小儿重症喘息性疾病机械通气时压力-容积曲线的应用

Application of dynamic pressure-volume curve in mechanical ventilation treatment of children with severe asthmatoid disease

目的探讨小儿重症喘息性疾病机械通气治疗时是否能够使用呼气末正压（PEEP），以及如何确定最佳PEEP的简捷方法。方法采取自身对照法，记录儿科重症监护室（PICU）中23例需要机械通气的重症喘息性疾病患儿的准静态压力．容积（P-V）曲线，确定P-V曲线上低位转折点（LIP），将PEEP分别设定在准静态曲线的0cmH2O、LIP、LIP＋2cmH20（1cmH2O=0．098kPa）三组，以相同的潮气量和吸人氧浓度（FiO2）分别给予定容机械通气，各水平PEEP维持30min后监测肺呼吸力学和血流动力学参数、动脉血气改变。结果23例重症喘息性疾病患儿的准静态LIP为（2．70±2．DO）cmH2O。当PEEP为LIP＋2cmH2O时，动脉血氧分压（PaO2），FiO2及肺顺应性均显著提高（P〈0．01），动态肺顺应性最高，吸气峰压为（22．30±3．00）cmH2O，平均气道压为（14．11±1．01）cmH2O，且对平均动脉压及心率无明显影响。与PEEP为0cmH2O相比较，动脉血二氧化碳分压（PaCO2）无明显区别。结论小儿重症喘息性疾病时，应用PEEP是安全的，选择准静态P-V曲线的LIP＋2cmH2O作为PEEP水平时可获较佳治疗效果，且不会加大CO2的潴留，对血流动力学也无明显影响。

Objective To determine optimal positive end expiratory pressure （PEEP） in mechanical ventilation in children with severe asthmatoid disease based on the quasistatic pressure-volume （P-V） curve. Methods A self-control study was done on 23 children with severe asthmatoid disease in the pediatric intensive care unit（PICU）. Quasistatic lung P-V curve of these patients was analyzed and the lower inflection point （LIP） from P-V curve was determined. Three different PEEP （0 cm H20, LIP, LIP＋2 cm H20,1 mm H20 = 0.098 kPa） were given to the patients. The effects of PEEP at different levels on gas exchange, hemodynamic and airway pressure were observed. Results The quasistatic LIP were （2.70 ±2.00） cm H2O. When PEEP was increased to the level of LIP ＋ 2 em H2O,PaO2 / FiO2 and lung compliance improved significantly （P 〈 0.01 ） and dynamic lung compliance was the highest, peak inspiratory pressure was （22.30 ± 3.00） cm H2O and mean airway pressure was（ 14.11 ±1.01 ） cm H2O, without obvious adverse effects on mean arterial blood pressure and heart rate. There was no difference in PaCO2,when compared PEEP = 0 cmH2O to PEEP = LIP ＋ 2 cmH2O. Conchmion The application of PEEP is safe. LIP ＋ 2 cm H20 from quasistatic P-V curve could be set as the optimal PEEP under which mechanical ventilation has the best efficacy and do not aggravate CO2 retention and abnormality of hemodynamics in children with severe asthmatoid disease.