Effects of controlled mechanical ventilation on respiratory muscle contractile properties in rabbits

We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles. Experimental prospective study in a university laboratory. Nineteen rabbits were randomly allocated to two groups: control (n=10) or mec...

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Bibliographic Details
Published in:Intensive care medicine 2003, Vol.29 (1), p.103-110
Main Authors: CAPDEVILA, Xavier, LOPEZ, Sandrine, BERNARD, Nathalie, RABISCHONG, Emmanuel, RAMONATXO, Michèle, MARTINAZZO, Guilhem, PREFAUT, Christian
Format: Article
Language:English
Subjects:
Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy
Animals
Biological and medical sciences
Diaphragm - physiopathology
Diaphragm - ultrastructure
Emergency and intensive respiratory care
Intensive care medicine
Intercostal Muscles - physiopathology
Intercostal Muscles - ultrastructure
Medical sciences
Muscle Contraction
Muscle Fatigue - physiology
Muscle Fibers, Skeletal
Rabbits
Random Allocation
Respiration, Artificial - adverse effects
Statistics, Nonparametric
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Summary:We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles. Experimental prospective study in a university laboratory. Nineteen rabbits were randomly allocated to two groups: control (n=10) or mechanically ventilated (MV; n=9) for 51+/-3 h. Respiratory muscles contractile properties were analyzed before and after a fatigue protocol using in vivo isometric 1-s tetanic contraction characteristics in both muscles: peak tetanic force, contraction time, relaxation time, and total contraction time. Both muscle fiber type proportions, diameter, and cross-sectional areas were measured using ATPase staining. The MV rabbits showed significant weight loss in both muscles, accompanied by a reduced peak tetanic force (9.96+/-3.2 vs. 7.44+/-2.2 N for diaphragm of control and MV animals respectively), fatigue resistance index, and increased relaxation time (57.5+/-8.7 vs. 85.8+/-9.4 ms for diaphragm of control and MV animals) and contraction time. These impairments in the MV group worsened after the fatigue runs. Both muscle showed a significant atrophy of type IIa and IIb fibers but a stability in type I fibers cross-sectional area. Mechanical ventilation in rabbits produces alterations in contractile properties of the diaphragm and 5th external intercostal muscle, increases both muscles fatigue, and promotes atrophy of type II fibers.
ISSN:0342-4642
1432-1238
DOI:10.1007/s00134-002-1548-3