title: Interactive effects of corticosteroid and mechanical ventilation on diaphragm muscle function.
abstract: Information on the interactive effects of methylprednisolone, controlled mechanical ventilation (CMV), and assisted mechanical ventilation (AMV) on diaphragm function is sparse. Sedated rabbits received 2 days of CMV, AMV, and spontaneous breathing (SB), with either methylprednisolone (MP; 60 mg/kg/day intravenously) or saline. There was also a control group. In vitro diaphragm force, myofibril ultrastructure, αII-spectrin proteins, insulin-like growth factor-1 (IGF-1), and muscle atrophy F-box (MAF-box) mRNA were measured. Maximal tetanic tension (P(o)) decreased significantly with CMV. Combined MP plus CMV did not decrease P(o) further. With AMV, P(o) was similar to SB and controls. Combined MP plus AMV or MP plus SB decreased P(o) substantially. Combined MP plus CMV, MP plus AMV, or MP plus SB induced myofibrillar disruption that correlated with the reduced P(o). αII-spectrin increased, IGF-1 decreased, and MAF-box mRNA increased in both the CMV group and MP plus CMV group. Short-term, high-dose MP had no additive effects on CMV-induced diaphragm dysfunction. Combined MP plus AMV impaired diaphragm function, but AMV alone did not. We found that acute, high-dose MP produces diaphragm dysfunction depending on the mode of mechanical ventilation.
authors.affiliation: Department of Medicine, VA Long Beach Healthcare System, 5901 East 7th Street, Long Beach, California 90822, USA. csassoon@uci.edu
authors.forename: Catherine S H
authors.initials: CS
authors.lastname: Sassoon
authors.forename: Ercheng
authors.initials: E
authors.lastname: Zhu
authors.forename: Liwei
authors.initials: L
authors.lastname: Fang
authors.forename: Kannan
authors.initials: K
authors.lastname: Ramar
authors.forename: Guang-Yu
authors.initials: GY
authors.lastname: Jiao
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Caiozzo
mesh_terms: D000305:Adrenal Cortex Hormones / Q000633:toxicity*; D000818:Animals; D003964:Diaphragm / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018908:Muscle Weakness / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D011817:Rabbits; D012121:Respiration, Artificial / Q000009:adverse effects*; D012133:Respiratory Paralysis / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology
chemical_list: D000305:Adrenal Cortex Hormones