Bauer K, Pasel K, Uhrig C, Sperling P, Versmold H
Department of Pediatrics, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Germany.
Pediatr Res. 1997 Jan;41(1):139-44. doi: 10.1203/00006450-199701000-00022.
Complete sampling of expired air is essential for accurate O2 consumption(CO2 production) [VO2(VCO2)] measurements with flow-through indirect calorimetry. In preterm infants complete sampling is critical, because only low sampling flows can be used. The accuracy of the various breath sampling systems at low flows and their patient compatibility is untested. We therefore measured 1) the accuracy of VO2(VCO2) measurements with a face mask, a head hood, and a canopy in vitro at low sampling flows; 2) the effect of breathing on measurements with the face mask; and 3) the effect of breath sampling systems on activity and body temperature of preterm infants. VO2(VCO2) were measured with a Deltatrac II. In vitro we used a methanol miniburner incorporated into a doll, which could simulate low VO2(VCO2) and tidal breathing. In vivo we studied seven preterm infants < 1500 g. With the face mask VO2(VCO2) measurements were accurate at a flow of 3 L/min (error -1 +/- 0.8%), when tidal volume was < 15 mL/breath and the distance between mask and manikin < 1 cm. With hood and canopy VO2(VCO2) were underestimated at a flow of 3 L/min (error -13 +/- 1% and -14 +/- 5%), and results were markedly influenced by body position. For accurate measurements, the hood needed a flow of 4.5 L/min, the canopy 8.3 L/min. In vivo the face mask did not increase heart rate, respiration, activity, or rectal temperature, but hood and canopy increased rectal temperature by 0.3-0.4 degree C. For VO2(VCO2) measurements in infants < 1500 g, a face mask should be used, which is accurate at low flows and does not change body temperature. Accuracy at low flows and patient compatibility of breath sampling systems should be evaluated and reported for VO2(VCO2) measurements in preterm infants.
对于采用流通式间接测热法准确测量氧气消耗量（二氧化碳产生量）[VO₂（VCO₂）]而言，完全采集呼出气体至关重要。在早产儿中，完全采样至关重要，因为只能使用低采样流量。各种低流量呼吸采样系统的准确性及其与患者的兼容性尚未经过测试。因此，我们进行了以下测量：1）在低采样流量下，体外使用面罩、头罩和帐式罩测量VO₂（VCO₂）的准确性；2）呼吸对面罩测量的影响；3）呼吸采样系统对早产儿活动和体温的影响。VO₂（VCO₂）采用Deltatrac II进行测量。在体外，我们使用一个内置在玩偶中的甲醇微型燃烧器，它可以模拟低VO₂（VCO₂）和潮式呼吸。在体内，我们研究了7名体重<1500 g的早产儿。使用面罩时，当潮气量<15 mL/次呼吸且面罩与人体模型之间的距离<1 cm时，在3 L/min的流量下VO₂（VCO₂）测量准确（误差-1±0.8%）。使用头罩和帐式罩时，在3 L/min的流量下VO₂（VCO₂）被低估（误差-13±1%和-14±5%），并且结果受身体位置的影响显著。为了进行准确测量，头罩需要4.5 L/min的流量，帐式罩需要8.3 L/min的流量。在体内，面罩不会增加心率、呼吸、活动或直肠温度，但头罩和帐式罩会使直肠温度升高0.3 - 0.4摄氏度。对于体重<1500 g的婴儿进行VO₂（VCO₂）测量时，应使用面罩，其在低流量下准确且不会改变体温。对于早产儿VO₂（VCO₂）测量，应评估并报告呼吸采样系统在低流量下的准确性及其与患者的兼容性。
