Phillips Justin S, Pangilinan Lance P, Mangalindan Earl R E, Booze Joseph L, Kallet Richard H
Respiratory Care Services, Department of Anesthesia and Perioperative Care, University of California, San Francisco at Zuckerberg San Francisco General Hospital, San Francisco, California.
Respir Care. 2017 Jan;62(1):78-85. doi: 10.4187/respcare.05111.
Accurately measuring the partial pressure of end-tidal CO (P ) in non-intubated patients is problematic due to dilution of expired CO at high O flows and mask designs that may either cause CO rebreathing or inadequately capture expired CO. We evaluated the performance of 2 capnographic O masks (Cap-ONE and OxyMask) against a clinically expedient method using a standard O mask with a flow-directed nasal cannula used for capnography (CapnoLine) in a spontaneous breathing model of an adult and child under conditions of normal ventilation, hypoventilation, and hyperventilation.
An ASL-5000 simulator was attached to a manikin face with a catheter port, through which various CO/air mixtures were bled into the ASL-5000 to achieve a P of 40, 65, and 30 mm Hg. Both P and inspired P were measured at O flows of 5, 10, 15, and 20 L/min (adult model) and 2, 4, 6, 8, and 10 L/min (pediatric model).
P decreased to varying degrees as O flow increased, depending upon the breathing pattern. Although all devices appeared to perform reasonably well under normal and hyperventilation conditions, the clinically expedient method was associated with substantially more CO rebreathing. P usually deteriorated more under simulated hypoventilation, regardless of the measurement method.
Both of the specially designed O capnography masks provided reasonably stable P without significant CO rebreathing at the commonly used O flows. Because of their open design, P measured at high O flows may produce artificially lower readings that may not reflect arterial CO levels compared with lower O flows.
在非插管患者中准确测量呼气末一氧化碳分压（PetCO）存在问题，这是由于高氧流量下呼出的一氧化碳被稀释，以及面罩设计可能导致一氧化碳重复吸入或无法充分收集呼出的一氧化碳。我们在成人和儿童的自主呼吸模型中，在正常通气、通气不足和通气过度的条件下，将两种二氧化碳波形图氧面罩（Cap-ONE和OxyMask）与一种临床便捷方法进行了性能评估，该临床便捷方法使用带有用于二氧化碳波形图的流量导向鼻导管的标准氧面罩（CapnoLine）。
将一台ASL-5000模拟器通过导管端口连接到人体模型面部，通过该端口将各种一氧化碳/空气混合物注入ASL-5000，以实现40、65和30mmHg的PetCO。在5、10、15和20L/min（成人模型）以及2、4、6、8和10L/min（儿科模型）的氧流量下测量PetCO和吸入氧分压。
随着氧流量增加，PetCO根据呼吸模式不同程度下降。尽管所有设备在正常和通气过度条件下似乎表现都相当良好，但临床便捷方法与更多的一氧化碳重复吸入相关。无论测量方法如何，在模拟通气不足时PetCO通常恶化更明显。
两种专门设计的氧二氧化碳波形图面罩在常用氧流量下均能提供相当稳定的PetCO，且无明显的一氧化碳重复吸入。由于其开放式设计，与低氧流量相比，在高氧流量下测量的PetCO可能会产生人为降低的读数，可能无法反映动脉血二氧化碳水平。
