Chest Wall Motion after Thixotropy Conditioning of Inspiratory Muscles in Healthy Humans

Abstract

Abstract:Inspiratory muscle conditioning at a lower or higher lung volume based on the principles of muscle thixotropy causes acute changes in end-expiratory chest wall and lung volumes. The present study aimed to demonstrate the time course of effects of this conditioning on both end-expiratory chest wall volume and thoracoabdominal synchrony. We measured chest wall motion with respiratory induction plethysmography at 0.5, 1, 2, 3, and 6 min after conditioning at three different lung volumes in 15 healthy men. After conditioning at total lung capacity -20% inspiratory capacity, increases in end-expiratory chest wall volume were significant at 0.5, 1, and 2 min (P < 0.05), being most obvious at 0.5 min (∆0.24 ± 0.20 liter). After conditioning at residual volume, reductions in end-expiratory chest wall volume were significant at any time point (P < 0.05), being most obvious at 0.5 min (∆0.16 ± 0.08 liter). Conditioning at functional residual capacity had little effect on the volume. Spirometric inspiratory capacity at 6 min after conditioning at residual volume (2.68 ± 0.35 liter) was higher than the baseline value (2.53 ± 0.31 liter, P < 0.05). Reductions in the phase angle, quantified by the KonnoMead diagram, occurred after conditioning at residual volume at any time point (P < 0.05), being most obvious at 2 min (∆3.47 ± 3.02 degrees). In conclusion, there is a 6-min time course of changes in end-expiratory chest wall volume after conditioning. More synchronous motion between the rib cage and abdomen occurs after conditioning at residual volume.

Effect of thixotropy conditioning of inspiratory muscles on the chest wall response to CPAP

“…The decreases in end‐expiratory and end‐inspiratory Vcw after conditioning at RV 10 were shared by the rib cage and abdominal compartments, which is consistent with previous findings under resting conditions 9 . However, under CPAP, the rib cage deflation was clearly larger than the abdominal deflation.…”

“…After conditioning at FRC 10 , however, changes in end‐expiratory Vcw under CPAP were not significant. It has previously been shown that conditioning at FRC during resting breathing has little effect on end‐expiratory Vcw of the respiratory system 7–9 . These findings suggest that the relative length of inspiratory muscles at the time of conditioning is a factor that influences inspiratory muscle thixotropy.…”

“…Inspiratory muscle conditioning based on the principles of muscle thixotropy acutely alters the end‐expiratory position of the respiratory system during resting breathing 6–11 . Thixotropy conditioning of inspiratory muscles involves inspiratory muscle contraction at an inflated or deflated lung volume because inspiratory muscles shorten and lengthen with lung inflation and deflation, respectively 12–15 .…”

“…Thixotropy conditioning of inspiratory muscles involves inspiratory muscle contraction at an inflated or deflated lung volume because inspiratory muscles shorten and lengthen with lung inflation and deflation, respectively 12–15 . Conditioning performed below FRC, which corresponds to hold‐long conditioning of inspiratory muscles, is followed by decreases in end‐expiratory chest wall volume (Vcw); conditioning performed above FRC, which corresponds to hold‐short conditioning of inspiratory muscles, is followed by increases in end‐expiratory Vcw 7–9 . As conditioning may cause history‐dependent changes in the plastic properties of the lung and other structures in the chest wall, these changes might contribute to the thixotropic phenomena of respiration.…”

“…Hold‐long conditioning of inspiratory muscles decreases end‐expiratory Vcw during resting breathing 7–9 . Nevertheless, it is still uncertain whether this conditioning would decrease the level of inflation of the respiratory system.…”