Mechanical ventilation results in diaphragmatic contractile dysfunction

Recent evidence suggests that prolonged mechanical ventilation (48-260 hours) results in a significant decrease in maximum diaphragmatic force generation in both rats and baboons. These experiments tested the hypothesis that relatively short duration (18 hours) CMV results in a significant depression of diaphragmatic maximal specific force production (specific Po). Adult (female) Sprague Dawley rats were randomly divided into one of two groups: 1) control (CON; n = 6); and 2) 18 hours of controlled mechanical ventilation (CMV; n = 6). Mechanically ventilated animals were anesthetized, intubated, and ventilated with room air. CMV animals were fed enterally with a gastric catheter and arterial blood pressure, pH, and blood gas homeostasis were maintained throughout the 18 hours of mechanical ventilation. Control animals were not anesthetized or mechanically ventilated during the experimental period. Diaphragmatic contractile properties were assessed in vitro at 37oC by analysis of force-frequency characteristics. Eighteen hours of CMV resulted in a significant reduction (