Imanaka H, Hess D, Kirmse M, Bigatello L M, Kacmarek R M, Steudel W, Hurford W E
Harvard Medical School, Boston, Massachusetts, USA.
Anesthesiology. 1997 Mar;86(3):676-88. doi: 10.1097/00000542-199703000-00021.
Various systems to administer inhaled nitric oxide (NO) have been used in patients and experimental animals. We used a lung model to evaluate five NO delivery systems during mechanical ventilation with various ventilatory patterns.
An adult mechanical ventilator was attached to a test lung configured to separate inspired and expired gases. Four injection systems were evaluated with NO injected either into the inspiratory circuit 90 cm proximal to the Y piece or directly at the Y piece and delivered either continuously or only during the inspiratory phase. Alternatively, NO was mixed with air using a blender and delivered to the high-pressure air inlet of the ventilator. Nitric oxide concentration was measured from the inspiratory limb of the ventilator circuit and the tracheal level using rapid- and slow-response chemiluminescence analyzers. The ventilator was set for constant-flow volume control ventilation, pressure control ventilation, pressure support ventilation, or synchronized intermittent mandatory ventilation. Tidal volumes of 0.5 l and 1 l were evaluated with inspiratory times of 1 s and 2 s.
The system that premixed NO proximal to the ventilator was the only one that maintained constant NO delivery regardless of ventilatory pattern. The other systems delivered variable NO concentration during pressure control ventilation and spontaneous breathing modes. Systems that injected a continuous flow of NO delivered peak NO concentrations greater than the calculated dose. These variations were not apparent when a slow-response chemiluminescence analyzer was used.
NO delivery systems that inject NO at a constant rate, either continuously or during inspiration only, into the inspiratory limb of the ventilator circuit produce highly variable and unpredictable NO delivery when inspiratory flow is not constant. Such systems may deliver a very high NO concentration to the lungs, which is not accurately reflected by measurements performed with slow-response analyzers.
多种吸入一氧化氮（NO）给药系统已应用于患者和实验动物。我们使用肺模型在不同通气模式的机械通气过程中评估了五种NO输送系统。
将一台成人机械通气机连接到一个用于分离吸入和呼出气体的测试肺上。对四种注射系统进行了评估，NO分别注入Y形管近端90 cm处的吸气回路中，或直接注入Y形管处，并持续输送或仅在吸气阶段输送。另外，使用混合器将NO与空气混合后输送到通气机的高压空气入口。使用快速和慢速响应化学发光分析仪从通气机回路的吸气支路和气管水平测量一氧化氮浓度。通气机设置为恒流容量控制通气、压力控制通气、压力支持通气或同步间歇强制通气。评估了潮气量为0.5升和1升、吸气时间为1秒和2秒时的情况。
在通气机近端预混NO的系统是唯一一种无论通气模式如何都能保持NO输送恒定的系统。其他系统在压力控制通气和自主呼吸模式下输送的NO浓度可变。持续注入NO的系统输送的NO峰值浓度高于计算剂量。使用慢速响应化学发光分析仪时，这些变化并不明显。
当吸气流量不恒定时，以恒定速率（连续或仅在吸气期间）将NO注入通气机回路吸气支路的NO输送系统会产生高度可变且不可预测的NO输送。此类系统可能会向肺部输送非常高的NO浓度，而慢速响应分析仪进行的测量无法准确反映这一情况。
