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Mode of Mechanical Ventilator
柳營奇美醫院呼吸治療科呼吸治療組長
龔淑貞
模式 (Mode)•模式的定義─
–病人與呼吸器交互作用,以完成一個呼吸器循環 (ventilator cycle) 的方法
–並沒有任何一種呼吸器模式是最好的–醫護人員的經驗與技巧才是決定一個呼吸器模式成功與否最重要的關鍵
Mode of MV
• Conventional methods of ventilator support
--CMV, A/C, PCV, VCV, IMV, SIMV, PSV
• Alternative methods of ventilator support
--IRV, MMV, APRV, Bi-phasic, Servo-controlled pressure(Paug, VAPS, PRVC, Auto-flow, APV) , PAV, ATC, ASV
• Control mechanical ventilation(CMV) -- time trigger, volume or pressure, no
effort at Pt.
• Assist-control Ventilation( A/C) -- Time or Pt trigger -- Set: f, Sensitivity., type of breath(V or P)
(1) flow controlled, volume cycled (VV): flow, volume preset, Vt reach →flow ends
(2) pressure controlled, time cycled (PV): pressure,Ti preset, Ti reach →cycle off
Assisted vs. ControlledAssisted vs. Controlled
Time (sec)
Assisted ControlledPressure (cmH20)
Volume Ventilation(VV)
• Set the volume delivered during the mandatory breath
• VV guarantees volume (C,R ↑↓→V 不變 ) • Lung worsens,↑peak and alveolar P. →overdiste
ntion →change flow pattern 改善• High volume give high peak and plateau P.• Set parameter(7200 ; 900)• Flow controlled, Time or Pt trigger, volume li
mit, Volume cycle
Controlled Mode (Volume-Targeted Ventilation)
Controlled Mode (Volume-Targeted Ventilation)
Preset VT
Volume Cycling
Dependent onCL & Raw
Time (sec)Time (sec)
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Preset Peak Flow
Time triggered, Flow limited, Volume cycled Ventilation
Pressure Ventilation (PV)
• Preset a pressure, P. limit ventilation(PCV, PSV)
• 影響 Vt : △P, Ti, TC (R, C), continuous flow rate (initial flow →P. waveform shape)
• 優點 : ↓A. overdistention, ↑distribution, constant P., ↑MAP.
• 缺點 :variability by volume
Controlled Mode (Pressure-Targeted Ventilation)
Controlled Mode (Pressure-Targeted Ventilation)
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Time (sec)Time (sec)
Time-Time-Cycled
Set PC level
Time Triggered, Pressure Limited, Time Cycled Ventilation
比較 PCV vs VCV
• ↑ Oxygenation(↑ MAP) - PCV : PIP-PEEP*Ti / TCT+PEEP...…. 正方
形 - VC : ½(PIP-PEEP*Ti / TCT+PEEP)... 三角
形• ↑ gas exchange• ↓ PIP• 容易 lung healing
Assisted ventilation
-- Pt trigger ( PSV, VS, PAV)
-- Preset volume or pressure, no mandatory
breath -- time interval 不一定相等
Assisted Ventilation
• F5-20
Assisted Mode(Volume-Targeted Ventilation)
Assisted Mode(Volume-Targeted Ventilation)
Time (sec)Time (sec)
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Preset VT
Volume Cycling
Patient triggered, Flow limited, Volume cycled Ventilation
Assisted Mode (Pressure-Targeted Ventilation)
Assisted Mode (Pressure-Targeted Ventilation)
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Set PC level
Time (sec)Time (sec)
Time-Cycled
Patient Triggered, Pressure Limited, Time Cycled Ventilation
Pressure Supported Ventilation(PSV)
• Pressure – targeted (or limit), Pt – trigger
• Patient-initiated, patient-terminated
• 自動調整 maintains flow to reach preset PSV level keep this pressure until expiration
The end of inspiration(PSV)
• Decrease of peak flow to specific threshold
• Above the fixed PSV level (1 to 3 cmH2O), sudden exp. effort from patient
• A time end of the insp.
Flow criterion: % of inspiratory Flow criterion: % of inspiratory peak flowpeak flow
Pressure
Pressure Support
Flow ETS
PEEP
Peak Flow
Wider ETS range
ETS can improve synchrony and change Ti of spontaneous breaths
P
F
Too late switchover Proper switchover Too early switchover
PSVPSV
Time (sec)
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Flow CyclingFlow Cycling
Set PS level
Set PS level
Patient Triggered, Flow Cycled, Pressure limited Mode
IMV / SIMV
• IMV -- Time trigger, continuous (neonatal)or demand flow -- open IMV( 通大氣 ), close IMV( 儲存袋 ) -- demand flow 外接 peep, 無法代償 ,trigger 困難→ WOB↑
• SIMV -- Pt or time trigger -- Wait for the next insp. Effort ( time window)
SIMV+PS(Volume-Targeted Ventilation)
SIMV+PS(Volume-Targeted Ventilation)
Flow
Pressure
Volume
(L/min)
(cm H2O)
(ml)
Set PS level
PS Breath
Flow-cycled
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
SIMV + PS (Pressure-Targeted
Ventilation)
SIMV + PS (Pressure-Targeted
Ventilation)
PS Breath
Set PS levelSet PC levelSet PC level
Time (sec)
Time-Cycled Flow-Cycled
CPAPCPAP
Time (sec)Time (sec)
CPAP level
Flow(L/m)
Pressure(cm H2O)
Volume(mL)
Inverse Ratio Ventilation (IRV)
• Techniques to increase I / E ratio
(1) VCIRV
-- slowing the flow rate → flow cycle 結束 -- use a inspiratory pause → time cycle 結束 (2) PCIRV -- increase Ti → time cycle 結束
Improving PaO2 with IRV
• Higher mean Paw• By the short Te →end exp. P.↑(intrinsic P.)• Improved distribution due to low mean insp.
flow• Physiologic effect
-- ↓intrapulmonary shunt, improved V/Q
matching, ↓dead space ventilation
PCIRV
• Selection I / E ratio in a PEEP- like effect• Trap gas and ↑FRC and MAP
• Monitor compliance, auto-PEEP, SvO2 and C.O.
• Will drop Vt as the auto-PEEP developed
( P = PIP – EEP)△
• Auto-PEEP : measurement by flow waveform
Mandatory Minute Ventilation(MMV)
• Allows spontaneously breath but ensure MV• Ventilator support automatically adjusts, can
be achieved by ↑PSV level or mandatory breaths ( veolar or CPUI )
• But Pt with low Vt and high RR will not initiate the ventilator support
• Disadvantages – Alveolar ventilation not monitor, ↓clinician evaluation, MMV level not well defined
MMV
• T10-1
Methods of delivery ( MMV )
• Change in mechanical breaths -- Bear 5, Erica, CPUI, Sechrist 2200B
• Change in tidal volume -- Veolar (change the PS level), Servo 300(VS)
• Target VE, maintain adequate ventilation • During weaning – 80% on A/C, 90% on
IMV• Set lower VE→ if Pt is alkalosis or hypocarbic
(PaCO2↓)
Servo–controlled Pressure Ventilation
A) Pressure augmentation → real breath by breath
*Paug – Bear 1000 *VAPS – Bird 8400sti
B) Closed-loop pressure ventilation →next breath
*PRVC and VS – Servo 300
*Auto - flow – Drager (Evita )
*APV – Galileo
C) PAV(proportional assisted ventilation), ASV(adaptic support v
entilation), ATC(automatic tube compensation)
Initial setting for Pressure Augmentation
• Paug only work with VV, target volume, an upper pressure limit (Bear 1000, 8400sti )
• Set P.= Pplateau – PEEP • Set appropriate flow rate:
-- >30% for peak flow for a PS breath
-- high enough Ti does not longer than Te
-- lower than the actual peak flow→ Paw↑ -- Select rectangular flow wave form ( )
• Weaning:
-- CL ↑ → Vt ↑ => reduce the P. and adjust flow rate
Peak flow100Lpmpressure 25cmH2Ovolume set 0.8 L
Peak flow100Lpmpressure 25cmH2Ovolume set 0.8 L
Dement peak flow 80Lpmset flow 40Lpm sustained until volume set 0.8 L
Dement peak flow 80Lpmset flow 40Lpm sustained until volume set 0.8 L
Insufficient pressure levelflow setting may too lowTI is increased acheved Vt
Insufficient pressure levelflow setting may too lowTI is increased acheved Vt
PS breath with high flow demand(strong active insp.)volume delivry before the flow decreases(flow drop 30% of peak flow into expiratory)
PS breath with high flow demand(strong active insp.)volume delivry before the flow decreases(flow drop 30% of peak flow into expiratory)
No p’t effort the breath is timeset flow 40Lpm(rectangular waveform) to deliverde Vt 0.8L
No p’t effort the breath is timeset flow 40Lpm(rectangular waveform) to deliverde Vt 0.8L
P’t triggerP’t trigger No P’t trigger
No P’t triggerP’t trigger
P’t triggerP’t trigger
P’t trigger
pressure spikepressure spike
Closed – loop Pressure Ventilation
• Insp. Pressure is regulated, calculation of previous breath, in next breath 校正
• Decelerating flow of PCV with volume guarantee ( )
• PRVC - VS (Servo 300 ), Auto flow (Drager ), APV(Galileo)
PRVC vs. VS
• Volume target ventilation, pressure regulator
• PRVC – Pt or time trigger, time cycle VS – Pt trigger, flow cycle (5% of peak flow in Servo
300)
• 4 test breath -- First one 5 (300c) or 10 (300a) cmH2O
-- The next 3 breaths will deliver 75% of the set Vt -- Calculates compliance for the previous breath and adjust
insp. P. level (<3 cmH2O) on the next breath
Auto - flow
• Volume ventilation 之下 , 使 MV 自動調節 Insp. flow( depended on lung C, R )to change pressure, flow wave form→
• 與 PRVC 不同點 : – allow Pt in any phases for spontaneous
breath– 包括 Bi-level V., IPPV, SIMV, MMV
AutoFlow - In Action
Set desired - Freq, Tinsp ,VT and PEEP
Set Upper Paw alarm(-5cmH2O)
Set Upper Insp. VT alarm
Insp. Pressure will automatically adjust (+3cmH2O)to equal set VT
Paw
Pinsp. = f (VT,C)
PEEPt
TI
1
Paw
TE
Flow
t
f
without spontaneous breathing with spontaneous breathing
VT
Adaptive Pressure Ventilation Adaptive Pressure Ventilation (APV) (APV)
1. The inspiratory pressure is adjusted within this range:(PEEP + 5cmH2O) to (high pressure alarm limit -10cmH2O)
2. If monitored TV is higher or lower than the TV(target).the insp pressure is gradually adjusted by up to 2cmH2O at per breath
Adaptive Pressure Ventilation Adaptive Pressure Ventilation (APV) (APV)
VT
Flow
PressureHigh Pressure limit -10cmHHigh Pressure limit -10cmH22OO
PEEP+5cmHPEEP+5cmH2OO
+2cmH+2cmH2O/breathO/breath
Proportional assisted ventilation( PAV )
• Pressure, flow and volume delivery are proportional to Pt spontaneous effort (Evita-PPS)
• Pressure produces by the ventilator depends on -- insp. flow and volume demanded by Pt effort ( 不需 setting)
-- only set amplification ( work load 的 ? % ) of ventilator response to Pt effort
• Disadvantages : – only provide for assisted ventilation– cannot compensate for system leaks– resistance and compliance measured aren’t real
time.
Proportional Pressure Support PPS
Airway pressureAirway pressure
Resistance
Compliance
Breathing musclesBreathing muscles
R
C
Pmus
Paw
Paw
Pmus P PC
V R Vaw mus 1 .
The Equation of Motion
Proportional Pressure Support PPS
• If R and C of the patient are known, deviations from normal values can be targeted and appropriately compensated
• During PPS, the patient should feel as if his lung mechanics are healthy
Automatic tube compensation ( ATC )
• The flow in a difference in pressure between the two ends of the tube(E-T)
• Compensates for the flow depend P. drop across the tracheal tube ( a function, not a mode )
• The narrower the tube’s diameter→ WOB ↑
• The length of the tube → no significant on Rtube
• Setting – the size of tube
– amount of compensation
( 100% or partially )
What is Tube Compensation?
• Not a mode, but a spontaneous breath type
• Accurately overcomes the imposed inspiratory WOB through an artificial airway
• Hybrid of PS (but more efficient at overcoming tube resistance)
• Controls the patients carinal pressure to a constant preset PEEP value during inspiration
• TC adds appropriate pressure to keep carina pressure at preset PEEP
Tube Compensation - What the Carina SeesHigher Circuit Pressure
No Decreased Carina Pressure
Paw
PS Limitations For ET-Tube Compensation• PS may under-support the WOB early in the inspirator
y phase when flows are high
• As patients wake, sleep, become agitated etc, PS is unable to compensate for variable demands
10PCIRC
cmH2O
INSP
Lmin
EXP
7.5
5
2.5
0
-5
-10
80604020
020
-80
40
60
V.
0 4 8 12s2 6 10
Higher Flow
Insufficient Support
On Evita, in Action
Green curve shows the calculated
tracheal pressure in combination
with increased airway pressure
Then What Is APRV?• APRV is similar but utilizes a very short expiratory time for
Pressure Release– this short time at low pressure allows for ventilation
• APRV always implies an inverse I:E ratio• All spontaneous breathing is done at upper pressure level
Spontaneous Breaths
P
T
“Release”
Airway pressure relieve ventilationAPRV
• Two level of CPAP, applied for set periods time, allows spontaneous breathing to occur at both level
• Set P high and P low and time spent at each level ( Th
igh, Tlow )
• If P’t isn’t spontaneous, PCIRV and APRV 是不能辨別
• Is a CPAP system, allow augmentation of alveolar ventilation 經由短暫 interrupting CPAP(relieve P. )
• Gas movement → by decreasing Paw below
APRV
• 傳統 pressure – limited IRV vs. APRV 之間關係 :
-- CPPV vs. IMV• Advantages : 1) Low peak Paw 2) Low intrathoracic P. 3)↑ V/Q matc
hing• Disadvantages : 1) ↓ transpulmonary P. ( 排除 CO2會有問題 ) 2) 沒有 spontaneous breath 時為 PCIRV 3) Effect of airway and circuit resistance on ventilation 4) Interference with spontaneous ventilation
Pressure Oriented Ventilation
• Spontaneous breathing on elevated pressure level with short pressure releases for improved CO2 eliminationsimple to adjust Thigh, Tlow, Phigh, Plow
• FiO2 and Ramp setting are still present
• Apnea ventilation with adjustable alarm time Tapnea
Paw
Flow
Phigh
PlowThigh
Tlow
t
t
14:39
add. settings
Other Modees
CPAPASB
MMV
ILV
0
20
40
60
80
Paw
-10
Other
Ventilation
---
---
IPPVAssist E ** ***
48
5
4.4
0.9
mbarPhoch
Ptief
Thoch
Ttiefmbar
s
sAPRV
Mode
APRV (optional)APRV (optional)
Purpose of APRV
• ALI : ↓ FRC→ elastic WOB↑→ arterial hypoxemia
not ventilatory failure
• Restoration of FRC to reverse hypoxemia before ventilatory failure occur
• Indication :
* ↓ Clung with oxygenation failure ex : ARDS
* Ventilation failure may be 不適用 ( auto-PEEP, PaCO2↑ )
Clinical use of APRV• Adjustment of CPAP (P high) result in pul. Gas
exchange and lung mechanics, by monitor of
-- PaO2, SpO2, PvO2, SvO2 or BP and HR• After P-high, relieve Paw to P-low (△P ), meas
ure Vt, 如必要↑ P-high level or ↓ P-low• If frequency release ↑, 則 release time (Tlow) 應逐漸↓ , 避免因 air trapping ↓→ Vt ↓
• Volume change depends on TC (C*R) -- C ↓ → release time ↓(<1.5sec) -- Airway obstruction → release time ↑
Guidelines for Adjusting APRV - Timing Variables
• Set frequency that results in acceptable alveolar ventilation– adjusted to maintain desired levels of PaCO2 / pH
– usual starting rate 6 - 10 b/min
• Release time 1- 2 seconds for adults (1 - 1.5 more common)– often set to achieve a slight amount of auto-PEEP
Guidelines for Adjusting APRV - Pressure Variables
• Upper PEEP level 10-30cmH2O determined by compliance, adjusted to achieve desired MAP and oxygenation
• Lower PEEP level 3-5 cmH2O adjusted to affect FRC, MAP, and thus oxygenation
• Oxygenation can be affected by increasing MAP through:– increasing PEEPL – increasing PEEPH if less than 30 - 35 cmH20– lengthening TH if changes to either set frequency or TL is
acceptable
Which patients may be poor candidates for APRV
• Patients with increased airway resistance
• Who are unable to empty their lungs in 2 seconds
• Asthma and COPD patients
• Examining expiratory flow pattern to determine increased resistance can be a reliable indicator
Bi–phasic Positive Airway Pressure
• Use the same principle as APRV• Pressure target with freedom of
spontaneous breath on two level • Synchronization of spontaneous and
mechanical ventilation (trigger window) with BiPAP
What is BiLevel Ventilation?• Cycling between the two pressure levels can be synch
ronized to patient breathing– BiLevel timing settings or triggered by patient eff
ort• The two pressure levels are called PEEPH and PEEPL
• The two timing levels are TH and TL
P
T
Synchronized Transitions
PEEPHIGH
PEEPLOW
TLOW
THIGH
Synchronized Transitions
What is BiLevel Ventilation?• At either pressure level the patient can breathe
spontaneously– spontaneous breaths may be supported by PS
– if PS is set higher than PEEPH, PS supports spontaneous breath at upper pressure
T
PEEPHigh + PS
P
PEEPL
PEEPH
Pressure Support
Depiction of DuoPAP Ventilation
Spontaneous Breaths
Synchronized Transitions
Clock Transition
PHIGH + PS
PLOW + Psupport
Spontaneous Breaths
P
T
PHIGH
PLOW/PEEP/CPAP
PLOW
PHIGH
P
T
BIPAP* allows Spontaneous Breathingduring the Mandatory Stroke
• Reduction of the invasivness of Ventilation
• Reduction of Sedation
• One Ventilation Mode from Intubation to Weaning
• More comfortable for the Patient
• Fewer Alarms (easier handling)
PCV
Spontaneous Breathing
BIPAP
BIPAP and the Synchronisation of Spontaneous Breathing
P
t
Exp. Trigger
Insp. Trigger
Trig. Window
Trig. Window
• The set BIPAP phase synchronises with Spontaneous Breath
• Smooth synchronisation of the mandatory strokes with appropriate time window
• Flow-trigger in Inspiration and Expiration
3 New BiLevel Settings• Timing button
• Upper pressure level button - PEEPH
• Lower pressure level button - PEEPL
f1
min16
0 5
V-TRIG.
TH
S1.75
1.75
1:1.14
2.0
P
%50
O2
%50
_PCIRC
cmH2O25
PSPSUPP
H2O15
VSENSL
min5
BiLEVEL PC
10 %
PEEPH
20 cmH2O
PEEPL
5.0 H2Ocm
ESENS
3.75
cm
1.75
THIGH Setting
• TH can then be directly adjusted
• Range 0.2 to 30 seconds
f1
min16
0 5
V-TRIG.
3.75
TH
S1.75
1:1.14
2.0
P
%50
H2O
PEEPH
20 cmO2
%50
_PCIRC
cmH2O25
PSPSUPP
H2O15
VSENSL
min5
BiLEVEL PC
10 %
PEEPL5.0 cm
H2O
ESENS
1.75
cm
THIGH : TLOW Setting• When I:E ratio is locked, TH : TL is is the displayed button
and can be adjusted directly
• Range 1:299 to 149:1
f1
min16
0 5
V-TRIG.
3.75
1.75
1:1.14
2.0
P
%50
H2O
PEEPH
20 cmO2
%50
_PCIRC
cmH2O25
PSPSUPP
H2O15
VSENSL
min5
BiLEVEL PC
10 %
PEEPL5.0 cm
H2O
TH : TL 1: 1.14
ESENS
cm
TLow Setting• When TL is locked on the breath timing bar, TL is present
on the timing button and can be set directly
• Range .2 seconds or higher
f1
min16
0 5
V-TRIG.
3.75
1.75
1:1.14
P
%50
H2O
PEEPH
20 cmO2
%50
_PCIRC
cmH2O25
PSPSUPP
H2O15 cmVSENS
Lmin5
BiLEVEL PC
10 %
PEEPL5.0 cm
H2O
ESENS
TL
S2.0
2.0
APRV versus BIPAP different philosophies
BIPAP
Pinsp
CPAP
Ventilation
Phigh
Plow
APRV
Adaptic Support Ventilation (ASV )
Machine- and/or patient-triggered.Gas delivery is pressure-controlled for both
mandatory and spontaneous breaths. Pressure levels are identical.
Mandatory breaths are time-cycled if they were NOT triggered by the patient; spontaneous breaths are flow-cycled.
ASVASV
Pinsp
PEEP
No patient activity:
* Machine-triggered+ Time-cycled
Patient is active:
* Patient-triggered+ Flow-cycled
Flow I
Flow E * *
+ +
Optimal breath patternOptimal breath pattern
0
500
1000
1500
2000
0 20 40 60
f bpm
Vt m
l
1+2a*RCexp*(MV-V‘D)/VD -1f-target =
a*RCexp
Lung-protective rulesLung-protective rules (boundary conditions)(boundary conditions)
0
500
1000
1500
2000
0 20 40 60
f (b/min)
Vt (
ml)
DD
AA
CC
BB
5 test breaths
10*Vd10*Vd
5 b/min5 b/min 20/RCexp20/RCexp
2*Vd2*Vd
Optimal breath pattern: Lung Optimal breath pattern: Lung protective strategy protective strategy
Avoid:a:apneab:volume/barotraumac: AutoPEEPd: excessive VD ventilationon /tachypnea
0
500
1'000
1'500
2'000
0 10 20 30 40
Frequency in breaths per minute
Vt
in m
l
a
b
c
d
結語• 呼吸器是用來活命 (supportive) 而不是用來治病 (curative or therapeutic) 的─– 支持衰竭的呼吸系統 (failing respiratory system) ,直到病人的呼吸功能因治療或自然回復功能
– 避免呼吸器引起之「醫源性肺損傷」 (iatrogenic lung injury) 與其他併發症
• 不要用呼吸器來延長死亡過程─– 癌症末期病人– 末期之慢性呼吸衰竭– 無復原希望之疾病
Thanks for your attention