CIENCIASMEDICASNEWS: Physiological mechanisms of sex differences in exertional dyspnea: role of neural respiratory motor drive

sábado, 9 de noviembre de 2013

Physiological mechanisms of sex differences in exertional dyspnea: role of neural respiratory motor drive

+ Author Affiliations

McGill University, Canada

↵* Corresponding author; email: dennis.jensen@mcgill.ca

Abstract

The purpose of this study was to elucidate the physiological mechanisms of sex differences in exertional dyspnea. We compared detailed measures of neural respiratory motor drive (diaphragm EMG expressed as a % of maximal EMGdi [EMGdi%max]), breathing pattern, operating lung volumes, dynamic respiratory mechanics (tidal esophageal [Pes,tidal%peak], and transdiaphragmatic [Pdi,tidal%peak] pressure swings expressed as a % of their respective peak values), and sensory intensity and unpleasantness ratings of dyspnea during symptom-limited incremental cycle exercise in healthy young women (n=25) and men (n=25). The tidal volume to forced vital capacity ratio (V_T%FVC), breathing frequency, EMGdi%max, Pes,tidal%peak, Pdi,tidal%peak, and sensory intensity and unpleasantness ratings of dyspnea were higher, while dynamic inspiratory capacity and inspiratory reserve volume (IRV) were lower at a standardized absolute ventilation (V_E) of 55 l min^-1 during submaximal exercise in women vs. men (all p< 0.05). By contrast, sex had no demonstrable effect on the inter-relationships between exercise-induced increases in V_T%FVC, EMGdi%max, and sensory intensity and unpleasantness ratings of dyspnea. The results of this study suggest that sex differences in the intensity and unpleasantness of exertional dyspnea in health likely reflect the awareness of a relatively higher neural respiratory motor drive (or EMGdi%max) needed to achieve any given V_E during exercise in the setting of relatively greater dynamic mechanical constraints on V_T expansion in women.