Coates A L, Fletcher M E, Dundas I, Stocks J
Portex Department of Paediatric Anaesthesia, Institute of Child Health, London, England.
Pediatr Pulmonol. 1995 May;19(5):299-306. doi: 10.1002/ppul.1950190509.
The single breath test for the measurement of respiratory system resistance and compliance in newborns consists of an end inspiratory occlusion which is subsequently released, allowing expiration to proceed through a pneumotachograph (PNT). The measured flow is then integrated to give volume. The simplicity of the test is one of the major reasons for its popularity. However, some investigators have cautioned against the use of an occlusion distal to the PNT because pressurization of the PNT may introduce artifacts in the flow measurement. Despite this caution, many commercial systems use a pressurized PNT. This study investigated the errors that would result from pressurization of the PNT by providing a step function of flow to two infant PNTs, a Fleisch #0 and a Hans Rudolph 4500, in the unpressurized and pressurized state. In each case there was an initial rapid rise of the flow signal, followed by some overshoot and oscillations that rapidly died out. The overshoot and oscillations for the Hans Rudolph PNT were greater when pressurized whereas pressurization had little effect on the Fleisch PNT. Unpressurized, the two were similar. In either case, the artifact introduced by pressurization of the PNT died out so quickly that it would have little effect on any measurement in an infant.
用于测量新生儿呼吸系统阻力和顺应性的单次呼吸试验包括一次吸气末阻断，随后阻断解除，使呼气通过呼吸流速计（PNT）进行。然后对测得的流量进行积分以得出容积。该试验的简单性是其广受欢迎的主要原因之一。然而，一些研究人员警告不要在PNT远端使用阻断，因为PNT增压可能会在流量测量中引入伪像。尽管有此警告，许多商业系统仍使用增压的PNT。本研究通过向两个婴儿用PNT（一个Fleisch #0和一个Hans Rudolph 4500）在未增压和增压状态下提供阶跃流量函数，研究了PNT增压可能导致的误差。在每种情况下，流量信号最初都会迅速上升，随后出现一些过冲和振荡，这些过冲和振荡会迅速消失。Hans Rudolph PNT在增压时的过冲和振荡更大，而增压对Fleisch PNT影响很小。在未增压时，两者相似。在任何一种情况下，PNT增压引入的伪像消失得非常快，以至于对婴儿的任何测量几乎没有影响。
