Farré Ramon, Montserrat Josep M, Ballester Eugeni, Navajas Daniel
Unitat de Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Spain.
Chest. 2002 Jan;121(1):196-200. doi: 10.1378/chest.121.1.196.
Continuous positive airway pressure (CPAP) is widely applied as a home treatment during sleep. Conventional CPAP devices are based on a blower to generate nasal pressure and to maintain air washout from the circuit. Because common CPAP systems do not incorporate alarms, failure in the device or in the electric supply could result in rebreathing.
To assess the potential rebreathing to which a patient could be subjected after CPAP failure.
Four conventional CPAP devices, PV100 (Breas Medica; Molnlycke, Sweden), CP90 (Taema; Antony, France), and SoloPlus and BiPAP (Respironics, Murrysville, PA), and three common exhalation ports (Whisper Swivel [Respironics], Plateau [Respironics], and 4-mm orifice) were tested in a bench study. Rebreathing after failure was assessed by measuring the resistance of the exhalation port (REP) and the resistance of the tubing plus CPAP device (RTUB), and by measuring O(2) and CO(2) concentrations in the nasal mask in a subject breathing through a CPAP system.
REP was much higher (approximately 30 cm H(2)O x s/L) than RTUB (approximately 1 cm H(2)O x s/L). Most (approximately 90%) of the breathing tidal volume would flow from/to the tubing plus CPAP device, which represents a dead space (> or = 0.5 L) similar to the patient's tidal volume. After CPAP failure, end-tidal O(2) in the mask changed from 16.8 to 9.2% and end-tidal CO(2) in the mask changed from 4.2 to 6.2%. By contrast, O(2) and CO(2) did not change when a nonrebreathing valve was placed in the mask.
Common CPAP systems run a risk of inducing rebreathing in case of failure. This risk could be easily avoided by including a passive valve in the apparatus.
持续气道正压通气（CPAP）作为一种睡眠期间的家庭治疗方法被广泛应用。传统的CPAP设备基于一个鼓风机来产生鼻内压力并维持回路中的气体排出。由于普通的CPAP系统没有配备警报装置，设备故障或电源故障可能导致重新呼吸。
评估CPAP失败后患者可能面临的潜在重新呼吸情况。
在一项实验研究中测试了四种传统的CPAP设备，PV100（瑞典莫恩利克的布雷亚斯医疗公司）、CP90（法国安东尼的泰玛公司）以及SoloPlus和BiPAP（宾夕法尼亚州默里斯维尔的瑞思迈公司），还有三个常见的呼气端口（瑞思迈的Whisper Swivel、瑞思迈的Plateau以及4毫米孔口）。通过测量呼气端口阻力（REP）和管路加CPAP设备的阻力（RTUB），以及通过测量受试者通过CPAP系统呼吸时鼻罩内的氧气和二氧化碳浓度来评估失败后的重新呼吸情况。
REP（约30厘米水柱×秒/升）比RTUB（约1厘米水柱×秒/升）高得多。大部分（约90%）的呼吸潮气量会流入/流出管路加CPAP设备，这代表了一个与患者潮气量相似的无效腔（≥0.5升）。CPAP失败后，面罩内的呼气末氧气从16.8%变为9.2%，面罩内的呼气末二氧化碳从4.2%变为6.2%。相比之下，当在面罩中放置一个非重复呼吸阀时，氧气和二氧化碳没有变化。
普通的CPAP系统在出现故障时存在诱发重新呼吸的风险。通过在设备中加入一个被动阀可以很容易地避免这种风险。
