[Physiopathology of chronic respiratory insufficiency]

The host of chronic respiratory abnormalities responsible for an abnormal hematosis or for a handicap can be termed generically as chronic respiratory insufficiency. Hypoxemia can be the consequence of perturbations of oxygen transfer (fibrosis), of abnormal ventilation-perfusion ratios (venous admixture, chronic obstructive pulmonary disease [COPD]), or of hypoventilation (neuromuscular diseases). Hypercapnia can stem from hypoventilation (neuromuscular diseases), or from abnormal ventilation-perfusion ratios (dead space effect) (COPD). An imbalance between the capacity of the respiratory muscle to produce negative inspiratory pressures and the load they are faced with is a source of hypercapnia, and of dyspnoea and handicap independently of hematosis (COPD, neuromuscular diseases). The effects of hypoxemia on cellular functions make chronic respiratory insufficiency a systemic disease.