Time course of diaphragm function recovery after mechanical ventilation in an animal model

Abstract

Several studies have shown that controlled mechanical ventilation (CMV) results in rapid and severe diaphragmatic dysfunction. The recovery response of the diaphragm to normal function after mechanical ventilation is not known, although these data may have an impact on weaning from the ventilator. We examined the time‐course of diaphragm function recovery in an animal model of CMV.Anesthetized rats were submitted to 24h of CMV followed by either 1h, 2h or 3h of spontaneous breathing (SB) or to 24–27h of CMV.There were no differences in blood pressure, blood gases, body weight or muscle weights between the four groups. The in vitro diaphragm force‐frequency curve was similar in the CMV group and in the CMV groups followed by 1h or 2h of SB. Three hours of SB after CMV resulted in a significant improvement of the diaphragm force compared to all other groups. Diaphragm cross sectional area (CSA) of the type I and type IIa fibers was similar in all groups, while the CSA of the type IIx/b fibers was significant increased in the CMV + 3h SB group (+27%, p<0.05) compared to CMV. No differences were observed in the activity of calpain and caspase‐3 between the four groups.These data show that reloading the diaphragm for 3h after CMV results in a significant improvement of the diaphragm force together with an increase in the CSA of the type IIx/b muscle fibers.Supported by FWO‐Flanders G.0893.11 and AstraZeneca Pharmaceuticals