通过分析机械通气呼气相超早期流量时间曲线的形态与影响因素，来协助临床分析患者的呼吸状态。

选择顺应性不同的两种模肺与阻力不同的两种气道进行分列组合（4种），然后与PB840呼吸机相连。不同组合下分别设置3种不同的吸气末点（呼气起点）状态场景，场景一：相同的肺泡压（Pa₀）与呼气末正压（PEEP），不同的回路压（Pc₀）；场景二：相同的Pc₀与PEEP，不同的Pa₀；场景三：相同的Pc₀与Pa₀，不同的PEEP。通过锁屏及调节呼吸机屏幕坐标轴刻度，观察呼气相超早期流量时间曲线的形态特点。比较不同组合及场景下，Pc₀、Pa₀、PEEP、呼吸系统顺应性（C）、气道阻力（R）对呼气相超早期流量时间曲线形态的影响。

1．超早期流量时间曲线形态特点：主要由两个关键点决定，流量峰点（呼气最大流量点，V1）及流量折点（流量快速下降与缓慢下降的交点，V4）。且这两点与压力时间曲线存在对应关系。2.（1）相同的C、R及Pa₀、PEEP，不同的Pc₀时：Pc₀增大，V1增大，V4无变化；（2）相同的C、R及Pc₀、PEEP，不同的Pa₀时：Pa₀增大，V1、V4均增大；但V4增加程度小于V1增加程度；（3）相同的C、R及Pc₀、Pa₀，不同的PEEP时：PEEP增高，V1、V4减小；（4）相同的C及Pc₀、Pa₀、PEEP时：R增大，V1、V4减小；（5）相同的R及Pc₀、Pa₀、PEEP时：C增大，V1、V4无明显变化。

呼气流量峰点正相关因素为呼气初始回路压力及肺泡内压，负相关因素为PEEP值及气道阻力。呼气流量折点正相关因素为呼气初始肺泡内压，负相关因素为PEEP值及气道阻力。呼气流量峰点与折点的距离，在呼吸机设置相同时，与患者气道阻力呈正相关，与呼吸系统顺应性呈负相关关系。

To analyze the respiratory state of patients receiving mechanical ventilation by analyzing the shapes and influence factors of flow-time curve in the super early phase of expiration.

Two test lungs with different compliance (C) and two tubes with different resistance (R) were prepared. Four combinations were developed with one test lung coupled with one tube. The test lungs and tubes were then connected to a PB840 ventilator. The start points of expiratoration (the end point of inspiration) were set in three scenarios with different ventilation mode. First: different circuit pressure (Pc₀) and same alveolar pressure (Pa₀) and PEEP. Second case: different Pa₀ and same Pc₀ and PEEP. Third: different PEEP and same Pc₀ and Pa₀. The characteristics of the flow-time curves were observed. The effects of Pc₀, Pa₀, PEEP, C and R on the flow-time curves were also observed.

1．Two key points determined the morphological characteristics of flow-time curves in the super early phase. One was the point of peak flow (the maximum expiratory flow, V1). The other was the break point (the intersection point between the rapid decline and slow decline of flow volume, V4). 2. (1) The higher Pc₀ was, the greater V1 was, when the C, R, Pa₀, and PEEP were kept the same. (2) The higher Pa₀ was, the greater V1 and V4 were, when the C, R, Pc₀, and PEEP were kept the same. However, the degree of V4 rise is less than V1 rise. (3) The higher PEEP was, the smaller V1 and V4 were, when C, R, Pc₀, and Pa₀ were kept the same. (4) The greater R was, the smaller V1 and V4 were, when C,Pc₀, Pa₀, and PEEP were kept the same. (5) V1 and V4 did not change obviously when C changed, and Pc₀, Pa₀ and PEEP were kept the same.

The pressure of the circuit and the pressure of the alveolus at the end of inspiration affect the peak expiratory flow positively. But PEEP and the airway resistance do negatively. The pressure of the alveolus at the end of inspiration affects the break expiratory flow positively. But the PEEP value and airway resistance do negatively. The airway resistance affects the distance between the peak point and the break point positively. But the compliance does negatively.