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Obstructive Pattern

Basic physiology:

  1. During an obstruction in airways, there is decrease in expiratory flow which become more pronounced when expiration is more forceful.
  2. Hallmark is decrease in expiratory flow rates. 
  3. FEV1 is markedly reduced and FVC is mildly reduced so that ratio of FEV1 / FVC is highly reduced.
  4. Diffusion capacity is normal except emphysema where it is reduced. 

Important Points:


Causes of Obstructive airway diseases:

  1. Asthma
  2. COPD
  3. Bronchiectasis
  4. Cystic Fibrosis
  5. Bronchiolitis

Restrictive Pattern

  1. Hallmark is decrease in TLC and VC (Reduce lung volume).
  2. FEV1 is mildly reduced but FVC is highly reduced so that ratio of FEV1 / FVC is normal or increased.
  3. Diffusion capacity is reduced.











Decreased (<0.7)

Unchanged but Increased in emphysema





Normal or increased

Highly reduced


Restrictive lungs diseases are characterized by decreased compliance and normal or increased FEV1/FVC

  1. The hallmark of restrictive lungs disease is a decrease in lung volumes primarily TLC and V.C (FVC is decreased)
  2. Compliance decreases in restrictive lung disease. Compliance is usually unaffected in obstructive lung disease except in emphysema where it is increase.
  3. Emphysema is associated with an increased static compliance.
  4. In surfactant deficiency leads to atelectasis. That causes reduced compliance.


Compliance is a measure of 'distensibility' and is measured as a change in lung volume per unit change in pressure.

  1. Static Compliance
    1. Static compliance indicates compliance when the lungs are at rest
    2. Static compliance values reflect true lung compliance alone
    3. Static compliance reflects elasticity of the lung and is not affected by airway resistance because there is no flow
    4. Reduced static compliance indicates rigid lung tissue
    5. Causes of reduced static compliance
      1. Interstitial fibrosis (Fibrosing alveolitis)      
      2. Atelectasis
      3. Pulmonary edema                    
      4. Pneumonia          
      5. ARDS
    6. Reduced static compliance is usually also associated with a decreased dynamic compliance due to associated airway resistance 

Increased static compliance indicates easily expandable lung   Example – Emphysema


Extra Edge:

Emphysema is associated with an increased static compliance but decreased dynamic compliance due to associated increased airway resistance.

  1. Dynamic compliance
    1. Dynamic compliance indicates compliance when air flow is occurring
    2. Dynamic compliance values reflect lung compliance along with airway resistance
    3. Dynamic compliance is affected by both elasticity of the lung and airway resistance
    4. Reduced Dynamic compliance (without change in static compliance(without change in static compliance) indicates ed airway resistance
      1. Obstruction
      2. Bronchospasm (Allergic Asthma)
      3. Collapse of small airways etc
    5. Reduced Dynamic compliance with reduced static compliance
    6. Most conditions where static compliance is reduced are also associated with reduced dynamic compliance due to associated increase in airway resistance

Causes of different restrictive pattern


Restrictive - Parenchymal Restrictive- Extraparenchymal
1.    Sarcoidosis 1.    Guillane-Barre syndrome
2.    Idiopathic pulm fibrosis 2.    Myasthenia Gravis
3.    Pneumoconiosis 3.    Diaphragmatic paralysis
4.    Drugs (Amiodarone) 4.    Cervical spine injury
5.    Radiation 5.    Kyphosis
6.    ARDS 6.    Obesity
  7.    Ankylosing Spondylosis

Extra Edge:
Pulmonary function tests in restrictive lung diseases
  1. Intrinsic restrictive disease
  2. Extrinsic restrictive diseases
  3. Decreased RV
  4. Normal RV
Extra Edge:

Severe kyphoscoliosis is a restrictive extra-parenchymal disease and presents with normal RV & decreased TLC on pulmonary function tests.


Single Breath DLCO Study for Diffusion Capacity

  1. In interstitial lung diseases the transfer capacity of the lungs is reduced. The diffusing capacity of lung for carbon monoxide (DLCO) is reduced in all patients with intrinsic lung disorders.
  2. In obstructive lung diseases the transfer capacity of the lung is not affected.
  3. The DLCO is not affected in patients with. Extraparenchymal restrictive lung diseases i.e. the restrictive lung diseases caused due to chest wall or muscular disorders.     
  4. A normal DLCO value in restrictive diseases excludes intrinsic lung disease and indicates extrinsic lung disorders due to chest wall pleura or neuromuscular lung disease.
  5. The DLCO is the most sensitive parameter and findings may be abnormal even when the lung volumes are preserved. 

Decrease value of DLCO is seen in­

  1. Emphysema
  2. Interstitial lung disease
  3. Recurrent pulmonary emboli
  4. Anemia
  5. Severe CHF
  6. Pulmonary artery hypertension

Increased level of DLCO is seen in­

  1. Mild CHF (Due to pulmonary flow) (Note - It is increase in mild CHF and reduce in Severe CHF)
  2. Alveolar hemorrhage
  3. Polycythemia               
  4. Left to right shunts
  5. In Goodpasture’s syndrome alveolar hemorrhage occurs therefore (DLCO) is increased.
Extra Edge:

Infiltrative lung disease being a intrinsic (parenchymal) restrictive disease, TLC, VC & compliance all are reduced.


Important Points:

  1. Other investigations is respiratory diseases
  2. Radionuclide scans Q Ventilation/perfusion (V/Q) scans are used to diagnose pulmonary Q embolism.
    1. Computed tomography
    2. High resolution CT (HRCT) is used to diagnose
      1. Interstitial lung disease
      2. Bronchiectasis.
      3. Emphysema
    3. Spiral CT pulmonary angiography is used in the diagnosis of PE. It is the investigation of choice for screening of PE. (PNQ)
    4. Note: Previously investigation of choice for screening of PE was V/Q scan.
    5. Pulmonary angiography is also used for confirming diagnosing of PE and pulmonary hypertension Q.
  3. Fiberoptic bronchoscopy.
    1. Diagnostic indications:
      1. Suspected lung carcinoma
      2. Slowly resolving pneumonia
      3. Pneumonia in the immunosuppressed
      4. Interstitial lung disease
    2. Therapeutic indications:
      1. Aspiration of mucus plugs causing lobar collapse
      2. Removal of foreign bodies.
  4. Bronchoalveolar lavage (BAL) is performed at the time of bronchoscopy by instilling and aspirating a known volume of warmed, buffered 0.9% saline into the distal airway.
    Diagnostic indications:
    1. Suspected malignancy
    2. Pneumonia in immunosuppressed (especially HIV)
    3. Suspected TB (if sputum negative)
    4. Interstitial lung diseases (eg sarcoidosis, extrinsic allergic alveolitis, histiocytosis)  

Therapeutic indications: alveolar proteinosis.



  1. Hypoxia (give supplemental O2)
  2. Transient fever
  3. Transient CXR shadow
  4. Infection (rare).


Central Cyanosis

Peripheral Cyanosis

Causes are

  1. Decreased arterial Oxygen saturation
    1. Decreased atmospheric pressure, high altitude
    2. B Impaired pulmonary function
      1. Alveolar hypoventilation (chronic bronchitis) MC cause
      2. Impaired O2 diffusion
    3. Anatomic shunts
      1. CHD'S (Rt → Lt)        
      2. Pulmonary A-V fistula
      3. Multiple small intrapulmonary shunts
  2. Hemoglobin abnormalities
    1. Methemoglobinemia
    2. Sulfhemoglobinemia
    3. Carboxyhemoglobinemia

Cause are­

  1. It results from vasoconstriction and diminished peripheral blood flow e.g.
    1. Reduced cardiac output
    2. Cold exposure
    3. Redistribution of blood flow from extremities
    4. Arterial obstruction
    5. Venous obstruction


Extra Edge:
  1. Pulse oximetry allows non-invasive assessment of peripheral O2 saturation (SpO2).
  2. It provides a useful tool for monitoring those who are acutely ill or at risk of deterioration.
  3. On most pulse oximeters, the alarm is set at 90%.
  4. Erroneous readings may be caused by: dyshaemoglobinaemias, and carbon monoxide poisoning.


Controversy about the definition of cyanosis: Traditionally cyanosis is define as de oxygenated Hb >5gm% but in Harrison 18th edition page no 288, it says to be >4gm%.

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