Department of Intensive Care and Anesthesiology, Fondazione Poliambulanza, Brescia, Italy.
Department of Intensive Care and Anesthesiology, University of Brescia, Brescia, Italy.
J Clin Monit Comput. 2021 Aug;35(4):913-921. doi: 10.1007/s10877-020-00552-5. Epub 2020 Jul 2.
Pressure support ventilation (PSV) should be titrated considering the pressure developed by the respiratory muscles (P) to prevent under- and over-assistance. The esophageal pressure (P) is the clinical gold standard for P assessment, but its use is limited by alleged invasiveness and complexity. The least square fitting method and the end-inspiratory occlusion method have been proposed as non-invasive alternatives for P assessment. The aims of this study were: (1) to compare the accuracy of P estimation using the end-inspiration occlusion (P) and the least square fitting (P) against the reference method based on P; (2) to test the accuracy of P and of P to detect overassistance, defined as P ≤ 1 cmHO. We studied 18 patients at three different PSV levels. At each PSV level, P, P, P were calculated on the same breaths. Differences among P, P, P were analyzed with linear mixed effects models. Bias and agreement were assessed by Bland-Altman analysis for repeated measures. The ability of P and P to detect overassistance was assessed by the area under the receiver operating characteristics curve. Positive and negative predictive values were calculated using cutoff values that maximized the sum of sensitivity and specificity. At each PSV level, P was not different from P (p = 0.96), whereas P was significantly lower than P. The bias between P and P was zero, whereas P systematically underestimated P of 6 cmHO. The limits of agreement between P and P and between P and P were ± 12 cmHO across bias. Both P ≤ 4 cmHO and P ≤ 1 cmHO had excellent negative predictive value [0.98 (95% CI 0.94-1) and 0.96 (95% CI 0.91-0.99), respectively)] to identify over-assistance. The inspiratory effort during PSV could not be accurately estimated by the least square fitting or end-inspiratory occlusion method because the limits of agreement were far above the signal size. These non-invasive approaches, however, could be used to screen patients at risk for absent or minimal respiratory muscles activation to prevent the ventilator-induced diaphragmatic dysfunction.
压力支持通气（PSV）应根据呼吸肌产生的压力（P）进行滴定，以防止过度辅助和辅助不足。食管压力（P）是评估 P 的临床金标准，但由于据称具有侵袭性和复杂性，其应用受到限制。最小二乘法拟合方法和吸气末阻断法已被提出作为评估 P 的非侵入性替代方法。本研究的目的是：（1）比较基于 P 的参考方法，比较吸气末阻断法（P）和最小二乘法拟合法（P）估计 P 的准确性；（2）测试 P 和 P 检测过度辅助的准确性，定义为 P≤1cmHO。我们研究了 18 例在三种不同 PSV 水平下的患者。在每个 PSV 水平，同一呼吸上计算 P、P 和 P。用线性混合效应模型分析 P、P 和 P 之间的差异。采用重复测量的 Bland-Altman 分析评估偏差和一致性。通过接受者操作特征曲线下面积评估 P 和 P 检测过度辅助的能力。使用最大化敏感性和特异性之和的截止值计算阳性和阴性预测值。在每个 PSV 水平，P 与 P 无差异（p=0.96），而 P 明显低于 P。P 与 P 之间的偏差为零，而 P 系统地低估了 P 6cmHO。P 与 P 之间以及 P 与 P 之间的一致性界限在偏倚的情况下为±12cmHO。P≤4cmHO 和 P≤1cmHO 均具有出色的阴性预测值[分别为 0.98（95%CI 0.94-1）和 0.96（95%CI 0.91-0.99）]，以识别过度辅助。由于一致性界限远远超过信号大小，因此最小二乘法拟合或吸气末阻断法无法准确估计 PSV 期间的吸气努力。然而，这些非侵入性方法可用于筛选存在或最小化呼吸肌激活风险的患者，以防止呼吸机诱导的膈肌功能障碍。
