Effects of Face Masks on the Multiple Dimensions and Neurophysiological Mechanisms of Exertional Dyspnea.

INTRODUCTION: During the Coronavirus disease (COVID-19) pandemic, public health officials widely adopted the use of face masks (FM) to minimize infections. Despite consistent evidence that FMs increase dyspnea, no studies have examined the multidimensional components of dyspnea or their underlying physiological mechanisms. METHODS: In a randomized cross-over design, sixteen healthy individuals (n = 9 females, 25 ± 3 y) completed incremental cycling tests over three visits, where visits 2 & 3 were randomized to either surgical FM or no mask control. Dyspnea intensity and unpleasantness were assessed throughout exercise (0-10 Borg scale) and the Multidimensional Dyspnea Profile was administered immediately following exercise. Crural diaphragmatic electromyography (EMGdi) and esophageal pressure (Peso) were measured using a catheter to estimate neural respiratory drive and respiratory muscle effort, respectively. RESULTS: Dyspnea unpleasantness was significantly greater with the FM at the highest equivalent submaximal work rate achieved by a given participant in both conditions (iso-work) (5.9 ± 1.7 vs. 3.9 ± 2.9 Borg 0-10 units, P = 0.007) and at peak exercise (7.8 ± 2.1 vs. 5.9 ± 3.4 Borg 0-10 units, P = 0.01) with no differences in dyspnea intensity ratings throughout exercise compared to control. There were significant increases in the sensory quality of "smothering/air hunger" (P = 0.01) and the emotional response of "anxiousness" (P = 0.04) in the FM condition. There were significant increases in EMGdi and esophageal pressure at select submaximal work rates, but no differences in heart rate, pulse oximetry derived arterial oxygen saturation or breathing frequency throughout exercise with FMs compared to control. FM significantly reduced peak work rate and exercise duration (both P = 0.02). CONCLUSIONS: FMs negatively impact the affective domain of dyspnea and increase neural respiratory drive and respiratory muscle effort during exercise, although the impact on other cardiorespiratory responses are minimal.

Cardiorespiratory physiology, exertional symptoms, and psychological burden in post-COVID-19 fatigue.

Fatigue is a common, debilitating, and poorly understood symptom post-COVID-19. We sought to better characterize differences in those with and without post-COVID-19 fatigue using cardiopulmonary exercise testing. Despite elevated dyspnoea intensity ratings, V̇O2peak (ml/kg/min) was the only significant difference in the physiological responses to exercise (19.9 ± 7.1 fatigue vs. 24.4 ± 6.7 ml/kg/min non-fatigue, p = 0.04). Consistent with previous findings, we also observed a higher psychological burden in those with fatigue in the context of similar resting cardiopulmonary function. Our findings suggest that lower cardiorespiratory fitness and/or psychological factors may contribute to post-COVID-19 fatigue symptomology. Further research is needed for rehabilitation and symptom management following SARS-CoV-2 infection.