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Time course of diaphragm function recovery after mechanical ventilation in an animal model
Debby Thomas, Karen Maes, Anouk Agten, Marc Decramer, Ghislaine Gayan-Ramirez.
Laboratory of Pneumology, KU Leuven, Leuven, Belgium
Rationale: Several studies have previously shown that controlled mechanical ventilation (CMV)
results in rapid and severe diaphragmatic dysfunction. On the other hand, the recovery response of
the diaphragm to normal function after mechanical ventilation is not known, although these data
may have an impact on weaning from the ventilator. Therefore we examined the time-course of
diaphragm function recovery in an animal model of CMV.
Methods: Rats were anesthetized and submitted to 24-27h of CMV or to 24h of CMV followed by
either 1h, 2h or 3h of spontaneous breathing (CMV + 1h SB, CMV + 2h SB, and CMV + 3h SB,
respectively).
Results: There were no differences in blood pressure, blood gases, body weight or muscle weights
between the four groups. The in vitro diaphragm force-frequency curve was similar in the CMV, CMV
+ 1h SB and CMV + 2h SB groups. Three hours of SB after CMV resulted in a significant improvement
of diaphragm force compared to the other groups (eg, maximal tetanic force: +29% vs CMV, p<0.01).
Diaphragm cross sectional area (CSA) of the type I and type IIa fibers was similar in all groups, while
the CSA of the type IIx/b fibers was significant increased in the CMV + 3h SB group (+27% vs CMV,
p<0.05). No differences were observed in the activity of the proteolytic enzymes calpain and caspase3. Protein oxidation was similar in the diaphragm of all groups.
Conclusions: These data show that, in rats, reloading the diaphragm for 3h after CMV is sufficient to
result in a significant improvement of the diaphragm force together with an increase in the CSA of
the type IIx/b muscle fibers.
Funded by: FWO-Flanders G.0893.11 and AstraZeneca Pharmaceuticals
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