Non-pulmonary factors affecting survival in patients completing pulmonary rehabilitation

Patients referred to pulmonary rehabilitation usually have advanced chronic obstructive lung disease (COPD). This disease is a common cause of death in developed countries, ranking fourth as a cause of death in the United States, behind heart disease, cancer, and stroke. The three-year survival following outpatient pulmonary rehabilitation is approximately 80%. Clearly, markers of disease severity such as the degree of airways obstruction, arterial blood gas abnormality, degree of pulmonary hypertension, and the need for hospitalizations predict mortality in this disease. However, because of substantial co-morbidity, patients with COPD often die with their disease rather than from their disease. Thus, only 45 to 63% of deaths in patients with advanced lung disease are directly due to the disease itself. Factors other than primary disease severity that predict mortality in COPD include nutritional depletion, exercise endurance, functional performance, and even social factors such as marital status. Thus, once the chronic lung disease progresses to the point where referral is made to pulmonary rehabilitation, non-pulmonary factors are also important predictors of survival. This underscores the importance of a holistic approach to the patient with advanced lung disease, and the need for a comprehensive severity grading system that includes more than the forced expiratory volume in 1 sec (FEV1).