| This study aimed to investigate the causes of dyspnea during exercise, particularly focusing on restrictions of the external
thoracic cavity. Dyspnea experienced during exercise under abnormal restrictive ventilation constraints (VE) may result
from a neuromechanical uncoupling of the respiratory system. Our findings revealed associations between VE and
respiratory pattern, dynamic operating lung volume, chest size, and chest cavity size. Using the chest wall strapping (CWS)
technique, we simulated a mild restrictive lung deficit. Esophageal catheterization allowed for the measurement of sensory
intensity, breathing pattern, and mean arterial pressure (MAP). Incremental cycle tests were conducted under two
conditions: unrestricted control and CWS at 21.6 ± 0.5%. We observed significant increases in electromyography of the
diaphragm (EMGdi) and transdiaphragmatic pressure-time product (PTPdi) during exercise with CWS. Interestingly,
EMGdi did not exhibit a different relationship with tidal volume, maximal expiratory flow, or PTPdi, suggesting no
alteration in synaptic function. Furthermore, sensory intensity and unpleasantness ratings increased with CWS. However,
EMGdi did not correlate with intensity, nor did it increase with CWS, regardless of whether dyspnea intensity or
unpleasantness increased. Our findings suggest that neuromechanical uncoupling under abnormal tidal volume expansion
restrictions may contribute to VE, although the underlying mechanism remains unclearddd |
