Use of an iridium-oxide transcutaneous carbon dioxide electrode on adult surgical patients

A new iridium/iridium-oxide electrode heated to 42 degrees C was used to monitor transcutaneous carbon dioxide levels during surgery in 27 adult patients. The purpose of this study was to compare arterial and transcutaneous CO2 values. This metal electrode performed similarly to glass CO2 electrodes. In addition, its lower operating temperature may reduce the risk of skin injury and more quickly reflect changes in local tissue perfusion.     

Transcutaneous carbon dioxide and oxygen tension measured at different temperatures in healthy adults

Transcutaneous carbon dioxide tension (tc-pco2) at 37, 39, 41, 43, and 45 degrees C, and transcutaneous oxygen tension (tc-po2) at 41, 43, and 45 degrees C were measured simultaneously in 10 healthy adults during hyperventilation and inhalation of O2/CO2 gas. Nine electrodes were applied to each subject: Five CO2 electrodes, one O2 electrode, and three combined O2/CO2 electrodes. The CO2 electrodes had negligible temperature coefficients in the calibration gases, but the O2 electrodes showed an increase in po2 of 4.5% per degree C. With skin application, tc-pco2 increased approximately 4% per degrees C between 37 and 45 degrees C, which is close to the anaerobic temperature coefficient of pco2 in blood. The tc-po2 increases on the skin with increasing temperature appeared to be more dependent on changes in blood flow in skin, but in the temperature range 43 to 45 degrees C, tc-po2 showed the expected decrease in the temperature coefficient with increasing po2. The correlation between transcutaneous and capillary pco2 was close at all transcutaneous electrode temperatures, even 37 degrees C, provided the skin was preheated (via the electrode) to 45 degrees C. For tc-po2, an electrode temperature of at least 43 degrees C was necessary to produce a reasonable correlation between tc-po2 and capillary po2. The combined O2/CO2 electrodes measured slightly higher pco2 values than the single CO2 electrodes, but there were no differences in po2 readings, stabilization time, imprecision, or electrode drift between the two electrode types. The imprecision (CV, %) of tc-pco2 and tc-po2 measurements was approximately twice that of the corresponding capillary blood-gas measurements.     

Detection of exercise-induced lactic acidosis using transcutaneous carbon dioxide

Transcutaneous PCO2 (PtcCO2) measurements were used to monitor changes in systemic lactate levels during exercise. PtcCO2 increased in all 17 male volunteers, and this increase was significantly correlated with increases in measured plasma lactate concentration. In six volunteers, the PtcCO2 increase was greatest during the last minutes of work, indicating rapid lactic acid elimination from the muscles. In these six subjects, the rate of this increase also correlated significantly with the lactate increase. This technique is potentially of interest for detecting fatigue in athletes and for monitoring lactoacidosis as an indicator of circulatory impairment in shock patients.     

Ab initio-enabled phase transition prediction of solid carbon dioxide at ultra-high temperatures

Carbon dioxide is one of the fundamental chemical species on Earth, but its solid-phase behavior at high pressures is still far from well understood and some phases remain uncertain or unknown, which increases the challenge to predict its structures. The difficulty of theoretical prediction arises from the high cost of structure screening and the low accuracy of applicable methods. In this study, we employed an ab initio computational study on solid carbon dioxide phases I and VII at high pressure and predicted their structures, energies and phase transition using the second-order Møller–Plesset perturbation (MP2) theory. Compared to the classical force field method and density-functional theory (DFT), MP2 is capable of describing covalent, ionic, hydrogen-bonds, and dispersion interactions accurately. The equation of state, vibrational spectra and Gibbs free energy were calculated, which agree well with the experimental results. We reproduced the structure of phase VII and the predicted phase boundary between phases I and VII occupying the reasonable region in the phase diagram.

Carbon dioxide is one of the fundamental chemical species on Earth, but its solid-phase behavior at high pressures is still far from well understood and some phases remain uncertain or unknown, which increases the challenge to predict its structures.     

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.     

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.     

Evaluation of transcutaneous and end-tidal carbon dioxide levels during inhalation sedation in volunteers

Measurement of end-tidal carbon dioxide (P_ETCO₂) is useful because of its noninvasiveness, continuity, and response time when sudden changes in ventilation occur during inhalation sedation. We compared the accuracy of P_ETCO₂ using a nasal mask and nasal cannula with the accuracy of transcutaneous carbon dioxide (TC-CO₂) and determined which method is more useful during inhalation sedation in volunteers. We used a modified nasal mask (MNM) and modified nasal cannula (MNC) for measurement of P_ETCO₂. The capnometer measured P_ETCO₂ in the gas expired from the nasal cavity by means of two devices. The volunteers received supplemental O₂ by means of each device at a flow rate of 6 L/min. After the volunteers lay quietly for 5 min with a supply of 100 % O₂, they received supplemental N₂O by means of each device at concentrations of 10, 20, and 25 % for 5 min and 30 % for 25 min. The correlation coefficient was poorer in the MNM than in the MNC, and the mean difference between TC-CO₂ and P_ETCO₂ in the MNM was greater than that in the MNC. The difference between the TC-CO₂ and P_ETCO₂ ranged from 3 to 6 mmHg in the MNM and from 2 to 5 mmHg in the MNC. The difference between two variables against the TC-CO₂ and the CO₂ waveforms obtained by means of the two devices were within the clinically acceptable range. Our two devices can provide continuous monitoring of P_ETCO₂ with a supply of N₂O/O₂ in patients undergoing inhalation sedation.     

Regional carbon dioxide monitoring: a different look at tissue perfusion

Adequate tissue oxygenation is one of the main therapeutic goals for the critically ill patient. Until recently, the perfusion status of the critically ill and injured has been assessed by global indices such as blood pressure, heart rate, and urine output. However, these global parameters are inadequate in that they fail to demonstrate the actual perfusion status of a patient. Research has shown the splanchnic region to be a pivotal organ bed in response to shock. Because this region shows early signs of hypoperfusion and hypoxia, its monitoring provides for more effective and complete resuscitation. To that end, gastric tonometry offers a noninvasive means by which early symptoms of low flow can be determined, allowing for optimization of tissue perfusion and patient outcome. The most proximal segment of the gastrointestinal tract offers promising information regarding tissue perfusion with the use of sublingual capnography.     

Factors influencing transcutaneous oxygen and carbon dioxide measurements in adult intensive care patients

Transcutaneous PO2 (PtcO2) is suggested to reflect tissue oxygenation in intensive care patients, whereas transcutaneous PCO2 (PtcCO2) is advocated as a noninvasive method for assessing PaCO2. In 24 critically ill adult patients (mean Apache II score 14.2, SD 4.7) we investigated the impact of variables that are commonly thought to determine PtcO2 and PtcCO2 measurements. A linear correlation was found between PtcO2 and PaO2 (r = 0.6; p less than or equal to 0.0001) and between PtcO2 and mean arterial blood pressure (MAP; r = 0.42; p less than or equal to 0.003). Cardiac index (CI) correlated with tc-index (PtcO2/PaO2; r = 0.31; p less than or equal to 0.03). There was no relationship between PtcO2 and hemoglobin concentration (Hb) and the position of the oxygen dissociation curve (ODC). Stepwise multiple regression analysis demonstrated a significant influence of PaO2 and MAP on PtcO2. The contribution of CI, Hb and the ODC was not significant. Only 40% of the variability of a single PtcO2 measurement could be explained by PaO2 and MAP. A significant linear correlation was demonstrated between PtcCO2 and PaCO2 (r = 0.76; p less than or equal to 0.0001) but not between PtcCO2 and CI, MAP and arterial base excess (BEa). Stepwise multiple regression analysis revealed an influence of PaCO2 and of CI on PtcCO2; 66% of the variability of a single PtcCO2-value could be explained by PaCO2 and CI. Our data demonstrate that transcutaneous derived gas tensions result from complex interaction between hemodynamic, respiratory and local factors, which can hardly be defined in ICU-patients.     

Massive subcutaneous emphysema and hypercarbia: complications of carbon dioxide absorption during extraperitoneal and intraperitoneal laparoscopic surgery--case studies

The laparoscopic approach to surgery is being used with greater frequency as our healthcare system continues to strive for shorter hospital stays and improved postoperative patient recovery times. However, laparoscopy is not without potential complications. This article presents 2 patient case studies. The cases differ in surgical technique. One patient's laparoscopic surgery involved an extraperitoneal approach. The second patient's surgery involved an intraperitoneal approach. Massive subcutaneous emphysema developed in both patients. The phenomenon of subcutaneous emphysema associated with laparoscopic surgery will be defined and discussed.     

Characteristics of transcutaneous carbon dioxide tension monitors in normal adults and critically ill patients

The performance of three electrodes used for transcutaneous carbon dioxide (tcPCO₂) monitoring is compared in 15 healthy volunteers and 26 critically ill adults. All three electrodes showed good correlation between tcPCO₂ and arterial blood PCO₂ (PaCO₂) with a correlation coefficient (r) greater than 0.86. There was little difference in the performance characteristics of the three monitors. They may be usefully employed to estimate PaCO₂ values when used with a modified calibration recommended by the manufacturers.     

二氧化碳气腹对腹腔镜手术患者肾功能的影响

目的 研究不同的二氧化碳(CO2)气腹持续时间对患者肾功能的影响.方法 2009年10月至2011年12月行腹腔镜手术患者89例,根据手术时间不同分成3组,即T1组(＜1 h)、T2组(1～2h)和T3组(＞2 h);所有患者分别于术前、术后10 min、1h、24h检测血肌酐、尿肌酐和尿微量白蛋白.结果 T1组和T2组中患者术后内生肌酐清除率(Cer)较术前差异均无统计学意义(P均＞0.05),T3组中患者术后10 min Ccr较术前显著降低,差异有统计学意义(P＜0.05),术后1h和24h逐渐升高;尿微量白蛋白/尿肌酐比值(A/C)3组患者在术后均较术前显著升高,差异均有统计学意义(P均＜0.05),但术后3组之间差异无统计学意义(P ＞0.05);T1组中≥60岁和＜60岁患者术后的肾功能比较差异均无统计学意义(P均＞0.05),T2、T3组中≥60岁患者在术后24h中Ccr均低于＜60岁患者,差异有统计学意义(P均＜0.05).结论 长时间的CO2气腹可对肾功能产生显著的急性影响,在≥60岁的患者中更加明显,但在较短的时间内肾功能可逐渐恢复.     

Comparison of transcutaneous oxygen and carbon dioxide monitors in normal adults and critically ill patients.

The performance characteristics of two transcutaneous combined PO2 (tcPO2) and PCO2 (tcPCO2) sensors were compared with single tcPO2 and tcPCO2 electrodes in critically ill patients. The relationship between arterial blood gases (PaO2, PaCO2) and transcutaneous values was linear. Correlation coefficients (r) varied from 0.79 to 0.87 for tcPO2 and 0.92 to tcPCO2. The tcPO2 readings were always lower than PaO2 values, but the tcPCO2, with modified calibration of the electrodes, did not differ significantly from PaCO2. There was no significant difference of clinical importance in the performance of the three monitoring systems.     

Changes in transcutaneous carbon dioxide, oxygen saturation, and respiratory rate after interscalene block

BACKGROUND: We used transcutaneous (TC) carbon dioxide (CO2) monitoring to prospectively evaluate changes in respiratory status after interscalene anesthesia in 45 adults (40 successful and 5 unsuccessful blocks). METHODS: TC-CO2 oxygen saturation and respiratory rate were recorded every minute for 5 minutes before block and every 2 minutes for a total of 30 minutes (15 data sets) after injection of the local anesthetic solution. RESULTS: After successful block, TC-CO2 increased from 41 +/- 5 mm Hg to a maximum value of 44 +/- 6 mm Hg (P < 0.0001) and the respiratory rate increased from 14 +/- 2 breaths/min to a maximum of 20 +/- 4 breaths/min (P < 0.001). The increase in TC-CO2 was > or = 5 mm Hg in 11 patients and > or = 10 mm Hg in 4 patients, with a maximum increase of 12 mm Hg. Of the 600 TC-CO2 data points recorded (15 each from the 40 patients with a successful block), 62 (10.3%) showed a TC-CO2 value of 50 mm Hg or greater, with a maximum value of 57 mm Hg. No significant change in TC-CO2 or respiratory rate was seen in the five patients with unsuccessful block. CONCLUSION: After interscalene blockade, we found an increase in respiratory rate and hypercarbia that resulted in no clinically significant effect.     

Dobutamine and gastric-to-arterial carbon dioxide gap in severe sepsis without shock

OBJECTIVES: To evaluate the effect of an early dobutamine infusion on gastrointestinal perfusion in patients with severe sepsis. DESIGN: Prospective, randomized, controlled, multicenter clinical study. SETTING: Six medical and/or surgical intensive care units (ICU) of teaching hospitals. PATIENTS: Forty-two patients with severe sepsis. INTERVENTIONS: Patients were divided into two groups according to gastric-to-arterial CO2 gap (DeltaCO2) [normal DeltaCO2 group ( n=17): DeltaCO2 < or = 8 mmHg; increased DeltaCO2 group ( n=25): DeltaCO2 > 8 mmHg]. Patients within each group were then randomized to receive either dobutamine (5 microg/kg per min) or saline for 72 h. MEASUREMENTS AND MAIN RESULTS: SAPS II was similar in both groups [group 1: 44.0 (33.0-56.5); group 2: 48.5 (40.5-59.0), p=0.27]. At ICU admission, mean arterial pressure was lower in the high DeltaCO2 group [73.0 (67.0-79.5) mmHg, p=0.03] than in the normal DeltaCO2 group [84.0 (73.7-104.0) mmHg] while blood lactate [normal DeltaCO2 group: 1.6 (0.8-2.3); high DeltaCO2 group: 1.6 (1.1-1.9) mmol/l] was similar for the two groups. DeltaCO2 was significantly lower in the normal DeltaCO2 group [5.0 (2.0-6.0) mmHg)] than in the high DeltaCO2 group [11.0 (10.0-19.0) mmHg]. Dobutamine infusion did not significantly change hemodynamics, blood lactate concentration or tonometric parameters in any group within the first 72 h and had no particular beneficial effect in this population. CONCLUSIONS: An early infusion of dobutamine at a fixed dose of 5 microg/kg per min during the first 72 h of severe sepsis does not influence gastric DeltaCO2.     

Noninvasive carbon dioxide monitoring during neurosurgical procedures in adults: end-tidal versus transcutaneous techniques

BACKGROUND: We prospectively compared transcutaneous (TC) versus end-tidal (ET) carbon dioxide monitoring during neurosurgical procedures in adults. METHODS: After calibration and an equilibration time for the TC-CO2 monitor, arterial blood gas (ABG) values were obtained as clinically indicated. The PaCO2 values were compared with the values recorded by the noninvasive monitors (TC and ET). RESULTS: The ET-CO2 to PaCO2 difference was 6.1 +/- 5.6 mm Hg, and the TC-CO2 to PaCO2 difference was 3.7 +/- 2.9 mm Hg. The difference between the PaCO2 and ET-CO2 was 3 mm Hg or less in 17 of 57 values, while the difference between the PaCO2 and TC-CO2 was 3 mm Hg or less in 35 of 57 values. Linear regression analysis of ET-CO2 versus PaCO2 revealed a slope of 0.381 +/- 0.007. Linear regression analysis of TC-CO2 versus PaCO2 revealed a slope of 1.17 +/- 0.008. CONCLUSION: Transcutaneous CO2 monitoring provides a more accurate estimate of PaCO2 than ET-CO2 monitoring during neurosurgical procedures.     

Optical properties and photoactivity of carbon nanodots synthesized from olive solid wastes at different carbonization temperatures

Carbon nanodots (CNDs) have many fascinating properties, such as optical properties (UV-Visible absorption and fluorescence emission), which make them good candidates in many applications, such as photocatalysts for the degradation of several organic pollutants. This study aims to synthesize CNDs from olive solid wastes at different carbonization temperatures from 300 to 900 °C and study the effect on the optical properties of the CNDs, such UV-Vis, fluorescence, quantum yield, and energy bandgap, in addition to the influence on the photoactivity of the CNDs as photocatalysts for the degradation of methylene blue (MB). CNDs were prepared from olive solid wastes (OSWs) by pyrolysis at different temperatures (300–900 °C) for conversion to carbonized material, and then oxidized chemically in the presence of hydrogen peroxide (H₂O₂). It was found that an increase in the carbonization temperature of the OSWs leads to an increase in the product yield with a maximum value at 500 °C, and it then decreased dramatically. On the other hand, a decrease in fluorescence due to the diminishment of oxygen groups and the destruction of the surface of the CNDs was observed. The higher quantum yield (5.17%) and bandgap (2.77 eV) were achieved for CNDs prepared from OSWs that carbonized at 300 °C. The rate and degradation efficiency of MB were studied with the different synthesized CNDs, and it was found that an increase in the carbonization temperature leads to a decrease in the rate and degradation efficiency of MB, with the highest degradation rate of 0.0575 min⁻¹ and degradation efficiency of 100% after 120 minutes of light irradiation being realized for the sample carbonized at 300 °C.

Carbon nanodots with different optical properties and photoactivity degrees as photocatalysts for the degradation of methylene blue are successfully synthesized from olive solid wastes at different carbonization temperatures.