Chest wall kinematics during cough in healthy subjects

Aim: The study of kinematics of the chest wall (CW) could allow us to define the relative deflationary contribution of its compartments during fits of coughing. We hypothesized that if forces applied to the lung apposed rib cage are not commensurate with those applied to the abdomen-apposed rib cage, cough could result in rib cage distortion. Methods: In 12 (five women) healthy subjects we evaluated the volumes of CW (Vcw) and its compartments: the lung apposed rib cage, the abdomen apposed rib cage and the abdomen, by optoelectronic plethysmography. The loop of volume of the lung apposed rib cage/volume of the abdomen apposed rib cage allowed the calculation of mean rib cage distortion, resulting in a dimensionless number which, when multiplied by 100, gives percentage distortion. Each subject performed voluntary single and prolonged coughing efforts at functional residual capacity (FRC) and after maximal inspiration (max). The normal level of mean distortion was set at < 0.5%. Results: The three compartments contributed to reducing end-expiratory Vcw during cough at FRC and prolonged maximum cough, with the latter resulting in the greatest CW deflation. Mean rib cage distortion did not differ between men and women (P > 0.1), but tended to significantly increase from single to prolonged Cough Max (1.3% +/- 1.0 vs. 2.3% +/- 1.6, respectively; P = 0.06). Conclusion: Rib cage distortion may ensue during coughing, probably as a result of uneven distribution of forces applied to the rib cage.