Mahutte C K, Jaffe M B, Sassoon C S, Wong D H
Department of Medicine, Long Beach Veterans Affairs Medical Center, CA 90822.
Crit Care Med. 1991 Oct;19(10):1270-7. doi: 10.1097/00003246-199110000-00009.
To determine cardiac output from measurements of CO2 production (VCO2), and arterial (SaO2) and mixed venous (SvO2) oxygen saturations, using a modified Fick equation, in which cardiac output = VCO2/[k (SaO2 - SvO2)], where k represents a constant.
A metabolic measurement cart was used to measure VCO2 and oxygen consumption (VO2) at 3-min intervals. SaO2 and SvO2 were measured via a pulse oximeter and a fiberoptic right heart catheter, respectively. The initial value of k for each study was determined from initial simultaneous measurements of thermodilution cardiac output, VCO2, SaO2, and SvO2 via the equation k = VCO2/[cardiac output (SaO2 - SvO2)]. The value of k was assumed to remain constant for the entire study period. Thereafter, cardiac outputs calculated from k and the measurements of VCO2, SaO2, and SvO2 were compared with the simultaneously obtained cardiac outputs determined by thermodilution. Similarly, cardiac outputs calculated from the traditional oxygen Fick equation, where cardiac output = VO2/[13.4 x hemoglobin (SaO2 - SvO2)], were compared with the simultaneously acquired cardiac outputs determined by thermodilution.
Surgical ICU in a Veterans Affairs Medical Center.
Seven postoperative patients, mechanically ventilated using the intermittent mandatory ventilation mode, were studied over a mean period of 4 hrs.
Cardiac output (obtained from VCO2 and oximetry saturations) was closely related to thermodilution cardiac output: with linear regression showing r2 = .96 and standard error of the estimate = 0.59 L/min, n = 21; and, with bias and precision = 0.17 and 0.68 L/min, respectively. The traditional oxygen Fick cardiac output was also closely related to the thermodilution cardiac output (r2 = .81, standard error of the estimate = 1.46 L/min, n = 22; bias and precision = 0.31 and 1.46 L/min, respectively).
The proposed method for calculating cardiac outputs solely from VCO2 and oximetry saturations yields results that correspond closely to thermodilution determined cardiac outputs. The method is simple and avoids the difficulties in the Fick method associated with accurate VO2 measurement. This approach may be suitable for continuous cardiac output monitoring in critically ill patients.
使用改良的菲克方程，通过测量二氧化碳产生量（VCO₂）、动脉血氧饱和度（SaO₂）和混合静脉血氧饱和度（SvO₂）来测定心输出量，其中心输出量 = VCO₂/[k (SaO₂ - SvO₂)]，k为常数。
使用代谢测量推车每隔3分钟测量VCO₂和氧耗量（VO₂）。分别通过脉搏血氧饱和度仪和光纤右心导管测量SaO₂和SvO₂。每项研究的k初始值由热稀释法心输出量、VCO₂、SaO₂和SvO₂的初始同步测量值通过公式k = VCO₂/[心输出量 (SaO₂ - SvO₂)]确定。假设k值在整个研究期间保持不变。此后，将根据k以及VCO₂、SaO₂和SvO₂测量值计算出的心输出量与同时通过热稀释法获得的心输出量进行比较。同样，将根据传统氧菲克方程（心输出量 = VO₂/[13.4 × 血红蛋白 (SaO₂ - SvO₂)]）计算出的心输出量与同时通过热稀释法获得的心输出量进行比较。
退伍军人事务医疗中心的外科重症监护病房。
7例术后患者，采用间歇强制通气模式进行机械通气，平均研究时长为4小时。
（通过VCO₂和血氧饱和度测量获得的心输出量）与热稀释法心输出量密切相关：线性回归显示r² = 0.96，估计标准误差 = 0.59 L/分钟，n = 21；偏差和精密度分别为0.17和0.68 L/分钟。传统氧菲克法心输出量也与热稀释法心输出量密切相关（r² = 0.81，估计标准误差 = 1.46 L/分钟，n = 22；偏差和精密度分别为0.31和1.46 L/分钟）。
仅根据VCO₂和血氧饱和度计算心输出量的方法得出的结果与热稀释法测定的心输出量密切相符。该方法简单，避免了菲克法中与准确测量VO₂相关的困难。这种方法可能适用于危重症患者的心输出量连续监测。
