Jarreau P H, Louis B, Dassieu G, Desfrere L, Blanchard P W, Moriette G, Isabey D, Harf A
Service de Médecine Néonatale, Centre Hospitalier Universitaire Cochin-Port Royal, Assistance Publique-Hôpitaux de Paris-Université Paris V, 75014 Paris, France.
J Appl Physiol (1985). 1999 Jul;87(1):36-46. doi: 10.1152/jappl.1999.87.1.36.
Endotracheal tubes (ETTs) constitute a resistive extra load for intubated patients. The ETT pressure drop (DeltaP(ETT)) is usually described by empirical equations that are specific to one ETT only. Our laboratory previously showed that, in adult ETTs, DeltaP(ETT) is given by the Blasius formula (F. Lofaso, B. Louis, L. Brochard, A. Harf, and D. Isabey. Am. Rev. Respir. Dis. 146: 974-979, 1992). Here, we also propose a general formulation for neonatal and pediatric ETTs on the basis of adimensional analysis of the pressure-flow relationship. Pressure and flow were directly measured in seven ETTs (internal diameter: 2.5-7.0 mm). The measured pressure drop was compared with the predicted drop given by general laws for a curved tube. In neonatal ETTs (2.5-3.5 mm) the flow regime is laminar. The DeltaP(ETT) can be estimated by the Ito formula, which replaces Poiseuille's law for curved tubes. For pediatric ETTs (4.0-7.0 mm), DeltaP(ETT) depends on the following flow regime: for laminar flow, it must be calculated by the Ito formula, and for turbulent flow, by the Blasius formula. Both formulas allow for ETT geometry and gas properties.
气管内导管（ETT）对插管患者而言构成了一个额外的阻力负荷。ETT压力降（ΔP(ETT)）通常由仅适用于一种ETT的经验方程来描述。我们实验室先前表明，对于成人ETT，ΔP(ETT)由布拉修斯公式给出（F. 洛法索、B. 路易斯、L. 布罗沙尔、A. 哈尔夫和D. 伊萨贝。《美国呼吸与危重症医学杂志》146: 974 - 979, 1992）。在此，我们还基于压力 - 流量关系的无量纲分析，为新生儿和儿科ETT提出了一种通用公式。在7根ETT（内径：2.5 - 7.0毫米）中直接测量了压力和流量。将测得的压力降与弯曲管通用定律给出的预测压降进行了比较。在新生儿ETT（2.5 - 3.5毫米）中，流动状态为层流。ΔP(ETT)可通过伊藤公式估算，该公式取代了弯曲管的泊肃叶定律。对于儿科ETT（4.0 - 7.0毫米），ΔP(ETT)取决于以下流动状态：对于层流，必须通过伊藤公式计算，对于湍流，则通过布拉修斯公式计算。这两个公式都考虑了ETT的几何形状和气体特性。
