US Army Institute of Surgical Research, Fort Sam Houston, Texas 78234, USA.
Shock. 2012 Jan;37(1):103-9. doi: 10.1097/SHK.0b013e3182391862.
The relationship between end-tidal carbon dioxide (EtCO(2)) and arterial carbon dioxide (PaCO(2))-if better defined-could facilitate the difficult task of ventilation in prehospital trauma patients. We aimed to study the PaCO(2)-EtCO(2) relationship before, during, and after chest trauma, hemorrhage, and resuscitation in swine. Twenty-four swine were intubated, anesthetized, and monitored in an animal intensive care unit during three phases: phase 1 (day 1, healthy animals); phase 2 (day 2, injury), which consisted of blunt chest trauma, hemorrhage, and resuscitation; and phase 3 (day 2, after injury). "Respiratory maneuvers" (changes in respiratory rate and tidal volume [TV], intended to vary the PaCO(2) over a range of 25 to 85 mmHg, were performed during phases 1 and 3. End-tidal CO(2) and PaCO(2) were recorded after each respiratory maneuver and analyzed using linear regression. During phase 1, PaCO(2) and EtCO(2) were strongly correlated (r(2) = 0.97, P < 0.01). During phase 2, animals developed decreased oxygenation (PaO(2):FiO(2) [fraction of inspired oxygen] ratio <200) and hypotension (mean arterial pressure, 20-50 mmHg); the PaCO(2)-EtCO(2) relationship deteriorated (r(2) = 0.25, P < 0.0001). During phase 3, oxygenation, hemodynamics, and the PaCO(2)-EtCO(2) relationship recovered (r(2) = 0.92, P < 0.01). End-tidal CO(2) closely correlates to PaCO(2) in healthy animals and after injury/resuscitation across a wide range of respiratory rates and tidal volumes. Once oxygenation and hemodynamics are restored, EtCO(2) can be used to predict PaCO(2) following chest trauma/hemorrhage and should be considered for patient monitoring. This work demonstrated that EtCO(2) alone can reliably be used to estimate PaCO(2) in uninjured subjects and in those subjects who have been resuscitated from severe injury. Immediately after blunt chest injury, the correlation between EtCO(2) and PaCO(2) is temporarily unstable. Under these circumstances (with abnormal oxygenation and/or hemodynamics), greater caution and other monitoring tools may be required.
动脉血二氧化碳（PaCO2）与呼气末二氧化碳（EtCO2）之间的关系——如果能得到更好的定义——可能有助于解决院前创伤患者通气这一难题。我们的目的是研究猪胸部创伤、出血和复苏前、中、后的 PaCO2-EtCO2 关系。24 头猪在动物重症监护病房插管、麻醉和监测，分为三个阶段：第 1 阶段（第 1 天，健康动物）；第 2 阶段（第 2 天，受伤），包括钝性胸部创伤、出血和复苏；第 3 阶段（第 2 天，受伤后）。在第 1 阶段和第 3 阶段进行了“呼吸动作”（改变呼吸频率和潮气量[TV]，旨在使 PaCO2 在 25 至 85mmHg 范围内变化）。在每次呼吸动作后记录 EtCO2 和 PaCO2，并使用线性回归进行分析。在第 1 阶段，PaCO2 和 EtCO2 呈强相关性（r2=0.97，P<0.01）。在第 2 阶段，动物出现低氧血症（吸入氧分数[FiO2]比值<200）和低血压（平均动脉压 20-50mmHg）；PaCO2-EtCO2 关系恶化（r2=0.25，P<0.0001）。在第 3 阶段，氧合、血液动力学和 PaCO2-EtCO2 关系恢复（r2=0.92，P<0.01）。健康动物和受伤/复苏后，EtCO2 与 PaCO2 密切相关，可在广泛的呼吸频率和潮气量范围内使用。一旦氧合和血液动力学恢复，就可以使用 EtCO2 来预测胸部创伤/出血后的 PaCO2，这应被视为患者监测的一种手段。这项工作表明，在未受伤的患者和从严重损伤中复苏的患者中，单独使用 EtCO2 就可以可靠地估计 PaCO2。在钝性胸部损伤后立即，EtCO2 与 PaCO2 之间的相关性暂时不稳定。在这种情况下（伴有异常氧合和/或血液动力学），可能需要更加谨慎并使用其他监测工具。
