Voluntary activation of the human diaphragm in health and disease.
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 and 2) 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.
Sinderby
C
C
Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, Montreal, Quebec H3C 3J7, Canada H3A 2B2.
Beck
J
J
Spahija
J
J
Weinberg
J
J
Grassino
A
A
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003964:Diaphragm / Q000294:innervation / Q000502:physiology* / Q000503:physiopathology; D004576:Electromyography; D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D011051:Poliomyelitis / Q000503:physiopathology; D015656:Respiratory Mechanics / Q000502:physiology; D014109:Total Lung Capacity / Q000502:physiology