title: Assist-control mechanical ventilation attenuates ventilator-induced diaphragmatic dysfunction.
abstract: Controlled mechanical ventilation induced a profound diaphragm muscle dysfunction and atrophy. The effects of diaphragmatic contractions with assisted mechanical ventilation on diaphragmatic isometric, isotonic contractile properties, or the expression of muscle atrophy factor-box (MAF-box), the gene responsible for muscle atrophy, are unknown. We hypothesize that assisted mechanical ventilation will preserve diaphragmatic force and prevent overexpression of MAF-box. Studying sedated rabbits randomized equally into control animals, those with 3 days of assisted ventilation, and those with controlled ventilation, we assessed in vitro diaphragmatic isometric and isotonic contractile function. The concentrations of contractile proteins, myosin heavy chain isoform, and MAF-box mRNA were measured. Tetanic force decreased by 14% with assisted ventilation and 48% with controlled ventilation. Maximum shortening velocity tended to increase with controlled compared with assisted ventilation and control. Peak power output decreased 20% with assisted ventilation and 41% with controlled ventilation. Contractile proteins were unchanged with either modes of ventilation; myosin heavy chain 2X mRNA tended to increase and that of 2A to decrease with controlled ventilation. MAF-box gene was overexpressed with controlled ventilation. We conclude that preserving diaphragmatic contractions during mechanical ventilation attenuates the force loss induced by complete inactivity and maintains MAF-box gene expression in control.
authors.affiliation: Departmen of Medicine, VA Long Beach Healthcare System, 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: Vincent J
authors.initials: VJ
authors.lastname: Caiozzo
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D001696:Biomechanical Phenomena; D003964:Diaphragm / Q000737:chemistry / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000032:analysis; D009133:Muscular Atrophy / Q000209:etiology / Q000503:physiopathology; D009135:Muscular Diseases / Q000209:etiology* / Q000503:physiopathology; D011817:Rabbits; D012121:Respiration, Artificial / Q000009:adverse effects*; D044843:SKP Cullin F-Box Protein Ligases / Q000032:analysis; D024744:Skeletal Muscle Myosins / Q000032:analysis
chemical_list: D000199:Actins; D009124:Muscle Proteins; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; D024744:Skeletal Muscle Myosins