王书鹏 秦英智 徐磊 张纳新

    【摘要】 目的 论证根据压力容积(PV)曲线二阶导数图形寻找曲线拐点的可行性，并与逐步线性回归法测定拐点的方法进行比较。 方法 6只成年健康绵羊麻醉后行气管切开，纤维支气管镜温生理盐水肺泡灌洗法建立急性呼吸窘迫综合征(ARDS)模型，用低流速法描记灌洗前及灌洗后的准静态PV曲线，利用Findgraph软件建立数学模型及分析曲线特征。 结果 应用多元线性回归及Boltzmann公式对正常及ARDS PV曲线的吸气支和呼气支均能达到理想的拟合效果，利用二阶导数图形可以准确获得PV曲线的特征点，利用此方法测定的吸气支下拐点(LIP)与逐步线性回归法所测的LIP+2 cm H2O(1 cm H2O=0.098 kPa)有很高的相关性。 结论 对于ARDS患者，PV曲线的二阶导数图形可以准确提供曲线拐点的信息，有利于呼吸机参数的设定。

    【关键词】 压力容积曲线；数学模型；曲线拟合；急性呼吸窘迫综合征

    Establishment of a mathematical model of static pressurevolume curve in acute respiratory distress syndrome WANG Shupeng, QIN Yingzhi, XU Lei, ZHANG Naxin. Intensive Care Unit, Tianjin Third Central Hospital, Tianjin 300170, China

    【Abstract】 Objective To explore the use of second derivate in seeking the inflection points of pressurevolume (PV) curves and compare it with the stepbystep regression method. Methods Under general anesthesis, tracheotomy was done in 6 adult sheep, warm physiological saline was used to lavage the respiratory, followed by alveolar lavaged via tract through bronchofiberscope to reproduce acute respiratory distress syndrome (ARDS). The low flow technique was used to trace the PV curves before and after the saline lavage, and features of the curves were analyzed with the software of Findgraph. Results The above two methods fit the PV data well with good accuracy both in inflation and deflation limbs in normal and ARDS animals. From the graph of second derivate, the characteristic points of the PV curves could be exactly obtained , and the low inflection points obtained by this method were well correlated with lower inflection point (LIP) +2 cm H2O (1 cm H2O=0.098 kPa) obtained by stepbystep regression method. Conclusion The graph of second derivate gained from PV curves is useful to describe the inflection points, so that it can be helpful in instructing in setting the required parameters of the ventilator in the treatment of ARDS. ......