Short-Duration Mechanical Ventilation Enhances Diaphragmatic Fatigue Resistance but Impairs Force Production

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Andrew Shanely Ph.D, Associate Professor (Creator)
Appalachian State University (ASU )
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Abstract: Study objectives: Mechanical ventilation (MV) is a life-support measure for patients who cannot maintain adequate alveolar ventilation. Following prolonged MV, difficulty in weaning patients from the ventilator canoccur, and it has been postulated that difficult weaning is linked to respiratory muscle dysfunction. We tested thehypothesis that 18 h of controlled MV will diminish diaphragmatic maximal tetanic specific tension (force percross-sectional area of muscle) without impairing diaphragmatic fatigue resistance.Design: To test this postulate, adult Sprague-Dawley rats were randomly classified into one of two experimentalgroups: (1) control group (n = 8), and (2) 18-h MV group (n = 6). MV-treated animals were anesthetized,tracheostomized, and received room air ventilation. Animals in the control group were acutely anesthetized butdid not receive MV. Muscle strips from the mid-costal diaphragm were removed from both experimental groups,and contractile properties were studied in vitro to determine the effects of MV on diaphragmatic endurance andmaximal force production. Diaphragmatic endurance was investigated by measuring tension development duringrepeated contractions throughout a 30-min fatigue protocol.Results: MV resulted in a reduction (p 0.05) in diaphragmatic maximal specific tension (control group, 26.8 ± 0.2Newtons/cm2 vs MV group, 21.3 ± 0.6 Newtons/cm2). Compared to the control group, diaphragms from MVtreatedanimals maintained higher (p 0.05) percentages of the initial force production throughout the fatigueprotocol. The observed improvement in fatigue resistance was associated with an increase in diaphragmaticoxidative and antioxidant capacity as evidenced by increases (p 0.05) in both citrate synthase and superoxidedismutase activities. However, by comparison to the control group, diaphragms from MV-treated animalsgenerated less (p 0.05) absolute specific force throughout the fatigue protocol.Conclusions: These data indicate that 18 h of MV enhances diaphragmatic fatigue resistance but impairsdiaphragmatic specific tension.

Additional Information

R. Andrew Shanely, Jeff S. Coombes, A. Murat Zergeroglu, Alistair I. Webb, and Scott K. Powers (2003) "Short-Duration Mechanical Ventilation Enhances Diaphragmatic Fatigue Resistance but Impairs Force Production" Chest 123:195-201 Version of Record available @ (doi:10.1378/chest.123.1.195)
Language: English
Date: 2003
fiber-type, muscular-endurance, respiratory-muscles

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