Bloch Konrad E, Russi Erich W, Kaplan Vladimir
Pulmonary Division, University Hospital of Zürich, Rämistrasse 100, CH-8091 Zürich, Switzerland.
Clin Sci (Lond). 2004 Jun;106(6):589-98. doi: 10.1042/CS20030325.
In the present study, our aim was to investigate whether the variability of conductance over the course of inspiration reflects flow limitation. Pressure/flow conditions in the upper airway were modelled by a collapsible tube within a rigid chamber and a pump simulating respiration. Instantaneous conductance was estimated every 20 ms as flow/resistive pressure, and its variability during inspiration expressed as the 90th/50th percentile ratio. Accuracy of this ratio to quantify flow limitation was evaluated by observing whether it changed predictably with adjustments of model parameters. To illustrate the potential of this ratio to quantify flow limitation in a clinical setting, we recorded pneumotachographic airflow and oesophageal pressure in 11 patients with obstructive sleep apnoea during nasal continuous positive airway pressure (CPAP) ventilation, and observed changes in the 90th/50th percentile ratio of inspiratory lung conductance induced by mask pressure titration. Rising pressure surrounding the collapsible tube from subatmospheric to positive values induced progressive inspiratory collapse and increased 90th/50th percentile ratios of inspiratory conductance as predicted. Changes in flow limitation induced by other model modifications were also correctly tracked by the 90th/50th conductance percentile ratio. Increasing mask pressure during CPAP ventilation in sleep apnoea patients from subtherapeutic to therapeutic pressure levels was associated with the expected decrease in the 90th/50th percentile ratio of inspiratory lung conductance from a mean of 6.5+/-3.1 to 1.6+/-0.3 ( P <0.001). We conclude that variability of inspiratory conductance quantified by the 90th/50th percentile ratio may serve as a measure of flow limitation that is independent of the absolute value of conductance.
在本研究中，我们的目的是调查吸气过程中传导率的变异性是否反映气流受限。上气道的压力/流量状况通过刚性腔内的可塌陷管和模拟呼吸的泵进行建模。每20毫秒以流量/阻力压力估算瞬时传导率，其在吸气过程中的变异性表示为第90/50百分位数之比。通过观察该比值是否随模型参数的调整而可预测地变化，评估该比值量化气流受限的准确性。为了说明该比值在临床环境中量化气流受限的潜力，我们记录了11例阻塞性睡眠呼吸暂停患者在鼻持续气道正压通气（CPAP）期间的呼吸流速仪气流和食管压力，并观察面罩压力滴定引起的吸气肺传导率第90/50百分位数比值的变化。正如预测的那样，可塌陷管周围压力从低于大气压升至正值会导致逐渐的吸气塌陷，并增加吸气传导率的第90/50百分位数比值。第90/50传导率百分位数比值也正确地跟踪了其他模型修改引起的气流受限变化。睡眠呼吸暂停患者在CPAP通气期间将面罩压力从低于治疗水平增加到治疗压力水平，与吸气肺传导率第90/50百分位数比值从平均6.5±3.1预期下降到1.6±0.3相关（P<0.001）。我们得出结论，以第90/50百分位数比值量化的吸气传导率变异性可作为一种与传导率绝对值无关的气流受限测量指标。
