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Respiratory muscle function in the critically ill 

Respiratory muscle function in the critically ill
Chapter:
Respiratory muscle function in the critically ill
Author(s):

Theodoros Vassilakopoulos

and Charis Roussos

DOI:
10.1093/med/9780199600830.003.0077
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date: 27 February 2020

The inspiratory muscles are the diaphragm, external intercostals and parasternal internal intercostal muscles. The internal intercostals and abdominal muscles are expiratory. The ability of a subject to take one breath depends on the balance between the load faced by the inspiratory muscles and their neuromuscular competence. The ability of a subject to sustain the respiratory load over time (endurance) depends on the balance between energy supplied to the inspiratory muscles and their energy demands. Hyperinflation puts the diaphragm at a great mechanical disadvantage, decreasing its force-generating capacity. In response to acute increases in load the inspiratory muscles become fatigued and inflammed. In response to reduction in load by the use of mechanical ventilation they develop atrophy and dysfunction. Global respiratory muscle function can be tested using maximum static inspiratory and expiratory mouth pressures, and sniff pressure. Diaphragm function can be tested by measuring the transdiaphragmatic and twitch pressures developed upon electrical or magnetic stimulation of the phrenic nerve.

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