Sly P D, Bates J H
Meakins-Christie Laboratories, McGill University, Montreal, Canada.
Pediatr Pulmonol. 1988;4(4):219-24. doi: 10.1002/ppul.1950040406.
The interrupter technique involves measuring pressure changes at the airway opening following abrupt interruption of airflow, and relies on rapid equilibration of alveolar and airway opening pressures. Following airway occlusion one generally sees a rapid change in airway opening pressure, Pinit, which reflects the resistive pressure drop across the system, followed by a secondary, slower pressure change, Pdif, which reflects the tissue visco-elastic properties together with any redistribution of gases occurring between lung units at different pressure at the time of interruption. Physical factors in the measuring equipment, i.e., the time taken for valve closure and the presence of a proximal compliant compartment, can cause errors in the calculation of resistance and elastance using the interrupter technique. A computer model was used to determine the effects of these factors on the calculation of resistance and elastance in normal infants, premature infants, and infants with bronchopulmonary dysplasia. The elastance from 25 ml of dead space gas did not introduce significant errors into the measurements in any group of infants, but the presence of an unsupported upper airway caused errors of up to 245%. Increasing valve closure time introduced progressively larger errors into the calculation of resistance and elastance. To keep these errors acceptably small, an occlusion valve should close in 20 ms or less.
阻断器技术涉及在气流突然中断后测量气道开口处的压力变化，并依赖于肺泡压力和气道开口压力的快速平衡。气道阻塞后，通常会观察到气道开口压力Pinit迅速变化，这反映了整个系统的阻力性压力降，随后是二次较慢的压力变化Pdif，它反映了组织的粘弹性特性以及在阻断时不同压力下肺单位之间发生的任何气体再分布。测量设备中的物理因素，即阀门关闭所需的时间以及近端顺应性腔室的存在，可能会导致使用阻断器技术计算阻力和弹性时出现误差。使用计算机模型来确定这些因素对正常婴儿、早产儿和支气管肺发育不良婴儿的阻力和弹性计算的影响。25毫升死腔气体产生的弹性在任何一组婴儿的测量中都不会引入显著误差，但无支撑的上气道的存在会导致高达245%的误差。增加阀门关闭时间会在阻力和弹性计算中引入越来越大的误差。为了将这些误差保持在可接受的小范围内，阻断阀应在20毫秒或更短时间内关闭。
