Work of breathing during arm bracing in normal male subjects

OBJECTIVE: Although chronic obstructive pulmonary disease patients get relief from their dyspnea by arm bracing, the mechanics of this effect are unknown. This study aimed to investigate the mechanisms by which arm bracing affects dyspnea by measuring the work of breathing (WOB) in the arm bracing posture. METHODS: Six normal male subjects were studied in two standing postures: erect and with their arms braced. For the arm bracing posture, the subjects leaned forward with their arms stretched and rested their hands on a platform. Respiratory frequency was set at 20 tidal breaths/min with the use of a metronome, and tidal volume was set at 1 L by observing the lung volume on a monitor. All the subjects randomly adopted the two postures, and a preset respiratory pattern was measured for 30 s in each posture. Lung volume and flow rate were measured using a hot-wire flowmeter. Esophageal pressure was measured using a 12-cm balloon catheter. The WOB was estimated using modified Campbell diagrams. RESULTS: Lung volume increased and inspiratory resistive WOB decreased, while inspiratory elastic WOB increased significantly with arm bracing compared with that of the erect posture (P < 0.05). CONCLUSION: Arm bracing posture increases the chest wall expansion thereby increasing the end-expiratory lung volume and decreasing the inspiratory resistive WOB among healthy individuals.