肺复张对肺内/外源性急性呼吸窘迫综合征模型犬呼吸生理和肺形态学影响的比较

Comparative study of recruitment maneuver guided by pressure-volume curve on respiratory physiology and lung morphology between acute respiratory distress syndrome of pulmonary and extrapulmonary origin in canine models

目的 探讨以压力-容积（P-V）曲线为导向的肺复张（RM）策略对肺内/外源性急性呼吸窘迫综合征（ARDSexp/ARDSp）模型犬呼吸生理和肺形态学的影响.方法 将24只健康杂种犬按随机数字表法均分为两组,分别以静脉注射油酸0.1 ml/kg复制ARDSexp模型,以气管内注入盐酸2 ml/kg复制ARDSp模型.每种模型再随机均分为肺保护通气策略（LPVS）组和LPVS＋RM组.LPVS组采用LPVS进行机械通气（MV）;LPVS＋RM组先进行以P-V曲线为导向的RM,RM采用压力控制通气（PCV）,压力上限为高位转折点（UIP）,呼气末正压（PEEP）为低位转折点（LLP）＋2 cm H2O（1 cm H2O=0.098 kPa）,维持60 s后再按LPVS进行MV.两组MV时间均为4 h.观察动物基础状态（成模前）及RM前后的氧合指数（PaO2/FiO2）、呼吸力学指标变化;采用低流速法记录准静态P-V曲线并计算UIP、LIP ;根据肺CT比较不同肺充气区容积占全肺容积的百分比.结果 成模前和RM前两组PaO2/FiO2及UIP、LIP比较差异均无统计学意义.RM后4 h,两种模型LPVS＋RM组PaO2/FiO2和肺顺应性（Crs）均较同模型LPVS组显著升高[ARDSexp模型PaO,/FiO2（mm Hg,1 mm Hg=0.133 kPa）：263.9±69.2比182.8±42.8,Crs（ml/cm H2O）：11.3±4.2比9.7±3.7;ARDSp模型PaO2/FiO2（mm Hg）：193.4±33.5比176.4±40.2,Crs（ml/cm H2O）：10.1±3.9比9.0±3.9,P＜0.05或P＜0.01],气道压力明显低于同模型LPVS组[ARDSexp模型吸气峰压（PIP,cm H2O）：24.1±7.4比30.2±8.5,气道平台压（Pplat,cm H2O）：19.1±7.3比25.6±7.7;ARDSp模型PIP（cm H2O）：26.6±8.4比29.6±10.3,Pplat（cm H2O）：21.9±7.3比25.1±8.4,P＜0.05或P＜0.01];且ARDSexp模型改善程度较ARDSp模型更为显著（P＜0.05或P＜0.01）.两种模型LPVS＋RM组肺组织闭合区和充气不足区所占比例均较同模型LPVS组明显减少,正常充气区所占比例明显增加[ARDSexp模型闭合区：（9.9±3.1）%比（16.3±5.2）%,充气不足区：（10.2±4.2）%比（23.4±6.7）%,正常充气区：（76.2±12.3）%比（57.5±10.1）%;ARDSp模型闭合区：（14.3±4.8）%比（1 8.2±5.1）%,充气不足区：（17.4±6.3）%比（24.1±5.9）%,正常充气区：（63.2±10.7）%比（54.6±11.3）%,P＜0.05或P＜0.01];且ARDSexp模型各充气区所占比例改善程度均明显优于ARDSp模型（均P＜0.05）.结论 对于不同原因ARDS,以P-V曲线为导向的RM均具有增加肺氧合、改善肺顺应性和肺组织通气的作用,且对ARDSexp的治疗效果明显优于ARDSp.

Objective To determine effects of recruitment maneuver （RM） guided by pressure-volume （P-V） curve on respiratory physiology and lung morphology in canine models of acute respiratory distress syndrome of pulmonary or extrapulmonary origin （ARDSp and ARDSexp）. Methods Twenty-four healthy dogs were randomly divided into two groups with 12 dogs each： ARDSexp and ARDSp. Each dog in ARDSexp group was injected with oleic acid 0. 1 ml/kg through femoral vein, and each dog in ARDSp group received hydrochloric acid 2 ml/kg via trachea. Subsequently, dogs with both models were randomly subdivided into lung protective ventilation strategy （LPVS） group and LPVS＋RM group, respectively. Dogs in LPVS group were given LPVS only without RM. RM guided by P-V curve was performed in LPVS＋RM group followed by LPVS and pressure controlled ventilation （PCV） mode was selected. Phigh was set at upper inflection point （UIP） of the P-V curve, positive end-expiratory pressure （PEEP） was set at lower inflection point （LIP）＋2 cm H2O （1 cm H2O=0. 098 kPa）, and the duration of RM was 60 seconds. The duration of mechanical ventilation （MV） in both subgroups was 4 hours. The oxygenation index （PaO2/FiO2）, relative lung mechanical indexes were measured in two ARDS models before establishment of ARDS model, and before and after RM. The UIP and LIP were calculated with P-V curve. The percentage of different volume in ventilation of lung accounting for total lung volume was compared by CT scan.Results The PaO2/FiO2, UIP and LIP did not showed significant differences among all groups before ARDSand before RM. PaO2/FiO2 and respiratory system compliance （Crs） were significantly elevated in LPVS＋RM group of both models 4 hours after RM compared with corresponding LPVS group [PaO2/FiO2（mm Hg,1 mm Hg=0. 133 kPa） of ARDSexp model： 263. 9±69. 2 vs. 182.8±42. 8, Crs （ml/cm H2O） of ARDSexp model： 11.3±4. 2 vs. 9. 7±3. 7; PaO2/FiO2（mm Hg） of ARDSp model： 193. 4±33.5 vs. 176. 4±40. 2, Crs （ml/cm H2O） of ARDSp model： 10.1±3.9 vs. 9.0±3.9, P〈0. 05 or P〈0.01], and the airway pressure was significantly declined compared with corresponding LPVS group [peak inspiratory pressure （PIP）,cm H2O） of ARDSexp model： 24. 1±7. 4 vs. 30. 2±8. 5, plateau pressure （Pplat, cm H2O） of ARDSexp model： 19.1±7.3 vs. 25.6±7.7; PIP （cm H2O） of ARDSp model： 26.6±8.4 vs. 29.6±10.3, Pplat （cm H2O） of ARDSp model： 21.9±7. 3 vs. 25.1±8.4, P〈0. 05 or P〈0. 01]. Moreover, PaO2/FiO2, Crs,PIP and Pplat were improved better in ARDSexp model than ARDSp model （P〈 0. 05 or P〈 0. 01）.Compared with LPVS maneuver, RM plus LPVS maneuver could significantly decrease the proportion of closure and hypoventilation region, and increase the proportion of normal ventilation region in both models [closure region of ARDSexp model ： （9.9±3.1） % vs. （16. 3± 5. 2） %, hypoventilation region of ARDSexp model： （10. 2±4.2）% vs. （23. 4±6. 7）%, normal ventilation region of ARDSexp model： （76. 2±12. 3）%vs. （57.5±10. 1）%; closure region of ARDSp model： （14.3±4. 8）% vs. （18. 2±5.1）%, hypoventilation region of ARDSp model ： （17.4±6. 3） % vs. （ 24. 1 ± 5. 9） 0%, normal ventilation region of ARDSp model ：（63. 2 ± 10. 7 ） % vs. （ 54. 6±11.3 ） %, P 〈 0. 05 or P 〈 0. 01]. All of the ventilation regions were better improved with ARDSexp model than ARDSp model （all P〈0. 05）. Conclusion RM guided by P-V curve could help obtain better oxygenation, improve pulmonary compliance and lung ventilation in ARDSexp and ARDSp, and better treatment effects are seen in ARDSexp dogs than ARDSp dogs.