Flow Index, a numerical expression of the shape of the inspiratory flow-time waveform recorded during pressure support ventilation, is associated with patient inspiratory effort. The aim of this study was to assess the accuracy of Flow Index in detecting high or low inspiratory effort during pressure support ventilation and to establish cutoff values for the Flow index to identify these conditions. The secondary aim was to compare the performance of Flow index,of breathing pattern parameters and of airway occlusion pressure (P0.1) in detecting high or low inspiratory effort during pressure support ventilation. Data from 24 subjects was included in the analysis, accounting for a total of 702 breaths. Breaths with high inspiratory effort were defined by a pressure developed by inspiratory muscles (Pmusc) greater than 10 cmH2O while breaths with low inspiratory effort were defined by a Pmusc lower than 5 cmH2O. The areas under the receiver operating characteristic curves of Flow Index and respiratory rate, tidal volume,respiratory rate over tidal volume and P0.1 were analyzed and compared to identify breaths with low or high inspiratory effort. Pmusc, P0.1, Pressure Time Product and Flow Index differed between breaths with high, low and intermediate inspiratory effort, while RR, RR/VT and VT/kg of IBW did not differ in a statistically significant way. A Flow index higher than 4.5 identified breaths with high inspiratory effort [AUC 0.89 (CI 95% 0.85–0.93)], a Flow Index lower than 2.6 identified breaths with low inspiratory effort [AUC 0.80 (CI 95% 0.76–0.83)]. Flow Index is accurate in detecting high and low spontaneous inspiratory effort during pressure support ventilation.

中文翻译：

---

流量指数准确识别压力支持通气期间吸气努力低或高的呼吸

流量指数是压力支持通气期间记录的吸气流量-时间波形形状的数值表达，与患者的吸气努力有关。本研究的目的是评估流量指数在压力支持通气期间检测高或低吸气努力的准确性，并确定流量指数的截止值以识别这些情况。次要目的是比较流量指数、呼吸模式参数和气道阻塞压力 (P0.1) 在检测压力支持通气期间吸气努力高低方面的性能。来自 24 名受试者的数据被纳入分析，总共 702 次呼吸。吸气用力高的呼吸定义为吸气肌产生的压力 (Pmusc) 大于 10 cmH2O，而吸气用力低的呼吸定义为 Pmusc 低于 5 cmH2O。分析并比较流量指数和呼吸频率、潮气量、呼吸频率与潮气量和P0.1的接收者操作特征曲线下面积，以确定吸气努力低或高的呼吸。Pmusc、P0.1、压力时间乘积和流量指数在高、低和中等吸气努力的呼吸之间存在差异，而 IBW 的 RR、RR/VT 和 VT/kg 没有统计学显着差异。流量指数高于 4.5 识别出高吸气努力的呼吸 [AUC 0.89 (CI 95% 0.85–0.93)]，流量指数低于 2.6 识别出低吸气努力的呼吸 [AUC 0. 80 (CI 95% 0.76–0.83)]。Flow Index 可准确检测压力支持通气期间的自主吸气努力的高低。