Does the level of obesity impact on the respiratory function in adults?

Abstract

Obesity is frequently associated to breathing disorders. In order to investigate if and how the level of obesity impact on the respiratory function, 10 obese class 2 (median age: 51 years; BMI: 38.7 kg/m2, 5 females), 7 obese class 3 patients (41 years; 45.7 kg/m2, 3 females) and 10 non-obese subjects (49 years; 23.9 kg/m2, 5 females) were studied. Patients were characterized by abdominal obesity, with abdominal volume occupying the 40% and 42% in class 2 and 3, being higher (p<0.001) than non-obese group (31%). Spirometry and lung volumes did not differ between the two classes, while the supine position induced an important reduction of functional residual capacity. At rest, breathing frequency was higher in class 3 (19 breaths/min, p=0.025). In supine position obese patients breathed with higher minute ventilation (class 12.1: L/min, class 2: 11.4 L/min) and lower ribcage contribution (class 3: 4.9%, class 2: 6.1%) than non-obese subjects (7.5 L/min, p= 0.001 and 31.1%, p=0.003, respectively), indicating thoracic restriction. Otherwise healthy obesity might not be characterized by restrictive lung pattern. Other sign of restriction could be poor thoracic expansion at rest in supine position, resulting in increased ventilation. Class 3 obesity made respiratory rate further increase.