Variables related to increased mortality following out-patient pulmonary rehabilitation

Abstract

Although patients with advanced pulmonary diseases have significant improvement in exercise ability and functional status following comprehensive out-patient pulmonary rehabilitation (OPR), their long-term prognosis once they have reached this stage of their diseases remains poor. To further evaluate predictors of increased mortality in these patients, we related patient characteristics and short-term outcome obtained during OPR assessment of 158 patients to subsequent survival. The time period from OPR to death or collection of survival data was 40.0 +/- 17.1 months. The following variables were tested individually and in stepwise fashion using a proportional hazards model: 1) age; 2) gender; 3) pulmonary diagnosis; 4) prebronchodilator forced expiratory volume in one second (FEV1); 5) arterial oxygen tension (Pa,O2) and arterial carbon dioxide tension (Pa,CO2); 6) body mass index (BMI); 7) pre- and post-OPR 12 min walking distance (12-MW); 8) pre- and post-OPR quality of life, using the Chronic Respiratory Disease Questionnaire (CRDQ); 9) number and type of nonpulmonary diagnoses; and 10) number of medications. Separate survival analyses were performed for all deaths (the total group), respiratory deaths only (nonrespiratory deaths excluded), and nonrespiratory deaths only (respiratory deaths excluded). Forty three patients (27%) died during the study period; and the 3 year survival was 80%. For all three survival analyses, the post-OPR 12-MW was the most significant variable related to prognosis: patients with low timed walking distance had increased mortality both from respiratory and nonrespiratory causes. Other variables related to increased mortality included: elevated Pa,CO2; low pre-OPR 12-MW; reduced Pa,O2; low FEV1; low BMI, increased number of medications, and increased CRDQ dyspnoea. These results indicate that the timed walking distance following out-patient pulmonary rehabilitation is an important predictor of survival in patients with advanced pulmonary disease.