Objective  To investigate the effect of mild hypothermia on diaphragmatic function and its underlying mechanisms in a murine model of post-cardiopulmonary resuscitation.  Method  Forty male Wistar rats were randomly assigned into one of five groups: a sham control group (Sham, n=6), a normothermia group (NT, n=10), a normothermia resuscitated group (NTR, n=10), a mild hypo-thermia group (MT, n=10), and a mild hypothermia resuscitated group (MTR, n=10). The body temper-ature of rats in NTR and MTR groups were maintained at (37±0.5°C) and (33±0.5°C) after cardiopulmo-nary resuscitation, respectively and the rats were mechanically ventilated for 12 hours. The body tem-perature of rats in NT and MT groups were maintained at 37±0.5°C and (33±0.5°C) after sham surgery and the rats were kept on mechanical ventilation for 12 h. The body temperatures of rats in Sham group were maintained at 37±0.5°C after sham surgery and the rats breathed spontaneously for 12 h. At the end of experiments, diaphragmatic contractile properties and cross-sectional area (cross-sectional area, CSA), levels of malondialdehyde, TNF-α and IL-6 in the diaphragm were measured. Morphological change of the diaphragm was also observed by routine staining.

Result  Diaphragmatic contractile properties and CSAs were decreased in all the interventional groups in comparison with the Sham group (P<0.05). Compared with MT group, diaphragmatic contractile properties and CSAs were also significantly decreased, otherwise, levels of MDA, TNF-α and IL-6 were increased in the NT, NTR and MTR group (P<0.05). Compared with NTR group, diaphragmatic contractile properties and CSAs were significantly increased, whereas levels of MDA, TNF-α and IL-6 were significantly decreased in the MTR group (P<0.05).

Conclusion  Mild hypothermia alleviates the reduction of diaphragmatic contractile properties and fiber size after cardiopulmonary resuscitation, and these beneficial effects potentially associated with inflammatory response inhibition and oxidative stress amelioration in the diaphragm.

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