[Chronic respiratory insufficiency: evaluation, evolution, prognosis].

Abstract

Chronic respiratory failure (CRF) is a major cause of morbidity and mortality. It is estimated that in France at least 60,000 patients exhibit severe CRF and that about 15,000 patients die each year from CRF. Chronic obstructive pulmonary disease (COPD) (chronic obstructive bronchitis, emphysema and their association) is by far the first cause of CRF (90% of the cases). The clinical picture of CRF depends on the causal disease, but exertional dyspnea is observed in almost all patients. Pulmonary function testing allows to assess whether the ventilatory defect is obstructive (COPD), restrictive or mixed. Severe CRF is usually defined by a Pa02 < 55 mmHg, in a stable state of the disease, with or without hypercapnia (PaC02 > 45 mmHg). The two major complications of CRF are acute exacerbations of the disease, with clinical and gasometric worsening, and pulmonary hypertension which may lead with time to right heart failure. Prognosis is poor in CRF since the 5 year survival rate is of 50% in COPD patients. Under long-term oxygen therapy (LTOT) the survival rate has been somewhat improved, being of 60-65% at 5 years. The best prognostic indices in CRF complicating COPD are the level of FEV1, Pa02, PaC02, the level of pulmonary artery mean pressure (PAP) and age. In COPD patients under LTOT the best prognostic indices are PAP and age.