Breuer J, Waidelich F, Irtel von Brenndorff C, Sieverding L, Rosendahl W, Baden W, Gass M, Apitz J
Department of Paediatrics, University of Tübingen, Germany.
Eur J Pediatr. 1997 Jun;156(6):460-2. doi: 10.1007/s004310050639.
The aim of the present study was to analyse the time response to nitric oxide (NO) dosing changes as well as the formation of nitrogen dioxide (NO2) with different ventilation systems, respirator settings and application sites during NO inhalation. The inspired NO and NO2 concentrations were continuously measured using chemiluminiscence within a dummy ventilatory system equipped with two different respirator systems (Siemens Servo 900c and Bear BP 2001). NO was either introduced into the afferent limb of the ventilatory circuit close to the endotracheal tube (site A) or into the so-called low pressure port of the Servo 900c respirator, far away from the endotracheal tube (site B). In addition, the decay of the inspired NO concentration after cessation of the NO gas flow was studied. This decay was considerably prolonged when NO was introduced at site B (time constants: tau = 7.19 min versus tau = 0.29 min). Within the concentration range studied (0-25 ppm NO) a linear correlation between the NO and NO2 concentration was found. At site A and an inspired oxygen concentration of > 0.95 NO2 formation amounts to 1.14% +/- 0.11% of the NO concentration. Using this value one can calculate the NO2 formation for a given NO dose. For example, when 40 ppm NO are applied, a concentration of 0.45 ppm NO2 can be expected, which is well below the relevant toxic concentrations. However, when NO was introduced at site B, NO2 formation was significantly increased to 1.61% +/- 0.16%. Passage of the ventilated gas through soda lime led only to a slight and insignificant reduction in NO2 concentration. The continuous flow respirator BP 2001 showed a significantly lower NO2 concentration when compared to the non-continuous flow respirator Servo 900c (0.64 +/- 0.11% vs.1.14 +/- 0.11%).
The application of NO close to the endotracheal tube is associated with a much faster response of the actual inspired NO concentration to dosing changes and shows the lowest NO2 formation. In order to avoid toxic NO2 concentrations, an upper limit of 40 ppm NO is recommended for continuous NO inhalation.
本研究的目的是分析一氧化氮（NO）剂量变化的时间响应，以及在吸入NO期间不同通气系统、呼吸机设置和应用部位二氧化氮（NO₂）的形成情况。在配备两种不同呼吸机系统（西门子Servo 900c和熊牌BP 2001）的模拟通气系统中，使用化学发光法连续测量吸入的NO和NO₂浓度。NO要么在靠近气管内导管处引入通气回路的传入肢体（部位A），要么引入远离气管内导管的Servo 900c呼吸机的所谓低压端口（部位B）。此外，还研究了NO气流停止后吸入的NO浓度的衰减情况。当在部位B引入NO时，这种衰减显著延长（时间常数：τ = 7.19分钟对τ = 0.29分钟）。在所研究的浓度范围内（0 - 25 ppm NO），发现NO和NO₂浓度之间存在线性相关性。在部位A且吸入氧浓度> 0.95时，NO₂的形成量相当于NO浓度的1.14% ± 0.11%。使用该值可以计算给定NO剂量下的NO₂形成量。例如，当应用40 ppm NO时，预计NO₂浓度为0.45 ppm，远低于相关毒性浓度。然而，当在部位B引入NO时，NO₂的形成显著增加至1.61% ± 0.16%。通气气体通过苏打石灰仅导致NO₂浓度略有且不显著的降低。与非连续流呼吸机Servo 900c相比，连续流呼吸机BP 2001显示出显著更低的NO₂浓度（0.64 ± 0.11%对1.14 ± 0.11%）。
在气管内导管附近应用NO与实际吸入的NO浓度对剂量变化的响应快得多相关，并显示出最低的NO₂形成。为避免有毒的NO₂浓度，建议连续吸入NO的上限为40 ppm。
