Children's Hospital Medical Center of Akron, Akron, OH, USA.
Respir Care. 2011 Dec;56(12):1893-900. doi: 10.4187/respcare.01204. Epub 2011 Jun 17.
Limited data are available to describe the CPAP effects that can be expected when using high flow with a traditional nasal cannula.
To describe the relationship between the pressure generated at the airway opening and flow through a nasal cannula using a simulated infant model. We hypothesized that positive pressure generated by a standard cannula at flows > 2 L/min would be minimal and clinically unimportant.
Nares were simulated with holes drilled in a plastic fixture. A nares template for CPAP prongs served as a sizing template for the holes. Small, medium, and large nares fixtures were constructed and connected to a lung simulator that simulated spontaneous breathing. Respiratory muscle pressure was simulated by setting a waveform and adjusting the amplitude to deliver a range of tidal volumes (V(T)) from 3 mL to 12 mL. Lung compliance and resistance were set at 0.5 mL/cm H(2)O and 125 cm H(2)O/L/s, respectively. Nasal cannulas were inserted in the model nares. We assured that the prong occlusion of the nares did not exceed 50%. Cannula flow was adjusted from 2-6 L/min in 1-L/min increments. Data were averaged over 20 breaths. Mean airway pressure and percent change in V(T) were recorded.
The greatest effect on V(T) (mean ± SD 0.16 ± 0.10 mL) and pressure change (mean ± SD 0.7 ± 0.5 cm H(2)O) occurred with the premature cannula. The least effect on pressure (mean ± SD 0.3 ± 0.22 cm H(2)O) and V(T) change (mean ± SD 0.01 ± 0.02 mL) occurred with the infant cannula.
Clinically important pressures were not generated by high flows with a standard nasal cannula. The differences in spontaneous V(T) across all flows were negligible.
使用传统鼻导管时，高流量能产生的 CPAP 效果的数据有限。
描述使用模拟婴儿模型时，在气道开口处产生的压力与通过鼻导管的流量之间的关系。我们假设标准鼻导管在流量>2L/min 时产生的正压很小，临床意义不大。
在塑料固定装置上钻孔模拟鼻孔。CPAP 鼻塞的鼻塞模板用作孔的尺寸模板。构建了小、中、大鼻孔固定器，并将其连接到模拟自主呼吸的肺模拟器上。通过设置波形并调整幅度来模拟呼吸肌肉压力，以提供从 3mL 到 12mL 的一系列潮气量 (V(T))。肺顺应性和阻力分别设置为 0.5mL/cmH(2)O 和 125cmH(2)O/L/s。将鼻导管插入模型鼻孔。我们确保鼻塞对鼻孔的阻塞不超过 50%。以 1L/min 的增量从 2-6L/min 调节导管流量。数据在 20 次呼吸中平均。记录平均气道压力和 V(T)的变化百分比。
对 V(T)（平均 ± SD 0.16 ± 0.10mL）和压力变化（平均 ± SD 0.7 ± 0.5cmH(2)O）影响最大的是早产鼻塞。对压力（平均 ± SD 0.3 ± 0.22cmH(2)O）和 V(T)变化（平均 ± SD 0.01 ± 0.02mL）影响最小的是婴儿鼻塞。
标准鼻导管的高流量不会产生临床重要的压力。所有流量下的自主 V(T)差异可以忽略不计。
