Schmitz B D, Shapiro B A
Department of Respiratory Care, Northwestern Memorial Hospital, Chicago, Illinois, USA.
Respir Care Clin N Am. 1995 Sep;1(1):107-17.
Capnography measures exhaled carbon dioxide and is most useful when applied directly to patient care. This is in circumstances of detecting misplacement of the tracheal tube, dysfunction of respiratory apparatuses, detection of abnormal lung function, successful cardiopulmonary resuscitation, and trending of deadspace changes. The least reliable application is to reflect alveolar ventilation (PaCO2). This application is most common during general anesthesia and weaning from mechanical ventilation. Provided the patient has a stable cardiac status, stable body temperature, absence of lung disease, and normal capnogram, PETCO2 monitoring may assist in estimating PaCO2. The use of capnography in patients with severe respiratory failure should be applied with careful reflection. The increased V/Q mismatch that is consistent with a widened P(a-ET) gradient, as well as worsening hypercapnea with increased peripheral carbon dioxide production, can lead to erroneous PETCO2 values. Capnography may be least useful in the sickest patients.
二氧化碳监测可测量呼出的二氧化碳，直接应用于患者护理时最为有用。这适用于检测气管导管误置、呼吸设备功能障碍、检测异常肺功能、成功的心肺复苏以及死腔变化趋势等情况。最不可靠的应用是反映肺泡通气（动脉血二氧化碳分压）。这种应用在全身麻醉和机械通气撤机期间最为常见。如果患者心脏状态稳定、体温稳定、无肺部疾病且二氧化碳波形图正常，呼气末二氧化碳分压监测可能有助于估算动脉血二氧化碳分压。在严重呼吸衰竭患者中使用二氧化碳监测时应谨慎考虑。与增大的肺泡动脉二氧化碳分压差一致的通气/血流比值失调增加，以及外周二氧化碳产生增加导致的高碳酸血症恶化，可能导致呼气末二氧化碳分压值出现误差。二氧化碳监测在病情最严重的患者中可能最无用。
