Sex-differences in respiratory mechanics during exercise in healthy aging

Purpose: Three studies were performed in order to comprehensively examine the combined effects of healthy aging and biological sex on respiratory mechanics and the perception of dyspnea during exercise in healthy adults. Methods: Study #1 (Chapter 2) investigated the mechanical ventilatory and sensory responses to incremental exercise in a group of younger men and women (20-30 years old), and older men and women (60-80 years old). Study #2 (Chapter 3) examined inspiratory muscle recruitment patterns during incremental exercise in a group of younger men and women (20-30 years old), and older men and women (60-80 years old). Study #3 (Chapter 4) assessed whether experimentally manipulating the magnitude of mechanical ventilatory constraint during moderate-intensity exercise would alter the perception of dyspnea in a group of older men and women. Conclusions: Healthy aging and biological sex independently increase the magnitude of ventilatory constraint during exercise in healthy adults. Specifically, older individuals and women have a higher work of breathing for a given minute ventilation, and a higher propensity towards expiratory flow limitation during exercise than men and younger individuals, respectively. Additionally, older women have a higher perception of dyspnea during exercise than older men, which could be explained by the combined effects of age and sex on mechanical ventilatory constraint during exercise (Study #1). Healthy aging and biological sex also independently affect the pattern of inspiratory muscle recruitment during exercise, where older individuals and women rely on extra-diaphragmatic inspiratory muscles to a greater extent than older individuals and women, respectively (Study #2). Despite these differences in respiratory mechanics, acutely manipulating the magnitude of mechanical ventilatory constraint during moderate-intensity exercise did not have an effect of the perception of dyspnea (Study #3). Collectively, the results of this thesis suggest that sex-differences in respiratory mechanics during exercise persist throughout the healthy aging process, but do not contribute to the increased sensations of dyspnea observed in healthy older women relative to healthy older men.Education, Faculty ofKinesiology, School ofGraduat

Impact of wearing a surgical and cloth mask during cycle exercise

We sought to determine the impact of wearing cloth or surgical masks on the cardiopulmonary responses to moderate-intensity exercise. Twelve subjects (n=5 females) completed three, 8-min cycling trials while breathing through a: non-rebreathing valve (laboratory control), cloth, or surgical mask. Heart rate (HR), oxyhemoglobin saturation (SpO2), breathing frequency (Fb), mouth pressure, partial pressure of end-tidal carbon dioxide (PetCO2) and oxygen (PetO2), dyspnea, were measured throughout exercise. A subset of n=6 subjects completed an additional exercise bout without a mask (ecological control). There were no differences in Fb, HR or SpO2 across conditions (all p>0.05). Compared to the laboratory control (0.90.7cmH2O[meanSD]), mouth pressure swings were greater with the surgical mask (4.70.9; pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Reliability of diaphragm voluntary activation measurements in healthy adults

Voluntary activation can be used to assess central fatigue of the diaphragm after tasks such as exercise or inspiratory muscle loading. Cervical magnetic stimulation (CMS) of the phrenic nerves elicits an involuntary contraction, or twitch of the diaphragm. This twitch is quantified based on a measure of transdiaphragmatic pressure (Pdi) and can be used to evaluate diaphragm contractile function and diaphragm voluntary activation (diaphragm-VA). The test-retest reliability of diaphragm-VA using CMS is currently unknown. Thirteen participants (4M:9F; 253 years) performed a series of interpolated twitch manoeuvres, which included a maximal inspiratory effort against a semi-occluded mouthpiece and two CMS-stimuli, one during the inspiratory manoeuvre and one after when the participant returned to functional residual capacity to quantify diaphragm-VA. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) measured between-day and within-session reliability of diaphragm-VA, respectively. Maximal diaphragm-VA values were 908% (SEM: 3.8%) and 917% (SEM: 3.8%) during visits 1 and 2 (p=0.781), respectively, and displayed ‘excellent’ between-day reliability (ICC:0.98; 95%CI:0.96-1.00; SEM: 1.5%). Our results suggest that assessing diaphragm-VA using CMS is reliable in young healthy adults. Measuring diaphragm-VA may provide additional insight into the consequences and mechanisms of diaphragm fatigue. Novelty bullets: • Magnetic stimulation of the phrenic nerves can reliably measure voluntary activation of the diaphragm • Diaphragm voluntary activation can be used to provide additional insight into fatigability of the diaphragm.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Lung volume recruitment acutely increases respiratory system compliance in individuals with severe respiratory muscle weakness

The aim of the present study was to determine whether lung volume recruitment (LVR) acutely increases respiratory system compliance (Crs) in individuals with severe respiratory muscle weakness (RMW). Individuals with RMW resulting from neuromuscular disease or quadriplegia (n=12) and healthy controls (n=12) underwent pulmonary function testing and the measurement of Crs at baseline, immediately after, 1 h after and 2 h after a single standardised session of LVR. The LVR session involved 10 consecutive supramaximal lung inflations with a manual resuscitation bag to the highest tolerable mouth pressure or a maximum of 50 cmH2O. Each LVR inflation was followed by brief breath-hold and a maximal expiration to residual volume. At baseline, individuals with RMW had lower Crs than controls (37±5 cmH2O versus 109±10 mL·cmH2O−1, p0.05). LVR had no significant effect on measures of pulmonary function at any time point in either group (all p>0.05). During inflations, mean arterial pressure decreased significantly relative to baseline by 10.4±2.8 mmHg and 17.3±3.0 mmHg in individuals with RMW and controls, respectively (both p<0.05). LVR acutely increases Crs in individuals with RMW. However, the high airway pressures during inflations cause reductions in mean arterial pressure that should be considered when applying this technique

Pectoralis muscle area and its association with indices of disease severity in interstitial lung disease.

RATIONALE The pathophysiology of interstitial lung disease (ILD) impacts body composition, whereby ILD severity is linked to lower lean mass. OBJECTIVES To determine i) if pectoralis muscle area (PMA) is a surrogate for whole-body lean mass in ILD, ii) whether PMA is associated with ILD severity, and iii) if the longitudinal change in PMA is associated with pulmonary function and mortality in ILD. METHODS Patients with ILD (n = 164) were analyzed retrospectively. PMA was quantified from a chest computed tomography scan. Peripheral oxygen saturation (SpO2), 6-min walk distance (6MWD), and pulmonary function were obtained as part of routine clinical care. Dyspnea and quality of life were assessed using the UCSD Shortness of Breath Questionnaire and European Quality of Life 5 Dimensions questionnaire, respectively. RESULTS PMA was associated with whole-body lean mass (p  0.05). The annual negative PMA slope was associated with annual negative slopes in FVC, FEV1, and DLCO (all p < 0.05), but not FEV1/FVC (p = 0.46). Annual slope in PMA was associated with all-cause mortality (hazard ratio = -0.80, 95% CI:0.889-0.959; p < 0.001). CONCLUSION In patients with ILD, PMA is a suitable surrogate for whole-body lean mass. A lower PMA is associated with indices of ILD severity, which supports the notion that ILD progression may involve sarcopenia

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease.

To minimize transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for coronavirus disease (COVID-19), the U.S. Centers for Disease Control and Prevention and the World Health Organization recommend wearing face masks in public. Some have expressed concern that these may affect the cardiopulmonary system by increasing the work of breathing, altering pulmonary gas exchange and increasing dyspnea, especially during physical activity. These concerns have been derived largely from studies evaluating devices intentionally designed to severely affect respiratory mechanics and gas exchange. We review the literature on the effects of various face masks and respirators on the respiratory system during physical activity using data from several models: cloth face coverings and surgical masks, N95 respirators, industrial respirators, and applied highly resistive or high-dead space respiratory loads. Overall, the available data suggest that although dyspnea may be increased and alter perceived effort with activity, the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise. There is no current evidence to support sex-based or age-based differences in the physiological responses to exercise while wearing a face mask. Although the available data suggest that negative effects of using cloth or surgical face masks during physical activity in healthy individuals are negligible and unlikely to impact exercise tolerance significantly, for some individuals with severe cardiopulmonary disease, any added resistance and/or minor changes in blood gases may evoke considerably more dyspnea and, thus, affect exercise capacity