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Whether mechanical ventilation causes disuse atrophy in humans has been unknown. To explore this issue, these authors compared biopsy specimens from diaphragms of 14 brain-dead organ donors (case patients; on ventilation for 18 to 69 hours) with biopsy specimens from diaphragms of eight patients undergoing surgery for benign conditions or stage 1 lung cancer (controls; on ventilation for 2 to 3 hours).
Compared with controls, the cases had significant diaphragm muscle-fiber atrophy (57% of slow-twitch fibers and 53% of fast-twitch fibers). The authors estimated that this degree of atrophy would produce a 50% loss of muscle strength. In addition, biochemical and gene-expression studies showed evidence that muscle inactivity increased cytosoli…