Predictive factors of lung function in patients with COPD and heart failure

Introduction: The studies in Chronic Obstructive Pulmonary Disease (COPD) and Heart Failure (HF) indicate that patients with obesity have a better lung function and prognosis, this is known as “The obesity paradox", however, studies use Body Mass Index (BMI), without contemplating the muscle mass. Objective: To determine the predictive factors of lung function in COPD and HF patients. Material and Methods: In a cross-sectional study. Subjects with a diagnosis of COPD and HF were included. Patients with cancer and HIV were excluded. Body composition was measured by bioelectrical impedance, the skeletal muscle mass index (SMMI) was obtained, according to the Janssen criteria. Pulmonary function was evaluated by post-bronchodilator spirometry in which the forced expiratory volume (FEV1). Results: 420 patients were recruited, age 70.5 ± 11.36 years, 47.2% were women, 41% had HF with preserved ejection fraction, 44.7% in NHYA class II, 38.5% had GOLD 2, the BMI was 28.33 ± 7.32 and FEV1 (%) 60.66 ± 24.1. The predictors of lung function were: per Kg/cm of SMMI the FEV1 increases 2.72% and by each unit of BMI increased 0.58% of FEV1. However, in those with pulmonary congestion the FEV1 decreased by 8.37% Conclusions: Although the increase of BMI is related to better lung function, in this study, we show that muscle mass is the best factor to predict it. "The obesity paradox" does a wrong reading, because the BMI does not distinguish between muscle mass and fat mass. Loss of muscle mass and pulmonary congestion have an adverse effect on lung function.