RESUMO
Objective:To investigate the protective effect of external diaphragm pacing on the prevention of ventilator-induced diaphragm dysfunction (VIDD) in rabbits and its mechanism.Methods:Eighty-five New Zealand white rabbits were randomly (random number) divided into the blank control group (BC, n=5), spontaneous breathing group (SB, n=20), volume control ventilation group (VC, n=20), external diaphragm pacing group (EDP, n=20), external diaphragm pacing and volume control ventilation group (EDP+ VC, n=20). After successful modeling, the rabbits in each group were treated accordingly except for the BC group. Rabbitss in the BC group were not mechanically ventilated, and the diaphragm was removed immediately after anesthetizing. Whole diaphragms of 5 rabbits per time point per other group were also collected after anesthesia at post treatment hour (PTH) 6 and on post treatment day (PTD) 1, 3, and 7. Diaphragm weight/body weight and diaphragm isometric contractile force of each group were measured. The pathological changes of diaphragmatic tissues were observed by HE staining. The protein expressions of Cyt c, RyR1, caspase-3, and p-mTORC1 were measured by Western blot. Repeated measures analysis of variance was used for the comparison between multiple groups of variables at different time points, and LSD- t test was used for the further comparison between two groups at the same time point, a P<0.05 was considered statistically significant. Results:Compared with the BC group, the VC group showed diaphragmatic pathological changes conformed to VIDD: DW/BW was decreased obviously; HE staining revealed obvious changes in diaphragmatic tissue; Diaphragmatic contractility was also significantly decreased; The expression of Cyt c and caspase-3 were increased while the expression of RyR1 and p-mTORC1 were decreased gradually with the extension of treatment time ( P<0.05). Compared the EDP+VC group with the VC group, with the extension of treatment time, DW, DW/BW, pathological damages and diaphragmatic contractility were improved [PTD 1: (0.80±0.05)kg vs (0.56±0.04) kg, PTD 3: (1.06±0.05) kg vs (0.47±0.03) kg, PTD 7: (1.24±0.10) kg vs (0.39±0.07) kg, all P<0.05; PTD 1: (2.05±0.54) vs (1.86±0.72), PTD 3: (2.19±0.61) vs (1.74±0.40), PTD 7: (2.46±0.62) vs (1.53±0.85), all P<0.05; PTD 1: (2.39±0.42) N/cm 2vs (1.91±0.25) N/cm 2, PTD 3: (2.57±0.62) N/cm 2vs (1.72±0.50) N/cm 2, PTD 7: (2.77±0.55) N/cm 2vs (1.54±0.33) N/cm 2, all P<0.05]. The expression of Cyt c and caspase-3 were decreased while the expression of RyR1 and p-mTORC1 were increased gradually in the EDP+VC group ( P<0.05). Conclusions:External diaphragm pacer plays a protective role in ventilator-induced diaphragm dysfunction, which can inhibit mitochondrial damage, reduce oxidative damage, and mitigate diaphragmatic atrophy and injury.