Pérez Fontán J J, Heldt G P, Gregory G A
Crit Care Med. 1985 Dec;13(12):1052-5. doi: 10.1097/00003246-198512000-00014.
To study the effects of a periodic pattern of gas flow on the dynamic behavior of infant endotracheal tubes, we measured the resistance (expressed as a function of gas flow) and inertia of endotracheal tubes of 2.5, 3.0, and 3.5-mm internal diameter under conditions of both periodic and quasisteady gas flow. We examined how resistance and inertia are affected by ventilatory rate, the direction of gas flow through the tube, and the expansion of the airway caliber at the junction of the tube and the trachea. The resistance of the endotracheal tubes was proportional to gas flow for ventilatory rates of 60, 90, and 120 breath/min and for quasisteady flow, indicating turbulence even at low flow rates. The resistance of the tubes was less sensitive to ventilatory rate, direction of flow, and expansion of the airway caliber than that of larger endotracheal tubes, a finding explained by the flow conditions defined by the Womersley and Reynolds numbers in these tubes. All tubes exhibited measureable inertia, as predicted from their small diameter. The resistive and inertial properties of the endotracheal tubes described in this report can be used to evaluate the contribution of the endotracheal tube to the dynamics of breathing in intubated infants.
为研究气流的周期性模式对婴儿气管内导管动态行为的影响，我们在周期性气流和准稳态气流条件下，测量了内径为2.5、3.0和3.5毫米的气管内导管的阻力（表示为气流的函数）和惯性。我们研究了通气频率、气流通过导管的方向以及导管与气管交界处气道口径的扩张如何影响阻力和惯性。对于60、90和120次呼吸/分钟的通气频率以及准稳态气流，气管内导管的阻力与气流成正比，这表明即使在低流速下也存在湍流。与较大内径的气管内导管相比，这些导管的阻力对通气频率、气流方向和气道口径扩张的敏感性较低，这一发现可通过这些导管中由沃默斯利数和雷诺数定义的流动条件来解释。正如根据其小直径所预测的那样，所有导管都表现出可测量的惯性。本报告中描述的气管内导管的阻力和惯性特性可用于评估气管内导管对插管婴儿呼吸动力学的影响。
