Abstract
Studies on respiratory muscle fatigue have focused on the diaphragm (DIA). We have found, however, that maximal static inspiratory pleural pressure (Pi max) is limited by the strength of the inspiratory muscles of the rib cage (RC). Failure to maintain Pi max during inspiratory endurance tasks might therefore result from fatigue of the RC muscles rather than DIA. To test this hypothesis, 5 trained subjects repeated maximal inspiratory efforts (duty cycle, 0.5) until Pi max could not be maintained. Subjects performed such efforts with a minimum of abdominal muscle recruitment. Before and after inspiratory efforts, DIA muscle strength was evaluated by measuring the transdiaphragmatic pressure generated during maximal expulsive efforts with an open glottis (Pdi max). (During expulsive efforts the DIA is maximally activated; thus, the Pdi obtained is a true index of DIA strength). Results (x±SD, *p<.01, paired t):
We conclude that (1) Pi max is not limited by DIA strength, and (2) because DIA strength was unchanged, failure to maintain Pi max in these subjects appeared to be due to fatigue of the inspiratory muscles of the RC. RC muscle fatigue may be important in the pathogenesis of respiratory muscle failure.
Supported by HL 07633.
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Hershenson, M., Kikuchl, Y., Wohl, M. et al. FATIGUE OF THE INSPIRATORY MUSCLES OF THE RIB CAGE IN HUMANS. Pediatr Res 21 (Suppl 4), 200 (1987). https://doi.org/10.1203/00006450-198704010-00204
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DOI: https://doi.org/10.1203/00006450-198704010-00204