A capnography and transcutaneous CO2 profile of bariatric patients during early postoperative period after opioid-sparing anesthesia.

Aim: It is difficult to maintain the necessary depth of sedation during bronchoscopy, and hypoxemia, hypoventilation, and undesirable cardiovascular effects are often encountered. Transcutaneous carbon dioxide monitoring is a reliable means of detecting hypoventilation. The aim of this study was to determine the effects of transcutaneous carbon dioxide (tPCO₂) monitoring on the amount of propofol required for sedation and examine sedation-induced hypoventilation and other adverse events requiring intervention, such as stopping the procedure to ventilate during flexible bronchoscopy. \nMethods: This prospective observational study included 60 patients undergoing bronchoscopy who were administered propofol. Of these, 30 patients were observed with transcutaneous carbon dioxide, and 30 were observed without. Propofol was used for sedation in all patients and the amount of propofol was compared between the groups monitored and not monitored transcutaneously for carbon dioxide. The sedation level was determined with the subjective sedation scale of the group that was not monitored. \nResults: No significant differences were found between the groups in terms of propofol consumption or the number of patients who required airway interventions during the procedure (P>0.05 for both). In this observational study, the partial carbon dioxide pressure in arterial blood was measured with a transcutaneous carbon dioxide monitor, which is a non-invasive method, and the maximum carbon dioxide value measured in prolonged interventions was 85 mmHg. Hypoxia was not observed in patients who developed hypoventilation.\nConclusions: Hypoventilation is inevitable during bronchoscopy. Transcutaneous carbon dioxide monitoring may be important for high-risk cardiovascular patients.

Transcutaneous monitoring and capnography are 2 surrogate methods of measuring arterial carbon dioxide levels employed by pediatric sleep laboratories. Both techniques are noninvasive, validated, and quantitative indirect predictors of arterial carbon dioxide level, and both have been widely adopted for use during pediatric and adult polysomnography (PSG). We hypothesized that there would be close agreement between the two techniques when compared in a pediatric population. Children referred for diagnostic polysomnography to the Pediatric Sleep Laboratory at the Alberta Children's Hospital from June 2000 to October 2003 were included. All subjects underwent an overnight computerized PSG as per American Thoracic Society standards, including both transcutaneous and end-tidal monitoring. A registered PSG technician manually scored studies and eliminated all CO2 data that was not interpretable. Total "uninterpretable data" time was calculated for both channels. Statistical analysis of the level of agreement between transcutaneous and end-tidal signals was performed using a Bland-Altman analysis. The PSG studies of 609 children (363 males), mean age 7.9 +/- 4.6 years (range 0.1-18.4), were reviewed. On average, interpretable data was available for 61.8% +/- 35.1% and 71.5% +/- 25.2 % of total recording time from the end-tidal and transcutaneous channels respectively. The maximum and mean CO2 measurements obtained by both devices showed close agreement with a mean difference of 0.1 +/- 5.4 mm Hg and 0.6 +/- 3.9 mm Hg respectively. Transcutaneous and end-tidal carbon dioxide monitoring during polysomnography are well tolerated and provide interpretable and comparable results in the majority of children.

To review the technology required for and the applications of transcutaneous carbon dioxide (TC-CO2) monitoring in infants and children. A computerized, bibliographic search regarding the applications of transcutaneous carbon dioxide (TC-CO2) monitoring in infants and children. Although the direct measurement of P(a)CO2 remains the gold standard, it provides only a single measurement of what is often a rapidly changing and evolving clinical picture. Given these concerns, there remains a clinical need for a means to continuously monitor P(a)CO2 without the need for repeated blood gas analysis. Although initially introduced into the neonatal intensive care unit; with improvements in the technology, TC-CO2 monitoring can now be used in infants, children and even adults. When compared with end-tidal carbon dioxide (ET-CO2) monitoring techniques, TC-CO2 monitoring has been shown to be equally as accurate in patients with normal respiratory function and more accurate in patients with shunt or ventilation-perfusion inequalities. TC-CO2 monitoring can be applied in situations that generally preclude ET-CO2 monitoring such as high frequency ventilation, apnea testing, and noninvasive ventilation. TC-CO2 monitoring has also been used in spontaneously breathing children with airway and respiratory issues such as croup and status asthmaticus as well as to monitor metabolic status during treatment of acidosis related to diabetic ketoacidosis. Transcutaneous carbon dioxide monitoring may be a useful adjunct in various clinical scenarios in infants and children. It should be viewed as a complimentary technology and may be used in combination with ET-CO2 monitoring.

The partial pressure of arterial carbon dioxide plays a critical role in assessing the acid-base and respiratory status of the human body. Typically, this measurement is invasive and can only be taken momentarily when an arterial blood sample is drawn. Transcutaneous monitoring is a noninvasive surrogate method that provides a continuous measure of arterial carbon dioxide. Unfortunately, current technology is limited to bedside instruments mainly used in intensive care units. We developed a first-of-its-kind miniaturized transcutaneous carbon dioxide monitor that utilizes a luminescence sensing film and a time-domain dual lifetime referencing method. Gas cell experiments confirmed the monitor's ability to accurately identify changes in the partial pressure of carbon dioxide within the clinically significant range. Compared to the luminescence intensity-based technique, the time-domain dual lifetime referencing method is less prone to measurement errors caused by changes in excitation strength, reducing the maximum error from ∼40% to ∼3% and resulting in more reliable readings. Additionally, we analyzed the sensing film by investigating its behavior under various confounding factors and its susceptibility to measurement drift. Finally, a human subject test demonstrated the effectiveness of the applied method in detecting even slight changes in transcutaneous carbon dioxide, as small as ∼0.7%, during hyperventilation. The prototype, which consumes 30.1 mW of power, is a wearable wristband with compact dimensions of 37 mm× 32 mm.

Transcutaneous gas monitoring is a useful tool to detect respiratory depression during bronchoscopy performed under propofol sedation

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition, respiratory failure being the commonest cause of death. Quality of life and survival can be improved by supporting respiratory function with non-invasive ventilation. Transcutaneous carbon dioxide monitoring is a non-invasive method of measuring arterial carbon dioxide levels enabling simple and efficient screening for respiratory failure. The aim of this study was to validate the accuracy of carbon dioxide level recorded transcutaneously with a TOSCA 500 monitor. It is a prospective, observational study of 40 consecutive patients with ALS, recruited from a specialist ALS clinic. The partial pressure of carbon dioxide (PCO(2)) in each patient was determined by both transcutaneous monitoring and by an arterialized ear lobe capillary blood sample. The carbon dioxide (CO(2)) levels obtained with these two methods were compared by Bland-Altman analysis. The results showed that the mean difference between arterialized and transcutaneous readings was - 0.083 kPa (SD 0.318). The Bland-Altman limits of agreement ranged from 0.553 to - 0.719 kPa. The difference was < 0.5 kPa in 90% of the recordings. Four of the 40 measurements had a difference of > 0.5 kPa, with a maximum recorded difference of 0.95 kPa. In conclusion, non-invasive carbon dioxide monitoring using a TOSCA monitor is a useful clinical tool in neurology practice. Users should be aware of the possibility of occasional inaccurate readings. A clinically unexpected or incompatible reading should be verified with a blood gas analysis, especially when a decision to provide ventilatory support is required.

Anesthetic management during rigid bronchoscopy in children can be challenging, and continuous end-tidal carbon dioxide (EtCO2) monitoring is often unachievable. Transcutaneous carbon dioxide (TcCO2) monitoring is strongly correlated with the partial pressure of carbon dioxide (PaCO2) and EtCO2. We aimed to investigate the incidence of hypercapnia in children undergoing rigid bronchoscopy. We enrolled patients aged < 18yr scheduled for rigid bronchoscopy in a prospective observational study. We recorded TcCO2 values from anesthesia induction to the postanesthesia care unit (PACU) stay. We ended monitoring when TcCO2 reached values ≤ 50mm Hg. The operating room (OR) team was blinded to the TcCO2. The outcome of primary interest was the incidence of hypercapnia (TcCO2 > 50mm Hg) in the OR. Other outcomes were the incidences of hypercapnia in the PACU and severe hypercapnia (TcCO2 > 90mm Hg), factors possibly related to hypercapnia (patient, surgery, or anesthesia factors), and the incidence of perioperative adverse events. A total of 30 patients were enrolled. The median [interquartile range (IQR)] age was 3.5 [1.5-8.0] yr. The incidence of hypercapnia was 100% in the OR and 60% in the PACU. Five cases (17%) presented with severe hypercapnia in the OR. The highest median [IQR] TcCO2 was 69 [61-79] mm Hg. The most common adverse event was oxygen desaturation (57%, 17/30). Patients with severe hypercapnia had long stays in the PACU. Hypercapnia was a frequent event in children undergoing rigid bronchoscopy and severe hypercapnia was associated with a long PACU stay. Further studies are needed to assess the utility of TcCO2 monitoring in guiding ventilatory interventions during these cases.

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. 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. We included 35 patients with a median apnoea duration of 25 min. Mean pH was 7.14 and mean arterial carbon dioxide tension was 11.2kPa at the termination of apnoeic oxygenation. Transcutaneous carbon dioxide monitoring initially slightly underestimated the arterial tension but at carbon dioxide levels above 10kPa it overestimated the value. Bias ranged from -0.55 to 0.81 kPa with limits of agreement between -1.25 and 2.11 kPa. 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.

To investigate the correlation and accuracy of transcutaneous carbon dioxide partial pressure (PTCCO2) with regard to arterial carbon dioxide partial pressure (PaCO2) in severe obese patients undergoing laparoscopic bariatric surgery. Twenty-one patients with BMI>35 kg/m2 were enrolled in our study. Their PaCO2, end-tidal carbon dioxide partial pressure (PetCO2), as well as PTCCO2 values were measured at before pneumoperitoneum and 30 min, 60 min, 120 min after pneumoperitoneum respectively. Then the differences between each pair of values (PetCO2–PaCO2) and. (PTCCO2–PaCO2) were calculated. Bland–Altman method, correlation and regression analysis, as well as exact probability method and two way contingency table were employed for the data analysis. 21 adults (aged 19–54 yr, mean 29, SD 9 yr; weight 86–160 kg, mean119.3, SD 22.1 kg; BMI 35.3–51.1 kg/m2, mean 42.1,SD 5.4 kg/m2) were finally included in this study. One patient was eliminated due to the use of vaso-excitor material phenylephrine during anesthesia induction. Eighty-four sample sets were obtained. The average PaCO2–PTCCO2 difference was 0.9±1.3 mmHg (mean±SD). And the average PaCO2–PetCO2 difference was 10.3±2.3 mmHg (mean±SD). The linear regression equation of PaCO2–PetCO2 is PetCO2 = 11.58+0.57×PaCO2 (r2 = 0.64, P<0.01), whereas the one of PaCO2–PTCCO2 is PTCCO2 = 0.60+0.97×PaCO2 (r2 = 0.89). The LOA (limits of agreement) of 95% average PaCO2–PetCO2 difference is 10.3±4.6 mmHg (mean±1.96 SD), while the LOA of 95% average PaCO2–PTCCO2 difference is 0.9±2.6 mmHg (mean±1.96 SD). In conclusion, transcutaneous carbon dioxide monitoring provides a better estimate of PaCO2 than PetCO2 in severe obese patients undergoing laparoscopic bariatric surgery.

Wearable smart health applications aim to continuously monitor critical physiological parameters without disrupting patients' daily activities, such as giving a blood sample for lab analysis. For example, the partial pressure of arterial carbon dioxide, the critical indicator of ventilation efficacy reflecting the respiratory and acid-base status of the human body, is measured invasively from the arteries. Therefore, it can momentarily be monitored in a clinical setting when the arterial blood sample is taken. Although a noninvasive surrogate method for estimating the partial pressure of arterial carbon dioxide exists (i.e., transcutaneous carbon dioxide monitoring), it is primarily limited to intensive care units and comes in the form of a large bedside device. Nevertheless, recent advancements in the luminescence sensing field have enabled a promising technology that can be incorporated into a wearable device for the continuous and remote monitoring of ventilation efficacy. In this review, we examine existing and nascent techniques for sensing transcutaneous carbon dioxide and highlight novel wearable transcutaneous carbon dioxide monitors by comparing their performance with the traditional bedside counterparts. We also discuss future directions of transcutaneous carbon dioxide monitoring in next-generation smart health applications.

The measurement of partial pressures of oxygen (O2) and carbon dioxide (CO2) is fundamental for evaluating a patient's conditions in clinical practice. There are many ways to retrieve O2/CO2 partial pressures and concentrations. Arterial blood gas (ABG) analysis is the gold standard technique for such a purpose, but it is invasive, intermittent, and potentially painful. Among all the alternative methods for gas monitoring, non-invasive transcutaneous O2 and CO2 monitoring has been emerging since the 1970s, being able to overcome the main drawbacks of ABG analysis. Clark and Severinghaus electrodes enabled the breakthrough for transcutaneous O2 and CO2 monitoring, respectively, and in the last twenty years, many innovations have been introduced as alternatives to overcome their limitations. This review reports the most recent solutions for transcutaneous O2 and CO2 monitoring, with a particular consideration for wearable measurement systems. Luminescence-based electronic paramagnetic resonance and photoacoustic sensors are investigated. Optical sensors appear to be the most promising, giving fast and accurate measurements without the need for frequent calibrations and being suitable for integration into wearable measurement systems.

Transcutaneous carbon dioxide (PtcCO2) monitoring is known to be effective at estimating the arterial partial pressure of carbon dioxide (PaCO2) in patients with sedation-induced respiratory depression. We aimed to investigate the accuracy of PtcCO2 monitoring to measure PaCO2 and its sensitivity to detect hypercapnia (PaCO2 > 60 mmHg) compared to nasal end-tidal carbon dioxide (PetCO2) monitoring during non-intubated video-assisted thoracoscopic surgery (VATS). This retrospective study included patients undergoing non-intubated VATS from December 2019 to May 2021. Datasets of PetCO2, PtcCO2, and PaCO2 measured simultaneously were extracted from patient records. Overall, 111 datasets of CO2 monitoring during one-lung ventilation (OLV) were collected from 43 patients. PtcCO2 had higher sensitivity and predictive power for hypercapnia during OLV than PetCO2 (84.6% vs. 15.4%, p < 0.001; area under the receiver operating characteristic curve; 0.912 vs. 0.776, p = 0.002). Moreover, PtcCO2 was more in agreement with PaCO2 than PetCO2, indicated by a lower bias (bias ± standard deviation; −1.6 ± 6.5 mmHg vs. 14.3 ± 8.4 mmHg, p < 0.001) and narrower limit of agreement (−14.3–11.2 mmHg vs. −2.2–30.7 mmHg). These results suggest that concurrent PtcCO2 monitoring allows anesthesiologists to provide safer respiratory management for patients undergoing non-intubated VATS.

Ambulatory transcutaneous carbon dioxide monitoring for children with neuromuscular disease

Arterial blood gases, oxygen, carbon dioxide, and the potential of hydrogen are the key indicators of respiratory status and should be continuously monitored for patients whose respiratory vital signs may alter frequently and rapidly. The arterial partial pressure of oxygen and carbon dioxide can be estimated with transcutaneous monitoring, which measures the partial pressure of oxygen and carbon dioxide diffusing from the skin. However, requiring a heating element and a large, expensive bedside monitor are the limitations of the traditional transcutaneous blood gas monitors preventing continuous monitoring outside a clinical setting. Therefore, we propose a miniaturized fluorescent thin film-based prototype, envisioned as a first-of-its-kind continuous transcutaneous carbon dioxide monitoring wearable device. The computation principle relies on measuring the fluorescence intensity of a carbon dioxide-sensitive thin film. The prototype monitor estimates the partial pressure of carbon dioxide ranging from 0 to 75 mmHg, covering the clinically significant range, 35–45 mmHg for healthy humans. The prototype is designed with a small form factor on a 60 mm×55 mm printed circuit board and consumes 64.33 mW, suitable to be translated into a wearable device in further design stages.

In neonates with post-asphyxial neonatal encephalopathy, further neuronal damage is prevented with therapeutic hypothermia (TH). In addition, fluctuations in carbon dioxide levels have been associated with poor neurodevelopmental outcome, demanding close monitoring. This study investigated the accuracy and clinical value of transcutaneous carbon dioxide (tcPCO2) monitoring during TH. In this retrospective cohort study in neonates, agreement between arterial carbon dioxide (PaCO2) values and tcPCO2 measurements during TH was determined. TcPCO2 levels during the first 24 h of hypothermia were tested for an association with ischemic brain injury on magnetic resonance imaging (MRI). Thirty-four neonates were included. Agreement (bias (95% limits of agreement)) between tcPCO2 and PaCO2 levels was 3.9 (-12.4-20.2) mm Hg. No relation was found between the body temperature and tcPCO2 levels. TcPCO2 levels differed significantly between patients with considerable and minimal damage on MRI; after 6 h (P = 0.02) and 9 h (P = 0.04). Although tcPCO2 provided a limited estimation of PaCO2, it can be used for trend monitoring during TH. TcPCO2 levels after birth could provide an early indicator of ischemic brain injury. This relation should be investigated in large prospective studies, in which adjustments for confounders can be made. Transcutaneous carbon dioxide measurements during therapeutic hypothermia in neonates show limited accuracy similar to measurements reported in normothermic neonates and can be used for trend monitoring. Low transcutaneous carbon dioxide levels during the first 24 h were associated with considerable ischemic brain injury on MRI. The value of transcutaneous carbon dioxide measurements during the first 24 h as an indicator of considerable ischemic brain injury on MRI should be investigated in future studies, adjusting for confounders. Transcutaneous oxygen measurements during therapeutic hypothermia showed an inaccuracy that could not be related to a low body temperature.