Dietrich K A, Romero M D, Conrad S A
Department of Pediatrics, Louisiana State University Medical Center, Shreveport.
JPEN J Parenter Enteral Nutr. 1990 Jul-Aug;14(4):408-13. doi: 10.1177/0148607190014004408.
The use of uncuffed endotracheal tubes (ETT) in pediatric patients raises concern over the accuracy of indirect calorimetry measurement in the presence of a gas leak around an ETT. We examined the effects of ETT gas leak on respiratory gas measurements in a dog model. Mongrel dogs (n = 12) were sedated, paralyzed, intubated, and placed on mechanical ventilation. Leak was achieved by adjusting cuff volume. Oxygen consumption (VO2), CO2 production (VCO2), respiratory exchange ratio (RER), and resting energy expenditure (REE) were measured at each leak pressure (Pleak). Peak inspiratory pressure (PIP), Pleak, inspiratory and expiratory tidal volume (VTinsp, VTexp), VE, end tidal CO2 (ETCO2), and blood gases were recorded at each leak pressure. VO2, VCO, and REE decreased significantly with increasing gas leak. There was a linear relationship between VO2, VCO2, and REE with both TVratio (VTexp/VTinsp) and Pdiff (PIP-Pleak). Multiple regression equations based on TVratio and Pdiff were obtained which allowed correction of the measurement error in VO2, VCO2, and REE, with correlation coefficients (R2) of 0.71, 0.75, and 0.73, respectively. ETT gas leak affects measurements of VO2, VCO2, and REE, but not RER. Measurements made with TVratio greater than 0.80 required no correction. Measurements made with TVratio greater than 0.45 could be corrected to actual values in our model with regression equations based on TVratio and Pdiff. We conclude that indirect calorimetry measurements can be useful in the presence of tracheal gas leak around an ETT.
在儿科患者中使用无套囊气管内导管（ETT）引发了人们对于在ETT周围存在气体泄漏情况下间接测热法测量准确性的担忧。我们在犬模型中研究了ETT气体泄漏对呼吸气体测量的影响。将杂种犬（n = 12）进行镇静、麻痹、插管，并置于机械通气。通过调整套囊容积来实现泄漏。在每个泄漏压力（Pleak）下测量氧耗量（VO2）、二氧化碳产生量（VCO2）、呼吸交换率（RER）和静息能量消耗（REE）。在每个泄漏压力下记录吸气峰压（PIP）、Pleak、吸气和呼气潮气量（VTinsp、VTexp）、每分钟通气量（VE）、呼气末二氧化碳（ETCO2）和血气。随着气体泄漏增加，VO2、VCO2和REE显著降低。VO2、VCO2和REE与潮气量比（VTexp/VTinsp）和压力差（PIP - Pleak）之间存在线性关系。获得了基于潮气量比和压力差的多元回归方程，可用于校正VO2、VCO2和REE的测量误差，相关系数（R2）分别为0.71、0.75和0.73。ETT气体泄漏会影响VO2、VCO2和REE的测量，但不影响RER。潮气量比大于0.80时进行的测量无需校正。在我们的模型中，潮气量比大于0.45时进行的测量可通过基于潮气量比和压力差的回归方程校正为实际值。我们得出结论，在ETT周围存在气管气体泄漏的情况下，间接测热法测量可能是有用的。
