PROGNOSIS OF SEVERELY HYPOXEMIC PATIENTS RECEIVING LONG-TERM OXYGEN-THERAPY

Two hundred seventy severely hypoxemic (PaO2 less than or equal to 55 mm Hg: mean +/- SD = 48 +/- 6) COPD patients (232 men) were selected f or long-term oxygen therapy (LTOT). They were old(mean = 66 +/- 8 year s), with severe airflow limitation (FEV(1) = 30 +/- 12 percent of pred icted), some CO2 retention (PaCO2 = 47 +/- 9 mm Hg), and compensated r espiratory acidosis. Eighteen percent of the patients presented some c omplicating pleuropulmonary diseases (pleural thickening, sequelae of tuberculosis, etc). Overall survival proportion was poor: 70, 50, and 43 percent at 1, 2, and 3 years, respectively. The Cox model showed th at the factors which independently reduced survival were lower CO tran sfer coefficient, smaller intrathoracic gas volume, more severe bronch ial obstruction, the fact that oxygen administration did not increase PaO2 above 65 mm Hg, increasing age, and the presence of chest wall ab normalities. When the patients were divided into three groups accordin g to mortality risk, the mean clinical and functional profile of the h igh-mortality risk group was consistent with the prevalence of emphyse matous lesions. Moreover, the best survivors fitted better into the '' bronchitic'' type; they showed a higher mean PaCO2, suggesting that so me degree of hypoventilation could delay muscular fatigue and improve survival. The difference in the proportion of ''emphysematous'' and '' bronchitic'' patients is a possible explanation for the variability of the mortality rate reported in literature.