Voluntary activation of the human diaphragm in health and disease

J Appl Physiol (1985). 1998 Dec;85(6):2146-58. doi: 10.1152/jappl.1998.85.6.2146.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Case-Control Studies
  • Diaphragm / innervation
  • Diaphragm / physiology*
  • Diaphragm / physiopathology
  • Electromyography
  • Female
  • Humans
  • Lung Diseases, Obstructive / physiopathology
  • Male
  • Maximal Voluntary Ventilation / physiology
  • Middle Aged
  • Motor Neurons / physiology
  • Muscle Contraction / physiology
  • Poliomyelitis / physiopathology
  • Respiratory Mechanics / physiology
  • Total Lung Capacity / physiology