在吸入氧分数阶跃变化后机械通气期间动脉血氧分压平衡所需的时间。

Time required for partial pressure of arterial oxygen equilibration during mechanical ventilation after a step change in fractional inspired oxygen concentration.

作者信息

Cakar N, Tuŏrul M, Demirarslan A, Nahum A, Adams A, Akýncý O, Esen F, Telci L

机构信息

Department of Anesthesiology and Intensive Care Medicine, Istanbul Medical Faculty, University of Istanbul, Capa Klinikleri, 34390 Capa, Istanbul, Turkey.

出版信息

Intensive Care Med. 2001 Apr;27(4):655-9. doi: 10.1007/s001340100900.

DOI:10.1007/s001340100900

PMID:11403067

Abstract

OBJECTIVE

To determine the time required for the partial pressure of arterial oxygen (PaO2) to reach equilibrium after a 0.20 increment or decrement in fractional inspired oxygen concentration (FIO2) during mechanical ventilation.

SETTING

A multi-disciplinary ICU in a university hospital.

PATIENTS AND METHODS

Twenty-five adult, non-COPD patients with stable blood gas values (PaO2/FIO2 > or = 180 on the day of the study) on pressure-controlled ventilation (PCV). Following a baseline PaO2 (PaO2b) measurement at FIO2 = 0.35, the FIO2 was increased to 0.55 for 30 min and then decreased to 0.35 without any other change in ventilatory parameters. Sequential blood gas measurements were performed at 3, 5, 7, 9, 11, 15, 20, 25 and 30 min in both periods. The PaO2 values measured at the 30th min after a step change in FIO2 (FIO2 = 0.55, PaO2[55] and FIO2 = 0.35, PaO2[35]) were accepted as representative of the equilibrium values for PaO2. Each patient's rise and fall in PaO2 over time, PaO2(t), were fitted to the following respective exponential equations: PaO2b + (PaO2[55]-PaO2b)(1-e-kt) and PaO2[55] + (PaO2[35]-PaO2[55])(e-kt) where "t" refers to time, PaO2[55] and PaO2[35] are the final PaO2 values obtained at a new FIO2 of 0.55 and 0.35, after a 0.20 increment and decrement in FIO2, respectively. Time constant "k" was determined by a non-linear fitting curve and 90% oxygenation times were defined as the time required to reach 90% of the final equilibrated PaO2 calculated by using the non-linear fitting curves.

RESULTS

Time constant values for the rise and fall periods were 1.01 +/- 0.71 min-1, 0.69 +/- 0.42 min-1, respectively, and 90% oxygenation times for rises and falls in PaO2 periods were 4.2 +/- 4.1 min-1 and 5.5 +/- 4.8 min-1, respectively. There was no significant difference between the rise and fall periods for the two parameters (p > 0.05).

CONCLUSION

We conclude that in stable patients ventilated with PCV, after a step change in FIO2 of 0.20, 5-10 min will be adequate for obtaining a blood gas sample to measure a PaO2 that will be representative of the equilibrium PaO2 value.

摘要

目的

确定在机械通气过程中，吸入氧分数（FIO2）增加或减少0.20后，动脉血氧分压（PaO2）达到平衡所需的时间。

设置

大学医院的多学科重症监护病房。

患者和方法

25例接受压力控制通气（PCV）的成年非慢性阻塞性肺疾病（COPD）患者，其血气值稳定（研究当天PaO2/FIO2≥180）。在FIO2 = 0.35时测量基线PaO2（PaO2b）后，将FIO2增加到0.55持续30分钟，然后降至0.35，通气参数无其他变化。在两个阶段的3、5、7、9、11、15、20、25和30分钟进行连续血气测量。在FIO2阶跃变化后第30分钟测量的PaO2值（FIO2 = 0.55时的PaO2[55]和FIO2 = 0.35时的PaO2[35]）被视为PaO2平衡值的代表。每位患者PaO2随时间的上升和下降，即PaO2(t)，分别拟合以下指数方程：PaO2b + (PaO2[55] - PaO2b)(1 - e-kt) 和PaO2[55] + (PaO2[35] - PaO2[55])(e-kt)，其中“t”指时间，PaO2[55]和PaO2[35]分别是FIO2增加和减少0.20后，在新的FIO2为0.55和0.35时获得的最终PaO2值。时间常数“k”通过非线性拟合曲线确定，90%氧合时间定义为达到通过非线性拟合曲线计算的最终平衡PaO2的90%所需的时间。