LONG-TERM OXYGEN-THERAPY IN PARENCHYMAL LUNG-DISEASES - AN ANALYSIS OF SURVIVAL

We have analysed the predictors of survival in patients starting long- term domiciliary oxygen therapy (LTO) for chronic hypoxia caused by pa renchymal lung disease. In 240 patients (136 males) LTO was started at a mean age of 70 yrs. Survivors have been followed up for a minimum o f 28 months (range 28-57 months). Interstitial fibrosis was the sole c ause of hypoxia in 51 patients, and late sequelae of pulmonary tubercu losis in 48 patients. More than one (mixed) disease caused hypoxia in 124 patients. Patients with tuberculosis (TB) started LTO with signifi cantly higher values of arterial carbon dioxide tension (PaCO2) and ma rkedly lower spirometry volumes than patients with interstitial fibros is. In the total patient group survival was correlated in the univaria te analysis to cause(s) of hypoxia, performance status and PaCO2 when breathing air. TB had a relatively good prognosis, whilst interstitial fibrosis implied a poor long-term survival. A PaCO2 of below 5.5 kPa and a poor performance class was associated with increased mortality r ates. In TB patients, survival was better when thoracic deformity cont ributed to hypoxia. In patients with interstitial fibrosis, a forced v ital capacity of below 2.1 l was associated with increased mortality. Concomitant chronic obstructive pulmonary disease was associated with better survival than interstitial fibrosis alone. In the multivariate analysis, survival was found correlated to performance status, presenc e or absence of thoracic deformity and forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). A high FEV1 and a low FVC were associated with increased mortality rates. After consideratio n of spirometry values, cause(s) of hypoxia, apart from thoracic defor mity, was not significantly associated with survival. The reason for t he increased mortality rate in patient developing chronic hypoxia at h igh FEV1 levels could be more advanced diffusion impairment or ventila tion-perfusion mismatch in patients developing chronic hypoxia at less advanced stages of obstruction.