Callaham M, Barton C
Department of Medicine, University of California, San Francisco.
Crit Care Med. 1990 Apr;18(4):358-62. doi: 10.1097/00003246-199004000-00002.
Capnography is a valuable tool in the management of cardiac arrest, since end-tidal CO2 (PetCO2) correlates well with cardiac output and there are no other suitable noninvasive ways to measure this important variable during resuscitation. Animal studies also suggest that PetCO2 correlates well with the likelihood of resuscitation, but this has never been confirmed in humans. We prospectively studied 55 adult, nontraumatic prehospital cardiac arrest patients. PetCO2 was monitored with an in-line sensor on arrival in the ED and throughout the arrest, which was managed by the usual advanced cardiac life-support treatment guidelines. Chest compression was carried out mechanically. Patients were assessed for return of spontaneous pulse as evidence of initial resuscitation; hospital discharge and long-term survival were not examined. Fourteen patients developed spontaneous pulses and were resuscitated, and 41 were not. The length and aggressiveness of treatment and CPR were not different between the two groups, nor were there differences in down time, resuscitation time, or other factors known to affect outcome. Patients who developed a pulse had a mean PetCO2 of 19 +/- 14 (SD) torr at the start of resuscitation, and those who did not had a mean PetCO2 of 5 +/- 4 torr (p less than .0001). This difference was significant both in nonperfusing rhythms (asystole and ventricular fibrillation) and in potentially perfusing rhythms (electromechanical dissociation). An initial PetCO2 of 15 torr correctly predicted eventual return of pulse with a sensitivity of 71%, a specificity of 98%, a positive predictive value of 91%, and a negative predictive value of 91%. A receiver operating curve was generated for sensitivity and specificity of the test at varying PetCO2 thresholds.
二氧化碳图是心脏骤停管理中的一项重要工具，因为呼气末二氧化碳（PetCO2）与心输出量密切相关，而且在复苏过程中没有其他合适的非侵入性方法来测量这一重要变量。动物研究还表明，PetCO2与复苏的可能性密切相关，但这一点在人类中从未得到证实。我们前瞻性地研究了55例成年非创伤性院前心脏骤停患者。患者到达急诊科时及整个心脏骤停过程中，使用在线传感器监测PetCO2，心脏骤停的处理遵循常规的高级心脏生命支持治疗指南。采用机械胸外按压。评估患者是否恢复自主脉搏作为初始复苏的证据；未对出院和长期生存情况进行检查。14例患者恢复自主脉搏并成功复苏，41例未成功复苏。两组之间治疗和心肺复苏的时长及力度无差异，停机时间、复苏时间或其他已知影响预后的因素也无差异。恢复脉搏的患者在复苏开始时的平均PetCO2为19±14（标准差）托，未恢复脉搏的患者平均PetCO2为5±4托（p<0.0001）。这种差异在无灌注节律（心搏停止和心室颤动）和潜在灌注节律（电机械分离）中均很显著。初始PetCO2为15托时，预测最终脉搏恢复的灵敏度为71%，特异度为98%，阳性预测值为91%，阴性预测值为91%。针对不同PetCO2阈值下该检测的灵敏度和特异度绘制了受试者工作特征曲线。
