Voluntary activation of the human diaphragm in health and disease
- 1 December 1998
- journal article
- research article
- Published by American Physiological Society in Journal of Applied Physiology
- Vol. 85 (6), 2146-2158
- https://doi.org/10.1152/jappl.1998.85.6.2146
Abstract
Intersubject comparison of the crural diaphragm electromyogram, as measured by an esophageal electrode, requires a reliable means for normalizing the signal. The present study set out 1) to evaluate which voluntary respiratory maneuvers provide high and reproducible diaphragm electromyogram root-mean-square (RMS) values and2) to determine the relative diaphragm activation and mechanical and ventilatory outputs during breathing at rest in healthy subjects (n = 5), in patients with severe chronic obstructive pulmonary disease (COPD,n = 5), and in restrictive patients with prior polio infection (PPI, n = 6). In all groups, mean voluntary maximal RMS values were higher during inspiration to total lung capacity than during sniff inhalation through the nose (P = 0.035, ANOVA). The RMS (percentage of voluntary maximal RMS) during quiet breathing was 8% in healthy subjects, 43% in COPD patients, and 45% in PPI patients. Despite the large difference in relative RMS (P = 0.012), there were no differences in mean transdiaphragmatic pressure (P= 0.977) and tidal volumes (P = 0.426). We conclude that voluntary maximal RMS is reliably obtained during an inspiration to total lung capacity but a sniff inhalation could be a useful complementary maneuver. Severe COPD and PPI patients breathing at rest are characterized by increased diaphragm activation with no change in diaphragm pressure generation.Keywords
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