HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:
Guest Access | Sign In via User Name/Password

This Article Full Text Free Full Text (PDF) Free Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by Shanely, R. A. Articles by Powers, S. K. Search for Related Content PubMed PubMed Citation Articles by Shanely, R. A. Articles by Powers, S. K.

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

^* From the Departments of Exercise and Sport Sciences, Center for Exercise Science (Mr. Shanely, and Drs. Coombes, Zergeroglu, and Powers), Physiologic Sciences (Dr. Webb), Physiology (Dr. Powers), University of Florida, Gainesville, FL; and Faculty of Medicine, Department of Sports Medicine (Dr. Zergeroglu), Ankara University, Ankara, Turkey. This work was supported by grants from the American Lung Association-Florida and the National Institutes of Health (R01 HL62361) awarded to Dr. Powers.

Correspondence to: Scott K. Powers, PhD, EdD, Center for Exercise Science, University of Florida, Rm 25 FLG, Gainesville, FL, 32601; e-mail:spowers{at}hhp.ufl.edu

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 can occur, and it has been postulated that difficult weaning is linked to respiratory muscle dysfunction. We tested the hypothesis that 18 h of controlled MV will diminish diaphragmatic maximal tetanic specific tension (force per cross-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 experimental groups: (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 but did 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 and maximal force production. Diaphragmatic endurance was investigated by measuring tension development during repeated 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 ± 0.2 Newtons/cm² vs MV group, 21.3 ± 0.6 Newtons/cm²). Compared to the control group, diaphragms from MV-treated animals maintained higher (p < 0.05) percentages of the initial force production throughout the fatigue protocol. The observed improvement in fatigue resistance was associated with an increase in diaphragmatic oxidative and antioxidant capacity as evidenced by increases (p < 0.05) in both citrate synthase and superoxide dismutase activities. However, by comparison to the control group, diaphragms from MV-treated animals generated 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 impairs diaphragmatic specific tension.

Key Words: fiber type • muscular endurance • respiratory muscles

This article has been cited by other articles:

				J. D. Pierce, C. Goodyear-Bruch, S. Hall, and R. L. Clancy Effect of dopamine on rat diaphragm apoptosis and muscle performance Exp Physiol, July 1, 2006; 91(4): 731 - 740. [Abstract] [Full Text] [PDF]

				K. C. DeRuisseau, R. A. Shanely, N. Akunuri, M. T. Hamilton, D. Van Gammeren, A. M. Zergeroglu, M. McKenzie, and S. K. Powers Diaphragm Unloading via Controlled Mechanical Ventilation Alters the Gene Expression Profile Am. J. Respir. Crit. Care Med., November 15, 2005; 172(10): 1267 - 1275. [Abstract] [Full Text] [PDF]

				A. T. Chang, R. J. Boots, M. G. Brown, J. Paratz, and P. W. Hodges Reduced Inspiratory Muscle Endurance Following Successful Weaning From Prolonged Mechanical Ventilation Chest, August 1, 2005; 128(2): 553 - 559. [Abstract] [Full Text] [PDF]

				K. C. DeRuisseau, A. N. Kavazis, M. A. Deering, D. J. Falk, D. Van Gammeren, T. Yimlamai, G. A. Ordway, and S. K. Powers Mechanical ventilation induces alterations of the ubiquitin-proteasome pathway in the diaphragm J Appl Physiol, April 1, 2005; 98(4): 1314 - 1321. [Abstract] [Full Text] [PDF]

				J. L. Betters, D. S. Criswell, R. A. Shanely, D. Van Gammeren, D. Falk, K. C. DeRuisseau, M. Deering, T. Yimlamai, and S. K. Powers Trolox Attenuates Mechanical Ventilation-induced Diaphragmatic Dysfunction and Proteolysis Am. J. Respir. Crit. Care Med., December 1, 2004; 170(11): 1179 - 1184. [Abstract] [Full Text] [PDF]

				T. Vassilakopoulos and B. J. Petrof Ventilator-induced Diaphragmatic Dysfunction Am. J. Respir. Crit. Care Med., February 1, 2004; 169(3): 336 - 341. [Full Text] [PDF]

				M. A. Zergeroglu, M. J. McKenzie, R. A. Shanely, D. Van Gammeren, K. C. DeRuisseau, and S. K. Powers Mechanical ventilation-induced oxidative stress in the diaphragm J Appl Physiol, September 1, 2003; 95(3): 1116 - 1124. [Abstract] [Full Text] [PDF]

				G. Z. Racz, G. Gayan-Ramirez, D. Testelmans, P. Cadot, K. De Paepe, E. Zador, F. Wuytack, and M. Decramer Early Changes in Rat Diaphragm Biology with Mechanical Ventilation Am. J. Respir. Crit. Care Med., August 1, 2003; 168(3): 297 - 304. [Abstract] [Full Text] [PDF]