Noninvasive monitoring of carbon dioxide: A comparison of the partial pressure of transcutaneous and end-tidal carbon dioxide with the partial pressure of arterial carbon dioxide

This study compares two noninvasive techniques for monitoring the partial pressure of carbon dioxide (Pco2) in 24 anesthetized adult patients. End-tidal PCO₂ (PETCO₂) and transcutaneous Pco₂ (PtcCO₂) were simultaneously monitored and compared with arterial Pco₂ (PaCO₂) determined by intermittent analysis of arterial blood samples. PETCO₂ and PtcCO₂ values were compared with PaCO₂ values corrected to patient body temperature (PaC0_2T) and PaCO₂ values determined at a temperature of 37°C (PaCO₂). Linear regression was performed along with calculations of the correlation coefficient (r), bias, and precision of the four paired variables:PETCO₂ versus PaCO₂ and PaCO_2T (n = 211), and PtcCO₂ versus PaCO₂ and PaCO_2T (n = 233). Bias is defined as the mean difference between paired values, whereas precision is the standard deviation of the difference. The following values were found forr, bias, and ± precision, respectively.PetCO₂ versus PaCO₂: 0.67, ?7.8 mm Hg, ±6.1 mm Hg;PETCO₂ versus PaCO_2T: 0.73, ?5.8 mm Hg, ±5.9 mm Hg;PETCO₂ versus PaCO₂: 0.87, ?1.6 mm Hg, ±4.3 mm Hg; PtcCO₂ versus PaC0_2T: 0.84, +0.7 mm Hg, ±4.8 mm Hg. Although each of thesePCO ₂ variables is physiologically different, there is a significant correlation (P < 0.001) between the noninvasively monitored values and the blood gas values. Temperature correction of the arterial values (PaCO_2T) slightly improved the correlation, with respect toPETCO₂, but it had the opposite effect for PtcCO₂. In this study, the chief distinction between these two noninvasive monitors was thatPETCO₂ had a large negative bias, whereas PtcCO₂ had a small bias. We conclude from these data that PtcCO₂ may be used to estimate PaCO₂ with an accuracy similar to that ofPetCO₂ in anesthetized patients.     

Effect of oral prednisolone on plasma levels of leukotriene E4 in asthmatic patients during a wheezing attack: A pilot study

To investigate whether oral prednisolone affects plasma levels of leukotriene E₄ (LTE₄) in asthmatic patients during a wheezing attack, we measured the concentration of LTE₄ in the femoral artery of five asthmatic patients during wheezing. The blood sampling was performed four times in each patient: during the first remission, during the attack without prenisolone treatment, during the attack with prednisolone treatment, and during the second remission. The presence of LTE₄ was confirmed by high-pressure liquid chromatography and radioimmunoassay. The mean ± SD amounts of LTE₄ during the first remission, during the attack without prednisolone, during the attack with prednisolone, and during the second remission were 32.66 ± 9.43, 86.38 ± 8.03, 49.6 ± 12.61, and 32.02 ± 9.16 pg/ml, respectively. In the five control subjects, the mean ± SD amount of LTE₄ was 22.2 ± 7.81 pg/ml. Based on these results, we conclude that oral prednisolone inhibits the release of LTE₄ from various cells accumulated in asthmatic lungs, resulting in an attenuation of the symptoms of bronchial asthma.     

Relationship between arterial carbon dioxide and end-tidal carbon dioxide when a nasal sampling port is used

End-tidal carbon dioxide (ETCO₂) values obtained from awake nonintubated patients may prove to be useful in estimating a patient’s ventilatory status. This study examined the relationship between arterial carbon dioxide tension (PaCO₂) and ETCO₂ during the preoperative period in 20 premedicated patients undergoing various surgical procedures. ETCO₂ was sampled from a 16-gauge intravenous catheter pierced through one of the two nasal oxygen prongs and measured at various oxygen flow rates (2, 4, and 6 L/min) by an on-line ETCO₂ monitor with analog display. Both peak and time-averaged values for ETCO₂ were recorded. The results showed that the peak ETCO₂ values (mean = 38.8 mm Hg) correlated more closely with the PaCO₂ values (mean = 38.8 mm Hg; correlation coefficient r = 0.76) than did the average ETCO₂ values irrespective of the oxygen flow rates. The time-averaged PaCO₂-ETCO₂ difference was significantly greater than the PaCO₂-peak ETCO₂ difference (P < 0.001). Values for subgroups within the patient population were also analyzed, and it was shown that patients with minute respiratory rates greater than 20 but less than 30 and patients age 65 years or older did not differ from the overall studied patient population with regard to PaCO₂-ETCO₂ difference. A small subset of patients with respiratory rates of 30/ min or greater (n = 30) did show a significant increase in the PaCO₂-ETCO₂ difference (P < 0.001). It was concluded that under the conditions of this study, peak ETCO₂ values did correlate with PaCO₂ values and were not significantly affected by oxygen flow rate. However, obtaining peak ETCO₂ values is clinically more difficult, especially when partial air-way obstruction is present.     

Transcutaneous arterial carbon dioxide pressure monitoring in critically ill adult patients

Objective To evaluate the accuracy of transcutaneous PCO₂ (PtcCO₂) as a surrogate for arterial PCO₂ (PaCO₂) in a cohort of adult critically ill patients in a medical intensive care unit (ICU). Design Prospective observational study comparing paired measures of transcutaneous and arterial PCO₂. Setting A 26-bed medical ICU. Patients Fifty ICU patients monitored with a SenTec Digital Monitor placed at the ear lobe over prolonged periods. Results A total of 189 paired PCO₂ measures were obtained. Twenty-one were excluded from analysis, because profound skin vasoconstriction was present (PCO₂ bias = −10.8 ± 21.8  mmHg). Finally, 168 were analysed, including 137 obtained during mechanical ventilation and 82 under catecholamine treatment. Body temperature was below 36°C for 27 measurements. Mean duration of monitoring was 17 ± 17 h. The mean difference between PaCO₂ and PtcCO₂ was −0.2 ± 4.6  mmHg with a tight correlation (R ² = 0.92, p > 0.01). PCO₂ bias did not significantly change among three successive measurements. Changes in PaCO₂ and in PtcCO₂ between two blood samples were well correlated (R ² = 0.78, p > 0.01). Variations of more than 8 mmHg in PtcCO₂ had 86% sensitivity and 80% specificity to correctly predict similar changes in PaCO₂ in the same direction. Catecholamine dose or respiratory support did not affect PtcCO₂ accuracy. Hypothermia has only a small effect on accuracy. No complication related to a prolonged use of the sensor was observed Conclusion Transcutaneous PCO₂ provides a safe and reliable trend-monitoring tool, provided there is no major vasoconstriction. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Driving pressure and arterial carbon dioxide tension during high-frequency jet ventilation in postoperative patients

To achieve normocarbia during conventional mechanical ventilation, ventilator settings are determined initially on the basis of body weight. The best ventilator settings for CO2 elimination during high-frequency jet ventilation (HFJV) have not been so clearly defined. A recent study has suggested that eucarbia will be obtained with HFJV when tidal volume (VT) per kg of body weight is kept within a narrow, well-defined range. In the same study, a "bench test" demonstrated that VT was directly proportional to the jet ventilator driving pressure (DP). The goal of our study was to confirm this recommended VT/kg to obtain eucarbia and to determine whether the relation observed between VT and DP in the laboratory was true clinically. We studied 14 patients admitted to the ICU for postoperative support. We determined a good correlation between DP and VT/kg (r = .811, p less than .001) for the group as a whole and a good inverse correlation between DP or VT/kg and PaCO2 for most individual patients; however, there was a poor inverse correlation between DP or VT/kg and PaCO2 for the group as a whole, due to wide patient-to-patient variation in the efficiency of jet ventilation. We conclude that there is no universal formula for setting jet ventilator DP or VT/kg to affect normocarbia in humans.     

脓毒性休克患者血中一氧化碳含量的变化与APACHEⅡ评分的关系

目的观察脓毒性休克患者血中一氧化碳含量的变化及其与APACHE Ⅱ评分的关系及意义.方法选择ICU脓毒性休克患者62例,在入ICU 24 h 内对每个患者进行APACHE Ⅱ评分,同时测动脉血中Hb和碳氧血红蛋白(COHb)含量,按照预后分为死亡组24例,存活组38例.另选同期无感染行择期手术的患者为对照组20例,测患者术前动脉血中Hb和COHb含量.结果对照组血中Hb含量为(135.1±9.3) g/L,脓毒性休克患者血中Hb含量较对照组略低,为(126.3±15.4) g/L,但差异无显著性.脓毒性休克患者血中COHb含量明显高于对照组,两组分别为(2.19±0.76)%和(0.64±0.31)%,P＜0.05.脓毒性休克患者APACHE Ⅱ各分段血中COHb含量与病死率随APACHE Ⅱ评分的增加而增加,COHb含量与APACHE Ⅱ评分呈显著正相关关系(r＝0.78,P＜0.05).死亡组血中COHb含量及APACHE Ⅱ评分高于存活组.结论内源性一氧化碳与脓毒性休克的病理机制密切相关,且与APACHE Ⅱ评分呈正相关关系,动态监测血中COHb含量的变化可能为预测病情提供参考.     

Transcutaneous measurements of carbon dioxide partial pressure in sick neonates

The authors measured the partial pressure of carbon dioxide transcutaneously (PtcCO2) in 15 sick newborns and compared the PtcCO2 to simultaneously measured partial pressure of arterial carbon dioxide (PaCO2). The PtcCO2 values reflected changes in the PaCO2 values. A linear regression on 106 paired PtcCO2 and PaCO2 values produced a correlation coefficient of 4 = 0.91 with a slope of 1.89 and a y-intercept of --9.4. The authors found the measurement of PtcCO2 to be a clinically useful method of continuously following the trend of PaCO2.     

心力衰竭患者低钠血症及与神经内分泌激素的关系

目的 对心衰患者治疗中出现的低钠血症及与血浆激素的关系等有关因素进行分析。方法 156例患者均测定入院时血钠浓度，并于入院后第二天清晨空腹抽血，用放射免疫法测定血浆心钠素(ANP)和肾素(RENIN)浓度。观察不N程度心衰患者的血钠浓度与患者基本情况及ANP浓度的关系。结果 提示年龄、心衰程度、心脏病的种类、药物的使用等均可对低钠血症的形成产生影响，ANP浓度增高者低钠血症数高于ANP浓度正常组。心衰患者治疗前的ANP浓度和血钠浓度间成负相关。结论 提示心衰时神经内分泌的激活是低钠的一个重要因素。有低钠血症者预后较差，病死率明显增高。     

Concordance between transcutaneous and arterial measurements of carbon dioxide in an ED

Background

Transcutaneous carbon dioxide pressure (PtcCO₂) has been suggested as a noninvasive surrogate of arterial carbon dioxide pressure (PaCO₂). Our study evaluates the reliability of this method in spontaneously breathing patients in an emergency department.

Patients and methods

A prospective, observational study was performed in nonintubated dyspneic patients who required measurement of arterial blood gases. Simultaneously and blindly to the physicians in charge, PtcCO₂ was measured using a TOSCA 500 monitor (Radiometer, Villeurbanne, France). Agreement between PaCO₂ and PtcCO₂ was assessed using the Bland-Altman method.

Results

Forty-eight patients (mean age, 65 years) were included, and 50 measurements were done. Eleven (23%) had acute heart failure; 10 (21%), pneumonia; 7 (15%), acute asthma; and 7 (15%), exacerbation of chronic obstructive pulmonary disease. Median PaCO₂ was 42 mm Hg (range, 17-109). Mean difference between PaCO₂ and PtcCO₂ was 1 mm Hg with 95% limits of agreement of − 3.4 to + 5.6 mm Hg. All measurement differences were within 5 mm Hg, and 32 (64%) were within 2 mm Hg.

Conclusion

Transcutaneous carbon dioxide pressure accurately predicts PaCO₂ in spontaneously breathing patients.     

血浆脑钠肽水平与急性冠状动脉综合征患者心血管事件的相关性研究

目的：探讨血浆脑钠肽（BNP）与急性冠状动脉综合征（ACS）患者发生主要不良心血管事件（MACE）的相关性。方法收集该院就诊的ACS患者210例,检查住院期间的BNP,并记录住院期间和出院后30dMACE的发生情况。根据BNP的不同,把ACS患者分成两组（A组：BNP＜100pg/mL;B组：BNP≥100pg/mL）,比较两组患者发生MACE的差异。结果B组患者的平均年龄为（65．9±11．4）岁,明显高于A组的（62．6±10．3）岁（P＝0．03）;B组ST段抬高型心肌梗死患者占53．7％,高于A组的34．3％（P＝0．005）;两组患者在性别、糖尿病、高血压、血脂异常和吸烟史等方面差异无统计学意义（P＞0．05）。住院期间,B组MACE的发生率为17．6％,明显高于A组的4．9％（P＝0．004）;B组心因性病死率和再发心肌梗死率均明显高于A组（P＜0．05）。入院至出院后1个月,B组MACE的发生率为33．3％,明显高于A组的9．8％（P＜0．01）;B组心因性病死率、再发心肌梗死率和再次血运重建率均明显高于A组（P＜0．05）。结论血浆BNP水平的增高,增加ACS患者短期MACE的发生率。临床上对BNP＞100pg/mL的ACS患者应给予更多的关注。     

呼气末二氧化碳分压监测在呼吸衰竭患者监护中的应用

目的 探讨呼气末二氧化碳分压(PetCO_2)和动脉血二氧化碳分压(PaCO_2)的相关性及其在呼吸衰竭患者监护中的临床应用意义和护理体会.方法 将112例入住ICU进行PetCO_2监测的患者按血流动力学情况分为2组,血流动力学较稳定的患者58例作为A组,血流动力学不稳定的患者54例作为B组.2组均接受气管插管呼吸机辅助通气,在通气支持2h后同时测定PetCO_2和PaCO_2并对结果进行分析.结果 A组患者的PetCO_2和PaCO_2显著相关,B组患者的PetCO_2和PaCO_2无显著相关.结论 对于血流动力学稳定的患者,PetCO_2和PaCO_2具有良好的相关性,可由PetCO_2来代替PaCO_2的监测,PetCO_2能迅速敏感地反映PaCO_2的变化,具有无创、连续、动态、简便、节约之优点.     

动脉弹性功能参数与脉压的关系

目的:分析3种动脉弹性功能参数[脉搏波传导速度(PWV)、大、小动脉弹性指数(C1和C2)、压力反射波增强指数(AI)]与脉压(PP)间的关系,寻找能敏感反映动脉弹性改变的指标。方法:选择429例高血压患者,同时检测PWV、C1和C2、AI,根据PP水平分成4组,然后分析PP与动脉弹性功能参数间的相关性,比较不同PP水平组动脉弹性功能参数的差异。观察60例PP≥60mmHg高血压患者,治疗后PP下降程度与各动脉弹性功能参数改善间的相关性。结果:PP与PWV正相关,与C1负相关。在不同脉压水平4组间,PWV、C1﹑C2均有显著性差异(P<0.05),AI值仅在脉压≥60mmHg与<60mmHg间差异有显著性(P<0.05)。PP减小与PWV降低呈正相关,与C1升高呈负相关,而与C2﹑AI改变无显著相关。结论:PWV、C1是敏感反映动脉弹性改善与PP减小的大动脉弹性功能指标。     

潮气末二氧化碳分压对心肺复苏结果的指导和预测作用

目的 探讨潮气末二氧碳(PetCO2)监测在心肺复苏(CPR)期间的临床意义并寻求定值以指导临床抢救.方法 采用回顾性研究方法,选择2003年5月至2009年3月解放军第四五一医院急诊科院内外非外伤性心搏骤停已明确原因的患者124例,监测心搏骤停患者在CPR过程中PetCO2的变化.结果 ①恢复自主循环(ROSC)的71例与未恢复的53例气管插管后性别、年龄、抢救时间比较P值分别为＜0.05,＜0.05,＜0.01,差异具有统计学意义,说明上述因素与复苏成功正相关,但性别和年龄与最终存活率无相关性.②最终存活者PetCO2水平高于未复苏成功者和虽复苏成功但最终院内死亡者,并与施救时间相关.③经过20 min的高级生命支持没有恢复自主循环者PetCO2平均水平在(6.7±1.2) mmHg(1mmHg =0.133 kPa),恢复自主循环者在(33.9±7.8) mmHg (P＜0.01),以20 min高级生命支持后PetCO2水平高于14.4 mmHg作为参考值预期死亡,阳性率和阴性率均为100％.结论 CPR过程中PetCO2的监测对复苏有指导和预测作用.     

Lack of agreement between tonometric and gastric juice partial carbon dioxide tension

Our goal was to compare measurement of tonometered saline and gastric juice partial carbon dioxide tension (PCO₂). In this prospective observational study, 112 pairs of measurements were simultaneously obtained under various hemodynamic conditions, in 15 critical care patients. Linear regression analysis showed a significant correlation between the two methods of measuring PCO₂ (r ² = 0.43; P < 0.0001). However, gastric juice PCO₂ was systematically higher (mean difference 51 mmHg). The 95% limits of agreement were 315 mmHg and the dispersion increased as the values of PCO₂ increased. Tonometric and gastric juice PCO₂ cannot be used interchangeably. Gastric juice PCO₂ measurement should be interpreted with caution.     

呼吸衰竭患者血氧与血乳酸浓度相关性的探讨

目的探讨呼吸衰竭患者血乳酸(LAC)浓度、血氧分压(PaO2)及其预后的相互关系,为判断此类患者的组织缺氧提供有价值的生化指标。方法用美国NOVAPHOXPLUSL血气、电解质、血乳酸仪测定呼吸衰竭患者的血LAC浓度和血气。结果患者的动脉血气、乳酸在治疗期间都有显著变化(P<0.01)。pH值与PaO2值越低,预后越差,而PaCO2值和血乳酸浓度越高,预后越差。其PaO2与血LAC呈明显的负相关(r=0.512,P<0.01)。结论血LAC与病情的危重程度有良好的相关性,血LAC的测定有助于了解组织细胞缺氧情况。呼吸衰竭患者需同时监测血气和血LAC。