Lin Hui-Ling, Fink James B, Zhou Yue, Cheng Yung-Sung
Respiratory Care Program, Chang Gung University, 259 Wen-Hwa 1st Road, Tao-Yuan, Taiwan.
Respir Care. 2009 Oct;54(10):1336-41.
A practitioner questioned whether moisture that collected in the ventilator circuit and spacer affected the delivery of aerosol from a pressurized metered-dose inhaler (pMDI). An in vitro model was used to quantify the impact of accumulated humidity in a pMDI spacer and ventilator over time.
A ventilator with an adult heated-wire ventilator circuit and humidifier was set to deliver adult settings. An impactor was placed between the endotracheal tube and the test lung to determine drug mass and mass median aerodynamic diameter of the aerosol delivered. An AeroVent pMDI spacer was placed in the inspiratory limb of the ventilator circuit and left in an open position. Eight actuations of HFA albuterol pMDI (720 microg) was administered at 1, 2, and 3 hours after the heater had reached equilibrium at 37 degrees C, and <10 min after turning off the heater/humidifier. The spacer was dried and returned to the heated circuit for additional testing. Samples were analyzed via spectrophotometer. One-way analysis of variance was applied (P<.05).
The delivered drug as a percent of emitted dose (mean+/-SD) was greater at hour one (23+/-2.1%) and with the dry spacer (21.8+/-3.3%) than at hours 2 and 3 or with humidifier off (11.4+/-3.8%, 12.3+/-0.8%, and 12.7+/-0.3%, respectively, P=.002). Mass median aerodynamic diameters with each comparison did not vary between conditions. Delivery efficiency was similar for the dry spacer and the spacer in the humidified circuit for one hour. However, once visible condensate occurred, drug delivery efficiency decreased by approximately 50%.
Aerosol delivery from a pMDI with spacer during mechanical ventilation was greater with a dry spacer and unchanged for the first hour after initiating heated humidification. Turning off the heated humidifier did not increase drug delivered.
一名从业者质疑呼吸机回路和储雾罐中积聚的水分是否会影响来自压力定量吸入器（pMDI）的气雾剂递送。使用体外模型来量化pMDI储雾罐和呼吸机中随时间积累的湿度的影响。
一台配备成人加热丝呼吸机回路和加湿器的呼吸机设置为成人模式。在气管内导管和测试肺之间放置一个撞击器，以确定递送的气雾剂的药物质量和质量中值空气动力学直径。一个AeroVent pMDI储雾罐放置在呼吸机回路的吸气支中，并保持打开位置。在加热器在37℃达到平衡后1、2和3小时，以及关闭加热器/加湿器后不到10分钟，给予8次HFA沙丁胺醇pMDI（720微克）的按压。储雾罐干燥后放回加热回路进行额外测试。通过分光光度计分析样品。应用单因素方差分析（P<0.05）。
作为喷出剂量百分比的递送药物（平均值±标准差）在第1小时（23±2.1%）和使用干燥储雾罐时（21.8±3.3%）高于第2和3小时或关闭加湿器时（分别为11.4±3.8%、12.3±0.8%和12.7±0.3%，P = 0.002）。各比较条件下的质量中值空气动力学直径在不同条件之间没有变化。干燥储雾罐和加湿回路中的储雾罐在一小时内的递送效率相似。然而，一旦出现可见冷凝物，药物递送效率下降约50%。
在机械通气期间，使用干燥储雾罐时，带储雾罐的pMDI的气雾剂递送量更大，并且在开始加热加湿后的第一小时内保持不变。关闭加热加湿器不会增加递送的药物量。
