The association between body weight and decreased lung volumes was demonstrated in a racially homogenous caucasian population.To determine if increased body mass index (BMI) is associated with decreased lung volume in a multi-racial patient population.
A retrospective cohort study was conducted of adult patients with a body mass index (BMI) > 20, who performed pulmonary function tests (PFT) at a large, Northeastern U.S. medical center between 2002 and 2007. All patients had a normal pre-bronchodilator FEV1/FVC ratio, residual capacity (RV) between 80% and 120% of predicted volume, and single breath diffusing capacity of the lung (DLCO) above the lower limit of normal after adjusting for the patient's alveolar volume. Lung volume was compared between patients of 5 BMI categories (20 to 25, > 25 to 30, > 30 to 35, > 35 to 40, and > 40) using analysis of variance.
A total of 392 patient charts were reviewed. Patients were primarily female (65.8%), African American (66.8%), and had a mean age of 51 years. There were 44, 104, 89, 75, and 80 patients in the 5 BMI categories listed above, respectively. Overall, lung volumes decreased linearly with increasing levels of BMI for all patients, regardless of races. ERV was markedly lower in increased BMI categories than lower BMI categories: 107.3, 80.8, 68.2, 53.8, and 54.2, respectively (p < 0.05, overall), and similarly for FRC: 104.0, 92.8, 87.7, 82.5, 81.7, respectively (p < 0.05, overall).
There is an inverse relationship between lung volumes and BMI in all races.Even morbid obesity, has relatively little effect on vital capacity (VC) or total lung capacity (TLC). However, expiratory reserve volume (ERV) and functional residual capacity (FRC) can be severely decreased as a result of the altered chest wall mechanics in obesity, regardless of race.
Obesity linearly decreases lung volumes,significantly ERV regardless of race.Our results will help pulmonologist when interpreting PFT results in obese patients with normal airway function.
Sudheer Nambiar, No Financial Disclosure Information; No Product/Research Disclosure Information