Thoracoabdominal Asynchrony Contributes to Exercise Limitation in Mild Asthmatic Subjects

Abstract

This study aimed to better understand how subjects with stable asthma and without exercise-induced bronchoconstriction respond to mild exercise. Breathing pattern, chest wall compartmental and operational volumes, and thoracoabdominal asynchrony were assessed in 11 stable asthmatic subjects and 10 healthy subjects at rest and during exercise in a cycle-ergometer through optoelectronic plethysmography. Dyspnea and sensation of leg effort were assessed through Borg scale. During exercise, with similar minute ventilation, a significant lower chest wall tidal volume (p = 0.003) as well as a higher respiratory rate (p < 0.05) and rapid shallow breathing (p < 0.05) were observed in asthmatic when compared to healthy subjects. Asthmatic subjects exhibited a significantly lower inspiratory (p < 0.05) and expiratory times (p < 0.05). Intergroup analysis found a significant higher end-expiratory chest wall volume in asthmatic subjects, mainly due to a significant increase in volume of the pulmonary ribcage (RCp; 170 ml, p = 0.002), indicating dynamic hyperinflation (DH). Dyspnea and sensation of leg effort were both significantly greater (p < 0.0001) in asthmatic when compared to healthy subjects. In addition to a higher thoracoabdominal asynchrony found between RCp and abdominal (AB) (p < 0.005) compartments in asthmatic subjects, post-inspiratory action of the inspiratory ribcage and diaphragm muscles were observed through the higher expiratory paradox time of both RCp (p < 0.0001) and AB (p = 0.0002), respectively. Our data suggest that a different breathing pattern is adopted by asthmatic subjects without exercise-induced bronchoconstriction during mild exercise and that this feature, associated with DH and thoracoabdominal asynchrony, contributes significantly to exercise limitation.

Measurement of chest wall motion using a motion capture system with the one-pitch phase analysis method

“…For asynchronous analysis, the inspiratory paradox time (IPT) and expiratory paradox time (EPT) of the upper RC, lower RC, and ABD were also calculated. These parameters were defined as the fraction of time relative to the total chest wall displacement signal (expressed as percentage), in which the compartmental signals decreased during inspiration (IPT) and increased during expiration (EPT) 25 , 26 , 28 , 29 .…”

Reference equations for tidal breathing parameters using structured light plethysmography

“…Phase-angle or thoraco-abdominal asynchrony has been used to assess respiratory function in children [ 6 , 7 , 27 ] and adults [ 8 , 28 ]. Based on our data, TAA is high and variable during early life and reduces in both magnitude and variability with age.…”

“…A higher TAA in the supine position compared to seated is shown in M ayer et al [ 29 ]. TAA in healthy subjects in a seated position is reported elsewhere [ 28 , 30 ]. The number of healthy subjects is low (n=10 and n=9 at rest, respectively), and the method for calculation of phase differs slightly from what has been used herein.…”

Highlights from the 2018 European Respiratory Society International Congress: sleep and clinical physiology

“…F regonezi et al . [93] carried out a study to ascertain whether chest wall and compartmental volume responses differ between mild asthmatic patients and healthy subjects. The study demonstrated that during mild exercise, asthma patients adopted a different breathing pattern to healthy individuals that was characterised by rapid shallow breathing, existence of end-expiratory chest wall dynamic hyperinflation, and thoraco-abdominal asynchrony between the rib cage and abdominal chest compartments.…”