tcPCO2 Values Research Articles

Pain-related changes in crSO2 among premature infants undergoing PICC insertion

Objective To evaluate the effectiveness of cerebral regional oxygen saturation (crSO2) values, measured using near-infrared spectroscopy (NIRS), in assessing pain associated with the peripherally inserted central catheter (PICC) in premature infants. Methods NIRS was used to measure the crSO2 levels of 48 premature infants with gestational age (GA) of < 32 weeks or a birth weight of < 1500 g. Premature infant pain profile (PIPP) scores, vital signs, transcutaneous oxygen tension (TcpO2), transcutaneous carbon dioxide tension (TcpCO2), and crSO2 values were monitored. One-way repeated measure analysis of variance was used to compare heart rate (HR), respiratory rate (RR), blood pressure (BP), peripheral oxygen saturation (SpO2), TcpO2, TcpCO2, and crSO2 values before (Time 1), during (Time 2), and after (Time 3) PICC insertion. The correlation between the PIPP scores at Time 2 and the fluctuations (values detected at Time 2 minus those at Time 1) of SpO2, TcpO2, and crSO2 were also analyzed. Results The PIPP score at Time 2 was significantly higher than those at Times 1 and 3. HR, RR, and BP values increased (p < .05), and SpO2 and crSO2 levels decreased at Time 2 (p < .05) compared with those at Time 1. Stratified analysis based on GA revealed significant differences in HR, RR, and crSO2 values between Times 1 and 2 in infants with a GA of ≥ 32 weeks. In infants with a GA < 32 weeks, significant differences were observed in HR, RR, SpO2, BP, and crSO2 values between Times 1 and 2. The fluctuation of the crSO2 level was strongly correlated with the PIPP score at Time 2 (r = −0.829, p < .001). A weak correlation was observed between the PIPP score at Time 2 and TcpO2 level fluctuation (r = 0.375, p = .009). No correlation was observed between the PIPP score at Time 2 and SpO2 level fluctuation (r = 0.242, p = .097). Conclusion The fluctuation of crSO2 levels strongly correlates with PICC procedural pain. Hence, crSO2 levels measured using NIRS may be used as an indicator for pain assessment in premature infants.

INFLUENCE OF THE AMOUNT OF COMPRESSION ON VENOUS AND ARTERIAL BLOOD FLOW VELOCITY AND SKIN MICROCIRCULATION OF THE LOWER EXTREMITY.

The aim: To determine the effect of compression on the venous and arterial velocity of the main blood flow of the lower limb and the skin microcirculation of the rear part of the foot. Materials and methods: 20 healthy subjects participated in this study: 11 men 11 (55%) men and 9 (45%) girls. The ankle brachial index (ABI), femoropop¬liteal index, femoral arterial blood flow velocity (AFV), venous blood flow velocity (VFV), transcutaneous oxygen pressure (tcPO2) and carbon dioxide pressure (tcPCO2) were measured. After the general measurements were taken, the tire was inflated to 10 mm Hg under general basic conditions and kept for three minutes. The experiment ended when no decrease in tcPO2 was observed between two consecutive pressure levels. Results: The average tire pressure to reach physiological zero was 80 mm Hg. for all participants. At 10 mmHg significant changes in indicators were found by 19% (p=0.0001). tcPCO2 values increased significantly at 10 mmHg (p=0.0319) and continued to increase until the end of the study. It was established that its values increased by 14% compared to the input data (p=0.0005). Conclusions: At the maximum compression of 60 mmHg the arterial blood flow rate decreased by 5.5 times (p=0.0001). TcPCO2 increases significantly when compressed by 10 mm Hg also in parallel with the decrease in the regional perfusion index, which begins at an external compression of 40 mm Hg, which is evidence of the deterioration of the perfusion of the skin of the anterior part of the foot in healthy subjects.

Ventilation Adjustment in ECT During COVID-19: Voluntary Hyperventilation is an Effective Strategy.

PurposeAirway management is a key objective in adapted electroconvulsive therapy (ECT) protocols during the COVID-19 pandemic to prevent infection. The objective of this study was to describe the effectiveness of a modified ventilation procedure designed to reduce aerosol-generating bag-mask ventilation (BMV) and isolate possible droplets while maintaining adequate respiratory gas values in ECT sessions.Materials and MethodsThis prospective study analyzed the results of the modified protocol applied over a month. Adaptations entailed preoxygenation and extension of the voluntary hyperventilation (VHV) time for two minutes before anesthesia induction, asking patients to hyperventilate with oxygen therapy via nasal cannula and while wearing a face mask. Thereafter, vigorous hyperventilation was avoided, and patients were only assisted with tightly sealed BMV until emergence from anesthesia, isolating the ventilation by using a single-use plastic device. Oxygen saturation (SpO2) and transcutaneous partial pressure of carbon dioxide (TcPCO2) were recorded throughout the session.ResultsThe study included 74 sessions of bilateral ECT with the modified ventilation protocol in 15 subjects. After VHV, the mean SpO2 increase was 2.12±2.14%, and the mean TcPCO2 decrease was 4.05±2.98 mmHg. TcPCO2 values at the moment of stimulus administration were 2.22±3.07 mmHg below pre-ECT values. The mean EEG seizure was 38.70±17.03 s, and postictal suppression was 68.31± 34.58% and 2.13±0.75 on a 0–3 scale. Brief desaturation (SpO2 <90) of 4–5 seconds duration was observed in 4 sessions.ConclusionThis modified ventilation protocol was effective during COVID-19, and it did not elicit significant side effects. In addition to avoiding vigorous BMV, it induced moderate hypocapnia, which has been tied to seizure optimization and less hypercapnia during the apnea period.

Transcutaneous CO2 Monitoring in Children Undergoing Tonsillectomy for Sleep Disordered Breathing.

Children undergoing tonsillectomy for sleep-disordered breathing are at risk for respiratory compromise when narcotics are administered. Severe complications resulting from hypoxia can include neuro-devastation and death. The objective of this prospective study was to evaluate the feasibility, accuracy, and utility of transcutaneous carbon dioxide (tcPCO2) monitoring during and after adenotonsillectomy. Prospective, Observational study. Twenty-nine children with sleep-disordered breathing scheduled for adenotonsillectomy were included in the study. Peri-operative measurements of tcPCO2 were compared against a single venous blood sample (PaCO2) and end-tidal (ET) CO2. The differences between ETCO2, tcPCO2 measures, and PaCO2 were examined using non-paired t-tests and linear regression. Parameters from PSG were recorded and associations with tcPCO2 values were performed using linear regression analysis. Group comparisons were made between pre-, intra-, and post-operative tcPCO2 measurements. Similar to ETCO2, there was good correlation of tcPCO2 to PaCO2. Children with lower oxygen (O2) saturation nadirs had higher peak CO2 levels during surgery and spent a greater proportion of time with CO2 > 50 mmHg in the recovery room (P < .01 and P < .08). Other PSG measures (apnea-hypopnea index, O2 desaturation index, and peak CO2) did not have any significant correlation. Frequent episodes of hypercapnia were noted intra- and post-operatively and mean tcPCO2 values during both periods were significantly higher than baseline (P < .001). tcPCO2 monitoring is viable in children undergoing adenotonsillectomy and can provide a good estimate of hypoventilation. tcPCO2 measurements may have particular benefit in the post-operative setting and may assist in identifying children at greater risk for respiratory complications. 4 Laryngoscope, 131:1410-1415, 2021.

Feasibilty of Transcutaneous pCO2 Monitoring During Immediate Transition After Birth-A Prospective Observational Study.

Background: According to recommendations, non-invasive monitoring during neonatal resuscitation after birth includes heart rate (HR) and oxygen saturation (SpO2). Continuous transcutaneous monitoring of carbon dioxide partial pressure (tcpCO2) may further offer quantitative information on neonatal respiratory status.Objective: We aimed to investigate feasibility of tcpCO2 measurements in the delivery room during immediate neonatal transition and to compare the course of tcpCO2 between stable term and preterm infants.Methods: Neonates without need for cardio-respiratory intervention during immediate transition after birth were enrolled in a prospective observational study. In these term and preterm neonates, we measured HR and SpO2 by pulse oximetry on the right wrist and tcpCO2 with the sensor applied on the left hemithorax during the first 15 min after birth. Courses of tcpCO2 were analyzed in term and preterm neonates and groups were compared.Results: Fifty-three term (gestational age: 38.8 ± 0.9 weeks) and 13 preterm neonates (gestational age: 34.1 ± 1.5 weeks) were included. First tcpCO2 values were achieved in both groups at minute 4 after birth, which reached a stable plateau after the equilibration phase at minute 9. Mean tcpCO2 values 15 min after birth were 46.2 (95% CI 34.5–57.8) mmHg in term neonates and 48.5 (95%CI 43.0–54.1) mmHg in preterm neonates. Preterm and term infants did not show significant differences in the tcpCO2 values at any time point.Conclusion: This study demonstrates that tcpCO2 measurement is feasible during immediate neonatal transition after birth and that tcpCO2 values were comparable in stable term and preterm neonates.

Comparison of monitored anaesthesia care and general anaesthesia in endobronchial coil treatment

ObjectiveThe aim of this study was to evaluate the efficacy and complications of two different anaesthesia methods in endobronchial coil treatment. MethodsIn this prospective, randomised study, the patients were divided into 2 groups; general anaesthesia with endotracheal intubation was performed in 17 patients (group GA), whereas monitored anaesthesia care (MAC) was performed in 15 patients by using a continuous infusion of propofol and remifentanil (group MAC). During the procedure, peripheral oxygen saturation (SpO2), transcutaneous partial carbon dioxide pressure (tcPCO2), cerebral oxygen saturation and patient state index were monitored. ResultsRemifentanil consumption was significantly reduced and the recovery duration was shorter in the group MAC compared to GA (p < 0.001). SpO2 values at minute 5 and 10 in group MAC were significantly lower than those for group GA (p < 0.001). The tcPCO2 values during the entire procedure were higher in group GA, and the difference between the groups was significant at minute 20 (p < 0.05) and 30 (p < 0.001). ConclusionMAC can be safely used in endobronchial coil treatment and considered as an alternative method to general anaesthesia for endobronchial coil treatment.

Clinical observation on monitoring different body parts of neonatal intensive care unit critically ill newborns by percutaneous oxygen partial pressure and carbon dioxide partial pressure

Objectives Study on the accuracy and influencing factors of neonatal intensive care unit (NICU) critically ill newborns different body parts monitoring by percutaneous oxygen partial pressure (TcpO2) and carbon dioxide partial pressure (TcpCO2), in order to provide a basis for non-invasive monitoring of critically ill newborns in ICU. Methods 60 cases of critically ill newborns requiring blood gas analysis were selected as research cases during July 2017 to March 2018 in Wuxi City Maternity and Child Hospital Neonatology. According to the randomized control principle, three groups were divided, chest group (20 cases), abdomen group (20 cases), leg group (20 cases). The chest group placed the electrodes of the transcutaneous gas analyzer on newborns′ anterior chest. The abdomen group placed the electrodes on newborns′ abdomen. And the leg group placed the electrodes on the inner thigh. PaO2 and PaCO2 values were collected from the blood gas results of critically ill newborns. TcpO2 and TcpCO2 values were recorded. And at the same time, the electrode shedding situation was observed as well. Compare transcutaneous data and arterial blood data, and do analysis. Result The chest group TcpO2 (69.05±9.17) mmHg(1 mmHg=0.133 kPa), TcpCO2 (46.9±10.57) mmHg, PaO2 (76.4±8.64) mmHg, PaCO2 (40.65±4.74) mmHg, the PaO2 and PaCO2 values were obviously different from the blood gas analysis results (t=-2.608, 2.413, P 0.05) . And the electrode sheet shedding rate was 30% in the chest group, 25% in the abdomen group, and 10% in the leg group, the three groups had no significant differences (χ2=2.553, P>0.05) . Conclusion NICU critically ill newborns thigh skin monitoring by percutaneous oxygen partial pressure and carbon dioxide partial pressure has high accuracy, and the electrode sheet shedding rate is relatively low. Therefore, it is a safe and effective clinical monitoring method, of great significance for monitoring changes in the condition of critically ill newborns. Key words: Neonatal intensive care unit; Critically ill newborns; Percutaneous oxygen partial pressure; Carbon dioxide partial pressure monitoring; Electrode shedding rate

Protocolized hyperventilation enhances electroconvulsive therapy

BackgroundHyperventilation is recommended in electroconvulsive therapy (ECT) to enhance seizures and to increase patients’ safety. However, more evidence is needed regarding its effects and the optimum method of application. MethodsThis prospective study involving 21 subjects compared two procedures, protocolized hyperventilation (PHV) and hyperventilation as usual (HVau), applied to the same patient in two consecutive sessions. Transcutaneous partial pressure of carbon dioxide (TcPCO2) was measured throughout all sessions. Ventilation parameters, hemodynamic measures, seizure characteristics, and side effects were also explored. ResultsPHV resulted in lower TcPCO2 after hyperventilation (p=.008) and over the whole session (p=.035). The lowest TcPCO2 was achieved after voluntary hyperventilation. Changes in TcPCO2 from baseline showed differences between HVau and PHV at each session time-point (all p<.05). Between- and within-subjects factors were statistically significant in a general linear model. Seizure duration was greater in PHV sessions (p=.028), without differences in other seizure quality parameters or adverse effects. Correlations were found between hypocapnia induction and seizure quality indexes. LimitationsSecondary outcomes could be underpowered. ConclusionsPHV produces hypocapnia before the stimulus, modifies patients’ TcPCO2 values throughout the ECT session and lengthens seizure duration. Voluntary hyperventilation is the most important part of the PHV procedure with respect to achieving hypocapnia. A specific ventilation approach, CO2 quantification and monitoring may be advisable in ECT. PHV is easy to apply in daily clinical practice and does not imply added costs. Ventilation management has promising effects in terms of optimizing ECT technique.

Preliminary Validation of Transcutaneous CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Monitoring in Patients Undergoing Cardiac Ablation Using Jet Ventilation

Objectives: There is no data in the current medical literature on efficacy or accuracy of transcutaneous (tcPCO2) monitoring during jet ventilation for cardiac ablation. The use of tcPCO2 during cardiac ablation procedures offers the opportunity to compare end-tidal and transcutaneous methods of CO2 measurement before and after the use of the jet ventilation. Comparison of these measurements with arterial blood gas CO2 levels allows evaluation of the accuracy of the tcPCO2 technique for use during jet ventilation. Design: Observational study; patients served as their own controls. Setting: Cardiac electrophysiology laboratory. Participants: 15 adult patients (9 M), ASA III-IV, aged 26 to 82 years (median 66 years) undergoing radiofrequency ablation for atrial fibrillation. Interventions: Jet ventilation (JV) versus conventional ventilation. Measurements and Main Results: Paired measurements of end-tidal CO2 (EtCO2) and transcutaneous CO2 (tcPCO2) were recorded during periods of conventional ventilation. Paired measurements of arterial blood CO2 (PaCO2) levels and tcPCO2 were recorded during JV. ABG samples were drawn at the anesthesiologist’s discretion to assess the patient’s respiratory status. The level of agreement between the three methods was compared using the Bland Altman plot. We found that tcPCO2 values consistently provided a close approximation to PaCO2 levels. The mean difference between tcPCO2 and EtCO2 values in baseline and post-JV was on the order of 3 - 5 mmHg, with standard deviation of 4 - 6 mmHg. This is well within the range of variability that is accepted in clinical practice. Conclusions: These preliminary results suggest that tcPCO2 provides an acceptable estimate of CO2 concentration in arterial blood during JV, as well as prior to and following JV.

Comparison of Fluid Types for Resuscitation in Acute Hemorrhagic Shock and Evaluation of Gastric Luminal and Transcutaneous Pco2in Leghorn Chickens

The objective of this study was to compare the effects of 3 different fluid types for resuscitation after experimentally induced hemorrhagic shock in anesthetized chickens and to evaluate partial pressures of carbon dioxide measured in arterial blood (Paco2), with a transcutaneous monitor (TcPco2), with a gastric intraluminal monitor (GiPco2), and by end tidal measurements (Etco2) under stable conditions and after induced hemorrhagic shock. Hemorrhagic shock was induced in 40 white leghorn chickens by removing 50% of blood volume by phlebotomy under general anesthesia. Birds were divided into 4 groups: untreated (control group) and treated with intravenous hetastarch (haes group), with a hemoglobin-based oxygen carrier (hemospan group), or by autotransfusion (blood group). Respiratory rates, heart rates, and systolic arterial blood pressure (SAP) were compared at 8 time points (baseline [T0]; at the loss of 10% [T10%], 20% [T20%], 30% [T30%], 40% [T40%], and 50% [T50%] of blood volume; at the end of resuscitation [RES]; and at the end of anesthesia [END]). Packed cell volume (PCV) and blood hemoglobin content were compared at 6 time points (T0, T50%, RES, and 1, 3, and 7 days after induced hemorrhagic shock). Measurements of Paco2, TcPco2, GiPco2, and Etco2 were evaluated at 2 time points (T0 and T50%), and venous lactic acid concentrations were evaluated at 3 time points (T0, T50%, and END). No significant differences were found in mortality, respiratory rate, heart rate, PCV, or hemoglobin values among the 4 groups. Birds given fluid resuscitation had significantly higher SAPs after fluid administration than did birds in the control group. In all groups, PCV and hemoglobin concentrations began to rise by day 3 after phlebotomy, and baseline values were reached 7 days after blood removal. At T0, TcPco2 did not differ significantly from Paco2, but GiPco2 and Etco2 differed significantly from Paco2. After hemorrhagic shock, GiPco2 and TcPco2 differed significantly from Paco2. The TcPco2 or GiPco2 values did not differ significantly at any time point in birds that survived or died in any of the groups and across all groups. These results showed no difference in mortality in leghorn chickens treated with fluid resuscitation after hemorrhagic shock and that the PCV and hemoglobin concentrations increased by 3 days after acute hemorrhage with or without treatment. The different CO2 measurements document changes in CO2-values consistent with poor perfusion and may prove useful for serial evaluation of responses to shock and shock treatment.

Transcutaneous PCO2 Measurement at Low Temperature for Reliable and Continuous Free Flap Monitoring: Experimental and Clinical Study.

Background:Measurement of transcutaneous oxygen pressure (TcPO2) and transcutaneous carbon dioxide pressure (TcPCO2) has been used for free flap monitoring. Because these values are obtained with sensor probes heated to 44°C, there is potential for low-temperature burns on skin flaps. We measured TcPO2 and TcPCO2 at 37°C in both animals and humans to determine the feasibility and safety of the procedure as a postoperative flap monitoring method.Methods:Twelve epigastric island flaps were elevated in rabbits, and TcPO2 and TcPCO2 were measured at 37°C before and after ligation of the pedicles. In addition, TcPO2 and TcPCO2 at 37°C were measured in healthy men. Subsequently, the method was applied to postoperative monitoring of free flaps in 49 clinical cases.Results:TcPO2 and TcPCO2 values were significantly affected by the experimental flap elevation. A rapid increase in TcPCO2 was observed with both arterial and venous occlusion. In the healthy men, TcPO2 and TcPCO2 were measurable at all skin surface sites. In the clinical cases of free flap transfer, TcPO2 values remained very low for at least 72 hours. TcPCO2 values ranged from 40 to 70 mm Hg for 72 hours in more than 80% of cases. In 2 cases, TcPCO2 values increased to more than 90 mm Hg, and exploration surgery was performed. These compromised flaps were saved by reanastomosis of the veins.Conclusions:Continuous monitoring of TcPCO2 at 37°C can provide objective information and alert doctors and nurses to the need for checking the free flap.

Evaluation of a combined transcutaneous carbon dioxide pressure and pulse oximetry sensor in adult sheep and dogs

To evaluate a combined transcutaneous carbon dioxide pressure (tcPCO(2)) and pulse oximetry sensor in sheep and dogs. 13 adult sheep and 11 adult dogs. During inhalation anesthesia, for the first 10 minutes following sensor placement, arterial blood gas was analyzed and tcPCO(2) was recorded every 2 minutes. Subsequently, the animals were hyper-, normo-, and hypoventilated. The simultaneously obtained tcPCO(2) and PaCO(2) values were analyzed by use of Bland-Altman statistical analysis. Mean +/- SD overall difference between tcPCO(2) and PaCO(2) 10 minutes after sensor application was 13.3 +/- 8.4 mm Hg in sheep and 8.9 +/- 12 mm Hg in dogs. During hyper-, normo-, and hypoventilation, mean difference (bias) and precision (limits of agreement [bias +/- 2 SD]) between tcPCO(2) and PaCO(2) values were 13.2 +/- 10.4 mm Hg (limits of agreement, -7.1 and 33.5 mm Hg) in sheep and 10.6 +/- 10.5 mm Hg (limits of agreement, -9.9 and 31.2 mm Hg) in dogs, respectively. Changes in PaCO(2) induced by different ventilation settings were detected by the tcPCO(2) sensor with a lag (response) time of 4.9 +/- 3.5 minutes for sheep and 6.2 +/- 3.6 minutes for dogs. The tcPCO(2) sensor overestimated PaCO(2) in sheep and dogs and followed changes in PaCO(2) with a considerable lag time. The tcPCO(2) sensor might be useful for noninvasive monitoring of changes but cannot be used as a surrogate measure for PaCO(2).

Transcutaneous Pco2 monitoring in critically ill adults: Clinical evaluation of a new sensor*

In critically ill patients, arterial blood gas analysis is the gold standard for evaluating systemic oxygenation and carbon dioxide partial pressure. A new miniaturized carbon dioxide tension Pco2-Spo2 single sensor (TOSCA, Linde Medical Sensors AG, Basel, Switzerland) continuously and noninvasively (transcutaneously) monitors both Paco2 and oxygen saturation by pulse oximetry (Spo2). The present study was designed to investigate the usability and the accuracy of this device in critically ill patients. Prospective clinical investigation. A 20-bed, university-affiliated, surgical intensive care unit. Patients admitted after major surgery, multiple trauma, or septic shock equipped with an arterial catheter. The heated (42 degrees C) sensor was fixed at the earlobe using an attachment clip. Transcutaneous Pco2 (TcPco2) measurements were correlated with Paco2 values (measured using a blood gas analyzer). In addition, the differences between Paco2 and TcPco2 values were evaluated using the method of Bland-Altman. We studied 55 patients, aged 18-80 (mean 57 +/- 15) yrs. A total of 417 paired measurements were compared. Correlation between TcPco2 and Paco2 was r = .86 (p < .01) in the Paco2 range of 24-101 mm Hg. Mean bias (+/-sd) between the two methods of measurement (Bland-Altman analysis) was 1.2 +/- 6.0 mm Hg with TcPco2 slightly overestimating arterial carbon dioxide tension. Nineteen percent of the measured values were outside of the acceptable clinical range of agreement of +/-7.5 mm Hg. The present study suggests that Paco2 can be acceptably assessed by measuring TcPco2 using the TOSCA Pco2-Spo2 sensor.

Prevention of ventilatory disturbance while in the face-down position after macular hole surgery.

The aim of the present study was to assess the effects of the face-down position on ventilatory function after macular hole surgery. The transcutaneous carbon dioxide tensions (tcPCO2) were measured in five patients who had undergone intraocular tamponade and in 17 normal subjects. The tcPCO2 measurements were done in patients following vitrectomy in the sitting position and in the prone position with their faces down over the semi-closed spaces of the conventional mats. In normal subjects, minute ventilatory volumes (V.E) were measured simultaneously with tcPCO2 in the sitting position and prone position. The newly introduced face-down mats (new mats) for the prone position were also tested in the normal subjects. In normal subjects, VE in the prone position with the conventional mats was significantly lower than that found in the sitting position (5.06 +/- 1.55 vs 6.06 +/- 1.64 L/min; P < 0.002). The tcPCO2 in the prone position was significantly higher than that in the sitting position (41.7 +/- 2.1 vs 38.0 +/- 1.9 mmHg; P < 0.0001). In post-vitrectomy patients, tcPCO2 in the prone position with the conventional mats was significantly higher than that in the sitting position (41.4 +/- 1.7 vs 38.6 +/- 2.2 mmHg; P < 0.02). The tcPCO2 in the prone position in normal subjects was significantly lower using new mats than that when using conventional mats. The use of conventional mats during a prone position, increased the tcPCO2 values when compared to the tcPCO2 values obtained during the sitting position in patients following vitrectomy. This could be due to either a decrease of the VE caused by limited thoracic movement or rebreathing of the exhaled gas over the semi-closed space, or both. The new mats might be useful in alleviating the increase of tcPCO2 by eliminating the rebreathing of the exhaled gas.

Transcutaneous CO2 tension effects of clonidine in paediatric caudal analgesia

In adults, clonidine when added to bupivacaine, results in no detectable respiratory depressant effect except when carbon dioxide challenge is performed. However, to date no investigations have quantified this in children. Twenty-four children (nine months to seven years) were randomized in a double-blind study into two groups. After induction, a caudal block was performed with 1 ml.kg-1 0.25% bupivacaine. Clonidine 1 microgram.kg-1 was added in the clonidine group, and 1 ml normal saline in the placebo group. Patients were monitored in the recovery room for three h from arrival to discharge with continuous pulse oximetry, respiratory rate, a transcutaneous CO2 tension (tcPCO2) every 15 min, and a four point sedation score every 30 min. Mean tcPCO2 and respiratory rate values were not different between the two groups. Apnoea and desaturation less than 97% were not observed. The sedation score decreased with time in both groups, and the score time interval was significantly higher in the clonidine group (P < 0.05). All the patients left the recovery room with a sedation score of 1, excepting four in the clonidine group with a sedation score of 2. Clonidine 1 microgram.kg-1 with 0.25% bupivacaine mixture in caudal analgesia in children did not induce an increase in tcPCO2 despite prolonged sedation.

Accuracy of End-Tidal and Transcutaneous Pco2 Monitoring During Sleep

Although it is intuitively desirable, the measurement of arterial carbon dioxide tension (PaCO2) during diagnostic polysomnography and nocturnal trials of positive pressure therapy is invasive and potentially expensive. The accuracy of end-tidal carbon dioxide tension (PETCO2) and transcutaneous carbon dioxide (tcPCO2) monitoring in these contexts has not been systematically evaluated. This investigation was undertaken to evaluate the accuracy of PETCO2 and tcPCO2 in patients undergoing polysomnography. Values of PETCO2 were compared with PaCO2 in 19 patients spontaneously breathing room air (condition 1), in 13 patients receiving supplemental oxygen via nasal cannula (condition 2), and in 22 patients receiving nocturnal positive pressure ventilatory assistance (all but one with continuous positive airway pressure or bilevel positive airway pressure) (condition 3). The accuracy of tcPCO2 monitoring during sleep was also examined by comparing tcPCO2 values with simultaneously recorded PaCO2 values obtained during sleep in patients undergoing nocturnal polysomnography. Data were collected using three commercially available brands of tcPCO2 monitors (capnograph R, n = 17 patients; capnograph S, n = 17; and capnograph N, n = 15). Accuracy of PETCO2--There was significant scatter in the PaCO2 vs PETCO2 relationship such that only 23 percent of the variability in PaCO2 was explained by variation of PETCO2 during condition 1 and only 15 percent and 20 percent of the variability in PaCO2 was explained by variation of PETCO2 during conditions 2 and 3, respectively. 21.3 percent of patients had average PETCO2 values in error by > 10 mm Hg during condition 1, while during conditions 2 and 3, 46.2 and 63.7 percent of patients had average values in error by > 10 mm Hg, respectively. Accuracy of tcPCO2--While capnographs S and N generally overestimated PaCO2 with a wide scatter, capnograph R tended to have offsetting overestimations and underestimations of PaCO2 with a wide scatter. With each capnograph, a relatively small portion of the variability of the PaCO2 was explained by variability of the tcPCO2 (r2 = 0.2, 0.45 and 0.64 for capnographs S, N, and R, respectively). Across the three capnographs, 43.1 to 66.7 percent of measurements were in error by > 10 mm Hg, and 5 to 20 percent of measurements reflected errors > 20 mm Hg. There was no consistent relationship between the tcPCO2 error and the level of PaCO2, nor was the tcPCO2 error consistent in individual patients. There was no relationship between tcPCO2 accuracy and body mass index. Neither PETCO2, measured within a face mask, nor tcPCO2 is a consistently accurate reflection of PaCO2. This limits the utility of these variables in monitoring patients during diagnostic and therapeutic sleep studies, and in particular, during trials of nocturnal ventilatory assistance where adequate levels of support are to be established and unacceptable hyperventilation and respiratory alkalosis must be recognized.

Measurement of Transcutaneous Carbon Dioxide in Low Birthweight Infants During the First Two Weeks of Life

With the advent of pulse oximetry, there has been a general decrease in the use of transcutaneous (Tc) blood gas monitoring in intensive care environments. The available data, however, suggest that arterial carbon dioxide pressure (PCO2) levels are best estimated by Tc methods. In this study, we report our experience using routine Tc PCO2 monitoring in 32 consecutive infants less than 2 weeks of age with birthweights less than 1500 g. A total of 644 simultaneous pairs (Tc PCO2 versus arterial PCO2) were obtained. Pairs were categorized according to a 2 x 2 matrix design based on sensor temperature (40 degrees or 43 degrees C) versus site of arterial sampling (umbilical [UAC] or peripheral artery catheter [PAC]). Sampling via the UAC resulted in excellent correlation between sample pairs at both sensor temperatures with similar regressions between groups. Sampling via the PAC, however, yielded poor correlation between sample pairs and a significantly different regression from both UAC groups. Based on these findings, we advocate the use of a sensor temperature of 40 degrees C in very low birthweight infants for tracking Tc PCO2 values. In addition, we suggest that inaccuracies in PAC sampling may lead to erroneous PCO2 determinations. We conclude that routine monitoring of Tc PCO2 is accurate and serves a useful and continuing role in the neonatal intensive care environment.

The influence of cutaneous factors on the transcutaneous pO2 and pO2 at various body sites

The transcutaneous partial pressures of oxygen (tcpO2) and carbon dioxide (tcpCO2) were measured at eight different sites in 10 adult male subjects with an electrode at a temperature of 44 degrees C. The mean tcpO2 values (mmHg) were significantly lower on the face (forehead 26.6, cheek 29.6) and the palm (26.4) than at other sites (60.6-69.6). The tcpCO2 values (mmHg) were only slightly higher on the face. Removal of the stratum corneum produced an average increase of the tcpO2 on the palm of 37.6 mmHg and on the forehead of 19.6 mmHg. However, in 10 children with an age range of 3-9 years, the difference in the mean pO2 between the cheek and forearm was very small. There was no significant difference in the cutaneous blood flow at 44 degrees C between the cheek, palm and forearm.

Normal range of fetal transcutaneous carbon dioxide tension during labour.

Fetal transcutaneous carbon dioxide tension (tc-PCO2) was monitored during 122 deliveries, using an electrode temperature of 44 degrees C in 80 cases and of 41 degrees C in 42 cases. Significant correlations between tc-PCO2 and umbilical artery blood PCO2 were found using both electrode temperatures, but the regression lines indicated a larger and more inconstant CO2-contribution from skin metabolism when the low electrode temperature was used. Normal range of tc-PCO2 was calculated at 41 degrees C and 44 degrees C electrode temperatures. Mean values of fetal tc-PCO2 were found to increase during normal labour, and especially in fetuses developing acidosis, but only four of six infants born with acidaemia had tc-PCO2 values exceeding the normal range.

Transcutaneous carbon dioxide measurements in the fetus during labor.

Continuous transcutaneous carbon dioxide partial pressure (tcPco2) was monitored in 40 spontaneous labors. The electrode was attached by glue fixation. An interpretable tracing was obtained in 36 cases. All cases but 2 were normal pregnancies. Thirty-two patients had epidural analgesia while the others had no analgesia. All infants had an Apgar score above 7 at five minutes after delivery and only two had a pH of the umbilical artery of less than 7.16. Mean duration of the recordings was 116 minutes (range: 15-300) and mean time for reaching steady-state was 27 minutes (range: 10-45 minutes). Mean value of tcPco2 was 48 mmHg (SD: 6) before 6 cm of dilatation, 47 mmHg (SD: 8) between 6 and 10 cm, and 47 mmHg (SD: 15) at the second stage of labor. Mean umbilical artery Pco2 was 48 mmHg (SD: 14) and mean umbilical artery pH was 7.25 (SD: 0.06). The range of tcPco2 obtained in these normal cases was 20 to 62 mmHg. Comparison of the results with those of other authors and with previous studies of normal labor and epidural analgesia show a higher tcPco2 compared to scalp Pco2. In contrast to other studies in these series no correlation was found in the series between umbilical artery Pco2 and tcPco2 values. This lack of correlation could be explained either by the small number of cases in which both measurements were available (9 cases) and by the small range of variation or by some inaccuracy in the measurements.(ABSTRACT TRUNCATED AT 250 WORDS)