Biometric approximation of diaphragmatic contractility during sustained hyperpnea

Abstract Imposing load on respiratory muscles results in a loss of diaphragmatic contractility that develops early, is independent of task failure, and levels off following the initial decrease. This study assessed the progression of diaphragmatic contractility during sustained normocapnic hyperpnea...

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Bibliographic Details
Published in:Respiratory physiology & neurobiology 2011-05, Vol.176 (3), p.90-97
Main Authors: Kabitz, Hans-Joachim, Walker, David Johannes, Schwoerer, Anja, Schlager, Daniel, Walterspacher, Stephan, Storre, Jan Hendrik, Roecker, Kai, Windisch, Wolfram, Vergès, Samuel, Spengler, Christina M
Format: Article
Language:English
Subjects:
Adult
Biological and medical sciences
Biometry - methods
Diaphragm - physiology
Diaphragmatic fatigue
Fundamental and applied biological sciences. Psychology
Humans
Hyperventilation - physiopathology
Male
Medical Education
Muscle Contraction - physiology
Muscle Fatigue - physiology
Oxygen Consumption - physiology
Pulmonary/Respiratory
Respiratory Mechanics - physiology
Respiratory muscle
Time Factors
Twitch transdiaphragmatic pressure
Vertebrates: respiratory system
Young Adult
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Summary:Abstract Imposing load on respiratory muscles results in a loss of diaphragmatic contractility that develops early, is independent of task failure, and levels off following the initial decrease. This study assessed the progression of diaphragmatic contractility during sustained normocapnic hyperpnea and applied a biometric approximation (hypothesis: non-linear decay). Ten healthy subjects performed three consecutive hyperpnea bouts (I:6 min warm up/II:9 min/III:task failure 28.6 ± 11.5 min; mean ± SD) at maximal voluntary ventilation fractions (I:30–60%/II:70%/III:70%), followed by recovery periods (I:18 min/II:6 min/III:30 min). Twitch transdiaphragmatic pressure (TwPdi) was assessed throughout the protocol. Bouts II and III induced diaphragmatic fatigue (TwPdi baseline vs. Recovery −19 ± 17% and −30 ± 16%, both p < 0.05 RM-ANOVA) while bout I did not. During sustained hyperpnea (II/III), TwPdi followed an exponential decay ( r2 = 0.91). The reduction in diaphragmatic contractility closely follows a non-linear function with an early loss in diaphragmatic contractility during sustained hyperpnea, levels off thereafter, and is independent of task failure. Thus, reasons other than diaphragmatic fatigue are likely to be responsible for task failure during sustained hyperpnea.
ISSN:1569-9048
1878-1519
DOI:10.1016/j.resp.2011.01.011