc tn hiu iu khin t h thng con c pht ti khi RF v h thng Audio con vi tn s sng mang l 2Mhz. Ti chng c a ti cc u d trong ti kh, cc u d thc hin chuyn i nng lng ca sng RF sang dng nng lng ca sng siu m v cho i qua tay ca bnh nhn. p sut trong ti kh c kim tra bi h thng iu khin con v kh p sut t n khong nh trc th qu trnh bm c dng li. Ti thi im ny, cc mch audio trong khi RF v khi audio h thng con s c iu khin bi cc tn hiu iu khin h thng con v cc tn hiu audiony s a cc tn s Doppler n khi iu khin logic. Cc tn hiu iu khin t h thng con c a ti khi h thng kh iu khin bm kh cho ti kh theo mt tc nh trc.

Hnh 1. 19: Cc khi chnh trong thit b o huyt p siu m

Ti p sut tm thu, ng mch ang b nn s m ra v mu bt u chy. S vn ng ca ng mch lm xut hin tn s Doppler khi sng siu m phn hi li. Tn hiu c chuyn i sang dng tn s audio v c nhn bit l im p sut tm thu bi h thng iu khin logic. Sau khi c 4 tn hiu c nhn bit y t cc thanh ghi th lc mi khng nh l im p sut tm thu. Mt cch kim tra khc l da vo cc tn hiu audio xc nh b rng v tn s ca cc xung phn hi t cc ng mch. Cc xung c b rng ln hn 125ms va tn s ln hn 250ms s b loi b ra bi h thng iu khin logic. Vic thit lp gii hn trn (240bit/s) theo nhp timca bnh nhn s c thit b t ng thc hin. Tng t nh vy cho gii hn di l 24bit/s. Ti p sut tm trng, p sut ca ti kh s cn bng hoc xp x ngng p sut ca ng mch. Khi h thng audio con s khng nhn c cc tn s Doppler na v vic c p sut tm trng c tin hnh. Khi p sut ca ti kh s cn bng vi p sut ca kh quyn v c gi nguyn cho n khi thc hin mt php o mi.1.5.4. Phng php o nhit Cc cm bin c s dng thng dng trng cc thit b o nhit l cc in tr nhit. S thay i gi tr in tr theo nhit c xc nh bng mch cu v c hin th bng mt nhit k. Di o nhit cho c th ngi thng t 30 420C.Trong trng hp hin th s th cc mch in thng x l trong monitor c biu din trn hnh 1.12. Ban u chuyn mch S1, S2 c t nh trong hnh 3.16, trong trng hp nym in p trn Rref ( 00C) c a vo u khng o ca b khuch i A1. Tn hiu t A1 c a ti c hai u o v khng o ca b khuch i A2. Tuy nhin trong thi gian ny t C u o ca b khuch i A2 s c np ti gi tr Vref 0C. Ti thi im m v tr cc chuyn mch c o li v u vo cu b khuch i A1 c ly t in tr nhit. ng thi u vo o t A1 n A2 c ni mch. Khi mt in th dng ln hnVref 0C xut hin tai u vo khng o ca b khuch i A2. S khc nhau gia u vo o v u vo khng o ca b khuch i A2 lm cho u ra ca n b m. Trong thi gian ny, t C phng in qua R2 cho n khi in p trn t C cn bng vi in p trn RT. Khi hai u vo ca b khuch i A2 tr nn cn bng th u ra ca n li tr li gi tr dng. Trn thc t th cc mch FET c s dng cho cc chuyn mch S1, S2, Cc xung tn s cao s c m trong khong thi gian m nhit c xc nh. Trong cc h thng theo di bnh nhn c hai knh o nhit thng c s dng. Cng ging nh vic ghi o in tim, y cc mch ra cng phi c cch ly qua cp bin i quang in.

Hnh 1. 20: S khi chi tit o nhit hin th s trc tip1.5.5. Phng php o nhp thCc u d thng c s dng trong vic o nhp th bao gm cc in tr nhit c t trc mi, cc vi mch hoc l cc u d khng c nh c t quanh ngc bnh nhn. Tr khng ca cc in cc v tn hiu c ly t vic xc nh CO2. Tn hiu nhp th c ly t bt k mt u d no c em khuch i v trong khong thi gian ny s thc hin o gia hai xung k tip nhau. Di o thng 0 50nhp/pht. Gm c 2 phng php in tr nhit v tr khng phiS dng in tr nhit:Dng in tr nhit nh cc u d. t in tr nhit gn ng qun o s thay i ca nhit kh th trong khi ht vo hoc th ra. in tr nhit c t trn cnh tay ca bnh nhn l mt mch cu Wheastone d a ra s thay i ca nhit trn. Mt b khuch i c s dng nhn tn hiu t mch cu, t tn hiu ny s thc hin m s nhp th /pht. Cc tn s tho s c lc b trc khi tn hiu c em i x l.Nu nh nhit khng kh th ra l trong khong nhit phng th s rt thun tin cho vic s dng mt in tr nhit phn bit s khc nhau gia hai nhit khi ht vo v th ra, t s to ra tn hiu in tt hn. Cn nu nhit khng kh khi th ra l cao hn th in tr nhit c th hot ng nhit phng. i khi cn phi o cho cc bnh nhn b bt tnh khi h khng iu khin c qu trnh th ca mnh na lc ny cn c s tr gip ca my.S dng tr khng phi:y l mt k thut dng xc nh nhp th mt cch gin tip. Trong phng php ny ngi ta s dg cc in cc t ln ngc bnh nhn( tt nht l cc in cc b mt), da vo tr khng phi xc nh quan h gia su nhp th v s thay i tr khng ca ngc. Trong k thut ny yu cu cn c cc dng c : mt n, ng dn, lu lng k, hoc ph dung k. Trong phng php ny th cc in cc b mt c s dng l thch hp nht.Cc in cc c gn ln ngc bnh nhn nhn bit ra tn hiu iu ch. Tn hiu c iu ch bng cch thay i tr khng ca c th cng vi chu k th. Cc in cc t gin tip xc vi da c h tr bi mt lp kem chuyn dng. Cc in cc khi tip xc vi da s to ra mt tr khng c 150 - 200. S thay i tr khng trong mi chu k th s dao ng trong khong 1% in tr gc trn.

Hnh 1. 21: Nguyn l phng php o tr khng phiHnh trn l s nguyn l phng php o tr khng phi hai in cc. Vic dng 2 in cc cm nhn tr khng th ch ph hp vi bnh nhn nm. V nu nh c bt c s dch chuyn no ca i tng th s lm thay i tr khng tip xc ca in cc. gim s thay i th ta s dng 4 in cc. Khi tn hiu pht ra t b dao ng k c a ti hai in cc, dng in t b dao ng k s khng i qua tr khng tip xc ca in cc o. Cc s ny thng c dng cho cc monitor m i tng o l tr em.1.5.6. Phng php o nng CO2Xc nh nng CO2 trong kh th ra l mt cch khc xc nh nhp th. Hnh 3.18 minh ha nng CO2 ht vo v th ra. Vic xc nh da vo cc tia hng ngoi c hp th t cc kh. Cc b lc cn thit c s dng tp trung cc kh c bit nh: CO2, CO, N2O trong thnh phn kh th ra, cc kh him v kh a nguyn t s khng hp th tia hng ngoi. Khi cho cc tia hng ngoi i qua kh th ra c cha mt hm lng CO2 th mt phn nng lng ca tia hng ngoi c hp th bi kh ny. Cc b cm nhn s nhn bit c s suy gim nng lng ca tia v thc hin chuyn i thnh tn hiu in. Tn hiu ny s c s dng tnh nhp th trung bnh.Trong cc phng php phn tch hp th hng ngoi, c 2 phng php o CO2 l sidestream v mainstream.Phng php o CO2 sidestreamPhng php ny ht th lin tc ly mu kh v phn tch hm lng CO2 ca mu . S thit lp khng ng tc th, kh d ra h thng mu, s ngng t hi nc l do tnh trng bao ph v tt c cc bi nguyn t l cc ngun gy li. Cc dng ng cc cht pha ch c nc c thit k ngn chn s i vo ca cc cht lng thnh ra s o c nh cc cht lng c hp th hng ngoi cao. Sau khi cc kh c phn tch, cc kh thi c th ly li gy m trc khi hydroxit natri vi hydroxit canxi trong hp nh.

Phng php o CO2 mainstream Phng php ny s phn tch ton b kh th ti mt thi im gy m. Cuvett o c t cng gn th c th t trong ng qun. Dng c phn tch s dng hp th hng ngoi pht hin CO2. ng c t nng ti 400C ngn chn s ngng t ca hi nc c mt trong cc kh. Ht vt cht nh nc nhy hoc nc ming t ng thng s gy ra sai lch do s hp th hng ngoi nu chng i vo trong ng cuvette. Tuy nhin, p ng thi gian ca dng c phn tch nhanh hn phng php CO2- sidestream, phng php khi ph k hoc cc dng c phn tch Raman. Tt c cc phng php o CO2 c chun nh k ngn chn s sai lch ca thit b.

Hnh 1. 22: Nng CO2 khi ht vo v th raHnh di a ra s khi trong vic phn tch kh CO2 trong hi th ra. Hai chm tia c cng tng ng nhau to ra cc tia hng ngoi t cc si t c gn trn mt na ca mi bnh ngng. B d gm c 2 phn ging ht nhau c cch bit bi mt lp kim loi mng. Cc u d c lm y bi cc mu CO2 tinh khit. Do s tp trung ca kh CO2 trong t bo phn tch nn chm tia trn b mt th nghim ca u d s yu hn l mt xem xt. Do kh b mt xem xt s c t nng hn b mt phn tch. Mng ngn y l mt tm ca t in. Cc chm tia hng ngoi c chn tn s 25Hz v tn hiu xoay chiu xut hin u d s c khuch i ph hp a ra nhp th tng ng.

Hnh 1.23: S khi ca qu trnh phn tch kh CO2 trong hi th1.5.7. Ghi tn hiu in tim ECGGhi tn hiu in timin tim ECG l cc hot ng in ca tim c to ra bi qu trnh co bp ca c tim. Vic theo di in tim ECG nhm kim tra mt s chc nng ca tim l rt quan trng trong vic theo di tnh trng ca bnh nhn trong sut qu trnh gy m bnh nhn trong phng m. Vic theo di ECG c s dng tnh nhp tim, phn tch chng to nhp, pht hin chc nng to nhp v chng thiu mu. Tn hiu in tim c ly trn da bnh nhn thng qua h thng in cc ECG v cp ni. S in cc c th l 3,5 hay 12 in cc tu theo loi my. Cng nhiu in cc th thng tin o c cng chnh xc. Tuy nhin hu ht cc Bedside thng s dng cp in tim tiu chun 3 hoc 5 in cc.V tr t in cc trn ngi bnh nhn tu thuc vo s in cc ca cp in tim.Vi h thng 3 in cc ( 3 o trnh ) cc in cc ny s c gn R/RA( right arm), L/LA ( left arm), F/LL( left leg) ca bnh nhn. i vi cp in tim 5 in cc th thm cc v tr C/V(chest) v N/RL(right leg). S lng o trnh ph thuc vo s in cc.Cc in cc ECG gn trn da bnh nhn thu nhn cc tn hiu in ECG v c ni vi mt mch u vo ca monitor bng cc dy dn/ cp. Cc tn hiu ECG thu c s c khuch i v x l bi modul hoc khi o ECG v sau d liu c chuyn ti BSM v hin th dng sng ECG trn mn hnh.

Hnh 1. 24: Cc o trnh chun

Hnh 1. 25: Cc o trnh chi n cc

Hnh 1. 26:Cc o trnh trc ngcNu s dng cp in tim 12 in cc ta s o c dng sng ca 12 o trnh trn. Nu s dng cp 3 hoc 5 in cc c dng sng ca 3 o trnh hoc 6.

Hnh 1. 27 in tim 12 knh ghi

Hnh 1. 28 in tim 6 knh ghi

Hnh 1. 29 in tim 3 knh ghi

Hnh 1. 30 in tim 3 knh ghi + 1 nhp tim chunCc in cc ECG gn trn da bnh nhn thu nhn cc tn hiu in ECG v c kt ni vi mt mch u vo ca monitor bng cc dy dn/ cp. Mch u vo bao gm mch cch ly v mch bo v. Mch cch ly c chc nng cch ly bnh nhn khi cc dng in nguy him c th pht ra trong qu trnh thu tn hiu ECG v mch bo v trnh monitor khng b ph hng bi cc in p cao c th xut hin trong qu trnh kh rung tim bnh nhn. B khuch i ECG gm b tin khuch i v b khuch i iu khin. Cc tn hiu ECG thu c ban u c bin rt nh s c khuch i vi sai c h s khuch i rt ln. B khuch i ny c tr khng u vo ln v t s Mode chung CMRR cao. B khuch i iu khin s khuch i cc tn hiu ECG ti mt bin ln v truyn tn hiu ECG ny ti b chuyn i AD v khi x l trung tm, s khi c m t nh hnh di:

Hnh 1. 31 S khi ca vic thu nhn v x l tn hiu ECG1.5.8. bo ha oxi trong mu SpO2Hemoglobin l mt loi protein v l thnh phn chnh ca cc t bo hng cu, n vn chuyn oxi t phi ni nng hay p lc oxi SpO2 rt cao, ti cc m ni m nng oxi thp. bo ha oxi SpO2 trong mu c nh ngha l t s gia lng oxi ti hn vi tng kh nng c th cha oxi ca mu ng mch, tc l t s gia oxi hmoglobin vi tng s hemoglobin trong mu ng mch theo cng thc:

: nng oxi hemoglobin : nng deoxigenhemoglobin ( khng mang oxi) bo ha xi c tnh xc nh hiu qu cu vic iu tr , chn on, ng thi cng cn cho theo di tnh trng v s pht trin ca mt s lai bnh. o bo ha xi ngi ta s dng pulse oximetor, cm bin ca thit b ny gm ngun sng kp, phtodetector.

Hnh 1. 32: S khi x l tn hiu ca Pulse Oximetor Nguyn l o SpO2: nh sng v tia hng ngoi c pht ra lin tc t ngun sng kp i xuyn qua m. Xng, m, sc t da v mu ng mch s hp th mt lng nh sng c nh theo thi gian. Cn ng mch thng s p v hp th cc lng nh sng khc nhau trong cc qu trnh tm thu v tm trng do dung lng mu s tng v gim trong cc qu trnh ny. T s nh sng c hp th ti thi im tm thu v tm trng s c chuyn i sang vic o nng bo ha oxi. Cc m c cu trc mng thng c chn o: ngn tay, ngn chn v tai. Phn nh sng i qua m s c thu nhn bi phtdetector v c chuyn i thnh tn hiu in, cng nh sng thu c cng ln th tn hiu in cng mnh. Photodetector gi cc tn hiu in cha thng tin v cng nh sng ny ti oximetor, oximetor s dng cc thng tin ny tnh ton phn trm tng i ca HbO2 v HHb, bo ha oxi SpO2 v nhp mch thng qua b vi x l tn hiu.

Hnh 1. 33 Hnh s hp th nh sng hng ngoi ca mu tnh mch, m, xng Tuy nhin nh sng khi xuyn qua v tr o khng ch b hp th bi mu ng mch m cn bi mu tnh mch v cc m khc. Do , cc thng tin m oximeter thu c bao gm thng tin t mu ng mch v cc t chc khc ngoi mu ng mch c o.1.5.9. o cung lng tim COCung lng tim l lng mu tim bm vo ng mch trong mt pht. Cung lng tim ph thuc vo th tch tm thu v nhp tim. Gi tr bnh thng ca cung lng tim 4.5 6lit/pht, cn khi vn ng nhiu th c th ln n 20 lit/pht. Theo di cung lng tim bit c lng mu qua tim tng hay gim. C 3 phng php xc nh cung lng tim phong php Fick, phng php pha long cht mu, phng php pha long nhit. Trong phng php pha long nhit l ph bin nhtPhng php Fick:y l phng php o chnh lch hm lng oxi gia ng mch v tnh mch. Phng php ny dng Oxi nh cht ch th v tng hm lng oxi trong mu tnh mch do n i qua phi dc theo ng thng xi th, do hm lng cn xc nh cung lng tim l CO = nng O2 trong ng thng/A VO2 khc. ng thng oxi ( mL/pht) c o bng mt thit b o dung tch phi c in y oxi cha mt thit b ht CO2. A VO2 khc c xc nh t hm lng oxi(mL/100mL mu) t bt k mt mu mu ng mch no v hm lng oxi (ml/100ml) ca mu ng mch phi. Hm lng oxi trong mu thng rt kh o. Tuy nhin, cc my phn tch kh trong mu m o nng pH, nng O2, nng CO2, t l th tch huyt cu v hemoglobin cung cp gi tr cho hm lng O2 bng cch tnh ton s dng ng cong phn tch oxi. C mt k thut chuyn mn nh bao gm cch xc nh ng thng oxi bi v oxi b hp th nhit c th nhng o c nhit phng trong thit b o dung tch phi. V vy, th tch ca oxi b hp th trong mt pht c nhn vi h s F.

Hnh 1. 34 S o Oxi trong ng vi mt dung k (phi) v phng php s dng tnh ton o th tchHnh trn l ph dung biu din s lin quan th tch trn mt ng dc c bn th hin mc ngng th(REL). dc nhn bit ng thng oxi nhit phng. Trong vn ny, s hp th oxi khng chnh xc l 400mL/pht 260C trong thit b o dung tch phi. Vi mt kh p vi p sut 750mHg, h s chuyn i ng vi th tch , nhit c th 370C v lm bo ha hi nc l:

Trong l nhit dung k, Pb l p sut kh p, v PH2O Ts c lyt bng hi nc (bng).

Hnh 1. 35 p sut kh p ca ncMt v d tnh ton n gin cho h s chnh xc F c a ra trong hnh m tnh ra gi tr ca F l 1.069. Tuy nhin, d dng s dng bng 3.1 cha h s chnh xc. V d, cho mt dung k nhit 260C v p sut kh p 750mHg, F= 1.0691. Ch rng h s dng F trong trng hp ny ch ng 6.9%. Li ng c th t hn li s dng trong tt c cc ln o khc. Mt v d c la chn trong A V khc l 20 15 mL/100mL, mu v nng trong ng thng l 400 x 1069; do cung lng tim l Phng php pha long cht muPhng php pha long cht mu( thuc nhum) l mt dng ca phng php pha long cht ch th. Dng dung dch xanh Methylene hoc xanh Indocianine sau khi trn hon ton trong tun hon phi s vo mu ng mch. Mu mu ng mch c o lin tc nng cht mu bng vic phn tch quang ph khi mu qua ngun sng hng ngoi. Cht mu dng cho php o lu lng phi ha tan trong nc, khng c, v trng v cho php xc dnh nng trong mu hay huyt tng ( cung lng tim). ghi li ng cong pha long c th dng quang mt k loi ng thy tinh hay loi earpiece hoc ng si quang. Quang mt k ng thy tinh l mt dng c o nng thuc nhum trong mch mu mt cch lin tc thng qua mt ng trong mch. Khi nng thuc nhum nh v phn tn u trong mu, th theo lut Lamber Beer ta c quan h gia mt quang I v nng cht mu (thuc nhum) :

Trong :: h s hp th: dy ca lp mu: khi lng cht ch th: mt quang khi = 0Tuy mt quang l hm phi tuyn i vi nng thuc nhum nhng vn t c u ra tuyn tnh theo c tnh loga ca ng nhn quang khi dng anot khng i. . nhy ca quang mt k c th hiu chun bng cch a mu cha thuc nhum vi nng xc nh vo ng thy tinh. Mc hiu chun c th b thay i bi cc gi tr hematocrit. Tuy vy, nu dng quang mt k lng sc s dng 2 bc sng trong mt bc sng th nhy vi thuc nhum cn bc sng cn li th khng nhng c hai u nhy vi hematocrit th c th b c s thay i .ng si quang cng c th s dng ghi ng cong pha long cht mu trong c th. Ti u ng, mu c chiu sng bi mt chm tia sng truyn qua b si quang v phn nh sng tn x ngc c d ti b tch sng quang nh mt b si quang khc. Tuy khc vi quang mt k loi ng thy tinh v loi ci tai m nh sng i qua mt lp c chiu dy xc nh nhng n vn t c ng cong hiu chun tng t gia nng thuc nhum trong mu v s thay i cng nh sng tn x. So snh vi quang mt k trong php o v tim th kt qu thu c c h s tng quan vo khong 0.9.Mt u im ca ng si quang l n c php ghi li ng cong pha long trong cc mch mu ln m khng b mo ging nh quang mt k lai ng thy tinh ( do phn b vn tc trong ng thy tnh) . C th ch to ng si quang nh s dng tr s sinh. Tuy nhin phng php ny cng t khi s dng.Phng php pha long nhitPhng php ny s dng mt cht ch th khng c chuyn ha l NaCl 0.9% hoc Dextrose 5% c lm lnh trong nc (D5W) c nhit thp hn nhit ca mu v c tim vo nh phi. Trong phng php ny thng dng cht lng lnh lm cht ch th do cht lng lnh t gy tn hi cho mu v m hn so vi cht lng nng. Hnh 3.43 minh ha phng php v ng cong pha long nhit c trng. Phng php pha long nhit da trn nhit thay i o c trong Cl v phng trnh sau bao gm iu kin xc nh r nhit (C) v khi lng (S) ca cht ch th (i) v mu (b). u Cathete tim dung dch ny c gn mt cm bin nhit xc nh c nhit ca dung dch tim. S thay i nhit ca mu do tim dch lnh ny c o ng mch phi nh mt b cm bin nhit th 2. Hai tn hiu ny c chuyn i thnh tn hiu in v c tch phn theo thi gian cho mt gi tr cung lng tim tng ng vi cung lng tim h thng. C biu thc:

Trong :V: th tch cht ch th c tim (mL): nhit trung bnh ca mu ng mch phi 0C)60: h s nhn khi chuyn i mL/s sang mL/phtA: vng di ng cong pha long (s. 0C)C: nhit chnh xc ca cht ch th (i) v mu (b)( cho Dextrose 5% v mu th tch hng cu c 40%)F : h s ng cho nhit truyn qua ng tim ( ng c ng knh 7F,F=0.825) H s cung lng tim l: Trong :CO: cung lng tim (mL/pht)53.46 = 60*1.08*0.825 minh ha mt ng cong pha long nhit, cung lng tim c tnh ton bng cch s dng ng cong pha long nh trong hnhV= 5mL ca Dextrose 5% trong nc=370C, = 00C, A=1.590CsC0 = 6220mL/pht

Hnh 1. 36 Phng php pha long nhit (a), v ng cong c trng (b)Mc d phng php pha long nhit l mt phng php chun trong y hc lm sng, n c mt vi khuyt im bi v nhit gim nhanh qua thnh ng, khi tim 5mL cht ch th cn phi c gi tr ph hp vi cung lng tim. Nu cung lng tim thp, tc l, ng cong pha long rt rng, n kh c mt gi tr chnh xc vi cung lng tim. C mt s thay i do cm ng th gy ra trong nhit mu PA m lm xo trn ng cong pha long khi n c bin thp. Mc d nhit phng D5W c th c s dng, D5W c lm lnh cung cp mt ng cong pha long tt hn v gi tr cung lng tim ng tin cy hn. Hn na, r rng nu nhit ca cht ch th bng nhit ca mu th s khng c ng pha long.Tuy nhin phng php ny vn c mt vi u im: cht ch th khng c hi nn c th thc hin lp li cc php o, ng cong pha long c ghi li d dng nh mt in tr nhit t trong mch mu v thnh phn quay vng l nh tch phn ca ng cong pha long l chnh xc. Gi thit c bn ca phng php pha long cht ch th l cht ch th khng c thot khi h thng mch mu gia v tr truyn vo v v tr o bi v nhit c th truyn qua thnh mch mu. nh hng ny khng ng k trong cc mch mu ln v t s gia din tch b mt trn th tch trong mt n v chiu di l nh. V th phng php pha long nhit vn thch hp cho cc php o cc mch mu ln. S quay vng cht ch th:Mt ng cong pha long l tng nh trong hnh 3.44 bao gm ng dc ng v mt ng suy gim theo lut hm s m trong cht ch th. Cc thut ton m o din tch ng cong pha long l khng kh vi mt ng cong. Tuy nhin, khi cung lng tim thp, c trng ca ng cong pha long l bin thp v rt rng. Thng th b dc ca ng cong b che khut bi s quay vng ca cht ch th hoc bi cc nhiu bin thp. Hnh di l mt ng cong pha long m b dc b che khut bi s quay vng ca cht ch th. R rng l rt kh xc nh im cui thc t ca ng cong, m thng c ch th theo thi gian khi nng cht ch th ri vo t l phn trm ln (v d 1%) ca bin ln nht (Cmax). Bi v b dc m t gn ng ng cong suy gim theo lut hm s m (e-kt), s iu chnh b dc lut hm m cho php khi phc ng cong m khng c li ca s quay vng bng cch cung cp ch yu nhn bit im cui cho ci c gi l first pass ca cht ch th.Trong hnh 1.29(b) l bin ca b dc ng cong, trong hnh (a) m t th bn loga v phn tun theo hm s m m t l mt ng thng. Khi s quay vng xut hin, cc im d liu trch so vi ng thng v do c th khng cn n v phn ng thng c th b ngoi suy theo t l phn trm ca nng ln nht bng 1% Cmax. S m t cc im d liu trn phn b ngoi suy c biu din li bng th nh trong hnh (a) ch r ng cong pha long khng b nhiu bi s quay vng.

Hnh 1. 37 ng cong pha long b che khut bi s quay vng (a), v th bn thut ton loga ca b dc(b)1.6. H thng monitor trung tm1.6.1. Gii thiu v h thng monitor trung tmH thng gim st bnh nhn cho php gim st t xa hang chc bnh nhn. Chng c to thnh t cc my mc c khc nng ni mng. Thng thng, chng bao gm mt hoc nhiu b cm bin, thit b hin th, thnh phn phn tch, thm vo l cc H thng trung tm gim st bnh nhn a thng s l mt loi thit b cung cp thng tin v y t c s dng rng ri trong lnh vc iu tr lm sng. H thng bao gm phn mm qun l v my tnh c tc cao, to nn mt mng li bng cch kt ni cc my theo di ging bnh.H thng monitor trungg tm c iu khin bi mt my tnh trang b nhng kt ni mi nht cng h thng knh. H thng ny c th thc hin nhng cng vic sau: Qun l theo thi gian thc cng lc 16-24 bnh nhn. Qun l v hin th cc ch s sinh l ca 16-24 bnh nhn theo thi gian thc trong 24 gi. m v phn tch tn hiu, ng thi bo ng khi c s c xy ra. T ng lu tr d liu v bnh nhn. D liu c truyn t CMS n cc my theo di ti ging bnh theo nh dng XML. C ng dng kt ni khng dy qun l t xa hoc kt ni vi H thng mng bnh vin 41.lin kt truyn thng.

Hnh 1.38 Mn hnh hin th h thngXu hng internet of things (IOT) m ra mt mng li gim st y t ni b v cng hiu qu m c ng dng trn nn lin kt truyn thng. Vi cc monitor c kh nng kt ni mng, chng c th gi d liu u ra ca chng ti trm gim st trung tm ICU, ni m mt c nhn c th gim st v hi p ti nhiu monitor ging bnh. Php o t xa linh hot c th tch hp ln cc mu m c mang theo trn ngi bnh nhn v truyn d liu ca bnh nhn thng qua kt ni d liu khng dy. Gim st k thut s to ra tnh kh dng m h tr pht trin ton phn ca s tch hp d liu sinh l t mng li gim st bnh nhn bn trong h s y t in t ca bnh vin v h thng biu k thut s, s dng cc tiu chun chm sc sc khe thch hp m c pht trin nh IEEE v HL7. Phng php mi hn ca biu d liu bnh nhn gim li trong ti liu bnh nhn v ton b s tiu th giy. Ngoi ra, s din gii ECG t ng tch hp t ng vo cc bng m chun on. Phn mm nhng ca cc monitor y t c th x l c m ha d liu theo chun ca chng v gi cc gi tin ti bn ng dng h s y t m c kh nng gii m chng v tng hp d liu y thnh mt trng thch hp. Kt ni ng di c th tn dng cho y hc t xa, ni m lin quan ti vic cung cp cc dch v chm sc sc khe.1.6.2. Xu hng pht trin h thng monitor trung tm hin nay H thng gim st trong bnh vinCc bnh vin phi i mt vi nhng thch thc hng ngy v theo di bnh nhn mt cch y trong c s y t ca h. Ngoi ra, bnh nhn cn c di chuyn lin tc t n v ny sang n v khc da trn mc tnh trng ca bnh v cc ging bnh trng. Gii php gim st ton c s y t l cn thit m bo rng thng tin gim st bnh nhn c cung cp mt cch chnh xc cho vic duy tr h s bnh nhn mt cch lin mch.Cc t chc chm sc sc khe hin i ngy nay i hi mng gim st c s y t mnh m m c th phc v theo di bnh nhn t hu nh bt k v tr no. Cc gii php gim st c s y y thnh cng mang n kt qu l t tc nghn cc dng di chuyn bnh nhn trong bnh vin, bnh nhn c c hi s dng ging bnh tt hn. Gim st ti ging bnhThng thng, gim st ti ging bnh c thm tnh nng l c th ci t c kh nng lin kt vi cc monitor ln hn, chi ph cao hn v c nhiu tnh nng hn. Cc la chn phn mm c th c mua thm thm cc tnh nng nng cao m t lm tng chi ph tng th. Do , cc ty chn ph hp vi chi ph c gii hn p ng cc rng buc v ngn sch.

Hnh 1.39 monitor ti ging bnh H thng gim st trung tm thng qua gim st ti ging bnhNgoi vic theo di bnh nhn trn c s c nhn, quan st t xa ca hng chc cc bnh nhn c th c kch hot thng qua h thng gim st bnh nhn trung tm. Cc h thng gim st c to thnh t cc my mc c kh nng kt ni mng nht qun ca mt hoc nhiu b cm bin, thit b hin th, cc thnh phn ch bin, v cc lin kt truyn thng cho hin th hoc ghi li kt qu nhng ni khc thng qua mng.H thng gim st bnh nhn trung ng c th gip cc bnh nhn, ngi chm sc, v y bc s thc hin cc quyt nh ng n hn. Ngoi vic cung cp d liu h tr cc y bc s vi cc quyt nh chn on v iu tr , chm sc tn ni c ci thin vi vic s dng cc h thng ny c cc d liu c th kch hot cnh bo hoc phn ng cung cp dch v ci thin kt qu sc khe.1.6.3. S cn thit ca h thng monitor trung tmH thng gim st bnh nhn c s dng qun l mt phm vi rng cc mi trng y t nh v liu php h hp, gic ng, cc dch v y t khn cp v di chuyn. Chng tr nn quan trng trong cc phng chm sc c bit. Ngoi ra, cc h thng theo di bnh nhn c minh chng l v cng cn thit cho cc phng phc hi, chm sc bnh nhn ngoi tr, X-quang, cc phng th nghim th thut, khoa tiu ha v nhiu ng dng khc.H thng gim st bnh nhn c th phc v cho mt s mc ch bao gm cung cp d liu h tr y bc s vi cc quyt nh chun on v s la chn phng php iu tr. Bn cnh , h thng cn gip cho bnh nhn, ngi chm sc, y bc s a ra nhng quyt nh gii quyt tnh hung chnh xc hn. Ngoi ra, tnh c ng trong vic chm sc c ci thin khi s dng d liu ca h thng nh l cc d liu dng cnh bo hoc kch hot cc dch v cung ng cn thit ngay lp tc ci thin sc khe cho bnh nhn ngoi tr.Theo di bnh nhn l vic kim tra lin tc tnh trng ca bnh nhn, c bng trc tip ln gin tip thng qua cc thit b gim st y t. Trong mi trng bnh vin, theo di bnh nhn l v cng quan trng trong iu hnh cc trng hp khn cp, chm sc c bit, cc n v chm sc c bit v nhiu lnh vc quan trng khc.Trong khi theo di bnh nhn c th lm gim nguy c ly nhin bnh v cc bin chng khc, cng nh l h tr thm cho bnh nhn cm thy thoi mi v yn tm trong thi gian bnh nhn ngoi tr ang c nh hng ti sinh l bi s bnh hay stress. Do , theo di cc phn ng sinh l ca bnh nhn l v cng quan trng xc nh tnh hiu qu ca cc bt k iu tr y t no. Thc t, h thng gim st bnh nhn vi cc tnh nng tin tin, kh nng kt ni khng dy hoc iu khin t xa l mt trong cc thit b y t pht trin nhanh nht hin nay. S dng cc cng ngh gim st bnh nhn mi c th em li kt qu l ch cn thm t nhn vin mi hn, tng kh nng lm vic cho cc nhn vin ang cng tc v gim thiu ri ro cng vic.

CHNG 2: GII PHP MNG CHO H THNG MONITOR TRUNG TM2.1. Tip cn cu trc m trong h thng gim st bnh nhnT vi thp k trc, cc k s v nh khoa hc s dng rng ri h thng giao tip truyn thng c trong ngnh cng nghip y t nh HPIB hoc mt s h thng bus ni tip nh Profibus, CAN bus,Trong thi i hin nay, cng ngh ngy cng pht trin c bit l trong lnh vc truyn thng m trong ngnh cng nghip y t. Xu hng ny c pht trin chuyn sang giao thc TCP/IP l bus ni b thay v cc thit k truyn thng nh GPIB, Profibus, CAN bus. Tip cn cu trc m ang dn ph bin trong ngnh cng nghip y t. Hu ht ton b nh sn xut thit b u s dng h thng bus mi nht cho giao din giao tip m cho sn xut thit b.Kt ni bus mi nht l kt ni rt thng minh bi nhiu l do nh d cm v chy thit b, thit b ngoi vi Universal Serial Bus (USB), kt ni tc cao nh IEEE 1394 v card iu khin mng tc cao.2.1.1. Nhng ng dng mi ca bus trong ngnh cng nghip hin nayT 10 nm qua, ng dng cc kt ni bus mi l rt chm trong ngnh cng nghip so vi h thng bus truyn thng. Ngy nay trong ngnh cng nghip, nhng bus nh IEEE 1394, Ethernet Controller v Universal Serial Bus (USB) c s dng trong quy m rng. Universal Serial Bus (USB) v b iu khin Ethernet s dng nh kt ni bus tiu chun cho th nghim v ng dng o lng trong ngnh cng nghip. Tuy nhin, nh chng ta bit cng ngh c pht trin tng ngy, v vy n l c hi kh tt s dng nhng loi thit b c h tr bus trong tng lai nh cng c th nghim v kim sot o lng trong mt khong thi gian di.Cng ngh mi trong cc h thng bus ca phn cng l mt l do s dng GPIB (bus giao din mc ch chung) trong ngnh cng nghip hin nay cho vic iu khin thit b v cho kt ni mng. Cc GPIB c thit k iu khin thit b v hy vng n s c dng trong nhiu nm th nghim v ng dng o lng trong ngnh cng nghip. i vi cng nghip sn xut Personal monitor system(PMS), s lng ln cc my PMS c s dng h thng bus truyn thng. V vy, cc nh sn xut nh National Instrument a ra c thit b bc cu vi s h tr ca GPIB, ngi dng c th kt ni h thng bus mi nht vi cc h thng bus c. Cc sn phm ny gip ngi s dng d dng kt ni bus cng ngh mi nht vo cc h thng c sau cc thit b c th cm v s dng vi s h tr ca cng ngh bus mi v cng c s dng kim sot thit b kim tra v h thng o lng trong ngnh cng nghip. Nhng sn phm bc cu gip kt ni cc h thng gim st bnh nhn c n vi h thng mng li bnh vin hin ti. C mt s sn phm bc cu c sn trong ngnh cng nghip dng cho kim tra v o lng ca cc thit b.2.1.2. GPIB iu khin bn phn cngc im ca B iu khin Ethernet vi GPIB: Tng thch vi Windows Vista, Windows XP v Windows 2000 H thng mng s to trang ch v chia s ln n 14 thit b GPIB vi cc mng khc nhau Giao thc cu hnh ng my ch (DHCP) v cng c th chnh cu hnh a ch IP v n tng thch vi 10BASE-T v 100BASE-TX iu khin mt mng TCP/IP Ethernet da trn chun IEEE 4882.1.3. T b iu khin Ethernet ti GPIP iu khin tc caoc im ca USB GPIB iu khin: Da trn chun IEEE 488.1, tc truyn ti ln ti 1,8 Mb/giy USB tc cao tng thch vi USB 1.x Khng yu cu kt ni cp GPIB, c tnh nng cm l chy Tng thch hon ton vi Windows Vista, Windows XP, Windows 2000, Windows Me, Windows 98, Mac OS X, v Linux IEEE 488.2 2.1.4. T USB tc cao ti GPIB iu khinc im ca USB GPIB iu khin: Da trn chun IEEE 488.1, tc truyn ti ln ti 1,8 Mb/giy USB tc cao tng thch vi USB 1.x Khng yu cu kt ni cp GPIB, c tnh nng cm l chy Tng thch hon ton vi Windows Vista, Windows XP, Windows 2000, Windows Me, Windows 98, Mac OS X, v Linux IEEE 488.2 92.1.5. Tip cn phn mm linh hot trong h thng cu trc mKh nng tng thch phn mm lun l mt vn quan trng trong ngnh cng nghip sn xut thit b c bit l khi cc th h bus mi nht c gii thiu. Trong ngnh thit b y t, vic pht trin h thng giao din nhiu nh cung cp ang ngy cng ph bin trong thi gian gn y. Phn mm c th duy tr kh nng tng thch vi bus mi cng nh bus c, trong khi vi ngnh thit b y t hin nay, vic s dng duy nht mt phn mm tiu chun dnh cho tt c cc thit b l mt hng i ng n. Hin nay nhng tiu chun c a ra l Nn tng thit b o (IVI Foundation) v Cu trc phn mm thit b o (VISA). IVI c pht trin vo nm 2001. H cho cc nh cung cp phn mm, phn cng, dng c v h thng a cung cp cho cc cp tng thch lm thnh vin. V vy, hin nay trong ngnh cng nghip hu ht cc nh cung cp s dng IVI v VISA gim thiu chi ph ca ngi dng cui, c bit khi ngi dng c nhu cu tng thch vi h thng bus mi.Mc ch chnh ca tiu chun ha phn mm l duy tr s tn ti trn th trng ca sn phm v tnh sn c cng lu cng tt. C th l: D dng s dng cc thit b c hiu sut ti u . Tng cng v duy tr kh nng tng thch lu di ca cc thit b thuc nhiu nh cung cp. Phn mm h tr cho h thng cu trc m cho nhiu nh cung cp . Ti s dng phn mm c v mi vi nhiu nh cung cp. Bo m chun h thng phn mm.

Hnh 2.1 S khi mch h thng gim st bnh nhn2.1.6. Tng quan v kt ni mng trong h thng trung tm gim st bnh nhnDo c tnh h thng c s kim sot ca trung tm, h thng monitor trung tm t vn kt ni mng cc b ln mt mc rt cn thit. duy tr lin tc, khng b tr, tnh phn hi cao, thc thi lnh theo thi gian thc, cc khung thng tin s dng trong h thng phi c ti u ha theo cc chun c a ra bi nh sn xut. Bn cnh , cc thit b h tr cu hnh mng cng cn phi p ng y yu cu c a ra. 2.1.7. H thng gim st bnh nhn s dng mt my chTrong CMS, my ch kt ni vi cc my khch ti ging bnh thng qua cc thit b mng v c quyn truy cp ti tt c chng. CMS c nhim v ghi li v qun l d liu bnh nhn theo thi gian thc. My ch c ci h iu hnh chuyn dng nh Windows NT Server, Windows 2008 hay LinuxTrong h thng gim st bnh nhn s dng mt my ch c 3 loi my ch: Cc my ch tp tin c chc nng qun l d liu a thng s theo thi gian thc cc ging bnh khc nhau. Cc my ch ng dng c chc nng nh mt c s d liu, ngoi ra chng cn c s dng lp trnh v nng cp cc my theo di ging bnh. Cc my ch in c dng in d liu t tt c cc my khch trong h thng.

Hnh 2.2 H thng trung tm qun l bnh nhn Nhng vn pht sinh vi h thng gim st bnh nhn s dng mt my chTrong thi i cng ngh hin nay, cc h thng qun l t xa ang tr nn ph bin. Vn ca cc h thng ny l vic lu tr d liu v nguy c qu ti i vi my tnh trung tm.Ngy nay, mng ni b trong cc bnh vin u c kt ni vi h thng thng tin bnh vin (HIS). Thng thng, my ch c mt s a cng lu d liu ca cc my khch. Nu my ch b sp hoc a cng b li, ton b h thng gim st bnh nhn s b nh hng cc b.Xut pht t thc t ny, cc nh nghin cu chia nh h thng trnh vic qu ti d liu. l vic a mng ng ng (Peer-to-Peer network) vo gii quyt nhng vn trn.Mng ng ng khng phi l mt khi nim mi, thm ch cn l kh c trong lnh vc cng ngh thng tin. Bn cht ca cc mng ng ng l chia s v lu tr d liu cc my ch h thng trong mng, t trnh gy ra vic qu ti. Mng tn ti di dng cc nt mng c kt ni vi nhau, cho php thc thi d liu gia cc mng mt cch trc tip hoc gin tip. Cc nt mng ca mng ng ng khng c im gc v c dng nh cc chu trnh x l l tng, lu tr d liu v bng thng ca cc nt mng qua mng.Trong PMS, theo mt nghin cu mi ca k s L v ng nghip, h pht trin mt ng dng m t hot ng ca mng ng ng, c th tng thch vi cc cm bin v thn nhit, huyt p v in tim. Nhm nghin cu xy dng m hnh tham chiu PARM, gip truyn thng d liu t ging bnh n my ch bnh vin , cho php cc bc s c th phn ng kp thi trc cc tnh hung khn cp.Ban u h xy dng mt m hnh nh th nghim, sau pht trin thnh nhng m hnh ln hn da trn PARM. PARM c tim nng pht trin tr thnh h thng chm sc y t in t, gip gim chi ph khm cha bnh do s dng mng ng ng.2.1.8. Mng ng ng vi h thng gim st bnh nhnMng ng ng c nhng u im nh: kt ni n gin, chia s d liu d dng v c bit l chi ph thp hn h thng s dng mt my ch. Vi vic s dng mng ng ng trong lnh vc chm sc sc khe, hiu qu cng vic s c nng ln: ci thin vic chm sc bnh nhn, cn i tng chi ph v gim nh cc cng vic bng tay, n gin nh thng tin bnh nhn c th c lu tr bng h thng mng.Mt s tnh nng ni bt ca mng ng ng ng dng trong mi trng bnh vin: Lu tr cc ch s sinh l ca bnh nhn thay v vit trn giy. Bnh nhn c th truy cp trang web ng k thng tin. D liu v bnh nhn c th c truy cp bt k lc no v bt k u trn th gii. Cc bc s c th khm bnh thng qua video thi gian thc. Hiu nng ca mng ng ngHiu nng l vn ln nht ca mi mng ng ng, v i vi CMS, chng ta cn chia s hay trao i mt lng d liu ln theo thi gian thc. Trong CMS, my ch v my khch s dng chung chun d liu.Mng ng ng c thit lp bng cch kt ni cc h thng gim st bnh nhn vi my ch thng qua cc hub hoc switch. Mc ch chnh ca vic ny l khi xy ra s c mt my ch th h thng gim st bnh nhn v cc my khch vn tip tc hot ng bnh thng.

Hnh 2.3 h thng gim st bnh nhn a thng s da trn mng ng ngTrong mng ng ng, cc my khch c thit lp chia s d liu mt cch bnh ng v c cng h iu hnh. Trong PMS, cc my ch v my khch u c quyn gi v nhn d liu cng nh lu tr v chia s chng. Mi my u c a ch IP d nhn din. u im ca mng qun l bnh nhn ngang hngMng ng ng c nhng u im r rng nh: D liu lun sn sng: D liu c phn b cc thnh phn ca mng, cho php truy cp lin tc. Thi gian lu tr di: D liu c th c lu tr trong mt khong thi gian di trn h thng. D liu c bo mt: Bo mt lun l vn ln vi bt k mng no. Nguy c ph bin nht l cc cuc tn cng t chi dch v (DOS) m trong mng nhn c qu nhiu yu cu cng mt lc gy ra tnh trng tc nghn ging nh c virus tn cng. Cc cuc tn cng DOS c th ph hy d liu v lm gin on hot ng ca mng trong mt khong thi gian nht nh. Trong mng ng ng, nguy c DOS l rt t do mng ng ng khng c mt trung tm qun l no. Ngoi ra, c mt s giao thc bo mt khc cng hot ng trong h thng nh IP-sec, SSL, VPN,2.2. B iu khin mng chun EthernetTrong h thng monitor trung tm, lin kt truyn thng mng l v cng quan trng. Do , vic quan tm ti cch thc kt ni mng sao cho hp l l v cng quan trng. Ty thuc vo tnh hnh thc t m khi lp t s dng cc thit b mng ph hp.2.2.1. Tng quan v mng Ethernet Gii thiu v EthernetEthernet l cng ngh khu vc ni b c s dng kt ni cc thit b mng khong cch gn, c vn hnh ch trong mt to nh. mc ti a, ngi ta c th s dng hng trm mt kt ni cc thit b Ethernet. Nhng kt ni cc thit b khong cch a l xa th khng th. Ngy nay, nh nhng tin b v mt cng n gh, ngi ta c th xem xt li tr ngi v mt a l ny, cho php mng li Ethernet m rng n hng chc kilmet. Gn y, n c phin bn 100 Mbps c gi l Fast Ethernet v 1000 Mbps gi l Gigabit Ethernet.

Thng s k thutCu hnh truyn thng : C cu trc dng tuyn phn on, ng truyn dng cp ng trc, tuy nhin mi thnh phn ca n c th l cu trc Star ( Star-wired bus). Tn hiu truyn trn mng c m ha theo kiu ng b.Quy cch k thut 802.3Vn tc truyn : 10Mbps,100Mbps,..10GbpsLoi cp : Cp ng trc mnh, cp ng trc dy, cp xon i, cp si quang.Chiu di ti a ca mt on cp tuyn l 500m, cc on tuyn ny c th c kt ni li bng cch dng cc b chuyn tip v khong cch ln nht cho php gia 2 nt l 2,8km.S dng tn hiu bng tng c bn, truy xut tuyn hoc tuyn token (token bus),giao thc l CSMA/CD, d liu chuyn i trong cc gi (64 1518 byte).Ngy nay, khi nim Ethernet thng c s dng ch mt mng LAN CSMA/CD, ph hp vi tiu chun 802.3, c im : Hot ng mc lin kt d liu Theo nguyn tc CSMA/CD cm bin sng mang c pht hin ng Thnh phn chnh: Phn cng mng : Cc thit b ni mng . Giao thc iu khin truy xut ng truyn. Khung Ethernet : n v d liu truyn trn mng.

2.2.2. Chun IEEE 802

Hnh 2.4 Chun IEEE 802.2Chc nng ca chun IEEE802.2: iu khin truy cp phng tin truyn (MAC-a ch MAC c 48 bit) quy nh vic truyn d liu ln phng tin truyn chia s. dng khung v nh a ch. Lin h vi cc thnh phn vt l c dng truyn thng tin. Kim sot kt ni lun l (LLC) C nhng chc nng kim sot qu trnh truyn thng vi tin cy cao Lm cu ni cho php giao tip chung. Nhn thng tin t tng mng bn gi v chuyn n cng thch hp ca bn ch.

Ethernet standards

Hnh 2.5 Chun IEEE802.2 trong m hnh TCP/IP2.2.3. Giao thc CSMA/CD truyn thng tin, mi giao tip mng phi lng nghe cho ti khi khng c tn hiu trong knh chung, lc ny n mi c th truyn thng tin. Nu mt giao tip mng thc hin truyn thng tin trong knh th gi l sng v cc trm khc phi ch i cho ti khi s truyn dn ny kt thc. Qu trnh ny gi l pht hin sng mng.Mi giao tip Ethernet u c c hi ngang nhau trong vic truyn thng tin trong mng (a truy nhp). Trong qu trnh truyn t u ny ti u kia ca Ethernet, nhng bt u tin ca khung cn phi i ti mi vng ca mng. Tc l c th c 2 giao tip mng cng thy mng ri v gi i cng 1 lc. Khi Ethernet pht hin s va chm v dng vic truyn v gi li cc khung. l qu trnh pht hin va chm.Giao thc CSMA/CD c thit k nhm cung cp c hi ngang bng truy nhp kn h chung cho mi trm trong mng. Sau khi gi tin c gi i mi trm trong mng s s dng giao thc CSMA/CD xem trm no s c gi tip sau.

Ethernet s dng CSMA/CDIEEE 802.3 (CSMA/CD): tiu chun ny nh ngha cc tnh cht c lin quan ti tng con MAC. Lp con MAC s dng k thut CSMA/CD nhm gii quyt s xung t d liu khi truyn trn mng.Tiu chun IEEE 802.3 m t cc phng php tn hiu (trn c bng tn c s v bng tn rng), tc d liu, cc phng tin v cu trc lin kt. Tiu chun ny quy nh c th cc phng tin truyn dn vt l nh cp xon, cp ng trc v cp quang.Bng tn c s (baseband): dnh ton b bng thng cho mt knh truyn (ch c mt tn hiu trn ng truyn).Bng tn rng (broadband): cho php nhiu knh truyn chia s mt phng tin truyn dn (chia s bng thng), thng c s dng cp xon, cp quang to ra nhiu knh truyn d liu. Kim sot vic truyn v nhn khung trn mng:Trm pht lng nghe tn hiu trn cp bng cch cm bin sng mng, nu ng cp rnh, n s pht d liu. Sau , trm pht tip tc kim tra tn hiu pht t cc trm khc: Nu khng c th tip tc pht n ht d liu v chuyn sang trng thi lng nghe. Nu c ng th pht tn hiu (Jamming) thng bo cho cc trm khc => dng pht trong 1 khong thi gian, ht ng , pht tip.Trm nhn: cc trm u nhn c khung d liu nh nhauKim tra kch thc khung phi ln hn kch thc ti thiu (64byte). N kim tra a ch ca trm khp vi a ch ch trn khungM CRC (cyclic redundancy check) trong khung hp l.Sau khi kim tra cc iu kin, d liu ca khung s c chuyn cho chng trnh ng dng mc trn.

Hnh 2.6 Cc trm truy nhp knhMt card mng c th bt u truyn ti bt k thi im no. Nhng n khng truyn nu cm nhn c rng mt (s) card khc ang truyn l cm nhn sng mng.Card mng ang truyn s hy b ngay vic truyn d liu khi n cm nhn c mt card khc ang truyn l s pht hin xung t.Trc khi c gng truyn li, card mng i mt thi on ngu nhin l truy cp ngu nhin. Gii thut CSMA/CD trong EthernetBc 1: Card mng nhn gam d liu t tng mng v to frame. Bc 2:Nu cm nhn thy knh truyn ri, n s bt u truyn frame i. Nu cm nhn thy knh truyn bn, n i khi knh truyn ri v truyn d liu.Bc 3: Nu card mng truyn xong ton b frame m khng pht hin thy victruyn d liu khc no, n xem nh vic truyn frame hon thnh.Bc 4:Nu card mng pht hin thy c s truyn d liu khc, n s hy b vic truyn d liu v gi tn hiu bi.Bc 5: Sau khi hy b vic truyn, card mng bc vo vn hi theo lut s m: sau ln xung t th m, card mng chn gi tr K ngu nhin t ( 0,1,2,2m-1). Card mng i K*512 bit times v tr li bc 2Trong :Tn hiu bi: m bo rng tt c cc trm ang truyn bit c xung t ang xy ra; 48 bit.Bit time: 1 microsec cho 10 Mbps Ethernet; vi K =1023, thi gian i 50msec.Vn hi theo lut s m:Ti nng: thi gian i ngu nhin s l di hn.Xung t u tin: chn K t (0,1), tr l K*512 bit times.Sau xung t th 2: chn K t (0,1,2,3..).Sau xung t th 10: chn K t (0,1,2,3.,1023).2.2.4. Cu trc khung

Hnh 2.7 Cu trc khungPreamble64bitng b gip xc nh ni bt u khung

Dest.Address48bita ch vt l my s nhn khung d liu

Src.Address48bita ch vt l my pht khung d liu

Type16bitXc nh loi d liu s dng giao thc trn

DataD liu t giao thc mc trn. Ti a 1500byte

CRC,FCS32bitM pht hin li trong khung d liu

Khun dng khung EthernetC bn kiu khun dng d liu khc nhau c s dng trong mng Ethernet bao gm Ethernet 802.2, Ethernet 802.3, Ethernet II, v Ethernet SNAP. Mi kiu khun dng c phn khc nhau v chng u c bn trng chung: a ch ngun (source addres), a ch ch (destination address), d liu (data) v trng kim tra li (error-checking). Cc kiu khun dng Ethernet c s dng thng thng nht l Ethernet 802.2 v Ethernet 802.3. Cc khun dng Ethernet c kch thc bin i t ti thiu 64 byte ti ti a 1518 byte. (Mi khun dng cha thng tin header kch thc 14 byte cng vi trng Frame Check Sequence chiu di 4 byte. Phn d liu ca khun dng c kch thc bin i t 46 byte ti ti a 1500 byte. Kch thc tng cng ca frame c tnh ton n gin bng cch cng kch thc ca tt c cc trng Nu trng d liu ca frame nh hn 46 byte, frame s c m thm trng pad kch thc ti thiu ca n l 46 byte. a ch EthernetMi host trong mt mng Ethernet (tht ra l tt c cc host trn th gii) c mt a ch Ethernet duy nht. M t mt cch k thut, a ch c gn vo card mng ch khng phi my tnh; n c ghi vo ROM trn card mng. Cc a ch Ethernet thng c in theo th thc m con ngi c th c c: mt dy gm 6 bytes c vit di dng thp lc phn, cch nhau bi du hai chm :. V d, 80:be:b2 l cch biu din d c ca a ch Ethernet sau : 00001000 00000000 10110001 11100100 10110001 00000010. m bo rng mi card mng c gn mt a ch duy nht, mi nh sn xut thit b Ethernet c cp cho mt phn u a ch (prefix) khc nhau. V d, Advanced Micro Devices c cp phn u di 24 bit x08002 (hay 8:0:2). Nh sn xut ny sau phi m bo phn ui (suffix) ca cc a ch m h sn xut ra l duy nht.Mi khung c pht ra Ethernet s c nhn bi tt c cc card mng c ni vi ng truyn. Mi card mng s so snh a ch ch trong khung vi a ch ca n, v ch cho vo my tnh nhng khung no trng a ch. a ch duy nht nh vy gi l a ch unicast. Ngoi ra cn c loi a ch broadcast l loi a ch qung b, c tt c cc bit u mang gi tr 1. Mi card mng u cho php cc khung thng tin c a ch ch l broadcast i n host ca n. Cng c mt loi a ch khc gi l multicast, trong ch mt vi bit u c t l 1. Mt host c th lp trnh iu khin card mng ca n chp nhn mt s lp a ch multicast. a ch multicast c dng gi thng ip n mt tp con (subset) cc host trong mng Ethernet. Thut ton truynMi my Ethernet, hay cn gi l my trm, hot ng c lp vi tt c cc trm khc trn mng, khng c mt trm iu khin trung tm. Tt c cc trm u thy frame truyn. Mi trm phi kim tra mi frame xc nh xem n c phi l ch ca frame hay khng. Mi trm u kt ni vi Ethernet thng qua mt ng truyn tn hiu chung cn gi l ung trung gian. Tn hiu Ethernet c gi theo chui, tng bit mt, qua ng trung gian ti tt c cc trm thnh vin. gi d liu trc tin trm cn lng nghe xem knh c ri khng, nu ri th mi gi i cc gi (d liu). C hi tham gia vo truyn l bng nhau i vi mi trm, tc l khng c s u tin. S thm nhp vo knh chung c quyt dnh bi nhm iu khin truy nhp trung gian MAC (Medium Access Control) c t trong mi trm. Khi mt tn hiu trn thit b trung gian Ethernet ti mi node c gn trn mng, a ch nhn c r rng trong Frame c th nhn din ra ngi nhn.c t Ethernet ban u c cp n vn collision c th xy ra trn LAN. Khi h tng mng l dng chung, bt k mt tn hiu in ny cng c truyn dn trn ng dy cng c th xung t vi mt tn hiu ca mt thit b khc. Khi hai hoc nhiu Ethernet frame chng lp ln ng truyn mt thi im no , collision xy ra.Collision s dn n cc li bit v mt frame (bit error). c t ca Ethernet nh ngha thut ton CSMA/CD (Carrier Sense Multiple Access with Collision Detection) gii quyt nhng collisions khng th trnh khi. CSMA/CD s gip gim thiu s collisions nhng khi n xy ra, CSMA/CD s ch ra vic cc my gi d liu s nhn ra collision v truyn li frame nh th no. Cc loi a ch khung Ethernet a ch Unicast : c dng khi 1 trm mun truyn khung n trm khc trn mng (1-1). Khi vng a ch ngun v ch l a ch ca cc trm.a ch Broadcast : dng khi 1 trm mun truyn khung n tt c cc trm khc trn mng (1-n). Khi vng a ch ch c tt c cc bit l (FF:FF:FF:FF:FF:FF)a ch Multicast : c dng khi 1 trm mun truyn khung n trm khc trn 1 mng con (subnet). Khi vng a ch c 3 byte u tin l 01:00:5E, cc byte cn li l a ch nhm.2.3. Mng khng dy2.3.1. Gii thiu v WLANWireless Lan l mt trong nhng cng ngh truyn thng khng dy c p dng cho mng cc b. S ra i ca n khc phc nhng hn ch m mng ni dy khng th gii quyt c, v l gii php cho xu th pht trin ca cng ngh truyn thng hin i. Ni nh vy thy c nhng li ch to ln m Wireless Lan mang li, tuy nhin n khng phi l gii php thay th ton b cho cc mng Lan ni dy truyn thng.Da trn chun IEEE 802.11 mng WLan i n s thng nht v tr thnh mng cng nghip, t c p dng trong rt nhiu lnh vc, t lnh vc chm sc sc khe, bn l, sn xut, lu kho, n cc trng i hc. Ngnh cng nghip ny kim li t vic s dng cc thit b u cui v cc my tnh notebook truyn thng tin thi gian thc n cc trung tm tp trung x l. Ngy nay, mng WLAN ang c n nhn rng ri nh mt kt ni a nng t cc doanh nghip. Li tc ca th trng mng WLAN ngy cng tng.2.3.2. Cch lm vic ca mng WLANMng WLAN s dng sng in t (v tuyn v tia hng ngoi) truyn thng tin t im ny sang im khc m khng da vo bt k kt ni vt l no. Cc sng v tuyn thng l cc sng mang v tuyn bi v chng thc hin chc nng phn pht nng lng n gin ti my thu xa. D liu truyn c chng ln trn sng mang v tuyn n c nhn li ng my thu. l s iu bin sng mang theo thng tin c truyn. Mt khi d liu c chng (c iu ch) ln trn sng mang v tuyn, th tn hiu v tuyn chim nhiu hn mt tn s n, v tn s hoc tc truyn theo bit ca thng tin bin iu c thm vo sng mang.Nhiu sng mang v tuyn tn ti trong cng khng gian ti cng mt thi im m khng nhiu vi nhau nu chng c truyn trn cc tn s v tuyn khc nhau. nhn d liu, my thu v tuyn bt sng (hoc chn) mt tn s v tuyn xc nh trong khi loi b tt c cc tn hiu v tuyn khc trn cc tn s khc.Trong mt cu hnh mng WLAN tiu biu, mt thit b thu pht, c gi mt im truy cp (AP - access point), ni ti mng ni dy t mt v tr c nh s dng cp Ethernet chun. im truy cp (access point) nhn, lu vo b nh m, v truyn d liu gia mng WLAN v c s h tng mng ni dy. Mt im truy cp n h tr mt nhm nh ngi s dng v vn hnh bn trong mt phm vi vi mt ti vi chc mt. im truy cp (hoc anten c gn ti n) thng thng c gn trn cao nhng thc t c gn bt c ni u min l khong v tuyn cn thu c.Cc ngi dng u cui truy cp mng WLAN thng qua cc card giao tip mng WLAN, m c thc hin nh cc card PC trong cc my tnh notebook, hoc s dng card giao tip ISA hoc PCI trong cc my tnh bn, hoc cc thit b tch hp hon ton bn trong cc my tnh cm tay. Cc card giao tip mng WLAN cung cp mt giao din gia h iu hnh mng (NOS) v sng tri (qua mt anten). Bn cht ca kt ni khng dy l trong sut vi NOS.2.3.3. Cc ty chn cng nghCc nh sn xut mng WLAN chn nhiu cng ngh mng khc nhau khi thit k gii php mng WLAN. Mi cng ngh c cc thun li v hn ch ring.Tri pha s cc h thng mng WLAN s dng cng ngh tri ph, mt k thut tn s v tuyn bng rng m trc y c pht trin bi qun i trong cc h thng truyn thng tin cy, an ton, trng yu. S tri ph c thit k hiu qu vi s nh i di thng ly tin cy, kh nng tch hp, v bo mt. Ni cch khc, s dng nhiu bng thng hn trng hp truyn bng hp, nhng i li to ra tn hiu mnh hn nn d c pht hin hn, min l my thu bit cc tham s ca tn hiu tri ph ca my pht. Nu mt my thu khng chnh ng tn s, th tn hiu tri ph ging nh nhiu nn. C hai kiu tri ph truyn i bng v tuyn: nhy tn v chui trc tip. Cng ngh tri ph nhy tn (Frequency Hopping pread Spectrum)Tri ph nhy tn (FHSS) s dng mt sng mang bng hp thay i tn s trong mt mu c my pht ln my thu. c ng b chnh xc, hiu ng mng s duy tr mt knh logic n. i vi my thu khng mong mun, FHSS lm xut hin cc nhiu xung chu k ngn.

Hnh 2.8 Tri ph nhy tnFHSS nhy tn t bng hp sang bng hp bn trong mt bng rng. c bit hn, cc sng v tuyn FHSS gi mt hoc nhiu gi d liu ti mt tn s sng mang, nhy n tn s khc, gi nhiu gi d liu, v tip tc chui nhy - truyn d liu ny. Mu nhy hay chui ny xut hin ngu nhin, nhng tht ra l mt chui c tnh chu k c c my thu v my pht theo di. Cc h thng FHSS d b nh hng ca nhiu trong khi nhy tn, nhng hon thnh vic truyn dn trong cc qu trnh nhy tn khc trong bng tn.

Hnh 2.9 Tri ph chui trc tip

Cng ngh tri ph chui trc tip (Direct Sequence Spread Spectrum)Tri ph chui trc tip (DSSS) to ra mt mu bit d cho mi bit c truyn. Mu bit ny c gi mt chip (hoc chipping code). Cc chip cng di, th xc sut m d liu gc b loi b cng ln (v tt nhin, yu cu nhiu di thng). Thm ch khi mt hoc nhiu bit trong mt chip b h hi trong thi gian truyn, th cc k thut c nhng trong v tuyn khi phc d liu gc m khng yu cu truyn li. i vi my thu khng mong mun, DSSS lm xut hin nhiu bng rng cng sut thp v c loi b bi hu ht cc my thu bng hp.B pht DSSS bin i lung d liu vo (lung bit) thnh lung symbol, trong mi symbol biu din mt nhm cc bit. Bng cch s dng k thut iu bin pha thay i nh k thut QPSK (kha dch pha cu phng), b pht DSSS iu bin hay nhn mi symbol vi mt m ging nhiu gi l chui gi ngu nhin (PN). N c gi l chui chip. Php nhn trong b pht DSSS lm tng gi to di bng c dng ph thuc vo di ca chui chip.Cng ngh bng hp (Narrowband)Mt h thng v tuyn bng hp truyn v nhn thng tin ngi dng trn mt tn s v tuyn xc nh. V tuyn bng hp gi cho di tn tn hiu v tuyn cng hp cng tt ch cho thng tin i qua. S xuyn m khng mong mun gia cc knh truyn thng c trnh bng cch kt hp hp l cc ngi dng khc nhau trn cc knh c tn s khc nhau.Mt ng dy in thoi ring rt ging vi mt tn s v tuyn. Khi mi nh ln cn nhau u c ng dy in thoi ring, ngi trong nh ny khng th nghe cc cuc gi trong nh khc. Trong mt h thng v tuyn, s dng cc tn s v tuyn ring bit hp nht s ring t v s khng can thip ln nhau. Cc b lc ca my thu v tuyn lc b tt c cc tn hiu v tuyn tr cc tn hiu c tn s c thit k.Cng ngh hng ngoi (Infrared)H thng tia hng ngoi (IR) s dng cc tn s rt cao, ch di tn s ca nh sng kh kin trong ph in t, mang d liu. Ging nh nh sng, tia hng ngoi IR khng th thm nhp cc i tng chn sng; n s dng cng ngh trc tip (tm nhn thng) hoc cng ngh khuch tn. Cc h thng trc tip r tin cung cp phm vi rt hn ch (0,914m) v tiu biu c s dng cho mng PAN nhng thnh thong c s dng trong cc ng dng WLAN c bit. Cng ngh hng ngoi hng kh nng thc hin cao khng thc t cho cc ngi dng di ng, v do n c s dng thc hin cc mng con c nh. Cc h thng IR WLAN khuch tn khng yu cu tm nhn thng, nhng cc cell b hn ch trong cc phng ring l.2.3.4. Giao thc truy cpy l mt c ch truy cp c bn, c gi Hm phi hp phn tn, v c bn l a truy cp cm bin sng mang vi c ch trnh xung t (CSMA/CA). Cc giao thc CSMA c bit trong cng nghip, m ph bin nht l Ethernet, l giao thc CSMA/CD (CD ngha l pht hin xung t).Giao thc CSMA lm vic nh sau: Mt trm truyn i cc cm bin mi trng, nu mi trng bn (v d, c mt trm khc ang pht), th trm s tr hon truyn mt lc sau, nu mi trng t do th trm c cho php truyn.Loi giao thc ny rt c hiu qu khi mi trng khng ti nhiu, do n cho php cc trm truyn vi t tr hon, nhng thng xy ra trng hp cc trm pht cng lc (c xung t), gy ra do cc trm nhn thy mi trng t do v quyt nh truyn ngay lp tc.Cc tnh trng xung t ny phi c xc nh, v vy lp MAC phi t truyn li gi m khng cn n cc lp trn, iu ny s gy ra tr ng k. Trong trng hp mng Ethernet, s xung t ny c on nhn bi cc trm pht i ti quyt nh pht li da vo gii thut exponential random backoff.Cc c ch d tm xung t ny ph hp vi mng LAN ni dy, nhng chng khng c s dng trong mi trng mng LAN khng dy, v hai l do chnh:1. Vic thc hin c ch d tm xung t yu cu s thi hnh ton song cng, kh nng pht v nhn ng thi, n s lm tng thm chi ph mt cch ng k.2. Trn mi trng khng dy chng ta khng th gi thit tt c cc trm nghe thy c nhau (y l s gi thit c s ca s d tm xung t), v vic mt trm nhn thy mi trng t do v sn sng truyn khng tht s c ngha rng mi trng l t do quanh vng my thu. vt qua cc kh khn ny, chun IEEE 802.11 s dng mt c ch trnh xung t vi mt s Ghi nhn tnh tch cc (Positive Acknowledge) nh sau:Mt trm mun truyn cm bin mi trng, nu mi trng bn th n tr hon. Nu mi trng rnh vi thi gian c ch r (gi l DIFS, Distributed Inter Frame Space, Khng gian khung Inter phn tn), th trm c php truyn, trm thu s kim tra m CRC ca gi nhn c v gi mt gi chng thc (ACK). Chng thc nhn c s ch cho my pht bit khng c s xung t no xut hin. Nu my pht khng nhn chng thc th n s truyn li on cho n khi n c tha nhn hoc khng c php truyn sau mt s ln pht li cho trc.Cm bin sng mang o (Virtual Carrier Sense) gim bt xc sut kh nng hai trm xung t nhau v chng khng th nghe thy nhau, chun nh ngha mt c ch Cm bin sng mang o:Mt trm mun truyn mt gi, trc ht n s truyn mt gi iu khin ngn gi l RTS (Request To Send) gm ngun, ch n, v khong thi gian giao dch sau (v.d. gi v ACK tng ng), trm ch s p ng (nu mi trng t do) bng mt gi iu khin p li gi l CTS (Clear To Send) gm cng thng tin khong thi gian.Tt c cc trm nhn RTS v/hoc CTS, s thit lp ch bo Virtual Carrier Sense ca n (gi l NAV, Network Allocation Vector, Vect nh v mng) cho khong thi gian cho trc, v s s dng thng tin ny cng vi Cm bin sng mang vt l (Physical Carrier Sense) khi cm bin mi trng.C ch ny gim bt xc sut xung t v vng my thu do mt trm n t my pht, lm ngn khong thi gian truyn RTS, v trm s nghe thy CTS v d tr mi trng khi bn cho n khi kt thc giao dch. Thng tin khong thi gian v RTS cng bo v vng my pht khi cc xung t trong thi gian ACK (bi cc trm nm ngoi phm vi trm nhn bit).Cn ch thng tin khong thi ACK v cc khung RTS v CTS l cc khung ngn, N cng lm gim bt mo u ca cc xung t, v chng c nhn dng nhanh hn khi n c nhn dng nu ton b gi c truyn, (iu ny ng nu gi ln hn RTS mt cch ng k, nh vy l chun cho php k c cc gi ngn s c truyn m khng c giao dch RTS/CTS, v iu ny c iu khin bi mt tham s gi l ngng RTS).Cc s sau cho thy mt giao dch gia hai trm A v B, v s thit lp NAV ca cc trm gn chng:

Hnh 2.10. Giao dch gia hai trm A v B, v s thit lp NAVTrng thi NAV c kt hp vi cm bin sng mang vt l cho bit trng thi bn ca mi trng.2.4. Cu hnh mng LAN2.4.1. Thit b Ethernet Ethernet cardc hai ch hot ng: Ch Half-Duplex ch ny, mi trm gi nh rng mi trng truyn c chia s bi nhiu hn hai trm, do n dng CSMA-CD. Mt trm khng th va nhn va gi d liu ti cng mt thi im. Tt c cc cp mng Ethernet u h tr ch Half-Duplex, v d cp ng trc (hin khng c dng na m ch yu dng cho cable TV), cp xon (loi ny ph bin nht), v cp quang (dng cho cc mng Ethernet nhanh vi phm vi rng). Ch Full-Duplex: ch ny, mt trm gi nh rng mi trng truyn c chia s bi ch hai my trm, v c knh truyn ring cho vic gi v nhn d liu. Do , CSMA-CD khng cn cn thit na, mi trm c th gi v nhn d liu cng lc. Cp xon v cp quang h tr ch ny. Ch : Mc d cp xon v cp quang cung cp cc knh truyn ring cho vic gi v nhn d liu, mt my trm ch half-duplex vn khng th gi v nhn d liu cng lc c (iu ny l do vi CSMA-CD, nu mt trm nhn c mt frame trong khi ang truyn mt fram khc, n s coi y l xung t). B lp y l mt thit b Physical Layer: n thao tc vi cc bit (tn hiu) ch khng phi vi cc frame. Dng ni hai cp Ethernet vi nhau. Khuch i tn hiu t mt cp v gi tn hiu qua on cp kia. Trong trng hp n nhn c tn hiu ng thi t hai on cp, mt tn hiu jamming s c gi ti c hai on cp, thng bo xung t. V d, mt mng Ethernet 10Mbps c th dng 4 b lp m rng chiu di ti a ca cp t 500m ti 2500m. Hub y l mt thit b Physical Layer: n thao tc vi cc bit (tn hiu) ch khng phi vi cc frame. Dng kt ni cc my trm hot ng ch Half-Duplex vi nhau. Sao chp tn hiu t mt trm ti cc trm khc. Mt vi loi hub khuch i tn hiu, cc loi khc th khng. Trong trng hp n nhn c nhiu tn hiu ng thi t cc trm khc nhau, mt tn hiu jamming s c gi ti tt c cc trm, thng bo xung t Tt c cc trm kt ni vi mt hub c cng mt min xung t (collision domain). Ethernet switch y l mt thit b Data Link Layer: n thao tc vi cc frame, c th c c header ca mt frame. Thng c dng kt ni cc my trm hot ng ch Full-Duplex vi nhau. Truyn frame ti mt my trm thch hp da trn a ch MAC ch ca frame. Thng thng, mt Ethernet switch c vng m lu-v-truyn cc frame. Lu rng ch Full-Fuplex khng c xung t, nn khng c frame no b mt do xung t, tuy nhin, mt vi frame c th b mt do trn b m.

Ethernet bridge Mt Ethernet switch cn c th c dng kt ni hai hay nhiu mng LAN vi nhau. Trong trng hp ny, n c gi l mt Ethernet bridge. y l thit b Data Link Layer: n thao tc vi cc frame. c dng kt ni nhiu mang LAN vi nhau, mi mng ny bao gm nhiu my trm kt ni vi nhau bng mt hub. N truyn frame ti mt mng LAN ph hp da trn a ch MAC ch ca frame. Nu mt mng LAN c hn hai my trm (bao gm tt c cc bridge ni vi n), th cng tng ng trn bridge phi hot ng ch Half-Duplex. Mi mng LAN c mt min xung t ring. iu ny c ngha l vic truyn nhiu ng thi trn mt mng LAN s gy ra xung t, nhng vic truyn ng thi trn nhiu mng LAN c th khng gy xung t. Mt vi loi bridge cao cp c th kt ni hai loi mng LAN khc nhau, v d ni Ethernet vi Token Ring. Trong trng hp ny, bridge phi chuyn i nh dng frame t dng ny sang dng kia.

Hnh 2.11 Ethernet bridge

Bridge Bridge chuyn mt frame n nhn c ti mng LAN thch hp da trn a ch MAC ch ca frame v bng chuyn tip (forwarding table). Bng ny gm hai ct nh sau: a ch MAC: l a ch MAC ca mt Ethernet card. Cng: Cng ca bridge m ni vi Ethernet card . Mt bridge s t ng in vo bng chuyn tip khi n hot ng (iu ny cng ng vi Ethernet switch). Do , chng ta khng phi cu hnh mt bridge bng tay, iu ny khin cho bridge cn c gi l transparent bridge. Mi khi n nhn c mt frame, n s in vo bng chuyn tip a ch MAC ngun ca frame v cng m n nhn c frame . Bridge chuyn tip mt frame nh th no? N tm trong bng xem c a ch MAC ch ca frame khng. Nu n tm thy, frame s c chuyn tip qua cng tng ng. Nu cng tng ng ny trng vi cng m n nhn c frame, frame ny s khng c chuyn tip. Nu n khng tm thy, n gi frame ti tt c cc cng, tr cng m n nhn c frame ny. Nu mt trm b tch khi LAN th lm sao? Mi dng trong bng c gn vi mt timer. Mi khi nhn c mt frame th timer ca dng tng ng c reset. Khi timer ht hn th dng s b xa. Nu mt trm c chuyn qua mt LAN khc th lm sao? Mi khi nhn c mt frame, bridge cp nht dng tng ng trong bng. Nu c lp th sao? i khi, chng ta thm cc bridge b sung vo gia hai mng LAN cung cp ng truyn d tha, phng trong trng hp mt ng truyn b gin on th ng truyn kia vn hot ng. Tuy nhin, chng ta phi m bo rng ch mt ng kt ni gia hai mng LAN trong tnh trng hot ng (active), cc ng kt ni khc phi b chn (standby). Nu c nhiu ng kt ni gia hai mng LAN, mt frame vi mt ch n bit s b truyn hai ln, mt frame vi mt ch n cha xc nh s gy ra broadcast nhiu ln (broadcast storm) Tt c cc bridge thc thi gii thut cy tn rng (Spanning Tree Algorithm) tm ngn nga cc vng lp (nhiu ng kt ni) gia hai mng LAN Tn ca gii thut xut pht t vic mt cy tn rng ni tt c cc nt ca mt th vi nhau, nhng khng cha vng lp. Gii thut ny xc nh mt bridge c th l root bridge, sau n m bo rng ch c mt ng kt ni tnh trng hot ng (active) t mt mng LAN tiroot bridge(v do , ch c mt ng kt ni hot ng gia hai mng LAN). Tt c cc bridge thc thi gii thut ny mt cch nh k, do , nu c li xy ra (mt bridge gp s c hoc mt link b hng), th mt cy tn rng mi s c to.2.4.2. Cu hnh mng WLANMng WLAN n gin hoc phc tp. C bn nht, hai PC c trang b cc card giao tip khng dy thit lp mt mng c lp bt c khi no m chng nm trong phm vi ca nhau. N c gi l mng ngang hng. Cc mng ny khng yu cu s qun tr hoc s nh cu hnh trc. Trong trng hp ny mi khch hng ch truy cp ti ti nguyn ca khch hng khc v khng thng qua mt nh phc v trung tm.

Hnh 2.12: Mt mng ngang hng khng dyVic thit lp mt im truy cp m rng phm vi ca mt mng, phm vi cc thit b lin lc c m rng gp i. Khi im truy cp c ni ti mng ni dy, mi khch hng s truy cp ti cc ti nguyn phc v cng nh ti cc khch hng khc. Mi im truy cp iu tit nhiu khch hng, s khch hng c th ph thuc vo s lng v c tnh truyn. Nhiu ng dng thc t vi mt im truy cp phc v t 15 n 50 thit b khch hng.

Hnh 2.13: Khch hng v im truy nhpCc im truy cp c mt phm vi hu hn, 152,4m trong nh v 304,8m ngoi tri. Trong phm vi rt ln hn nh kho hng, hoc khu vc c quan cn thit phi lp t nhiu im truy cp hn. Vic xc nh v tr im truy da trn phng php kho st v tr. Mc ch s ph ln vng ph sng bng cc cell ph sng chng lp nhau cc khch hng di chuyn khp vng m khng mt lin lc mng. Kh nng cc khch hng di chuyn khng ghp ni gia mt cm ca cc im truy cp c gi roaming. Cc im truy cp chuyn khch hng t site ny n site khc mt cch t ng m khch hng khng hay bit, bo m cho kt ni lin tc.

Hnh 2.14: Nhiu im truy cp v Roaming gii quyt cc vn c bit v topology, nh thit k mng chn cch s dng cc im m rng (Extension Point - EP) lm tng cc im truy cp ca mng. Cch nhn v chc nng ca cc im m rng ging nh cc im truy cp, nhng chng khng c ni dy ti mng ni dy nh l cc AP. Chc nng ca EP nhm m rng phm vi ca mng bng cch lm tr tn hiu t mt khch hng n mt AP hoc EP khc. Cc EP c ni tip nhau truyn tin t mt AP n cc khch hng rng khp, nh mt on ngi chuyn nc t ngi ny n ngi khc n mt m chy.

Hnh 2.15: Cch s dng ca mt im m rng (EP)Thit b mng WLAN cui cng cn xem xt l anten nh hng. Gi s c mt mng WLAN trong ta nh A ca bn, v bn mun m rng n ti mt ta nh cho thu B, cch 1,609 km. Mt gii php l s lp t mt anten nh hng trn mi ta nh, cc anten hng v nhau. Anten ti ta nh A c ni ti mng ni dy qua mt im truy cp. Tng t, anten ti ta nh B c ni ti mt im truy cp trong ta nh , m cho php kt ni mng WLAN thun tin nht.

Hnh 2.16: Cch s dng anten nh hngMng WLAN c lp (mang ngang hang)Cu hnh mng WLAN n gin nht l mng WLAN c lp (hoc ngang hng) ni cc PC vi cc card giao tip khng dy. Bt k lc no, khi hai hoc hn card giao tip khng dy nm trong phm vi ca nhau, chng thit lp mt mng c lp (hnh 1.6). y, cc mng ny khng yu cu s qun tr hoc s nh cu hnh trc.

Hnh 2.17: Mng WLAN c lp v mng WLAN c lp phm vi c m rng s dng im truy cp nh mt b chuyn tipCc im truy cp m rng phm vi ca mng WLAN c lp bng cch ng vai tr nh l mt b chuyn tip (hnh 1.7), c hiu