Does Size Matter When Calculating the “Correct” Tidal Volume for Pediatric Mechanical Ventilation?: A Hypothesis Based on FVC
Gina J. Kim, Christopher J.L. Newth, Robinder G. Khemani, et al
Chest 2018; 154: 77-83
Background 背景
Tidal volumes standardized to predicted body weight are recommended for adult mechanical ventilation, but children are frequently ventilated by using measured body weight. The goal of this study was to examine the difference in FVC (in milliliters per kilogram [mL/kg]) by using measured body weight compared with predicted body weight in children.
成年人机械通气时推荐根据理想体重对潮气量进行标化，但儿童机械通气时经常采用实际体重。本研究的目的旨在检验根据实际体重或理想体重对儿童的用力肺活量(FVC, ml/kg)进行校正的差异。
Methods 方法
This retrospective analysis included outpatient pulmonary function tests (PFTs) from two datasets. Dataset one included 6- to 19-year-old patients undergoing PFTs from the nationally representative Canadian Health Measures Survey. Dataset two included 6- to 20-year-old patients undergoing PFTs at a freestanding children’s hospital. FVC mL/kg values were analyzed against BMI z scores to show changes in FVC vs BMI between measured and predicted weight.
对于两个门诊患者肺功能检查(PFTs)数据集的回顾性分析。第一个数据集纳入有代表性的加拿大健康测定调查中接受PFTs的6-19岁患者。第二个数据集纳入了一家医院接受PFTs的6-20岁患者。将FVC根据BMI z评分（采用实际和理想体重）进行校正。
Results 结果
Dataset one included 5,394 PFTs from the Canadian survey. FVC from measured weight decreased as the BMI zscore group increased. The median FVC from measured weight was 81.4 mL/kg in the lowest BMI z score group and 51.7 mL/kg in the highest BMI z score group. FVC from predicted weight increased slightly with increasing BMI z score group. Dataset two included 8,472 patient PFTs from clinical measurement. A decline in median FVC from measured weight (from 69.4 to 37.6 mL/kg) as BMI z score group increased was also seen.
第一个数据集纳入加拿大调查中5394个PFTs结果。随着BMI z评分组增加，根据实际体重校正的FVC降低。最低BMI z评分组中，根据实际体重校正的FVC中位数为81.4 ml/kg，而最高BMI z评分组则为51.7 ml/kg。根据理想体重校正的FVC随着BMI z评分组增加而轻度增加。第二个数据集包括临床测定的8472名患者的PFTs结果。随着BMI z评分组增加，实际体重校正的FVC中位数也随之降低。
Conclusions 结果
FVC differs significantly when standardizing to measured weight vs predicted weight. Obese children have lung volumes reflecting their predicted body weight from height. Children with low or normal BMI have lung volumes reflecting measured body weight. These findings suggest that targeting tidal volume by using the lower of measured and predicted body weights would be the most lung-protective strategy.
根据实际体重或理想体重标化的FVC存在显著差异。肥胖儿童的肺容积受到根据身高推算的理想体重影响。BMI较低或正常的儿童肺容积受实际体重影响。这些结果提示，根据实际和理想体重中较小的数值设置潮气量可能更符合肺保护策略。
