Background

Occlusion pressure at 100 ms (P0.1), defined as the negative pressure measured 100 ms after the initiation of an inspiratory effort performed against a closed respiratory circuit, has been shown to be well correlated with central respiratory drive and respiratory effort. Automated P0.1 measurement is available on modern ventilators. However, the reliability of this measurement has never been studied. This bench study aimed at assessing the accuracy of P0.1 measurements automatically performed by different ICU ventilators.

Methods

Five ventilators set in pressure support mode were tested using a two-chamber test lung model simulating spontaneous breathing. P0.1 automatically displayed on the ventilator screen (P0.1_vent) was recorded at three levels of simulated inspiratory effort corresponding to P0.1 of 2.5, 5 and 10 cm H₂O measured directly at the test lung and considered as the reference values of P0.1 (P0.1_ref). The pressure drop after 100 ms was measured offline on the airway pressure–time curves recorded during the automated P0.1 measurements (P0.1_aw). P0.1_vent was compared to P0.1_ref and to P0.1_aw. To assess the potential impact of the circuit length, P0.1 were also measured with circuits of different lengths (P0.1_circuit).

Results

Variations of P0.1_vent correlated well with variations of P0.1_ref. Overall, P0.1_vent underestimated P0.1_ref except for the Löwenstein^® ventilator at P0.1_ref 2.5 cm H₂O and for the Getinge group^® ventilator at P0.1_ref 10 cm H₂O. The agreement between P0.1_vent and P0.1_ref assessed with the Bland–Altman method gave a mean bias of − 1.3 cm H₂O (limits of agreement: 1 and − 3.7 cm H₂O). Analysis of airway pressure–time and flow–time curves showed that all the tested ventilators except the Getinge group^® ventilator performed an occlusion of at least 100 ms to measure P0.1. The agreement between P0.1_vent and P0.1_aw assessed with the Bland–Altman method gave a mean bias of 0.5 cm H₂O (limits of agreement: 2.4 and − 1.4 cm H₂O). The circuit’s length impacted P0.1 measurements’ values. A longer circuit was associated with lower P0.1_circuit values.

Conclusion

P0.1_vent relative changes are well correlated to P0.1_ref changes in all the tested ventilators. Accuracy of absolute values of P0.1_vent varies according to the ventilator model. Overall, P0.1_vent underestimates P0.1_ref. The length of the circuit may partially explain P0.1_vent underestimation.

中文翻译：

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ICU呼吸机执行P0.1测量的准确性：一项基准研究。

背景

100 ms的闭塞压力（P0.1）定义为开始对闭合的呼吸回路进行吸气后100 ms测得的负压，与中央呼吸驱动和呼吸作用密切相关。现代化的呼吸机可进行自动P0.1测量。但是，从未研究过这种测量的可靠性。这项基准研究旨在评估由不同ICU呼吸机自动执行的P0.1测量的准确性。

方法

使用模拟自然呼吸的两腔肺测试模型对设置为压力支持模式的五台呼吸机进行了测试。自动显示在呼吸机屏幕上的P0.1（P0.1_通风口）记录在三个模拟吸气强度水平上，分别对应于在测试肺部直接测量的2.5、5和10 cm H ₂ O的P0.1，并作为参考P0.1的值（P0.1 _ref）。在自动P0.1测量（P0.1 _aw）期间记录的气道压力-时间曲线上，离线测量了100 ms之后的压降。将P0.1_排气孔与P0.1 _ref和P0.1 _{aw进行比较}。为了评估电路长度的潜在影响，还使用不同长度的_电路（P0.1_电路）测量了P0.1 。

结果

P0.1_排放口的变化与P0.1 _ref的变化密切相关。总体而言，P0.1_泄低估P0.1 _REF除了罗恩斯坦^®在P0.1通风机_REF 2.5厘米ħ ₂ O和用于洁定组^®呼吸机在P0.1_裁判10厘米ħ ₂ O. P0之间的协议。用Bland–Altman方法评估的1个_通气孔和P0.1 _ref的平均偏差为− 1.3 cm H ₂ O（一致极限：1和− 3.7 cm H ₂O）。的气道压力-时间分析和流量-时间曲线表明，所有除洁定组被测试的通风机^®呼吸机执行的至少100毫秒的闭塞测量P0.1。用Bland–Altman方法评估的P0.1_排气孔和P0.1 _aw之间的一致性给出了0.5 cm H ₂ O的平均偏差（一致性极限：2.4和− 1.4 cm H ₂ O）。电路长度会影响P0.1测量值。较长的电路与较低的P0.1_电路值相关。

结论

P0.1_通风口相对变化是公相关P0.1 _REF在所有测试的呼吸机的变化。P0.1_排气孔的绝对值的准确性会根据呼吸机的型号而变化。总体而言，P0.1_排放口低估了P0.1 _ref。电路的长度可以部分解释P0.1_通风孔的低估。