大鼠获得性漏斗胸形成过程中膈肌收缩功能的测定

Measurements of diaphragm contractive function during acquired pectus excavatum formation in rats

目的 通过对大鼠膈肌收缩力的动态测定探讨获得性漏斗胸形成过程中膈肌收缩功能的变化.方法 4周龄SD大鼠120只,按数字随机法分为研究组和对照组各60只.研究组行胸骨旁切断第5～7对肋软骨观察漏斗胸形成,对照组不做处理.分别于术后3 d及1、2、4、8、12周取每组10只动物膈肌标本,经体外灌流膈肌条,测量其单收缩张力、最大强直收缩力并进行组间t检验,对不同频率刺激下膈肌张力的测定结果进行方差分析.结果 术后第1周呼吸频率较快并逐渐出现胸骨区域下陷,2周即形成典型的漏斗胸并逐渐加重,4周后畸形稳定.术后3 d及1、2、4、8、12周研究组膈肌单收缩张力分别为（211.42±0.81）g/cm2、（208.27±0.86）g/cm2、（199.79±1.81）g/cm2、（196.23±1.75）g/cm2、（194.99±3.28）g/cm2和（196.40±1.73）g/cm2,在对照组分别为（212.97±0.44）g/cm2、（213.47±0.79）g/cm2、（211.72±1.71）g/cm2、（212.79±1.38）g/cm2、（212.63±1.90）g/cm2和（213.64±0.77）g/cm2;测得膈肌最大强直收缩力分别为（887.97±3.40）g/cm2、（874.74±3.60）g/cm2、（839.12±7.62）g/cm2、（824.17±7.38）g/cm2、（818.95±13.79）g/cm2和（824.89±7.25）g/cm2,在对照组分别为（894.49±1.86）g/cm2、（896.58±3.38）g/cm2、（889.23±7.19）g/cm2、（893.72±5.81）g/cm2、（893.06±7.97）g/cm2和（897.30±3.23）g/cm2.研究组各时间点测得膈肌单收缩张力、最大强直收缩力值均低于对照组,尤以术后3 d到2周时的测得值下降最为明显,组间差异均有统计学意义（P〈0.01）.刺激频率从10 Hz增加到100 Hz,两组动物膈肌收缩张力均增加,但研究组各种刺激频率下各时间点的结果均低于对照组,且差异有统计学意义（P〈0.01）;测得值在组内比较,研究组各时间点间的差异有统计学意义,尤其是术后3 d、1周和2周三个时间点测得值间的差异（P〈0.05）;而对照组内各时间点测得值间比较,差异均无统计学意义（P〉0.05）.结论 获得性漏斗胸大鼠膈肌收缩储备能力低于正常水平,膈肌收缩力随着漏斗胸形成而下降,即使畸形稳定后膈肌收缩力仍不能恢复.

Objective To explore the change of diaphragmatic muscle function during the formation of acquired pectus excavatum （PE）through dynamic measurements of diaphragm contraction force.Methods A total of 1204-week-old Sprague-Dawley （SD）rats were divided randomly into experimental and control groups （n = 60 each）.The 5-7 th couples of rib cartilage were cut off parasternum for PE model in experimental group but no intervention in control.Diaphragmatic muscle was harvested at 3 d,1 w,2 w,4 w,8 w and 12 w in 10 of each group.Peak twitch tension and maximum tetanic tension at appropriate stimulus and diaphragmatic muscle tension under stimulations with different frequencies were measured and the data were analyzed with t test and variance analysis statistically.Results Fast respiratory rate was taken on in 1 w after operation and then sternal area began to cave in animals of experimental group and a typical PE appeared 2 w later,aggravated gradually and stablized after 4 w in all model rats.The values of peak twitch tension of diaphragm at 3 d,1 w,2 w,4 w,8 w and 12 w after operation were （211 .42 ± 0.81 ）g/cm2 ,（208.27 ± 0.86） g/cm2 ,（199.79± 1 .81 ）g/cm2 ,（196.23 ± 1 .75 ）g/cm2 ,（194.99 ± 3.28 ）g/cm2 and （196.40 ± 1 .73）g/cm2 in experimental group and （212.97±0.44）g/cm2 ,（213.47±0.79）g/cm2 ,（211 .72± 1 .71）g/cm2 ,（212.79±1 .38）g/cm2 ,（212.63 ±1 .90）g/cm2 and （213.64±0.77）g/cm2 in control respectively.The values of maximum tetanic tension of diaphragm were （887.97 ± 3.40 ）g/cm2 , （874.74±3.60）g/cm2 ,（839.12 ±7.62）g/cm2 ,（824.17 ±7.38）g/cm2 ,（818.95 ± 13.79）g/cm2 and （824.89 ± 7.25 ）g/cm2 in experimental group and （894.49 ± 1 .86 ）g/cm2 ,（896.58 ± 3.38 ） g/cm2 ,（889.23 ± 7.19）g/cm2 ,（893.72 ± 5.81 ）g/cm2 ,（893.06 ± 7.97 ）g/cm2 and （897.30 ± 3.23）g/cm2 in control group respectively.The values of peak twitch tension and maximum tetanic tension of diaphragm in experimental group were lower than those in control group at each detecting time point especially from 3 d to 2 w,the inter-group difference was statistically significant （P 〈0.01）.The values of diaphragmatic contractive tension increased with higher stimulus frequency from 10 to 100 Hz in all rats but it was lower in experimental group than that in control group with statistical significance （P 0.05）.Conclusions The contractile reserve capacity of diaphragmatic muscle in acquired PE rat is lower than normal. Diaphragmatic contractive force decreases during the process of PE formation and there is a lower level of deformity even if which is stable.