ObjectiveTo investigate the effect of different degrees of pressure of sustained inflation (SI) in patients with acute respiratory distress syndrome (ARDS) after lung recruitment as the result of different negative pressure for sputum aspiration.Methods A prospective single-blind randomized controlled trial was conducted. The factorial analysis of variance was adopted. 150 patients with ARDS admitted to the emergency intensive care unit (ICU) of Chongqing Three Gorges Central Hospital from January 2012 to December 2014 were enrolled, and they were randomly divided into S1, S2, S3 group, with 50 patients in each group, suction pressure varying from 150, 175, to 200 mmHg (1 mmHg = 0.133 kPa) was respectively used in each group. Then the patients of each group were randomly subdivided into five subgroups of P0, P1, P2, P3, P4, with 10 patients in each group, and 0, 30, 35, 40, and 45 cmH2O (1 cmH2O = 0.098 kPa) were used for control pulmonary inflation pressure, respectively. The respiratory mechanics and the hemodynamic parameters were recorded, and they were compared before and after the sputum aspiration as well as lung recruitment with sustained inflation.Results The lung recruitment volume (mL: 87.56±28.47 vs. 109.38±34.63, t = 3.573,P = 0.001) and lung static compliance [Cst ( mL/cmH2O): 27.69±13.25 vs. 35.87±17.47,t = 2.814,P = 0.004] after sputum aspiration in the 150 patients were significantly lower than those before the sputum aspiration, and peak airway pressure [PIP (cmH2O): 24.16±8.28 vs. 18.63±6.67,t = 2.957,P = 0.005], airway plateau pressure [Pplat (cmH2O): 21.28±9.14 vs. 17.47±7.26,t = 2.089,P = 0.032], and mean airway pressure [Pm (cmH2O): 13.26±4.65 vs. 10.41±3.54,t = 3.271,P = 0.001] were significantly higher than those before the treatment. There were no significant differences in the lung recruitment volume, Cst, PIP, Pplat and Pm between groups with different negative pressure for sputum aspiration (F value was 0.809, 0.986, 1.121, 0.910, 1.043, andP value was 0.452, 0.381, 0.335, 0.410, 0.361), but statistical significance was found among different groups of different lung recruitment pressures (F value was 3.581, 5.028, 3.064, 3.036, 4.050, andP value was 0.013, 0.002, 0.026, 0.027, 0.007). There was no interaction between the two factors. After pairwise comparison, under the same negative pressure for sputum aspiration, lung recruitment volume and Cst in different lung recruitment pressures subgroups (P1, P2, P3, P4) were significantly higher than those of P0 subgroup, and PIP, Pplat, and Pm were significantly lower than those of P0 subgroup. There was no significant difference among P1, P2, P3 and P4 groups. There were no significant differences in mean arterial pressure (MAP) and pulmonary arterial pressure (PAP) among different groups with negative pressures for sputum aspiration and different lung recruitment pressures (negative pressure for sputum aspiration:F = 0.586,P = 0.561,F= 1.373,P = 0.264; lung recruitment pressure:F = 1.313,P = 0.280,F= 1.621,P = 0.186), there was no interaction between the two factors (F = 0.936,P = 0.497,F = 1.391,P = 0.227). The difference of heart rate (HR) in different negative pressure for sputum aspiration groups was not significant (F = 1.144,P = 0.328), and there were significant differences in different lung recruitment pressure groups (F = 3.297,P = 0.019), there was no interaction between the two factors (F = 1.277, P = 0.280). After pairwise comparison, under the same negative pressure for sputum aspiration, HR in P3 and P4 subgroups was significantly higher than that in P0, P1, and P2 subgroups (allP< 0.05).Conclusion 30 cmH2O and 35 cmH2O were the suitable pressure for SI in ARDS patients, and they were not affected by different negative pressure for sputum aspiration.%目的：探讨不同压力的控制性肺膨胀（SI）对急性呼吸窘迫综合征（ARDS）患者不同负压吸痰后肺复张的影响。方法前瞻性单盲随机对照研究设计，采用析因方差分析法，选择2012年1月至2014年12月重庆三峡中心医院急救重症加强治疗病房（ICU）收治的ARDS患者150例，按随机数字表法将其分为S1、S2、S3组，每组50例，分别应用150、175、200 mmHg（1 mmHg＝0.133 kPa）负压吸痰；然后每组再随机分为P0、P1、P2、P3、P4亚组，每组10例，分别采用0、30、35、40、45 cmH2O（1 cmH2O＝0.098 kPa）复张压力进行SI。记录并比较吸痰前后以及进行肺复张后患者的呼吸力学指标及血流动力学指标。结果150例患者吸痰后肺复张容积（mL：87.56±28.47比109.38±34.63，t＝3.573，P＝0.001）和肺静态顺应性〔Cst（mL/cmH2O）：27.69±13.25比35.87±17.47，t＝2.814，P＝0.004〕较吸痰前显著降低，气道峰压〔PIP（cmH2O）：24.16±8.28比18.63±6.67，t＝2.957，P＝0.005〕、气道平台压〔Pplat（cmH2O）：21.28±9.14比17.47±7.26，t＝2.089， P＝0.032〕、气道平均压〔Pm（cmH2O）：13.26±4.65比10.41±3.54，t＝3.271，P＝0.001〕较吸痰前明显升高。肺复张容积、Cst、PIP、Pplat、Pm在不同吸痰负压间差异无统计学意义（F值分别为0.809、0.986、1.121、0.910、1.043，P值分别为0.452、0.381、0.335、0.410、0.361），在不同肺复张压力间差异有统计学意义（F值分别为3.581、5.028、3.064、3.036、4.050，P值分别为0.013、0.002、0.026、0.027、0.007），且两因素不存在交互作用。两两比较后发现，在相同吸痰负压条件下，不同复张压力亚组（P1、P2、P3、P4）肺复张容积、Cst均明显高于其P0亚组，PIP、Pplat、Pm均明显低于P0亚组；而P1、P2、P3、P4亚组间差异无统计学意义。平均动脉压（MAP）、肺动脉压（PAP）在不同吸痰负压及不同肺复张压力间差异均无统计学意义（吸痰负压：F＝0.586、P＝0.561， F＝1.373、P＝0.264；肺复张压：F＝1.313、P＝0.280，F＝1.621、P＝0.186），而且两因素间不存在交互作用（F＝0.936、P＝0.497，F＝1.391、P＝0.227）；心率（HR）在不同吸痰负压间差异无统计学意义（F＝1.144，P＝0.328），在不同肺复张压间差异有统计学意义（F＝3.297，P＝0.019），且两因素间不存在交互作用（F＝1.277， P＝0.280）。两两比较发现，在相同吸痰负压条件下，P3、P4亚组HR明显高于P0、P1、P2亚组（均P＜0.05）。结论30 cmH2O和35 cmH2O为实施SI治疗ARDS患者的适合压力，且不受吸痰负压的影响。
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