Comparison of the transcutaneous oxygen and carbon dioxide tension in different electrode locations during general anaesthesia

BACKGROUND AND OBJECTIVE: The best place for the electrode of transcutaneous measurement of oxygen tension (tcPO2) and carbon dioxide tension (tcPCO2) during general anaesthesia was investigated in three different locations. METHODS: Fifteen patients for major abdominal surgery in the supine position were studied. The electrode of the TCM4 (Radiometer, Copenhagen, Denmark) was put on the chest, upper arm or forearm. TcPO2, tcPCO2, end-tidal carbon dioxide tension (etCO2), percutaneous oxygen saturation (SaO2), arterial oxygen tension (PaO2 ) and arterial carbon dioxide tension (PaCO2) were simultaneously measured at four different etCO2 concentrations and inhaled oxygen percentages and the location of the electrode was changed to other places to repeat the same measurement. In total, 12 measurements for each patient and 60 measurements for each place were performed. RESULTS: TcPO2 correlated better than SaO2 (R2 = 0.58) with PaO2 (R2 = 0.76), and tcPCO2 correlated well with PaCO2 (R2 = 0.76) and etCO2 (R2 = 0.74) when the electrode was put on the chest, while not on the upper arm or forearm (R2 < 0.5). However, limits of agreement were too big to use tcPO2 (bias, -67.9; limits of agreement, 16.5, -152.3) and tcPCO2 (bias, -0.47; limits of agreement, 8.7, -9.64) as surrogate measures of PaO2 and PaCO2, respectively even when the electrode was put on the chest. CONCLUSIONS: When the electrode was put on the chest, tcPO2 and tcPCO2 might be available as non-invasive monitors of oxygenation and CO2 status during general anaesthesia, while the absolute values were not interchangeable with PaO2 and PaCO2, respectively.     

Changes in transcutaneous oxygen tension during exercise in pulmonary emphysema.

Continuous measurements of transcutaneous oxygen tension (tcPO2) were made in 23 patients with radiological evidence of emphysema, at rest and during a maximal progressive exercise test. tcPO2 during the final phase of exercise was compared with tcPO2 at rest; the mean change (exercising minus resting value) in tcPO2 (delta tcPO2) was -0.8 mm Hg (SD 10.5, range -18 to +25) (-0.1 kPa (SD 1.4, range -2.4 to +3.3]. delta tcPO2 was correlated with: resting arterial oxygen tension (PaO2) (r = 0.606, p less than 0.005); resting arterial carbon dioxide tension (PaCO2) (r = -0.691, p less than 0.001); FEV1 % predicted (r = 0.688, p less than 0.001); vital capacity % predicted (r = 0.543, p less than 0.01); and transfer factor (TLCO) % predicted (r = 0.604, p less than 0.005). There was no significant difference between the delta tcPO2 of 10 patients who regularly produced sputum and of 13 patients with no sputum. delta tcPO2 appears to be more closely related to the severity of emphysema than to the presence or absence of chronic bronchitis. Pretreatment with fenoterol aerosol resulted in an increased work load in three out of 10 patients. Overall there was no change in delta tcPO2. In all except one patient there was a rise in tcPO2 after the end of exercise. In the 11 patients whose tcPO2 fell during exercise, tcPO2 returned to the resting value within two minutes of the cessation of exercise; this was followed by a further rise beyond the resting value, and a single postexercise arterial sample is therefore a poor indicator of the response of PaO2 to exercise. Measurement of TcPO2 is of value in following rapid changes in PaO2 during and after exercise and avoids the necessity for an indwelling arterial cannula.     

Effects of the electrode temperature of a new monitor, TCM4, on the measurement of transcutaneous oxygen and carbon dioxide tension

The transcutaneous measurement of oxygen (tcP_{O 2}) and carbon dioxide (tcP_{CO 2}) tensions may serve as a surrogate of arterial oxygen (Pa_O2) and carbon dioxide (Pa_{CO 2}) tensions, respectively. We investigated the effects of the electrode temperature of a new device, TCM4, on the measurement of tcP_{O 2} and tcP_{CO 2}. Twenty-five patients scheduled for major lower abdominal surgery were enrolled. The electrode of the TCM4 was attached to the chest, with its temperature set to 37°C, 40°C, 42°C, 43°C, or 44°C. tcP_{O 2}, tcP_{CO 2}, end-tidal carbon dioxide tension (Et_{CO 2}), Pa_{O 2}, and Pa_{CO 2} were simultaneously measured at various Et_{CO 2} levels and inhaled oxygen concentrations. The times required for stabilization of the tcP_{O 2} and tcP_{CO 2} values were measured. A Bland-Altman plot was used to compare the two measurements. The time required for stabilization was shorter with a higher electrode temperature, but the shortest time was still more than 150 s. TcP_{O 2} correlated well with Pa_{O 2} at 43°C and 44°C. TcP_{CO 2} correlated well with Pa_{CO 2} and Et_{CO 2} at 43°C. The bias and limits of agreement were larger with lower electrode temperature for TcP_{O 2}—Pa_{O 2}, tcP_{CO 2}—Pa_{CO 2}, and tcP_{CO 2}—Et_{CO 2}. We concluded that the electrode of the TCM4 should be heated to at least 43°C to measure tcP_{O 2} and tcP_{CO 2}. However, the absolute values of tcP_{O 2} and tcP_{CO 2} could not be used as surrogate measurements of Pa_{O 2} and Pa_{CO 2}, respectively.     

Effect of Intralipid infusion on transcutaneous oxygen and carbon dioxide tension in sick neonates

We evaluated the change in transcutaneous oxygen (tcPo2) and carbon dioxide (tcPco2) tension in response to 60 minutes' infusion of Intralipid (Kabi Vitrum (Saphar] (mean dose (0.16 +/- 0.07 g/kg/h) in neonates with lung disease (hyaline membrane disease or bronchopulmonary dysplasia). The tcPo2 was 10% lower following Intralipid infusion (P less than 0.05), whereas no significant change occurred in tcPco2 measurements. The data confirm the need for limited use of Intralipid in this category of patients.     

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.     

Pulmonary gas exchange during exercise in young asthmatic patients.

Pulmonary function was examined in 19 young asthmatic patients at rest and during two levels of excercise. Findings at rest included decreased flow rates, increased residual volume, normal minute (VE) and alveolar (VA) ventilation, increased ratio of physiological dead space to tidal volume (VD/VT), increased alveolar-arterial oxygen tension difference (A-a PO2), and mild arterial hypoxaemia and desaturation. On exercise there was a normal increase in VE and VA, the VD/VT and the A-a PO2 decreased towards normal, and arterial oxygen tension improved, approaching normal levels. Significant acidosis did not develop.     

Estimation of arterial oxygen tension in adult subjects using a transcutaneous electrode.

Transcutaneous oxygen tension (tcPO2) measured with a heated electrode was compared with arterial oxygen tension (PaO2) in three groups of adult patients-group A: 20 patients with chronic respiratory disease; group B: eight hypothermic patents studied immediately after cardiopulmonary bypass surgery; and group C: 14 patients in an intensive care unit who had in all 35 comparisons of tcPO2 and PaO2. For group A, the relationship of the two methods is given by the regression equation (in mmHg): tcPO2 = 0.88 PaO2 + 5.0 (standard error = 5.2: r = 0.93: p less than 0.001) and for group C tcPO2 = 0.69 PaO2 + 14.9 (standard error =12.0, r = 0.90: p less than 0.001). A method of in vivo calibration using a single arterial blood sample improved the reliability of the method in group C. In the group B patients there was no correlation between tcPO2 and PaO2 even when supplementary heating was applied to the skin. Continuous monitoring can reveal large fluctuations in arterial PO2 which would be missed by the use of intermittent arterial samples. The transcutaneous electrode can be employed usefully in intensive care monitoring of adult patients and in physiological studies where repeated arterial samples would otherwise be required.     

Effect of meperidine on oxygen consumption, carbon dioxide production, and respiratory gas exchange in postanesthesia shivering

Meperidine has been used to suppress postanesthesia shivering. However, its efficacy to date has only been assessed by observation of visible shivering. We measured the effect of meperidine on oxygen consumption (VO2), carbon dioxide production (VCO2) and pulmonary gas exchange in 14 otherwise healthy patients shivering after general anesthesia. Meperidine successfully suppressed visible shivering in all patients and was associated with significant decreases in VO2, and VCO2 and minute ventilation (VE) but not with return to basal levels. Arterial PCO2 levels remained unchanged at normal, whereas significant improvements occurred in pH and bicarbonate levels. Meperidine is an effective method of reducing the elevated metabolic demand of shivering.     

Hemodynamics and gas exchange during carbon dioxide insufflation for totally endoscopic coronary artery bypass grafting

BACKGROUND: In addition to single-lung ventilation (SLV), positive-pressure CO2 insufflation is mandatory for totally endoscopic coronary artery bypass grafting. Studies on the effects of unilateral CO2 insufflation on hemodynamics produced controversial results, and bilateral insufflation has not been studied to our knowledge. The present study sought to investigate hemodynamics and gas exchange during unilateral and bilateral CO2 insufflation in patients who underwent totally endoscopic coronary artery bypass grafting. METHODS: Eleven hemodynamic and gas exchange variables were monitored during 22 totally endoscopic coronary artery bypass grafting procedures with unilateral (n = 17) or bilateral (n = 5) CO2 insufflation at a pressure of 10 to 12 mm Hg. Data were obtained at baseline with double-lung ventilation, after institution of SLV, during insufflation, after cardiopulmonary bypass during SLV, and after return to double-lung ventilation. RESULTS: Arterial oxygen tension decreased significantly during SLV, whereas the peak inspiratory pressure increased. In addition, central venous pressure and heart rate increased significantly during insufflation, but mean arterial pressure remained unchanged. Although the end-tidal CO2 pressure did not change, arterial carbon dioxide tension increased progressively to a maximum of 44.6 +/- 5.9 mm Hg during unilateral insufflation, and 55.7 +/- 14.6 mm Hg during bilateral insufflation (p < 0.05 versus baseline and between groups). Mixed venous oxygen saturation declined during SLV regardless of CO2 insufflation and recovered to baseline once double-lung ventilation was restarted. Left and right ventricular ejection fractions remained unaltered. No patient required inotropic or vasopressor support. CONCLUSIONS: Carbon dioxide insufflation for totally endoscopic coronary artery bypass grafting with SLV had no adverse effects on hemodynamics. In contrast to a moderate increase of arterial carbon dioxide tension during unilateral insufflation, markedly elevated arterial carbon dioxide tension levels remain a cause of concern during bilateral insufflation.     

Carbon dioxide absorption and gas exchange during pelvic laparoscopy

Twelve ASA physical status I-II patients undergoing pelvic laparoscopy for infertility were enrolled in a study to quantify the effects of CO2 insufflation and the Trendelenburg position on CO2 elimination and pulmonary gas exchange, and to determine the minute ventilation required to maintain normocapnia during CO2 insufflation. Measurements of O2 uptake (VO2), CO2 elimination (VCO2), minute ventilation (VE), FIO2, and respiratory exchange ratio (RQ) were made during three steady states: control (C) taken after 15 min of normoventilation but before CO2 insufflation, after 15 min (L1) and 30 min (L2) of hyperventilation during CO2 insufflation. The FIO2 was controlled at 0.5 and arterial blood gases were used to calculate the oxygen tension-based indices of pulmonary gas exchange. After 15 min and 30 min of CO2 insufflation, the volume of CO2 absorbed from the peritoneal cavity was estimated at 42.1 +/- 5.1 and 38.6 +/- 6.6 (SEM) ml.min-1 respectively, increasing CO2 elimination through the lungs by about 30%. Hyperventilation of the lungs by a 20-30% increase in minute ventilation maintained normocapnia. Despite the CO2 pneumoperitoneum and Trendelenburg position, there was no impairment of pulmonary oxygen exchange as estimated by (A-alpha)DO2. This study demonstrated that a 30% increase in minute ventilation, achieved by increasing tidal volume to more than 10 ml.kg-1, is sufficient to eliminate the increased CO2 load and maintain normal pulmonary O2 exchange during pelvic laparoscopy.     

Use of transcutaneous oxygen sensors to titrate PEEP.

The relationship of transcutaneous oxygen tension (PtcO2) to arterial oxygen tension (PaO2), pulmonary shunt (Qsp/Qt), mixed venous oxygen tension (PVO2), and O2 delivery was determined in patients with respiratory failure in order to explore the possible usefulness of PtcO2 to titrate the level of positive end expiratory pressure (PEEP). Transcutaneous oxygen sensors were applied to the chest of surgical ICU adult patients who were in acute postoperative respiratory failure. The patients had mechanical ventilation with volume ventilators and an intermittent mandatory ventilation (IMV) rate, which allowed normal pH and arterial CO2 tension ventilation (PacO2). Swan-Ganz and arterial catheters were inserted. The blood volume was measured by iodinated I-125-serum albumin and brought into the normal range, before the study began, with appropriate volume therapy. Serial cardiorespiratory data were taken before and after PEEP was increased from zero to 20 cm H2O, in 5 cm increments. PtcO2 correlated well with PaO2 and PV-O2; it was inversely correlated with Qsp/Qt. PtcO2 correlated with O2 delivery in only seven severely ill patients mean alveolar-arterial oxygen tension difference [A-aDO2] was 380 mmHg and the pulmonary shunt was 37%). For the eight other patients, variations in the greatly elevated cardiac output associated with hypoxemia led to poor correlations between PtcO2 and O2 delivery. There was no significant depression of cardiac output in any of the studies. We conclude that the continuous noninvasive nature of PtcO2 monitoring greatly increased the safety and simplicity of PEEP optimization and respiratory management of adult patients with respiratory failure.     

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。     

Comparison of end-tidal and transcutaneous measures of carbon dioxide during general anaesthesia in severely obese adults

Background. Patients with severe obesity (body mass index (BMI)greater than 35 kg m^–2) present difficulties for end-tidalcarbon dioxide (FE'_CO2) monitoring. Previous studies suggestthat transcutaneous (TC) carbon dioxide measurements could bevaluable, so we compared FE' and TC measures with Pa_CO2 in severelyobese patients during anaesthesia. Methods. We studied patients with severe obesity (BMI     

A comparison of transcutaneous,end-tidal and arterial measurements of carbon dioxide during general anaesthesia

A randomized, prospective study was performed to evaluate the accuracy of a new transcutaneous carbon dioxide (CO2) monitor (Fastrac) during general anaesthesia. Twenty-two adult patients undergoing elective surgery were subjected to three different levels of minute ventilation by varying their respiratory rates in a randomized cross-over design. Simultaneous measurements of transcutaneous CO2 (PTCCO2) and arterial CO2 (PaCO2) were obtained at three levels of minute ventilation (low, medium and high). End-tidal CO2 (PETCO2) values were also recorded from a mass spectrometer (SARA) at each time period. A total of 66 data sets with PaCO2 ranging from 28-62 mmHg were analyzed. The PTCCO2 values demonstrated a high degree of correlation with PaCO2 over the range of minute ventilation (y = 0.904x + 6.36, r = 0.92, P less than 0.001). The PETCO2 measurement also demonstrated a generally good correlation with PaCO2 (y = 0.62x + 9.21, r = 0.89, and P less than 0.01). However, the PETCO2-PaCO2 gradients (mean 7.0 +/- 3.1 mmHg) were greater than the PTCCO2-PaCO2 gradients (mean 2.3 +/- 2.4 mmHg) at all three levels of minute ventilation (P less than 0.05). These differences were greatest when PaCO2 was in the high range (48-60 mmHg). We conclude that the new Fastrac CO2 monitor is accurate for monitoring carbon dioxide levels during general anaesthesia. The new transcutaneous devices provide an effective method for non-invasive monitoring of CO2 in situations where continuous, precise control of CO2 levels is desired.     

An evaluation of transcutaneous carbon dioxide partial pressure monitoring during apnea testing in brain-dead patients

BACKGROUND: Diagnosis of brain death usually requires an arterial carbon dioxide partial pressure (Paco2) of 60 mmHg during the apnea test, but the increase in Paco2 is unpredictable. The authors evaluated whether transcutaneous carbon dioxide partial pressure (Ptcco2) monitoring during apnea test can predict that a Paco2 of 60 mmHg has been reached. METHODS: The authors compared Ptcco2 measured with a transcutaneous ear sensor (V-Sign Sensor, Sentec Digital Monitoring System; SENTEC-AG, Therwil, Switzerland) and Paco2 obtained from arterial blood gas measurements in 32 clinically brain-dead patients. RESULTS: In the first 20 patients, the mean Paco2-Ptcco2 gradient was 0.7 +/- 3.6 mmHg at baseline and 8.7 +/- 7.1 mmHg after 20 min of apnea. Using receiver operating characteristic curve analysis (area under the curve: 0.983 +/- 0.013), the best threshold value of Ptcco2 to predict that a Paco2 of 60 mmHg had been reached was 60 mmHg (positive predictive value: 1.00 [0.93-1.00]). In the following 12 patients investigated with use of this Ptcco2 target value of 60 mmHg, the mean duration of the apnea test (11 +/- 4 vs. 20 +/- 0 min; P < 0.001), hypercapnia (74.0 +/- 4.9 vs. 98.3 +/- 20.0 mmHg; P < 0.001), acidosis (pH: 7.18 +/- 0.06 vs. 7.11 +/- 0.08; P < 0.001), and decrease in arterial oxygen partial pressure (-47 +/- 44 vs. -95 +/- 89; P < 0.05) at the end of the test were reduced as compared with the 20-min apnea test group. CONCLUSION: During the apnea test in brain-dead patients, a Ptcco2 of 60 mmHg accurately predicts that a Paco2 of 60 mmHg has been reached. This may allow a reduction in the duration of the apnea test and consecutively limit occurrence of complications.     

Arterial and transcutaneous oxygen tension measurement during hypotensive anaesthesia.

The values of oxygen tension (PO2) as measured by transcutaneous (at two different sites) and invasive methods were compared during hypotensive anaesthesia with sodium nitroprusside (SNP) in 15 patients. Generally the PO2 significantly decreased during and increased after SNP-induced hypotensive anaesthesia (p less than 0.001). A positive correlation was found between the ratios of change of invasive arterial oxygen tension (PaO2) and supraclavicular transcutaneous oxygen tension (tcPO2) both during (r = 0.64) and after (r = 0.83) hypotension. A similar correlation existed between the ratios of change of PaO2 and forearm tcPO2 only after (r = 0.66) but not during (r =0.33) hypotensive anaesthesia. It is concluded that any of the above methods can be used to give an assessment of PO2 changes during SNP-induced hypotension provided the prehypotensive value is measured. For quantitative measurement of PO2 the invasive method is the first choice. Supraclavicular tcPO2, however, can give an accurate result, while the forearm tcPO2 is the least sensitive.