Whitelaw W A, Derenne J P
Department of Medicine, University of Calgary, Alberta, Canada.
J Appl Physiol (1985). 1993 Apr;74(4):1475-83. doi: 10.1152/jappl.1993.74.4.1475.
Airway occlusion pressure has been used in the past two decades for assessing output of the respiratory controller. It gives a measurement of a weighted sum of the effect of all respiratory muscles active at a given time and, unlike ventilation or tidal volume, does not depend on the resistance or compliance of the respiratory system. In anesthetized subjects or animals, it gives a tracing of the time course of respiratory neuromuscular output through the respiratory cycle, modified by elimination of most phasic vagal stretch receptor feedback and perhaps slightly by activation of some chest wall reflexes. The original postulate that an occluded inspiration would be isometric and the measured pressure free from losses due to force-length and force-velocity has been shown to be incorrect. The volume at which occlusion takes effect, distortions of the chest wall during the maneuver, tonic vagal input, and strength of the muscles must be taken into account when the data are interpreted. Brief occlusions [pressure at 0.1 s (P0.1)] are useful in measuring output in the very first part of inspiration in conscious subjects but must be treated with a great deal of caution. They are most reliable when end-expiratory volume remains constant and there are no important phase lags between flow and pressure. Allowance may be necessary for damping of the pressure signal on its passing through the compliant upper airway. Changes in P0.1 may often be due to changes in the shape of the driving pressure wave without a proportionate change in overall output. The technique remains useful when its limitations are recognized. Because of its simplicity, it can be easily and usefully applied to a range of clinical investigations.
在过去二十年中，气道阻塞压一直用于评估呼吸控制器的输出。它测量的是在给定时间所有活跃呼吸肌作用的加权总和，与通气量或潮气量不同，它不依赖于呼吸系统的阻力或顺应性。在麻醉的受试者或动物中，它描绘了呼吸周期中呼吸神经肌肉输出的时间进程，由于消除了大部分相位性迷走神经牵张感受器反馈，并可能因一些胸壁反射的激活而略有改变。最初认为阻塞性吸气是等长的，且测量的压力不受力-长度和力-速度损失影响的假设已被证明是错误的。在解释数据时，必须考虑阻塞生效时的容积、操作过程中胸壁的变形、紧张性迷走神经输入以及肌肉力量。短暂阻塞[0.1秒时的压力（P0.1）]有助于测量清醒受试者吸气最初阶段的输出，但必须极其谨慎地对待。当呼气末容积保持恒定且流量和压力之间没有重要的相位滞后时，它们最为可靠。在压力信号通过顺应性上呼吸道时，可能需要考虑其阻尼。P0.1的变化通常可能是由于驱动压力波形状的改变，而总体输出没有成比例的变化。当认识到其局限性时，该技术仍然有用。由于其简单性，它可以轻松且有效地应用于一系列临床研究。
