Question

A patient with chronic respiratory failure 

A. Shows an enhanced respiratory sensitivity to inhaled carbon dioxide. 

B. Shows little or no respiratory response to hypoxia. 

C. Is likely to have a low blood bicarbonate level. 

D. Responds well when given 100 per cent oxygen to breathe. 

E. Must have been breathing oxygen-enriched air if alveolar P_CO2 is 150 mmHg (20 kPa).

Answer 1

A. False There is increased tolerance of high P_CO2 levels. 

B. False Sensitivity to low P_O2 remains and is important in maintaining ventilation. 

C. False HCO₃^-  levels rise to compensate for the raised P_CO2 in respiratory acidosis. 

D. False This could arrest ventilation by removing hypoxic drive; 24–28 per cent O₂ would do. 

E. True When breathing air, PO₂ + PCO₂ equal about 140 mmHg (19 kPa).