An evaluation of capnography monitoring during the apnoea test in brain-dead patients

BACKGROUND AND OBJECTIVE: Diagnosis of brain death usually requires the absence of spontaneous respiratory movements during the apnoea test and an arterial carbon dioxide partial pressure above 60 mmHg. On the other hand, although capnography (end-tidal CO(2)) is currently monitored in intensive care unit patients, it has not been evaluated during the apnoea test in brain-dead patients. Therefore, the aim of this prospective study was first to investigate the usefulness of capnography monitoring, and secondly to evaluate the variation of the carbon dioxide partial pressure-end-tidal CO(2) gradient during the apnoea test in clinically brain-dead patients. METHODS: After local Ethics Committee approval, 60 clinically brain-dead patients were investigated. End-tidal CO(2) was continuously recorded before, during and after the apnoea test. Arterial blood gases were sampled immediately before and after the apnoea test for calculation of the carbon dioxide partial pressure-end-tidal CO(2) gradient. RESULTS: The apnoea test was clinically positive in 58 patients, whereas end-tidal CO(2) was equal to 0 during the apnoea. During the 20-min apnoea test, carbon dioxide partial pressure increased from 40 +/- 7 to 97 +/- 19 mmHg (P < 0.001) with a rate of 2.8 +/- 0.9 mmHg min(-1), end-tidal CO(2) increased from 31 +/- 6 to 68 +/- 17 mmHg (P < 0.001) and carbon dioxide partial pressure-end-tidal CO(2) gradient increased from 9 +/- 4 to 29 +/- 10 mmHg (P < 0.001). In two patients, the apnoea test was clinically negative because of the occurrence of spontaneous respiratory movements, whereas capnography showed contemporaneously significant increases in end-tidal CO(2). CONCLUSIONS: End-tidal CO(2) should be systematically monitored and recorded, at least for medico-legal considerations, during the apnoea test in brain-dead patients. The high variability in the carbon dioxide partial pressure-end-tidal CO(2) gradient increase precludes any extrapolation of the carbon dioxide partial pressure from the end-tidal CO(2) at the end of the apnoea test.     

经皮氧分压和二氧化碳分压监测组织缺氧的可行性

休克的监测和治疗需要准确及时反映组织缺氧的指标,但是近年来肺动脉的应用受到质疑、监测局部组织代谢的胃粘膜张力计也逐渐淡出临床、能够应用到临床的反映组织缺氧的监测工具和指标非常有限,迫切需要探索其他技术方法,本文论述了经皮氧和二氧化碳分压监测能否用于组织缺氧的监测。     

组织CO2监测进展

组织CO2监测被认为是监测组织灌注的理想指标。舌下张力测定仪是近几年出现的监测组织灌注的新技术，和胃张力测定仪相比，它具有快速简单，临床超前，经济，无血液操作等优点，现综述如下。     

老年人单肺通气时呼气末二氧化碳监测的可信度

目的 观察老年人单肺通气(OLV)麻醉时P_(ET)CO_2C_2和PaCO_2的相关性,以评定P_(ET)CO_2监测在老年人单肺通气麻醉的可信度.方法 37例老年肺部肿瘤患者,胸腔镜下行胸部肿瘤切除、活检或肿瘤根治术,采用静脉复合全麻,术中行OLV.记录麻醉前及OLV 30、60、90、120、180和240min时BP、HR、SpO_2、P_(ET)CO_2和动脉血气,计算氧合指数(PaO_2/FiO_2)、动脉-呼气末二氧化碳分压差(P_(a-ET)CO_2),及对应时间点P_(ET)CO_2和PaCO_2的相关性.结果 除OLV 180 min时点外,术中各时点PaCO_2与P_(ET)CO_2有较好的相关性.术中5例发生低氧血症.结论 老年人OLV麻醉中P_(ET)CO_2不能完全反映PaCO_2的变化,长时间OLV者需同时行血气分析,以保证老年人的安全.     

The accuracy of transcutaneous carbon dioxide monitoring during laparoscopic surgery

BACKGROUND: Laparoscopic procedures are considered relatively low-invasive. However, there exists a small but important risk of developing complications related to carbon dioxide (CO2) insufflation. End-tidal CO2 (PetCO2) monitoring may not be a sufficient guide to adjust pulmonary ventilation during laparoscopic surgery, and arterial CO2 (PaCO2) monitoring is not always indicated. We evaluated the accuracy and feasibility of transcutaneous CO2 (PtcCO2) monitoring during laparoscopic surgery. METHODS: Thirty adult patients undergoing abdominal or gynecological laparoscopic surgery were studied. PtcCO2, PaCO2 and PetCO2 were measured before laparoscopy, and 30 and 60 minutes after beginning of CO2 insufflation. PtcCO2 and PaCO2 were also measured in the recovery room under spontaneous respiration. RESULTS: During operation, the PtcCO2 values demonstrated a high degree of correlation with PaCO2 (r = 0.92), and PetCO2 values also demonstrated generally a good correlation with PaCO2 (r = 0.85). The PtcCO2 PaCO2 gradient was -0.6 +/- 2.2 mmHg, while the PetCO2-PaCO2 gradient was -3.9 +/- 2.7 mmHg. In the recovery room, PtcCO2 values still demonstrated a high correlation with PaCO2 (r = 0.91). CONCLUSIONS: The transcutaneous devices provide an effective method for non-invasive monitoring of PCO2 in situations where continuous monitoring of CO2 levels is desired such as peri-operative period of laparoscopic surgery.     

呼气末二氧化碳分压监测在全麻拔管后苏醒期患者中的应用

目的 探讨呼气末二氧化碳分压监测在全身麻醉拔管后苏醒期患者中的应用效果。方法 选取全身麻醉手术结束拔除气管导管转入麻醉后苏醒室观察的320例患者为研究对象,采用随机数字表法分为对照组和观察组各160例。对照组常规单孔鼻导管吸氧3 L/min并持续监测心电图、呼吸、无创血压、血氧饱和度;观察组在对照组基础上持续监测呼气末二氧化碳分压数值和波形的变化并及时给予护理干预。比较两组低氧血症发生情况、高碳酸血症和呼吸暂停检出率、面罩加压给氧率和苏醒时间。结果 观察组低氧血症程度、面罩加压给氧率显著低于对照组,高碳酸血症、呼吸暂停检出率显著高于对照组,苏醒时间显著短于对照组(P<0.05,P<0.01)。结论 对麻醉后苏醒期拔除气管插管的患者,呼气末二氧化碳分压监测可及时发现呼吸暂停、高碳酸血症等呼吸异常事件,降低低氧血症的发生率,提高麻醉苏醒的安全性,缩短苏醒时间。     

Noninvasive carbon dioxide monitoring during one-lung ventilation: end-tidal versus transcutaneous techniques

OBJECTIVE: To compare transcutaneous CO(2) (TCCO(2)) and end-tidal CO(2) (ETCO(2)) monitoring during one-lung ventilation (OLV). DESIGN: Prospective study. SETTING: Operating room of a University Hospital. PARTICIPANTS: Fifteen patients undergoing thoracic surgical procedures in whom one-lung ventilation was deemed necessary. INTERVENTION: TC and ETCO(2) monitors were used simultaneously in the patients and compared with arterial blood gases (ABGs) during 2-lung ventilation and OLV.MEASUREMENTS AND MAIN RESULTS: During 2-lung ventilation (TLV), the ET to PaCO(2) difference was 3.9 +/- 1.6 mmHg, whereas the TC to PaCO(2) difference was 2.5 +/- 0.8 mmHg (p = 0.0049). During OLV, the ET to PaCO(2) difference increased to 5.8 +/- 2.3 mmHg, whereas the TC to PaCO(2) difference was 2.7 +/- 1.4 mmHg (p = 0.0049 for ET to PaCO(2) difference during OLV v TLV and p = 0.0004 for ET to PaCO(2) gradient v TC to PaCO(2) gradient during OLV). During TLV, the difference between the ET and PaCO(2) was < or = 5 mmHg in 13 of 15 patients, whereas the difference between the TC and PaCO(2) was < or = 5 mmHg in 15 of 15 patients (p = not significant). During OLV, the difference between the ET and the PaCO(2) was < or = 5 mmHg in 6 of 15 patients, whereas the difference between the TC and PaCO(2) was < or = 5 mmHg in 14 of 15 patients (p = 0.0052, odds ratio 21.0 for ET v TC techniques and p = 0.02, odds ratio 9.75 for ET to PaCO(2) during TLV v OLV). CONCLUSIONS: During OLV, TCCO(2) monitoring provides a more accurate estimate of PaCO(2) than ET techniques.     

Liver tissue partial pressure of oxygen and carbon dioxide during partial hepatectomy

Background. Data on tissue oxygen partial pressure (Pt_O2) andcarbon dioxide partial pressure (Pt_CO2) in human liver tissueare limited. We set out to measure changes in liver Pt_O2 andPt_CO2 during changes in ventilation and a 10 min period of ischaemiain patients undergoing liver resection using a multiple sensor(Paratrend^® Diametrics Medical Ltd, High Wycombe, UK). Methods. Liver tissue oxygenation was measured in anaesthetizedpatients undergoing liver resection using a sensor insertedunder the liver capsule. Pt_O2 and Pt_CO2 were recorded with FI_O2values of 0.3 and 1.0, at end-tidal carbon dioxide partial pressuresof 3.5 and 4.5 kPa and 10 min after the onset of liver ischaemia(Pringle manoeuvre). Results. Data are expressed as median (interquartile range).Increasing the FI_O2 from 0.3 to 1.0 resulted in the Pt_O2 changingfrom 4.1 (2.6–5.4) to 4.6 (3.8–5.2) kPa, but thiswas not significant. During the 10 min period of ischaemia Pt_CO2increased significantly (P<0.05) from 6.7 (5.8–7.0)to 11.5 (9.7–15.3) kPa and Pt_O2 decreased, but not significantly,from 4.3 (3.5–12.0) to 3.3 (0.9–4.1) kPa. Conclusion. Pt_O2 and Pt_CO2 were measured directly using a Paratrend^®sensor in human liver tissue. During anaesthesia, changes inventilation and liver blood flow caused predictable changesin Pt_CO2. Br J Anaesth 2004; 92: 735–7     

The accuracy of non-invasive carbon dioxide monitoring: a clinical evaluation of two transcutaneous systems

We determined the accuracy of two transcutaneous carbon dioxide monitoring systems (SenTec Digital Monitor with V-Sign Sensor and TOSCA 500 with TOSCA Sensor 92) for the measurement of single values and trends in the arterial partial pressure of carbon dioxide in 122 adult patients during major surgery and in 50 adult patients in the intensive care unit. One or several paired measurements were performed in each patient. The first measurement was used to determine the accuracy of a single value of transcutaneous carbon dioxide; the difference between the first and the last measurements was used to analyse the accuracy and to track trends. We defined a 95% limit of agreement of 相似文献   

呼气末二氧化碳分压监测用于心肺复苏及预后评估研究

目的 探讨呼气末二氧化碳分压(P_ETCO₂)监测在急诊科心肺复苏质量及预后评估中的价值,为临床终止CPR提供参考。方法 将急诊科收治的62例心脏骤停患者,根据复苏结果分为自主循环恢复组(ROSC组)32例和非自主循环恢复组(非ROSC组)30例,比较两组患者的一般资料及不同时间节点P_ETCO₂。根据复苏后7 d、28 d生存情况将自主循环恢复者分为生存组和死亡组,比较两组不同时间节点P_ETCO₂。绘制ROC曲线,根据约登指数得出预测ROSC、7 d及28 d生存率的最佳截断值。结果 ROSC组和非ROSC组发病地点、CPR持续时间、肾上腺素及5%碳酸氢钠累计使用剂量差异有统计学意义(均P<0.05);两组在心肺复苏10 min及之后各个时间节点的P_ETCO₂值差异有统计学意义(均P<0.05);复苏30 min以内,20 min时P_ETCO₂预测ROSC的曲...     

呼气末二氧化碳分压监测用于心肺复苏及预后评估研究

目的 探讨呼气末二氧化碳分压（PETCO2）监测在急诊科心肺复苏质量及预后评估中的价值，为临床终止CPR提供参考。方法 将急诊科收治的62例心脏骤停患者，根据复苏结果分为自主循环恢复组（ROSC组）32例和非自主循环恢复组（非ROSC组）30例，比较两组患者的一般资料及不同时间节点PETCO2。根据复苏后7 d、28 d生存情况将自主循环恢复者分为生存组和死亡组，比较两组不同时间节点PETCO2。绘制ROC曲线，根据约登指数得出预测ROSC、7 d及28 d生存率的最佳截断值。结果 ROSC组和非ROSC组发病地点、CPR持续时间、肾上腺素及5%碳酸氢钠累计使用剂量差异有统计学意义（均P<0.05）；两组在心肺复苏10 min及之后各个时间节点的PETCO2值差异有统计学意义（均P<0.05）；复苏30 min以内，20 min时PETCO2预测ROSC的曲线下面积最大（AUC=0.982， 95%CI：0.955~1.000），PETCO2最佳截断值为16.5 mmHg，敏感度和特异度分别为93.8%和96.7%，约登指数0.904。ROSC后7 d生存组与死亡组在ROSC时、心肺复苏15 min及之后各时间节点的PETCO2差异有统计学意义（均P<0.05）；心肺复苏20 min时PETCO2值预测ROSC后7 d生存率的曲线下面积最大（AUC=0.882, 95%CI：0.739~1.000），最佳截断值为30 mmHg，敏感度和特异度均为83.3%，约登指数0.667；ROSC后28 d生存组与死亡组在ROSC时、心肺复苏10 min及之后的各时间节点的PETCO2差异有统计学意义（均P<0.05），心肺复苏50 min时PETCO2值预测ROSC后28 d生存的曲线下面积最大（AUC=0.893，95%CI：0.764~1.000），最佳截断值为27.5 mmHg，其敏感度和特异度分别为100%和73.3%，约登指数0.733。结论 呼气末PETCO2能够指导急诊护理人员评价心脏骤停患者心肺复苏质量，并可作为预测患者临床结局的重要指标。     

Transcutaneous monitoring of partial pressure of carbon dioxide during endoscopic submucosal dissection of early colorectal neoplasia with carbon dioxide insufflation: a prospective study

Background  

The authors have reported that carbon dioxide (CO₂) insufflation is safe and effective for lengthy endoscopic submucosal dissection (ESD) with the patient under conscious sedation. However, CO₂ monitoring has not been assessed to clarify whether partial pressure of carbon dioxide (PCO₂) increases during this type of long procedure. This study aimed to monitor CO₂ before, during, and after ESD to investigate whether CO₂ insufflation is safe for patients receiving a lengthy ESD of early colorectal neoplasia under conscious sedation.     

Noninvasive monitoring of carbon dioxide during mechanical ventilation in older children: end-tidal versus transcutaneous techniques

We prospectively compared the accuracy of end-tidal CO(2) (ETCO(2)) and transcutaneous CO(2) (TCCO(2)) monitoring in older pediatric patients (4 yr or older) receiving mechanical ventilation for respiratory failure. ETCO(2) and TCCO(2) were simultaneously monitored and compared with arterial CO(2) (PaCO(2)) values when arterial blood gas analysis was performed. Eighty-two sample sets were compared. The ETCO(2) to PaCO(2) difference was 6.4 +/- 6.3 mm Hg, whereas the TCCO(2) to PaCO(2) difference was 2.6 +/- 2.0 mm Hg (P < 0.0001). The absolute difference of ETCO(2) and PaCO(2) was 5 or less in 47 of 82 measurements, whereas the absolute TCCO(2) to PaCO(2) difference was 5 or less in 76 of 82 measurements (P < 0.00001). Regression analysis of ETCO(2) and PaCO(2) values revealed a correlation coefficient of 0.5418 and an r value of 0.8745. Regression analysis of TCCO(2) and PaCO(2) values revealed a correlation coefficient of 1.0160 and an r value of 0.9693. Bland-Altman analysis revealed a bias of -5.68 with a precision of +/-6.93 when comparing ETCO(2) with PaCO(2) and a bias of 0.02 with a precision of +/-3.27 when comparing TCCO(2) and PaCO(2) (P < 0.00001). TCCO(2) monitoring provided an accurate estimation of PaCO(2) over a wide range of CO(2) values and was superior to ETCO(2) monitoring in older pediatric patients with respiratory failure. TCCO(2) monitoring may be considered as a useful adjunct to monitoring of ventilation in this patient population. IMPLICATIONS: The authors report on the accuracy of noninvasive, transcutaneous CO(2) monitoring during mechanical ventilation in children 4 yr or older. Application of this technique should be useful by decreasing the need for repeated, costly, and sometimes painful arterial blood gas analysis, and the continuity of assessment should facilitate proactive, rather than reactive, ventilator manipulations.     

Noninvasive intraoperative monitoring of carbon dioxide in children: endtidal versus transcutaneous techniques

BACKGROUND: The current study prospectively compares the accuracy of the intraoperative use of transcutaneous (Tc) and endtidal (PE) CO2 monitoring during surgical procedures in 30 paediatric patients, ranging in age from 6 months to 15 years (6.15 +/- 4.35 years) and in weight from 4.7 to 73 kg (24.9 +/- 18.2 kg). METHODS: Following calibration and an equilibration time for the TcCO2 monitor, arterial blood gas samples were obtained as clinically indicated. A total of 64 sample sets (PaCO2, PECO2 and TcCO2) were obtained from the 30 patients. RESULTS: The PECO2 to PaCO2 difference was 0.6-0.9 kPa (4.4 +/- 7.1 mmHg) while the TcCO2 to PaCO2 difference was 0.36-0.38 kPa (2.8 +/- 2.9 mmHg) (P=NS). The difference between the PaCO2 and PECO2 was 0.4 kPa (3 mmHg) or less in 37 of 64 sample sets while the difference between the PaCO2 and TcCO2 was 0.4 kPa (3 mmHg) or less in 49 of 64 sample sets (P=0.038). Linear regression analysis of PECO2 vs. PaCO2 revealed a slope of 0.434, r=0.8761, r2=0.7676. Linear regression analysis of TcCO2 vs. PaCO2 revealed a slope of 0.914, r=0.9472, r2=0.8972. CONCLUSIONS: Although in most circumstances, both noninvasive monitors of PCO2 provided a clinically acceptable estimate of PaCO2, TCCO2 provided a slightly more accurate estimate of PaCO2 during intraoperative anaesthetic care in children.     

单肺通气时PETCO2与PaCO2的关系

对２６例ＡＳＡＩ～Ⅱ级开胸肺手术的患者，分为Ａ、Ｂ两组，分别以双肺通气（ＴＬＶ）为对照行单肺通气（ＯＴＶ）或ＯＴＶ ＋术侧肺用Ｂａｉｎ回路行ＣＰＡＰ，测量ＴＬＶ３０分，ＯＬＶ３０分、６０分和Ｒ－ＴＬＶ３０分的ＰＥＴＣＯ２和ＰａＣＯ２值，观察两者的关系。结果表明，两组中ＯＬＶ时的ＰＥＴＣＯ２和ＰａＣＯ２均正常，但较ＴＬＶ时有升高的趋势（Ｐ＜０．０５），Ｒ－ＴＬＶ后又复原（Ｐ＞０．０５）；两组间ＯＬＶ时的测量值无差异（Ｐ＞０．０５），而ＰＥＴＣＯ２与Ｐ。ＣＯ２有密切的相关性（Ｐ＜０．０５）；Ｐ（ａ－ＥＴ）ＣＯ２和ＰＥＴＣＯ２的计算值在不同通气时无显著性差异，说明ＰＥＴＣＯ２可作为一种无创监测手段指导ＯＬＶ时的通气效果。     

Capnographic monitoring for carbon dioxide insufflation during endoscopic mucosal dissection: comparison of transcutaneous and end-tidal capnometers

Background

The use of carbon dioxide (CO₂) insufflation during endoscopic procedures is effective in reducing patient discomfort caused by bloating. However, transcutaneous arterial CO₂ (PtCO₂) monitoring usually is required for safety during long endoscopic procedures. To evaluate a new capnometer for monitoring end-tidal carbon dioxide (EtCO₂) concentrations and to compare PtCO₂ with EtCO₂ measured in the same patient, a prospective comparative study of EtCO₂ and PtCO₂ values measured simultaneously was designed.

Methods

The study enrolled 20 consecutive patients (18 men and two women; mean age, 70.1?years) with upper gastrointestinal neoplasms scheduled for endoscopic submucosal dissection (ESD) using conscious sedation with CO₂ insufflation, and EtCO₂ and PtCO₂ were simultaneously measured by each capnometer. Patient status was evaluated before ESD by the American Society of Anesthesiologists (ASA) physical status classification system, and eight patients were judged as class 1, nine patients as class 2, and three patients as class 3. The exclusion criteria ruled out patients with chronic obstructive pulmonary disease or ASA class 4 or 5 physical status. The correlation between EtCO₂ and PtCO₂ values and the availability of EtCO₂ capnography were investigated.

Results

The mean EtCO₂ value during ESD was 34.7?±?4.5?mmHg, and the mean PtCO₂ value was 51.6?±?2.4?mmHg. There was a statistically significant correlation between EtCO₂ and PtCO₂ (r?=?0.331; P?=?0.002). Hypoxic events (<90% oxygen saturation [SpO₂]) caused by decreased respiratory rate occurred for 12 patients. In 10 (83%) of 12 events, a significant reduction in EtCO₂ was seen before the decrease in SpO₂.

Conclusions

The EtCO₂ values correlated with the PtCO₂ values, and the respiratory monitoring methods allowed earlier detection of hypoxia during ESD with conscious sedation than transcutaneous monitoring. The EtCO₂ capnometer was considered to be available for the ESD procedure with the patient under conscious sedation using CO₂ insufflation.     

呼末二氧化碳分压监测在后腹腔镜手术中的作用

目的 探讨呼末二氧化碳分压(PETCO2)监测在后腹腔镜手术中的作用.方法 回顾分析72例择期行后腹腔镜手术的患者,依据PaCO2监测结果将患者分为两组,A组:各监测时点PaCO2＜60 mmHg;B组:气腹后至少有一个时间点PaCO2＞60 mmHg.分别于气腹前(T1)、气腹后30 min(T2)、60 min (T3)、90 min (T4)时记录各时间点的PaCO2、PETCO2,根据PETCO2及PaCO2计算每个时间点的Pa-ETCO2.结果 两组间比较:T1、T2时间点B组患者的PaCO2、PETCO2、Pa-ETCO2较A组无统计学差异(P＞0.05),T3、T4时间点B组患者的三项监测指标较A组有统计学差异(P＜0.05).两组组内比较:A组,T2-4与T1相比较,PaCO2、PETCO2、Pa-ETCO2均有统计学差异(P＜0.05),T3与T2、T4与T3、T4与T2比较三项监测指标均无统计学差异(P＞0.05):B组,T2-4与T1相比较,PaCO2、PETCO2、Pa-ETCO2均有统计学差异(P＜0.05或P＜0.01),随着气腹时间的延长,PaCO2、PETCO2两项监测指标均逐渐升高,T3与T2、T4与T3、T4与T2比较PaCO2有统计学差异(P＜0.05),PETCO2 T4与T2比较有统计学差异(P＜0.05).结论 后腹腔镜手术气腹后患者的PaCO2、PETCO2、Pa-ETCO2均会升高,尤其是体重指数＞30 kg/m2、术前肺功能检查轻至中度阻塞性通气障碍、术中发生皮下气肿的患者,PaCO2、PETCO2随时间的延长而呈进行性升高,单靠PETCO2监测不能完全满足对患者的监测需要,术中应该辅以动脉血气分析监测PaCO2.     

Transcutaneous monitoring of partial pressure of carbon dioxide in the elderly patient: a prospective, clinical comparison with end-tidal monitoring

STUDY OBJECTIVE: To evaluate the accuracy and precision of estimation of partial pressure of carbon dioxide (Pa(CO2)) using end-tidal or transcutaneous CO2 (TcP(CO2)) measurements during mechanical ventilation in the elderly patient. DESIGN: A prospective, observational study was conducted. SETTINGS: The study was done in the anesthesia department of a university hospital. PATIENTS: Seventeen anesthetized, mechanically ventilated patients older than 60 years were studied. INTERVENTIONS AND MEASUREMENTS: During standard sevoflurane anesthesia, and after proper calibration and an equilibration time of 30 minutes with stable hemodynamic and respiratory variables, arterial (Pa(CO2)), end-tidal (Pet(CO2)), and transcutaneous (TcP(CO2)) CO2 partial pressures were determined. In each patient, 1 to 5 sample sets (Pa(CO2), Pet(CO2), and TcP(CO2)) were obtained. MAIN RESULTS: A total of 45 sample sets were obtained from the patients studied. The Pa(CO2) values ranged between 21 and 58 mm Hg. The Pa(CO2) - Pet(CO2) tension gradient was 6 +/- 5 mmHg (95% confidence interval, -3 to 16 mmHg), whereas the Pa(CO2) - TcP(CO2) tension gradient was 2 +/- 4 mmHg (95% confidence interval, -6 to 9 mmHg) (P = 0.0005). The absolute value of the difference between Pa(CO2) and Pet(CO2) was 3 mm Hg or less in 7 of 45 sample sets (15%), whereas the absolute value of the difference between Pa(CO2) and TcP(CO2) was 3 mm Hg or less in 21 of 45 sample sets (46%) (P = 0.003). Linear regression analysis for TcP(CO2) versus Pa(CO2) showed a slope of 0.84 (r(2) = 0.73), whereas the linear regression analysis for Pet(CO2) versus Pa(CO2) showed a slope of 0.54 (r(2) = 0.50). CONCLUSION: Transcutaneous monitoring of CO(2) partial pressure gives a more accurate estimation of arterial CO(2) partial pressure than does Pet(CO2) monitoring.     

An evaluation of a noninvasive cardiac output measurement using partial carbon dioxide rebreathing in children

Cardiac output (CO) is an important hemodynamic measure that helps to guide the therapy of critically ill patients. Invasive CO assessment in infants and children is often avoided because of the inherent risks. A noninvasive CO monitor that uses partial rebreathing has been recently developed to determine CO via the Fick principle for carbon dioxide. There have been no clinical studies confirming its accuracy in pediatric patients. This is a prospective observational study of 37 children <12 yr of age who underwent cardiac catheterization. Under general anesthesia via an endotracheal tube without a leak, we made multiple CO measurements using thermodilution and compared them with noninvasively determined CO measurements. Paired measurements were analyzed for bias, precision, and correlation via Bland-Altman plot and linear regression. Noninvasive measurements showed a linear correlation with thermodilution CO assessment with an r value of 0.83 (P < 0.03). Bland-Altman analysis yielded a bias of -0.27 L/min and a precision +/-1.49 L/min. Cardiac index measurements demonstrated a decreased r value of 0.67 (P = 0.15) and a bias of -0.18 L . min(-1) . m(-2) and precision of +/-2.13 L . min(-1) . m(-2). Differences between partial rebreathing measurements and thermodilution measurements were largest in children with a body surface area of 0.6 m(2) body surface area and >300 mL tidal volume.