Rodrigues A C, Moreira L F, de Souza C L, Pettersen P C, Saldiva P H, Zin W A
Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Ilha do Fundö, Brazil.
Chest. 1993 Dec;104(6):1882-6. doi: 10.1378/chest.104.6.1882.
Nineteen rats were sedated, anesthetized, paralyzed, and mechanically ventilated. The respiratory, lung, and chest wall elastances (Est-rs, Est-L, Est-w); respiratory system, pulmonary, and chest wall total resistances (Rtot-rs, Rtot-L, Rtot-w); respiratory system, pulmonary, and chest wall initial resistances (Rinit-rs, Rinit-L, Rinit-w); and respiratory system, pulmonary, and chest wall difference resistances (Rdiff-rs, Rdiff-L, Rdiff-w) were determined before and after thoracotomy using the end-inflation occlusion method. Rinit reflects the Newtonian resistances and Rdiff represents the viscoelastic/inhomogeneous pressure dissipations in the system. Rtot = Rinit+Rdiff, ie, total resistance. The animals were submitted to either anterolateral thoracotomy (group A, n = 7), median sternotomy (group B, n = 6), or median sternotomy under PEEP while the lungs were exposed (group C, n = 6). In groups A and B, statistically significant increases in Rdiff-rs significantly augmented Rtot-rs. The former results were entirely secondary to significant increases in Rdiff-L, which naturally raised Rtot, L. Resistance was not altered in group C rats. Thus, anterolateral thoracotomy and median sternotomy increases Rtot-rs as a consequence of augmented Rdiff-L, but this finding could be prevented by the use of PEEP. Est-rs and Est-L increased in the three groups after surgery. Groups D and E were comprised of four animals each. Both underwent median sternotomy and in group E, PEEP was applied. Histopathologic examination of the lungs demonstrated a higher degree of lung collapse in group D.
19只大鼠被给予镇静、麻醉、肌松并进行机械通气。使用终末充气阻断法在开胸手术前后测定呼吸、肺和胸壁弹性（Est-rs、Est-L、Est-w）；呼吸系统、肺和胸壁总阻力（Rtot-rs、Rtot-L、Rtot-w）；呼吸系统、肺和胸壁初始阻力（Rinit-rs、Rinit-L、Rinit-w）；以及呼吸系统、肺和胸壁差异阻力（Rdiff-rs、Rdiff-L、Rdiff-w）。Rinit反映牛顿阻力，Rdiff代表系统中的粘弹性/非均匀压力耗散。Rtot = Rinit+Rdiff，即总阻力。将动物分为三组，分别接受前外侧开胸手术（A组，n = 7）、正中胸骨切开术（B组，n = 6）或在肺暴露时于呼气末正压（PEEP）下进行正中胸骨切开术（C组，n = 6）。在A组和B组中，Rdiff-rs的显著增加导致Rtot-rs显著增加。前者的结果完全是由于Rdiff-L的显著增加所致，这自然会使Rtot-L升高。C组大鼠的阻力未发生改变。因此，前外侧开胸手术和正中胸骨切开术会因Rdiff-L增加而导致Rtot-rs升高，但使用PEEP可预防这一发现。术后三组的Est-rs和Est-L均升高。D组和E组每组各有4只动物。两组均接受正中胸骨切开术，E组应用了PEEP。肺组织病理学检查显示D组肺萎陷程度更高。
