Bacon J P, Farney R J, Jensen R L, Walker J M, Cloward T V
Department of Medicine, University of Utah Medical Center, USA.
Chest. 2000 Nov;118(5):1441-9. doi: 10.1378/chest.118.5.1441.
Nasal continuous positive airway pressure (CPAP) is standard therapy for obstructive sleep apnea syndrome. The effective nasal mask pressure may be adversely affected by factors that increase system resistance (eg, long tubing and/or water condensation) and by dynamic variables (breathing frequency [f] and tidal volume [VT]). The present study was conducted in order to assess the performance of CPAP machines throughout a range of simulated clinical conditions.
Four currently used CPAP machines were tested at settings of 5, 10, 15, and 20 cm H(2)O using a pulmonary waveform generator to produce VTs of 0.4, 0.8, and 1.2 L at frequencies of 10, 20, and 30 breaths/min. Machines were tested under five conditions: 6-foot and 12-foot tubing, with and without an in-line humidifier, and 12-foot tubing with humidifier and water condensation.
Maximum and minimum mask pressure measurements were obtained during five respiratory cycles for each dynamic variable under each of the five conditions and CPAP settings (180 experiments on each of four CPAP models).
Using typical clinical parameters (VT, 0.4 L and 0.8 L; f, 10 breaths/min and 20 breaths/min; and CPAP, 5 to 15 cm H(2)O), mask pressure consistently varied above and below the set point when additional tubing and/or a humidifier were added to the system (0.7 to 2.9 cm H(2)O below and 0.5 to 1.0 cm H(2)O above the set pressure). Water condensation caused large pressure deviations (inspiratory pressure ranged from 3.5 to 5.6 cm H(2)O below set pressure, and expiratory pressure ranged from 0.7 to 3.5 cm H(2)O above set pressure).
Therapy and compliance could be adversely affected because some CPAP machines in current use do not maintain constant continuous mask pressure when tested using simulated conditions, especially when water condenses in the tubing.
鼻持续气道正压通气（CPAP）是阻塞性睡眠呼吸暂停综合征的标准治疗方法。有效的鼻罩压力可能会受到增加系统阻力的因素（如长管路和/或水凝结）以及动态变量（呼吸频率[f]和潮气量[VT]）的不利影响。进行本研究是为了评估CPAP机器在一系列模拟临床条件下的性能。
使用肺波形发生器，在5、10、15和20 cm H₂O的设置下，对四台目前使用的CPAP机器进行测试，以在10、20和30次呼吸/分钟的频率下产生0.4、0.8和1.2 L的潮气量。在五种条件下对机器进行测试：6英尺和12英尺的管路，有无在线加湿器，以及带有加湿器和水凝结的12英尺管路。
在五种条件和CPAP设置下，针对每个动态变量，在五个呼吸周期内获得最大和最小面罩压力测量值（对四个CPAP模型中的每一个进行180次实验）。
使用典型的临床参数（VT，0.4 L和0.8 L；f，10次呼吸/分钟和20次呼吸/分钟；以及CPAP，5至15 cm H₂O），当向系统中添加额外的管路和/或加湿器时，面罩压力始终在设定点上下变化（比设定压力低0.7至2.9 cm H₂O，比设定压力高0.5至1.0 cm H₂O）。水凝结导致较大的压力偏差（吸气压力比设定压力低3.5至5.6 cm H₂O，呼气压力比设定压力高0.7至3.5 cm H₂O）。
治疗和依从性可能会受到不利影响，因为在模拟条件下测试时，一些目前使用的CPAP机器不能保持恒定的持续面罩压力，尤其是当管路中有水凝结时。
