The Power Course

Which of the following is not a feature of respiratory failure


1 ) Hypoxia
2 ) Hypocapnia
3 ) Hypercapnia
4 ) None of the above


There two types of respiratory failure type 1 and type 2. In both hypoxia is a common feature but the difference is carbon dioxide. In type 1, Carbon dioxide in the blood is normal or reduced, but in type2 it is increased.

In Type 1 respiratory failure, localized hypoventilation in the lungs from disease like pneumonia, leads to reduced oxygenation and increases in carbon dioxide concentration of the blood, draining that area. This hypoxic blood, trigger hyperventilation in the rest of the lung fields, leading to carbon dioxide reduction without much correction in the oxygen concentration.  Thus in typ1 respiratory failure, hypoxia with hypo or normocarbia is seen.

In Type 2 respiratory failure there is generalized hypoventilation of lungs leading to hypoxia and hypercarbia 

Type 1 respiratory failure

In both acute and chronic type 1 respiratory failure pH is normal, PaO2 decreased less than 60mmhg, PaCO2 less than 50mmhg, bicarbonates is normal.

Causes of type 1 respiratory failure
Acute Chronic
Acute Asthma COPD
Pulmonary edema Lung Fibrosis
Pneumonia Lymphangitis carcinomatosa
Lobar Collapse Right to left shunts
Pulmonary embolus  

Type 2 respiratory failure

pH is normal in acute type 2 respiratory failure, but in chronic it may be decreased less the 7.3 (respiratory acidosis). PaO2 less than 50mmhg PaCo2 increased more than 50mmhg. Bicarbonates normal in acute but in chronic increased.

Causes of type 2 respiratory failure
Acute Chronic
Acute Severe asthma COPD
Acute exacerbation of COPD Sleep apnoea
Upper airway obstruction Kyphoscoliosis
Acute Neuropathies/paralysis Myopathies and muscular dystrophies
Narcotic drugs Ankylosing Spondylitis
Primary alveolar hypoventilation  
Flail chest injury  


None of the above

Last Modified : 25-Dec-2019

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