Intermittent spontaneous breathing protects the rat diaphragm from mechanical ventilation effects.
OBJECTIVE
Short-term mechanical ventilation has been proven to reduce diaphragm force and fiber dimensions. We hypothesized that intermittent spontaneous breathing during the course of mechanical ventilation would minimize the effects of mechanical ventilation on diaphragm force and expression levels of transcription factors (MyoD and myogenin).


METHODS
Randomized, controlled experiment.


METHODS
Animal basic science laboratory.


METHODS
Male Wistar rats, weighing 350-500 g.


METHODS
Anesthetized and tracheotomized rats were submitted to either 24 hrs of spontaneous breathing (SB, n = 5), 24 hrs of continuous controlled mechanical ventilation (CMV, n = 7), or controlled mechanical ventilation with intermittent spontaneous breathing: 60 mins every 5 hrs of mechanical ventilation repeated four times (ISB60, n = 8) or 5 mins every 5 hrs 55 mins of mechanical ventilation repeated four times (SB5, n = 9). They were compared with control animals free from intervention (C, n = 5).


RESULTS
The profile of the diaphragm force-frequency curve of the controls and SB group was significantly different from that of the ISB and CMV groups; especially, the mean asymptotic force was less in the ISB and CMV compared with controls and SB. CMV resulted in a significant decrease in the diaphragm type I (-26%, p < .05 vs. C) and type IIx/b (-39%, p < .005 vs. C and SB) cross-sectional area, whereas this was not observed in the ISB groups. Diaphragm MyoD protein expression was significantly decreased after ISB60 (-35%, p < .0001 vs. C and SB) and even more after CMV (-73%, p < .0001 vs. others). The same pattern was observed with myogenin protein levels. Positive relationships between diaphragm MyoD and myogenin protein levels and diaphragm force were observed.


CONCLUSIONS
The data demonstrated that intermittent spontaneous breathing during the course of mechanical ventilation may minimize the deleterious effect of controlled mechanical ventilation on diaphragm force, fiber dimensions, and expression of transcription factors.
Gayan-Ramirez
Ghislaine
G
Respiratory Muscle Research Unit, Laboratory of Pneumology and Respiratory Division, Katholieke Universiteit Leuven, Leuven Belgium.
Testelmans
Dries
D
Maes
Karen
K
Rácz
Gábor Z
GZ
Cadot
Pascal
P
Zádor
Ernö
E
Wuytack
Frank
F
Decramer
Marc
M
D000818:Animals; D003964:Diaphragm / Q000473:pathology / Q000503:physiopathology*; D015870:Gene Expression / Q000502:physiology; D066298:In Vitro Techniques; D007384:Intermittent Positive-Pressure Breathing; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000473:pathology / Q000502:physiology; D017570:MyoD Protein / Q000235:genetics*; D018008:Myogenin / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar; D012121:Respiration, Artificial; D012132:Respiratory Muscles / Q000473:pathology / Q000502:physiology
D017570:MyoD Protein; C503803:Myog protein, rat; D018008:Myogenin