RESUMEN

Transcutaneous carbon dioxide measurement (TcCO2) offers the ability to continuously and non-invasively monitor carbon dioxide (CO2) tensions when end-tidal monitoring is not possible. The accuracy of TcCO2 has not been established in anesthetized apneic patients with obesity. In this secondary publication, we present a methods comparison analysis of TcCO2 with the gold standard arterial PCO2, in adult patients with body mass index (BMI) > 35kg/m2 who were randomized to receive high flow or low flow nasal oxygenation during post-induction apnea. Agreement between PaCO2 and TcCO2 at baseline, the start of apnea and the end of apnea were assessed using a non-parametric difference plot. Forty-two participants had a median (IQR) BMI of 52 (40-58.5) kg/m2. The mean (SD) PaCO2 was 33.9 (4.0) mmHg at baseline and 51.4 (7.5) mmHg at the end of apnea. The bias was the greatest at the end of apnea median (95% CI, 95% limits of agreement) 1.90 mmHg (-2.64 to 6.44, -7.10 to 22.90). Findings did not suggest significant systematic differences between the PaCO2 and TcCO2 measures. For a short period of apnea, TcCO2 showed inadequate agreement with PaCO2 in patients with BMI > 35 kg/m2. These techniques require comparison in a larger population, with more frequent sampling and over a longer timeframe, before TcCO2 can be confidently recommended in this setting.

Asunto(s)

RESUMEN

BACKGROUND: The duration of apnoeic oxygenation with high-flow nasal oxygen is limited by hypercapnia and acidosis and monitoring of arterial carbon dioxide level is therefore essential. We have performed a study in patients undergoing prolonged apnoeic oxygenation where we monitored the progressive hypercapnia with transcutaneous carbon dioxide. In this paper, we compared the transcutaneous carbon dioxide level with arterial carbon dioxide tension. METHODS: This is a secondary publication based on data from a study exploring the limits of apnoeic oxygenation. We compared transcutaneous carbon dioxide monitoring with arterial carbon dioxide tension using Bland-Altman analyses in anaesthetised and paralysed patients undergoing prolonged apnoeic oxygenation until a predefined limit of pH 7.15 or PCO2 of 12 kPa was reached. RESULTS: We included 35 patients with a median apnoea duration of 25 min. Mean pH was 7.14 and mean arterial carbon dioxide tension was 11.2 kPa at the termination of apnoeic oxygenation. Transcutaneous carbon dioxide monitoring initially slightly underestimated the arterial tension but at carbon dioxide levels above 10 kPa it overestimated the value. Bias ranged from -0.55 to 0.81 kPa with limits of agreement between -1.25 and 2.11 kPa. CONCLUSION: Transcutaneous carbon dioxide monitoring provided a clinically acceptable substitute for arterial blood gases but as hypercapnia developed to considerable levels, we observed overestimation at high carbon dioxide tensions in patients undergoing apnoeic oxygenation with high-flow nasal oxygen.

Asunto(s)

RESUMEN

BACKGROUND: Improving tissue perfusion can improve clinical outcomes in surgical patients, where monitoring may aid clinicians in detecting adverse conditions and guide interventions. Transcutaneous monitoring (TCM) of oxygen (tcpO2) and carbon dioxide (tcpCO2) is a well-proven technology and could potentially serve as a measure of local circulation, perfusion and metabolism, but the clinical use is not thoroughly explored. The purpose of this proof-of-concept study was to investigate whether TCM of blood gasses could detect changes in perfusion during major vascular surgery. METHODS: Ten patients with peripheral arterial disease scheduled for lower limb major arterial revascularization under general anaesthesia were consecutively included. TcpO2 and tcpCO2 were continuously recorded from anaesthesia induction until skin closure with a TCM monitor placed on both legs and the thorax. Peripheral oxygen saturation was kept ≥94% and mean arterial blood pressure ≥65 mmHg. The primary outcomes were changes in tcpO2 and tcpCO2 related to arterial clamping and declamping during the procedure and analyzed by paired statistics. RESULTS: Femoral artery clamping resulted in a significant decrease in tcpO2 (-2.1 kPa, IQR-4.2; -0.8), p=.017)), followed by a significant increase in response to arterial declamping (5.5 kPa, IQR 0-7.3), p=.017)). Arterial clamping resulted in a statistically significant increase in tcpCO2 (0.9 kPa, IQR 0.3-5.4), p=.008)) and a significant decrease following declamping (-0.7 kPa, IQR -2.6; -0.2), p=.011)). CONCLUSION: Transcutaneous monitoring of oxygen and carbon dioxide is a feasible method for detection of extreme changes in tissue perfusion during arterial clamping and declamping, and its use for improving patient outcomes should be explored. Clinical Trials identifier: NCT04040478. Registered on July 31, 2019.

Asunto(s)

RESUMEN

BACKGROUND AND OBJECTIVES: Transcutaneous PCO2 and PO2 measurement systems offer non-invasive blood gas trend monitoring. The aim of this prospective study was to assess bias and precision of a transcutaneous PCO2 and PO2 measurement system incorporating a novel pO2 sensor (Sentec OxiVenT™) in neonates ≥34 weeks of gestational age (GA) admitted to intensive care. METHODS: Transcutaneous PCO2 and PO2 were compared to arterial and capillary blood gas measurements. Bias and precision were calculated by fitting linear mixed models to account for repeated measurements, and influence of clinical covariates on bias and precision was assessed. RESULTS: We obtained 611 paired transcutaneous and blood gas measurements in 110 patients (median GA 38.3 [interquartile range 36.1-39.7] weeks; age 9 [4-15] days; weight 3,000 [2,500-3,500] g). Transcutaneous PCO2 showed significant bias to arterial PCO2 (+0.61; 95% confidence interval 0.46, 0.76 kPa), but not to capillary PCO2 (-0.23; -0.46, 0.002 kPa). Bias of transcutaneous PO2 was significant to arterial PO2 (-2.50; -2.94, -2.06 kPa), while no significant bias compared to capillary PO2 was observed (+0.17; -0.30, 0.64 kPa). Precision intervals were ±1.8/2.0 kPa for arterial versus capillary PCO2 and ±4.9/3.3 kPa for arterial versus capillary PO2 comparisons, respectively. Further, sensor operating temperature (43°C vs. 42°C), soft tissue oedema, vasoactive drugs, weight, and GA significantly altered bias (p < 0.05). CONCLUSIONS: The tested transcutaneous blood gas measurement system showed no significant bias compared to capillary PCO2 and PO2, acceptable bias to arterial PCO2, and limited agreement with arterial PO2. Precision intervals were wide for all comparisons.

Asunto(s)

RESUMEN

BACKGROUND: Arterial blood gas analysis is the gold standard for monitoring of Pa CO2 and PaO2 during mechanical ventilation. However, continuous measurements would be preferred. Transcutaneous sensors continuously measure blood gases diffusing from the locally heated skin. These sensors have been validated in children mostly in intensive care settings. Accuracy in children during general anesthesia is largely unknown. AIMS: We conducted a study in children undergoing general anesthesia to validate the use and to determine the accuracy of continuous transcutaneous measurements of the partial pressures of PCO2 (tcPCO2 ) and PO2 (tcPO2 ). METHODS: A prospective observational study in a tertiary care pediatric hospital in The Netherlands, from April to October 2018, in children aged 0-18 years undergoing general anesthesia. Patients were included when endotracheally intubated and provided with an arterial catheter for regular blood sampling. Patients with a gestational age <31 weeks, burn victims, and patients with skin disease were excluded. TcPCO2 and tcPO2  measurements were performed with a SenTec OxiVenT™ sensor (SenTec AG). Accuracy was determined with an agreement analysis between arterial and transcutaneous PCO2 and PO2  values, and between arterial and endtidal PCO2 (etCO2 ) values, according to Bland and Altman, accounting for multiple measurements per subject. RESULTS: We included 53 patients (median age 4.1 years, IQR 0.7-14.4 years) and retrieved 175 samples. TcPCO2 -Pa CO2 agreement analysis provided a bias of 0.06 kPa (limits of agreement (LOA) -1.18 to 1.31), the etCO2 -Pa CO2 agreement showed a bias of -0.31 kPa (LOA -1.38 to 0.76). Results of the tcPO2 -PaO2 agreement showed a bias of 3.40 to 0.86* (mean tension) kPa. CONCLUSIONS: This study showed good agreement between Pa CO2 and tcPCO2 in children of all ages during general anesthesia. Both transcutaneous and endtidal CO2  measurements showed good accuracy. TcPO2 is only accurate under 6 months of age.

Asunto(s)

RESUMEN

Carbon dioxide (CO2) monitoring in human subjects is of crucial importance in medical practice. Transcutaneous monitors based on the Stow-Severinghaus electrode make a good alternative to the painful and risky arterial "blood gases" sampling. Yet, such monitors are not only expensive, but also bulky and continuously drifting, requiring frequent recalibrations by trained medical staff. Aiming at finding alternatives, the full panel of CO2 measurement techniques is thoroughly reviewed. The physicochemical working principle of each sensing technique is given, as well as some typical merit criteria, advantages, and drawbacks. An overview of the main CO2 monitoring methods and sites routinely used in clinical practice is also provided, revealing their constraints and specificities. The reviewed CO2 sensing techniques are then evaluated in view of the latter clinical constraints and transcutaneous sensing coupled to a dye-based fluorescence CO2 sensing seems to offer the best potential for the development of a future non-invasive clinical CO2 monitor.

Asunto(s)

RESUMEN

SIGNIFICANCE: The arterial carbon dioxide (CO2) partial pressure PaCO2 is a clinically relevant variable. However, its measurement requires arterial blood sampling or bulky and expensive transcutaneous PtcCO2 meters. While the spectrophotometric determination of hemoglobin species-such as oxy-hemoglobin (O2Hb) and deoxy-hemoglobin (HHb)-allowed for the development of pulse oximetry, the measurement of CO2 blood content with minimal discomfort has not been addressed yet. AIM: Characterizing human carbamino-hemoglobin (CO2Hb) absorption spectrum, which is missing from the literature. Providing the theoretical background that will allow for transcutaneous, noninvasive PaCO2 measurements. APPROACH: A tonometry-based approach was used to obtain gas-equilibrated, lysed, diluted human blood. Equilibration was performed with both CO2, dinitrogen (N2), and ambient air. Spectrophotometric measurements were carried out on the 235- to 1000-nm range. A theoretical background was also derived from that of pulse oximetry. RESULTS: The absorption spectra of both CO2Hb and HHb were extremely close and comparable with that of state-of-the-art HHb. The above-mentioned theoretical background led to an estimated relative error above 30% on the measured amount of CO2Hb in a subject's blood. Auxiliary measurements revealed that the use of ethylene diamine tetraacetic acid did not interfere with spectrophotometric measurements, whereas sodium metabisulfite did. CONCLUSIONS: CO2Hb absorption spectrum was measured for the first time. Such spectrum being close to that of HHb, the use of a theoretical background based on pulse oximetry theory for noninvasive PaCO2 measurement seems extremely challenging.

Asunto(s)

RESUMEN

Infantile hemangioma (IH) is the most common vascular tumor in infancy, and its physiopathology is not fully understood. Nevertheless, a hypoxic insult may be an essential element for the formation of an IH. Herein, we describe a case of a 25-week premature newborn who developed an IH after a post-burn scar and its evolution.

RESUMEN

BACKGROUND: High electrode temperature during transcutaneous monitoring is associated with skin burns in extremely premature infants. We evaluated the accuracy and precision of CO2 and O2 measurements using lower transcutaneous electrode temperatures below 42°C. METHODS: We enrolled 20 neonates. Two transcutaneous monitors were placed simultaneously on each neonate, with one electrode maintained at 42°C and the other randomized to temperatures of 38, 39, 40, 41, and 42°C. Arterial blood was collected twice at each temperature. RESULTS: At the time of arterial blood sampling, values for transcutaneously measured partial pressure of CO2 (PtcCO2 ) were not significantly different among test temperatures. There was no evidence of skin burning at any temperature. For PtcCO2 , Bland-Altman analyses of all test temperatures versus 42°C showed good precision and low bias. Transcutaneously measured partial pressure of O2 (PtcO2 ) values trended arterial values but had large negative bias. CONCLUSION: Transcutaneous electrode temperatures as low as 38°C allow an assessment of PtcCO2 as accurate as that with electrodes at 42°C.

Asunto(s)

RESUMEN

BACKGROUND: Transcutaneous monitors are utilized to monitor a patient's respiratory status. Some patients have similar values when comparing transcutaneous carbon dioxide (PtcCO2 ) values with blood gas analysis, whereas others show extreme variability. A retrospective review of data was performed to determine how accurately PtcCO2 correlated with CO2 values obtained by arterial blood gas (ABG) or capillary blood gas. METHODS: To determine whether PtcCO2 values correlated with ABG or capillary blood gas values, subjects' records were retrospectively reviewed. Data collected included the PtcCO2 value at the time of blood gas procurement and the ABG or capillary blood gas PCO2 value. Agreement of pairs of methods (ABG vs PtcCO2 and capillary blood gas vs PtcCO2 ) was assessed with the Bland-Altman approach with limits of agreement estimated with a mixed model to account for serial measurements per subject. RESULTS: A total of 912 pairs of ABG/PtcCO2 values on 54 subjects and 307 pairs of capillary blood gas/PtcCO2 values on 34 subjects were analyzed. The PCO2 range for ABG was 24-106 mm Hg, and PtcCO2 values were 27-133 mm Hg. The PCO2 range for capillary blood gas was 29-108 mm Hg, and PtcCO2 values were 30-103 mm Hg. For ABG/PtcCO2 comparisons, the Pearson correlation coefficient was 0.82, 95% CI was 0.80-0.84, and P was <.001. For capillary blood gas/PtcCO2 comparisons, the Pearson correlation coefficient was 0.77, 95% CI was 0.72-0.81, and P was <.001. For ABG/PtcCO2 , the estimated difference ± SD was -6.79 ± 7.62 mm Hg, and limits of agreement were -22.03 to 8.45. For capillary blood gas/PtcCO2 , the estimated difference ± SD was -1.61 ± 7.64 mm Hg, and limits of agreement were -16.88 to 13.66. The repeatability coefficient was about 30 mm Hg. CONCLUSIONS: Based on these data, capillary blood gas comparisons showed less variation and a slightly lower correlation with PtcCO2 than did ABG comparisons. After accounting for serial measurements per patient, due to the wide limits of agreement and poor repeatability, the utility of relying on PtcCO2 readings for this purpose is questionable.

Asunto(s)

RESUMEN

Noninvasive techniques are routinely used for assessment of tissue effects of lung ventilation. However, comprehensive studies of the response time of the methods are scarce. The aim of this study was to compare the response time of noninvasive methods for monitoring of gas exchange to sudden changes in the composition of the inspired gas. A prospective experimental study with 16 healthy volunteers was conducted. A ventilation circuit was designed that enabled a fast change in the composition of the inspiratory gas mixture while allowing spontaneous breathing. The volunteers inhaled a hypoxic mixture, then a hypercapnic mixture, a hyperoxic mixture and finally a 0.3% CO mixture. The parameters with the fastest response to the sudden change of O2 in inhaled gas were peripheral capillary oxygen saturation (SpO2) and regional tissue oxygenation (rSO2). Transcutaneous oxygen partial pressure (tcpO2) had almost the same time of reaction, but its time of relaxation was 2-3 times longer. End-tidal carbon dioxide (EtCO2) response time to change of CO2 concentration in inhaled gas was less than half in comparison with transcutaneous carbon dioxide partial pressure (tcpCO2). All the examined parameters and devices reacted adequately to changes in gas concentration in the inspiratory gas mixture.

Asunto(s)

RESUMEN

BACKGROUND: This work aimed to compare frequency of blood gas measurements per day of mechanical ventilation, occurrence of extreme blood gas CO2 values, and clinical outcomes among ventilated neonates managed with and without transcutaneous carbon dioxide (PtcCO2) monitors. This work also measures agreement between simultaneous PtcCO2 and blood gas CO2 measurements and ascertains factors that affect agreement. METHODS: This is a cohort study with retrospective analysis comparing 5,726 blood gas measurements and clinical outcomes for 123 neonates intubated for >48 h before and after the introduction of transcutaneous carbon-di-oxide monitoring devices in a single tertiary care unit. RESULTS: Median (interquartile range) blood gas frequency per mechanical ventilation day was 3.9 (2.6-5.3) and 2.9 (2.1-4.0) before and after PtcCO2 monitoring (P = .002) without differences in clinical outcomes at discharge. After adjusting for confounders using Poisson regression, this difference remained significant. The mean ± 2 SD blood gas-PtcCO2 difference was -5.2 ± 17.3 mm Hg. 64% of simultaneous blood gas-PtcCO2 measurements per subject were within ± 7 mm Hg. Greater bias was noted with arterial sample and during the use of high-frequency ventilation. CONCLUSION: Despite only moderate agreement between simultaneous PtcCO2 and blood gas measurements, PtcCO2 monitoring statistically decreased blood gas frequency among ventilated neonates without affecting the duration of mechanical ventilation or clinical outcomes at discharge. The clinical impact of this technology appears to be minimal.

Asunto(s)

RESUMEN

Non-invasive transcutaneous monitoring(TCM) of oxygen and carbon dioxide,with continuous,non-invasive characteristics,is in common use and significant in the neonatal intensive care unit (NICU),which can directly reflect critically ill newborns'changes of respiratory and circulatory function.This review describes how to use TCM appropriately,compares the advantages and disadvantages of TCM with other monitoring devices,introduces its application in neonatal transport and NICU.

RESUMEN

The electrical property between an electrode and skin or tissue is one of the important issues for communication performance of the transcutaneous communication system (TCS) using a human body as a conductive medium.In this study, we used a simple method to measure interface resistance between the electrode and skin on the surface of the body. The electrode-electrode impedance was measured by a commercially available LCR meter with changes in the distance between two electrodes on an arm of a healthy male subject, and we obtained the tissue resistivity and electrode-skin interface resistance using the cross-sectional area of the arm.We also measured transmission gain of the TCS on the surface of the body, and we investigated the relationship between electrode-skin interface resistance and transmission gain. We examined four kinds of electrodes: a stainless steel electrode, a titanium electrode, an Ag-AgCl electrode and an Ag-AgCl paste electrode. The stainless steel electrode, which had lower electrode-skin resistance, had higher transmission gain.The results indicate that an electrode that has lower electrode-skin resistance will contribute to improvement of the performance of the TCS and that electrode-skin interface resistance is one of valuable evaluation parameters for selecting an optimum electrode for the TCS.

Asunto(s)