Effects of body postures on respiratory muscle force and coughing in healthy people

The respiratory muscle force determines the intensity of cough force. A greater cough force for cleaning the airways is essential for preventing and managing pneumonia. Body posture can affect the onset of aspiration pneumonia. However, the effects of body posture on the respiratory muscle and cough forces remain unclear. Thus, we aimed to explore the influence of the four body postures on respiratory muscle force, cough pressure, subjective ease of coughing, and pulmonary function in healthy individuals. Twenty healthy individuals were included in this study. Body postures were 0-degree supine, 30- and 60-degree semi-recumbent, and 90-degree sitting. The maximal inspiratory and expiratory pressures, maximal cough pressure, subjective ease of coughing, and pulmonary function, including peak expiratory flow, were evaluated. We set the measured values in the supine posture to 100% and showed the relative values. The 60-degree posture showed stronger inspiratory (125.1 ± 3.9%, mean ± standard error [SE]) and expiratory (116.4 ± 3.0%) muscle force, cough pressure, more subjective ease of coughing, and greater peak expiratory flow (113.4 ± 3.0%) than the supine posture. The sitting posture also showed greater inspiratory muscle force and peak expiratory flow than the supine posture. The correlation coefficient for the 60-degree posture showed that the maximal inspiratory pressure was moderately correlated with the maximal expiratory pressure (r = 0.512), cough pressure (r = 0.495), and peak expiratory flow (r = 0.558). The above findings suggest the advantage of keeping a 60-degree posture and avoiding the supine posture to generate a greater cough force in the prevention and management of pneumonia.