Magnetic twitch assessment of diaphragm and quadriceps weakness in critically ill mechanically ventilated patients

Gerald S. Supinski, Paul F. Netzel, Philip M. Westgate, Elizabeth A. Schroder, Lin Wang, Leigh Ann Callahan

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Critically ill mechanically ventilated (MV) patients develop significant muscle weakness, which has major clinical consequences. There remains uncertainty, however, regarding the severity of leg weakness, the precise relationship between muscle strength and thickness, and the risk factors for weakness in MV patients. We therefore measured both diaphragm (PdiTw) and quadriceps (QuadTw) strength in MV patients using magnetic stimulation and compared strength to muscle thickness. Both PdiTw and QuadTw were profoundly reduced for MV patients, with PdiTw 19 % of normal and QuadTw 6% of normal values. There was a poor correlation between strength and thickness for both muscles, with thickness often remaining in the normal range when strength was severely reduced. Regression analysis revealed reductions in PdiTw correlated with presence of infection (p = 0.006) and age (p = 0.007). QuadTw best correlated with duration of MV (p = 0.036). Limb muscles are profoundly weak in critically ill patients, with a severity that mirrors the level of weakness observed in the diaphragm.

Original languageEnglish
Article number103789
JournalRespiratory Physiology and Neurobiology
StatePublished - Jan 2022

Bibliographical note

Publisher Copyright:
© 2021 Elsevier B.V.


  • Diaphragm weakness
  • Intensive care unit myopathy
  • Magnetic stimulation
  • Quadriceps twitch force generation
  • Quadriceps weakness
  • Transdiaphragmatic pressure generation

ASJC Scopus subject areas

  • General Neuroscience
  • Physiology
  • Pulmonary and Respiratory Medicine


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