Huang C C, Tsai Y H, Lin M C, Tsao T C, Hsu K H
Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Crit Care Med. 2001 Jan;29(1):88-95. doi: 10.1097/00003246-200101000-00020.
Gastric intramucosal PCO2 (PiCO2) and pH (pHi) are currently used as indices of the adequacy of splanchnic perfusion and as end points to guide therapeutic intervention. However, little is known about their spontaneous variability over time. The present study was designed to define the magnitude of spontaneous variability of PiCO2 and pHi in sedated medical intensive care unit (ICU) patients using an automated recirculating air tonometer and to test whether high-level positive end-expiratory pressure (PEEP) or inverse inspiratory/expiratory (I:E) ratio ventilation resulted in a greater variability than low PEEP with conventional I:E ratio ventilation.
Prospective study.
Medical ICU in a tertiary medical center.
Twenty-three acute respiratory failure patients.
After being sedated, patients were randomized to undergo pressure control ventilation at the following three settings: A, high PEEP (15 cm H2O) with conventional I:E ratio (1:2), and B, low PEEP (5 cm H2O) with inverse I:E ratio (2:1) alternately, and then C, low PEEP (5 cm H2O) with conventional I:E ratio (1:2). Each ventilation setting period lasted 1 hr.
The PiCO2 and pHi were measured at baseline (time 0), and at 15, 30, 45, and 60 mins thereafter. The corresponding coefficients of variation (CVs) of PiCO2 for overall pooled group and settings A, B, and C were 4.0%, 4.4%, 3.4%, and 4.2%, respectively. The corresponding CVs of pHi for overall pooled group and settings A, B, and C were 0.36%, 0.37%, 0.33%, and 0.4%, respectively. Analysis of variance showed no significant difference in the CVs of PiCO2 or pHi between the three settings. The 95% confidence interval is approximately +/-8% variability for PiCO2 and +/-0.7% variability for pHi.
In critically ill medical ICU patients with stable hemodynamics, the spontaneous variability of PiCO2 or pHi are not substantial. High PEEP (15 cm H2O) and inverse ratio ventilation (2:1), which does not change the cardiac output or hemodynamics, does not contribute to increased spontaneous variability in PiCO2 or pHi.
胃黏膜内二氧化碳分压（PiCO2）和pH值（pHi）目前被用作内脏灌注充足性的指标以及指导治疗干预的终点。然而，关于它们随时间的自发变异性知之甚少。本研究旨在使用自动循环空气眼压计确定镇静的医学重症监护病房（ICU）患者中PiCO2和pHi的自发变异程度，并测试高水平呼气末正压（PEEP）或反比吸气/呼气（I:E）比通气是否比低PEEP与传统I:E比通气导致更大的变异性。
前瞻性研究。
三级医疗中心的医学ICU。
23例急性呼吸衰竭患者。
患者镇静后，随机分组在以下三种设置下接受压力控制通气：A组，高PEEP（15 cm H2O）与传统I:E比（1:2）；B组，低PEEP（5 cm H2O）与反比I:E比（2:1）交替；然后C组，低PEEP（5 cm H2O）与传统I:E比（1:2）。每个通气设置期持续1小时。
在基线（时间0）以及此后的15、30、45和60分钟测量PiCO2和pHi。总体合并组以及A、B和C组PiCO2的相应变异系数（CV）分别为4.0%、4.4%、3.4%和4.2%。总体合并组以及A、B和C组pHi的相应CV分别为0.36%、0.37%、0.33%和0.4%。方差分析显示三种设置之间PiCO2或pHi的CV无显著差异。PiCO2的95%置信区间约为±8%的变异性，pHi为±0.7%的变异性。
在血流动力学稳定的重症医学ICU患者中，PiCO2或pHi的自发变异性不大。不改变心输出量或血流动力学的高PEEP（15 cm H2O）和反比通气（2:1）不会导致PiCO2或pHi的自发变异性增加。
