Department of Anesthesiology and Critical Care Medicine, Children's Hospital Los Angeles, Los Angeles, California.
Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, California.
Respir Care. 2021 Feb;66(2):205-212. doi: 10.4187/respcare.07937. Epub 2020 Aug 11.
The ventilatory ratio (VR) is a dead-space marker associated with mortality in mechanically ventilated adults with ARDS. The end-tidal alveolar dead space fraction (AVDSf) has been associated with mortality in children. However, AVDSf requires capnography measurements, whereas VR does not. We sought to examine the prognostic value of VR, in comparison to AVDSf, in children and young adults with acute hypoxemic respiratory failure.
We conducted a retrospective study of prospectively collected data from 180 mechanically ventilated children and young adults with acute hypoxemic respiratory failure. VR was calculated as (minute ventilation × [Formula: see text])/(age-adjusted predicted minute ventilation × 37.5). AVDSf was calculated as [Formula: see text].
VR and AVDSf had a moderate correlation (rho 0.31, < .001). VR was similar between survivors at 1.22 (interquartile range [IQR] 1.0-1.52) and nonsurvivors at 1.30 (IQR 0.96-1.95) ( = .2). AVDSf was lower in survivors at 0.12 (IQR 0.03-0.23) than nonsurvivors at 0.24 (IQR 0.13-0.33) ( < .001). In logistic regression and competing risk regression analyses, VR was not associated with mortality or rate of extubation at any given time (competing risk death; all > .3). An AVDSf in the highest 2 quartiles, in comparison to the lowest quartile (AVDSf < 0.06), was associated with higher mortality after adjustment for oxygenation index and severity of illness (AVDSf ≥ 0.15-0.26: odds ratio 3.58, 95% CI 1.02-12.64, = .047, and AVDSf ≥ 0.26: odds ratio 3.91 95% CI-1.03-14.83, = .045). At any given time after intubation, a child with an AVDSf ≥ 0.26 was less likely to be extubated than a child with an AVDSf < 0.06, after adjustment for oxygenation index and severity of illness (AVDSf ≥ 0.26: subdistribution hazard ratio 0.55, 95% CI 0.33-0.94, = .03).
VR should not be used for prognostic purposes in children and young adults. AVDSf added prognostic information to the severity of oxygenation defect and overall severity of illness in children and young adults, consistent with previous research.
通气比（VR）是与 ARDS 机械通气成人死亡率相关的死腔标志物。潮气末肺泡死腔分数（AVDSf）与儿童死亡率相关。然而，AVDSf 需要二氧化碳描记术测量，而 VR 则不需要。我们旨在研究 VR 在伴有急性低氧性呼吸衰竭的儿童和年轻成人中的预后价值，并与 AVDSf 进行比较。
我们对前瞻性收集的 180 例伴有急性低氧性呼吸衰竭的机械通气儿童和年轻成人的数据进行了回顾性研究。VR 通过以下公式计算得出：（分钟通气量×[公式：见文本]）/（年龄校正的预计分钟通气量×37.5）。AVDSf 通过以下公式计算得出：[公式：见文本]。
VR 和 AVDSf 具有中度相关性（rho 0.31， <.001）。存活者的 VR 为 1.22（四分位距 [IQR] 1.0-1.52），非存活者的 VR 为 1.30（IQR 0.96-1.95）（ =.2）。存活者的 AVDSf 为 0.12（IQR 0.03-0.23），而非存活者的 AVDSf 为 0.24（IQR 0.13-0.33）（ <.001）。在逻辑回归和竞争风险回归分析中，VR 与任何特定时间的死亡率或拔管率均无关联（竞争风险死亡；所有 >.3）。与最低四分位组相比，AVDSf 在最高两个四分位组（AVDSf < 0.06）与调整氧合指数和疾病严重程度后的死亡率较高相关（AVDSf ≥ 0.15-0.26：比值比 3.58，95%CI 1.02-12.64， =.047，AVDSf ≥ 0.26：比值比 3.91 95%CI-1.03-14.83， =.045）。在插管后的任何特定时间，与 AVDSf < 0.06 的儿童相比，AVDSf ≥ 0.26 的儿童不太可能拔管，在调整氧合指数和疾病严重程度后（AVDSf ≥ 0.26：亚分布风险比 0.55，95%CI 0.33-0.94， =.03）。
VR 不应用于儿童和年轻成人的预后目的。AVDSf 增加了氧合缺陷严重程度和儿童及年轻成人整体疾病严重程度的预后信息，这与之前的研究一致。
