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PATHOPHYSIOLOGY OF RESPIRATORY DISEASE

Dr Bridget Ellul

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CLASSIFICATION

� According to anatomical site• Upper / lower respiratory tract

� According to aetiology / pathogenesis• Genetic

• Cardiovascular

• Infections

• Hypersensitivity reactions

• Neoplasia

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RESPIRATORY DISEASES: Classification according to Anatomy

Upper RT:Nose, larynx, (trachea)� Congenital Disorders

(trachea)� Infections (nose, larynx)� Allergies (nasal polyps)� Tumours (larynx,

nasopharynx)

Lower RT:Bronchi, lungs, pleura� Congenital Disorders� Infections (bronchi, lung)

• Pneumonia, TB

� Obstructive Pulmonary Disease • OPD: Chronic Bronchitis &

Emphysema (bronchi and lung)• Bronchial Asthma (bronchi)

� Restrictive Pulmonary Disease (alveoli)

• Interstitial (infiltrative) lung disease� Pneumoconiosis� Hypersensitivity� Drugs, toxins, radiation

� Idiopathic fibrosis

� Vascular Diseases

• DVT , pulmonary embolism• Pulmonary Oedema

• ARDS - Adult Respiratory Distress Syndrome

� Tumours (bronchi, lung, pleura) 4

RESPIRATORY DISEASES: Classification according to Aetiology

AIRWAYS and LUNG� Congenital Disorders

• Hypoplasia, Sequestration� Vascular Diseases

• DVT , pulmonary embolism• Pulmonary Oedema• ARDS - Adult Respiratory

Distress Syndrome� Trauma

• Pneumothorax

� Obstructive Pulmonary Disease• COPD: Chronic Bronchitis

& Emphysema• Bronchial Asthma

� Restrictive Pulmonary Disease• Interstitial (infiltrative)

lung disease� Pneumoconiosis

� Hypersensitivity� Drugs, toxins, radiation

� Idiopathic fibrosis

� Tumours• Benign• Malignant

PLEURA� Tumours

� Pleural effusion

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SYMPTOMS

� Runny nose

� Excess sputum production

� Dyspnoea

� Cough

� Wheezing

� Chest pain

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SYMPTOMS

� Runny nose• Allergy

• Common cold

• Nasal blockage

� Excess mucus• Smoking – clear

• Infection – yellow/green

• Asthma – yellow (eosinophils)

• Bronchial carcinoma, TB, pneumonia – blood -haemoptysis

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SYMPTOMS

� Wheezing• Airflow limitation from any cause – not necessarily

asthma

� Chest pain• Pleuritic – sharp, worse on breathing• Rib pain• Retrosternal soreness – tracheitis• Constant dull chest wall pain – invasion by lung

carcinoma• Central chest pain with radiation to neck, arms –

cardiac• Shoulder pain – diaphragmatic pleura / MI

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Symptoms

Dyspnoea (difficulty in breathing)

� Pulmonary disease� Cardiovascular disease� Metabolic disease� Others

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CoughCauses of chronic cough

� COPD

� Asthma

� Gastro-oesophageal reflux -heartburn

� Post-nasal drip

� Post chest infection

� Medications 10

INVESTIGATION OF THE RESPIRATORY SYSTEM

� Lung Function Tests

� Blood Gas Analysis

� Radiology

� Histology

� Cytology

� Microbiology

� Others

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INVESTIGATION OF THE RESPIRATORY SYSTEM

HISTOLOGY

� Bronchial biopsy at bronchoscopy

� Lung biopsy• transbronchial• transthoracic• open wedge

� Lobectomy / whole lung� Pleural biopsy� Mediastinal biopsy� Lymph node biopsy, neck

CYTOLOGY

� Sputum� Bronchial aspirates /

washings / brushings� Bronchoalveolar lavage -

BAL

� Fine needle aspiration – FNA• transbronchial

• transthoracic

� Lymph node, neck, aspirate

� Pleural fluid

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INVESTIGATION OF THE RESPIRATORY SYSTEM

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Vascular Diseases

� Deep Vein Thrombosis• and pulmonary embolism

� Virchow’s triad:� endothelial injury� alterations in blood flow� hypercoagulability

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PULMONARY EMBOLUS

� 95% arise from thrombi in large veins, lower legs

� usually deep veins of calf muscles, DVT, or pelvic veins

� emboli travel to right side of heart and pulmonary trunk and if total blockage cause death

� if small no symptoms till late pulmonary hypertension

� pulmonary infarction if increase in venous pressure in lungs

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Respiratory Infections

Inflammations

� Upper Respiratory Tract Infection

• Viral/bacterial infection

� Lower Respiratory Tract Infection

• Pneumonia – Bacterial

• Pneumonia – Viral

• Pulmonary Tuberculosis

� Hypersensitivity reactions

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Respiratory Infections

� more frequent than infections of any other organ

� largest number of workdays lost in general population

� majority involve only the upper respiratory tractand are caused by viruses - trivial or mild diseases

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Impaired Defences of Respiratory Tract

� cough reflex• coma, anaesthesia, drugs - aspiration possible

� filtering function of nasopharynx� ciliary apparatus - action towards mouth

• cigarette smoke, hot gasses, corrosives, viruses

� secretion of IgA antibodies� phagocytic activity by alveolar macrophages

• alcohol, tobacco, smoke, excess oxygen

� accumulation of secretions• cystic fibrosis, bronchial obstruction

� alveolar fluid - surfactant, Igs, complement� cell mediated immunity

• chronic disease / cancer patients /treatment with chemotherapy• immune diseases / HIV infection

� virulent infections 18

The Respiratory System

Infection may be:

� primary - viral, bacterial, mycoplasmal, fungal

� secondary bacterial - following a viral infection

� secondary to irritants

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Upper Respiratory Tract Sepsis

Viral� common cold - commonest - different serotypes of rhinovirus� Influenza - influenza virus

Bacterial� healthy individuals - uncommon in developed countries

� Streptococcus in nose and throat

Acute laryngitis / epiglottitis

� Haemophilus influenzae type B or streptococcus pyogenes� swelling and mechanical inability in breathing� irritation by pollutants including smoke and corrosives and noxious

gases

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Lower Respiratory Tract Sepsis

� Pneumonia infection of alveolar spaces

host reaction - alveolar exudates

polymorphs, fibrin, oedema fluid resulting in consolidation

Classification

� Morphology• Bronchopneumonia, Lobar Pneumonia

� many organisms present with either pattern

� ? confluent bronchopneumonia / lobar radiologically

� Aetiology

� Clinical Setting

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Bronchopneumonia� inflammation starts in

bronchi - polymorphs, fibrin

� spreads to adjacent alveoli

� patchy foci coalesce

� consolidation� Streptococcus pneumoniae

� Haemophilus influenzae

� Staphylococcus pneumonia

� Klebsiella

� Pseudomonas aeruginosa

� Coliform bacteria

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Lobar Pneumonia

� virulent organism

� host vulnerability

� 90-95% Streptococcus

pneumoniae

� inflammation starts

in alveoli

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Pneumonia

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Pneumonia : Clinical Setting

Community Acquired Acute Pneumonia• Strep. Pneumoniae, H. influenzae, Moraxella catarrhalis,

Staph. aureus, Legionella, Klebsiella, Pseudomonas

Community Acquired Atypical Pneumonia• mycoplasma, chlamydia, coxiella, viruses

Nosocomial Pneumonia• Gram negative rods (Klebsiella, E. coli, Pseudomonas),

staphylococcus aureus (usually MRSA)

Aspiration Pneumonia

Pneumonia in Imunocompromised Host• CMV, Pneumocystis carinii, mycobacterium avium-

intracellulare, aspergillosis, candidiasis, “usual”organisms

For info

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Complications

� complete resolution if correct antibiotic

� uncommon complications

• pleural adhesions being the most common

• complications commoner with lobar pneumonia

� but <10% now die

• lung abscess

• septicaemia uncommon

• if severe pneumonia is not treated death may occur

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Viral Pneumonia

� interstitial pneumonia

� misnomer as interstitial infiltrate

• histiocytes, lymphocytes

� no alveolar exudate

� influenza virus / RSV / adenoviruses /rhinoviruses

Pneumonia – Other Organisms

� Atypical Bacteria – atypical pneumonia

• Mycoplasma

• Chlamydia

• Legionella

� Fungi

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PULMONARY TUBERCULOSIS� Mycobacterium tuberculosis� droplet infection from active TBPrimary Tuberculosis � in childhood - rare now� primary lesion - Ghon focus below

pleura, mid lung• tubercles - epithelioid granulomas

with caseation� bacteria spread to hilar lymph nodes� Ghon focus & nodes heal with fibrosis /

calcification� TB survives in foci and becomes source

of later infection� cell mediated immunity to antigens of

tubercle bacillus - positive tuberculin skin test - increased resistance to subsequent infection

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PULMONARY TUBERCULOSISSecondary Tuberculosis� people previously sensitised by a primary lesion� a new infection or by reactivation of microbe

• in chronic disease, steroid therapy, HIV

� apex of the upper and lower lobes� foci heal with fibrosis and calcification� haemoptysis with erosion of a vessel in the lung� coughing up of caseous material (cavities in the

lung) provides a source of infection to the other lung

� spread via lymph and blood spreads tuberculosis throughout the body (military TB)

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Respiratory Diseases

� Obstructive Pulmonary Disease -Airways• COPD: Chronic

Bronchitis & Emphysema

• Bronchial Asthma

� Restrictive Pulmonary Disease -Alveoli• Interstitial (infiltrative)

lung disease

� Pneumoconiosis

� Hypersensitivity

� Drugs, toxins,

radiation

� Idiopathic fibrosis

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Respiratory Diseases

� Obstructive Pulmonary Disease – Airways

� airflow limitation, not fully reversible

� progressive in most� abnormal inflammatory

response� expiratory flow rate

FVC N or �FEV1 �FEV1 : FVC is low

� Restrictive Pulmonary Disease – Alveoli

� restriction of air flow due to� reduced expansion of the

lung parenchyma � � total lung capacity, vital

capacity, residual volume, lung compliance

FVC �FEV1 N or �FEV1 : FVC is N or high

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CHRONIC BRONCHITIS

� clinical term� persistent cough with sputum

production for at least three months in at least two consecutive years

� middle-aged men especially smokers� smoke predisposes to infection by

interfering with ciliary action and causing direct damage to epithelium

� 10-25% of urban population due to irritation by inhaled pollutants

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CHRONIC BRONCHITIS

pathhsw5m54.ucsf.edu/overview/text.html

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Emphysema

� pathological term� condition of the lung characterised by

abnormal permanent enlargement of the air spaces distal to the terminal bronchiole, with destruction of their walls• elastases destroy elastin• free radicals from smoke

� commoner in men, � 50-80years� associated with heavy smoking

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Emphysema

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Emphysema: Pathogenesis� proteases (elastase) or� antiproteases (antielastase, alpha-1-

antitrypsin)�

elastin destruction in alveolar walls�

development of emphysema� in smokers there is lung infection with �

neutrophils and macrophages, which produce elastase � lung damage

� stimulated neutrophils release oxygen free radicals - cause damage

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Emphysema

Prognosis�with severe emphysema, cor pulmonale (heart disease secondary to lung disease) and congestive heart failuredevelop

�death due to right heart failure and respiratory failure 38

Asthma

� increased responsiveness of bronchial tree to various stimuli, resulting in paroxysmal constriction of the bronchial airways

� triggered by exposure to an allergen

� bronchospasm triggers severe dyspnoea and wheezing

� between attacks asymptomatic

� an unremitting attack, status asthmaticus, may prove fatal

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Asthma

� lungs are over distended

� bronchi occluded by thick mucous plugs

� eosinophils & oedema in bronchial walls

� hypertrophy of bronchial smooth muscle

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Types of Asthma Precipitating Mechanism Factors Immune Reaction

EXTRINSIC� Atopic (allergic) Specific allergens Type I (IgE)� Occupational Chemicals Type I� Allergic Antigens(spores) Type I and Type III

aspergillosis

INTRINSIC� Nonatopic Respiratory Tract Unknown; hyper

Infection reactive airways� Pharmacologic Aspirin � prostaglandins

� leukotrines

Hyper reactive airways, which respond to non-specific irritants - cold, exercise and stress

Asthma

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Asthma

Atopic or Allergic Asthma� commonest type� triggered by environmental antigens - dusts, pollen,

foods, house dust mite� family history common - allergic rhinitis, urticaria or

eczema� genetic predisposition� positive skin tests� classic Type I IgE hypersensitivity reaction

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RESTRICTIVE PULMONARY DISEASE � Disorders of chest wall or pleural space

• polio and kyphoscoliosis

� Interstitial or infiltrative diseases• > 150 different disease processes

• alveolar wall and capillary endothelium damage

• results in fibrosis

Main Causes

• Idiopathic fibrosis

• Pneumoconiosis - inhalation of inorganic atmospheric pollutants e.g. asbestos

• Hypersensitivity - organic material is inhaled, e.g. pigeon

fancier's lung due to protein from bird droppings

• Drugs, toxins, radiation

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Study Guide / Objectives

1. Classify the common respiratory diseases2. List the methods of investigation of the respiratory system3. Discuss the defence mechanisms of the respiratory system4. Discuss the importance of URT infections5. Discuss the pathogenesis and morphology of bronchopneumonia and

lobar pneumonia6. Differentiate between viral and bacterial pneumonia7. Write a short note on pulmonary tuberculosis8. Distinguish between obstructive and restrictive lung diseases, in terms

of lung function and morphological abnormalities9. Define chronic bronchitis and emphysema10. Briefly discuss the pathogenesis of chronic bronchitis and emphysema11. Outline the pathogenesis of asthma12. Describe the morphological changes that occur in asthma