Acute Care Surgery, University of Missouri, Columbia, Missouri 65203, USA.
Prehosp Disaster Med. 2013 Apr;28(2):87-93. doi: 10.1017/S1049023X12001768. Epub 2013 Jan 23.
End tidal CO2 (ETCO2) has been established as a standard for confirmation of an airway, but its role is expanding. In certain settings ETCO2 closely approximates the partial pressure of arterial CO2 (PaCO2) and has been described as a tool to optimize a patient's ventilatory status. ETCO2 monitors are increasingly being used by EMS personnel to guide ventilation in the prehospital setting. Severely traumatized and burn patients represent a unique population to which this practice has not been validated.
The sole use of ETCO2 to monitor ventilation may lead to avoidable respiratory acidosis.
A consecutive series of patients with burns or trauma intubated in the prehospital setting over a 24-month period were evaluated. Prehospital arrests were excluded. Absence of ETCO2 transport data and patients without an arterial blood gas (ABG) within 15 minutes of arrival were also excluded. Data collected included demographics, place and time of intubation, service performing intubation, ETCO2 maintained en-route to hospital, and ABG upon arrival. Further data included length of stay, mortality, and injury severity scores.
One hundred sixty patients met the inclusion criteria. Prehospital ETCO2 did not correlate with measured PaCO2 (R2 = 0.08). Mean ETCO2 was significantly lower than mean PaCO2 (34 mmHg vs 44 mmHg, P < .005). Patients arriving acidotic were more likely to die. Mean pH on arrival for survivors and decedents was 7.32 and 7.19 respectively (P < .001). Mortality, acidosis, higher base deficits, and more severe injury patterns were all predictors for a worse correlation between ETCO2 and PaCO2 and increased mean difference between the two values. Decedents and patients presenting with a pH <7.2 demonstrated the greatest discrepancy between ETCO2 and PaCO2. The data suggest that patients may be hypoventilated by prehospital providers in order to obtain a prescribed ETCO2.
ETCO2 is an inadequate tool for predicting PaCO2 or optimizing ventilation in severely injured patients. Adherence to current ETCO2 guidelines in the prehospital setting may contribute to acidosis and increased mortality. Consideration should be given to developing alternate protocols to guide ventilation of the severely injured in the prehospital setting.
呼气末二氧化碳（ETCO2）已被确立为确认气道的标准，但它的作用正在扩大。在某些情况下，ETCO2 非常接近动脉二氧化碳分压（PaCO2），并被描述为优化患者通气状态的工具。越来越多的 EMS 人员使用 ETCO2 监测仪在院前环境中指导通气。严重创伤和烧伤患者代表了一个尚未对此种实践进行验证的特殊人群。
单纯使用 ETCO2 监测通气可能导致可避免的呼吸性酸中毒。
对过去 24 个月内接受院前插管的烧伤或创伤患者进行了连续系列评估。排除院前性骤停。还排除了没有 ETCO2 转运数据和患者在到达后 15 分钟内没有动脉血气（ABG）的患者。收集的数据包括人口统计学资料、插管的地点和时间、进行插管的服务、在送往医院途中维持的 ETCO2 以及到达时的 ABG。进一步的数据包括住院时间、死亡率和损伤严重程度评分。
160 名患者符合纳入标准。院前 ETCO2 与测量的 PaCO2 无相关性（R2 = 0.08）。平均 ETCO2 明显低于平均 PaCO2（34mmHg 比 44mmHg，P <.005）。酸中毒到达的患者更有可能死亡。幸存者和死亡者的到达时平均 pH 值分别为 7.32 和 7.19（P <.001）。死亡率、酸中毒、更高的基础缺陷和更严重的损伤模式都是 ETCO2 与 PaCO2 之间相关性较差和两者之间差值增加的预测因素。死亡者和 pH <7.2 的患者表现出 ETCO2 与 PaCO2 之间最大的差异。数据表明，为了获得规定的 ETCO2，院前提供者可能会对患者进行过度通气。
ETCO2 是预测严重受伤患者 PaCO2 或优化通气的不足工具。在院前环境中遵守当前的 ETCO2 指南可能会导致酸中毒和死亡率增加。应考虑制定替代方案来指导严重受伤患者的院前通气。
