Transcutaneous Carbon Dioxide Measurements Research Articles

Accuracy of Transcutaneous Carbon Dioxide Measurement During Transcatheter Aortic Valve Replacement Under Monitored Anesthesia Care: A Prospective Observational Study.

Background Transcutaneous carbon dioxide tension (PtcCO2) measurement is a promising alternative to arterial carbon dioxide tension (PaCO2) measurement. PaCO2 measurement is invasive and intermittent, whereas PtcCO2 measurement is non-invasive and continuous. However, previous studies evaluating PtcCO2measurements did not include patients undergoing transcatheter aortic valve replacement (TAVR), who experience anticipated hemodynamic changes, particularly before and after valve placement. Therefore, we investigated whether PtcCO2 measurement could provide an alternative to PaCO2 measurement during transfemoral TAVR under monitored anesthesia care (MAC) with local anesthesia. Methodology We conducted a prospective observational study. We included all consecutive patients with severe aortic stenosis who were scheduled to undergo a transfemoral TAVR under MAC at our institution from November 1, 2020, to April 30, 2021. During the procedures, PaCO2 and PtcCO2 were concurrently monitored six times as a reference standard and index test, respectively. PtcCO2 was monitored continuously using a non-invasive earlobe sensor. The agreement between PtcCO2 and PaCO2 measurements was assessed using the Bland-Altman method, and the 95% limits of agreement were calculated. Based on previous studies, we determined that 95% limits of agreement of ±6.0 mmHg would be clinically acceptable to define PtcCO2 as an alternative to PaCO2. Results We obtained 88 measurement pairs from 15 patients. The lower and upper 95% limits of agreement between the PtcCO2 and PaCO2 measurements were -4.22 mmHg and 6.56 mmHg, respectively. Conclusions During TAVR under MAC with local anesthesia, PtcCO2 measurement could not provide a viable alternative to PaCO2 measurement to reduce high PaCO2 events. This study focused on comparing intraoperative periods before and after valve implantation. Therefore, further investigation is warranted to assess the impact of various factors, including the prosthetic valve type and the hemodynamic effects of balloon aortic valvuloplasty, on PtcCO2 measurement in TAVR.

P103 Utility of Capillary Blood Gases (CBGs) for measuring gas exchange in the Sleep Laboratory.

Abstract Introduction Arterial Blood Gases (ABGs) are used for assessing respiratory failure in clinical practice. ABGs also provide a useful verification tool for nocturnal Transcutaneous Carbon Dioxide (TcCO2) measurements. However, there are known complications to collecting ABGs. Conversely, CBG is less invasive and more accessible to clinical practice. We assessed CBGs as an alternative to ABGs to measure pCO2 and pO2, and its suitability for verifying TcCO2. We hypothesised that CBG sampling would be suitable for TcCO2 verification and would be a suitable ABG surrogate. Methods ABGs were sampled by Resident Medical Officers (RMOs) and CBGs were sampled by Sleep Scientists to validate TcCO2 at awake. Correlation between measures was assessed via Pearson and Spearman coefficients. ρ > 0.6 demonstrate a moderate positive correlation, with strengthening correlation as ρ approaches 1. Agreement between measurements was assessed via Bland-Altman plots. Results There was a moderately strong correlation between CBG vs TcCO2 (n=125) (ρ = 0.694, p < 0.001) and CBG vs ABG (pCO2) (n=29) (ρ = 0.725, p < 0.001), with a strong correlation for ABG vs TcCO2 (n=81) (ρ = 0.847, p < 0.001). Bland-Altman plots showed agreement between CBG, ABG and TcCO2. Conclusions There were strong positive correlations observed, with agreement seen across all measures of pCO2. This analysis demonstrates both the accuracy of nocturnal TcCO2 and the utility of CBG to verify TcCO2. Surrogate CO2 measures support positive patient outcomes and verification of gas exchange.

Prospective, observational study investigating the level of agreement between transcutaneous and invasive carbon dioxide measurements in critically ill emergency department patients

BackgroundTranscutaneous carbon dioxide (Ptcco2) measurement is a non-invasive surrogate marker for arterial carbon dioxide (Paco2), which requires invasive arterial blood sampling. Use of Ptcco2 has been examined in different clinical...

Improving the Clinical Interpretation of Transcutaneous Carbon Dioxide and Oxygen Measurements in the Neonatal Intensive Care Unit

Introduction: Transcutaneous blood gas monitoring allows for continuous non-invasive evaluation of carbon dioxide and oxygen levels. Its use is limited as its accuracy is dependent on several factors. We aimed to identify the most influential factors to increase usability and aid in the interpretation of transcutaneous blood gas monitoring. Methods: In this retrospective cohort study, transcutaneous blood gas measurements were paired to arterial blood gas withdrawals in neonates admitted to the neonatal intensive care unit. The effects of patient-related, microcirculatory, macrocirculatory, respiratory, and sensor-related factors on the difference between transcutaneously and arterially measured carbon dioxide and oxygen values (ΔPCO₂ and ΔPO₂) were evaluated using marginal models. Results: A total of 1,578 measurement pairs from 204 infants with a median [interquartile range] gestational age of 27³/₇ [26¹/₇–31³/₇] weeks were included. ΔPCO₂ was significantly associated with the postnatal age, arterial systolic blood pressure, body temperature, arterial partial pressure of oxygen (PaO₂), and sensor temperature. ΔPO₂ was, with the exception of PaO₂, additionally associated with gestational age, birth weight Z-score, heating power, arterial partial pressure of carbon dioxide, and interactions between sepsis and body temperature and sepsis and the fraction of inspired oxygen. Conclusion: The reliability of transcutaneous blood gas measurements is affected by several clinical factors. Caution is recommended when interpreting transcutaneous blood gas values with an increasing postnatal age due to skin maturation, lower arterial systolic blood pressures, and for transcutaneously measured oxygen values in the case of critical illness.

Pulmonary function tests for evaluating the severity of Duchenne muscular dystrophy disease.

In Duchenne muscular dystrophy (DMD), lung disease contributes significantly to morbidity and mortality. This study aimed to assess the usefulness of various pulmonary function tests in evaluating DMD severity. This retrospective study analysed lung function tests of patients with DMD-treated in the multidisciplinary respiratory neuromuscular clinic at Schneiders' Children Medical Center of Israel. Data were analysed according to age, ambulatory status and glucocorticoid treatment. Among 90 patients with DMD, 40/63 (63.5%) ambulatory patients and 22/27 (81.5%) nonambulatory patients successfully performed spirometry. Significant annual declines were demonstrated among nonambulatory patients, in percentile predicted forced vital capacity (3.8%) and in total lung capacity (5.5%) per year. The decline correlated with age and loss of ambulation but not with steroid treatment. Peak cough flow values were randomly distributed and did not correlate with age, ambulation or treatment. In nonambulatory patients, transcutaneous carbon dioxide measurement correlated significantly with age (r=0.55, p=0.02). Forced vital capacity, total lung capacity and transcutaneous carbon dioxide correlated with the clinical severity of disease in children with DMD. These measures may be useful in follow-up and clinical trials. A comparable correlation was not found for peak cough flow.

P090 Acceptability, Feasibility and Accuracy of Home Sleep Studies in Children with Neuromuscular Disorders

Abstract Introduction & Aims Nocturnal hypoventilation may indicate declining pulmonary function in children with Neuromuscular Disorders (NMD). Hypoventilation is diagnosed with polysomnography (PSG), but there are significant barriers to the routine performance of PSG in this population. Home-based sleep studies (HSS) may reduce burden on patients and their families. We assessed the acceptability, feasibility and diagnostic accuracy of HSS for children with NMD. Methods 11 participants, aged 5-15, underwent PSG. A HSS was conducted within two weeks for comparison that included measurement of transcutaneous carbon dioxide. Hypoventilation was defined as pCO2 >50mmHg for >25% of total sleep time. Acceptability was assessed by a survey completed by the families. Results Preliminary analysis shows HSS feasibility of 91% (10/11). Of 10 technically acceptable HSS, there was a concordant diagnosis in 9 (90%). Exploratory analysis shows higher total sleep time (529 vs. 431 minutes, p<0.05), slow wave sleep (132 vs. 99 minutes, p<0.05) and REM sleep (115 vs. 83 minutes, p<0.05) during HSS. Correlation was excellent between the percentage of total sleep time with pCO2 >50mmHg (κ=0.94, p<0.05) for PSG and HSS. 93% of families preferred HSS to laboratory PSG. Conclusion Preliminary analysis suggests home sleep studies that include transcutaneous carbon dioxide monitoring are feasible, acceptable and accurate when compared to PSG for diagnosing hypoventilation in children with NMD. These results imply that children may sleep better in the home environment. Further work is required to verify the diagnostic accuracy of home sleep studies in this group.

Transcutaneous carbon dioxide monitoring during therapeutic hypothermia for neonatal encephalopathy.

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.

A pilot crossover trial assessing the exercise performance patients with chronic obstructive pulmonary disease

Noninvasive ventilation improves exercise performance in patients with chronic obstructive pulmonary disease (COPD). However, the effect of helmet ventilation (HV) on the short-term self-paced exercise performance of patients with COPD remains unclear. This study investigated the use of HV during a 6 min walk test (6MWT) and analyzed its short-term cardiopulmonary outcomes in patients with stable COPD. A single-site crossover trial was conducted in a pulmonary rehabilitation outpatient department. A total of 20 stable patients with COPD without disability were enrolled. The participants performed 6MWTs with and without HV on two consecutive days. The outcome measures were the distance walked in the 6MWT and the physiological and cardiopulmonary parameters. The mean difference in meters walked between the HV-aided and unaided walk tests was 15.4 ± 37.2 (95% confidence interval: − 2.03 to 32.8 m; p = .145). During the 6MWT, the peak heart rate was significantly higher when walking was aided by HV than when it was unaided (p < .001). The energy expenditure index, walking speed, oxygen saturation nadir, and hemodynamic parameters were comparable. Although carbon dioxide levels inside the helmet increased after the walk test, the participants’ transcutaneous carbon dioxide measurements remained unchanged. HV did not improve the short-term self-paced exercise performance in patients with stable mild-to-moderate COPD. Further research should focus on noninvasive ventilation delivered via helmets in exercise training to determine the setting strategy, breathing circuit configuration, and effects of regular exercise.ClinicalTrial.gov: NCT04156724; IRB number: C108032.

Transcutaneous and End-Tidal CO₂ Measurements in Hypoxia and Hyperoxia.

BACKGROUND: Transcutaneous measurement of carbon dioxide (CO₂) has been proposed for physiological monitoring of tactical jet aircrew because in some clinical settings it mirrors arterial CO₂ partial pressure (Paco₂). End-tidal monitoring in laboratory settings is known to give high-fidelity estimates of Paco₂.METHODS: The correspondence between end-tidal (PETco₂) and transcutaneous Pco₂ (tcPco₂) was examined in healthy volunteers under laboratory conditions of hyperoxia and hypoxia. Rest and exercise, skin heating and cooling, hyperventilation, and induced CO₂ retention were employed.RESULTS: Neither measure followed all known changes in Paco₂ and tcPco₂ changed when the skin temperature near the probe changed. Bland-Altman analysis showed significant nonzero slopes under most conditions. Regression analysis indicated that oxygen partial pressure (Po₂) in tissue measured as transcutaneous Po₂ (tcPo₂) is an important explanatory variable for tcPco₂ in addition to PETco₂, and that local skin temperature also has an effect. Additionally, absorption atelectasis from breathing 100% O₂ may cause PETco₂ to deviate from Paco₂.DISCUSSION: Even as a trend indicator for Paco₂, tcPco₂ is not useful under conditions that resemble those in the highly dynamic tactical jet aircraft environment. PETco₂ is also not a good indicator of CO₂ status in pilots who breathe nearly 100% O₂.Shykoff BE, Lee LR, Gallo M, Griswold CA. Transcutaneous and end-tidal CO₂ measurements in hypoxia and hyperoxia. Aerosp Med Hum Perform. 2021; 92(11):864-872.

The utility of transcutaneous carbon dioxide measurements in the emergency department: A prospective cohort study.

BackgroundRapid identification of patients with occult injury and illness in the emergency department can be difficult. Transcutaneous carbon dioxide (TCO2) and oxygen (TO2) measurements may be non‐invasive surrogate markers for the identification of such patients.ObjectivesTo determine if TCO2 or TO2 are useful adjuncts for identifying severe illness and the correlation between TCO2, lactate, and end tidal carbon dioxide (ETCO2).MethodsProspective TCO2 and TO2 measurements at a tertiary level 1 trauma center were obtained using a transcutaneous sensor on 300 adult patients. Severe illness was defined as death, intensive care unit (ICU) admission, bilevel positive airway pressure, vasopressor use, or length of stay >2 days. TCO2 and TO2 were compared to illness severity using t tests and correlation coefficients.ResultsMean TO2 did not differ between severe illness (58.9, 95% CI 54.9–62.9) and non‐severe illness (58.0, 95% CI 54.7–61.1). Mean TCO2 was similar between severe (34.6, 95% CI 33–36.2) vs non‐severe illness (35.9, 95% CI 34.7–37.1). TCO2 was 28.7 (95% CI 24.0–33.4) for ICU vs. 35.9 (95% CI 34.9–36.9) for non‐ICU patients. The mean TCO2 in those with lactate > 2.0 was 29.8 (95% CI 25.8–33.8) compared with 35.7 (95% CI 34.9–36.9) for lactate < 2.0. TCO2 was not correlated with ETCO2 (r = 0.32, 95% CI 0.22–0.42).ConclusionTCO2 could be a useful adjunct for identifying significant injury and illness and patient outcomes in an emergency department (ED) population. TO2 did not predict severe illness. TCO2 and ETCO2 are only moderately correlated, indicating that they are not equivalent and may be useful under different circumstances.

Transcutaneous carbon dioxide pattern and trend over time in preterm infants.

BackgroundChronic lung disease remains a burden for extremely preterm infants. The changes in ventilation over time and optimal ventilatory management remains unknown. Newer, non-invasive technologies provide insight into these patterns.MethodsThis single-center prospective cohort study enrolled infants ≤32 0/7 weeks. We obtained epochs of transcutaneous carbon dioxide (TcCO2) measurements twice each week to describe the pattern of hypercarbia throughout their hospitalization.ResultsPatterns of hypercarbia varied based on birth gestational age and post-menstrual age (PMA) (p = 0.03), regardless of respiratory support. Infants receiving the most respiratory support had values 16–21 mmHg higher than those on room air (p < 0.001). Infants born at the youngest gestational ages had the greatest total change but the rate of change was slower (p = 0.049) compared to infants born at later gestational ages. All infants had TcCO2 values stabilize by 31–33 weeks PMA, when values were not significantly different compared to discharge. No rebound was observed when infants weaned off invasive support.ConclusionsHypercarbia improves as infants approached 31–33 weeks PMA. Hypercarbia was the highest in the most immature infants and improved with age and growth despite weaning respiratory support.Impact This study describes the evolution of hypercarbia as very preterm infants grow and develop.The pattern of ventilation is significantly different depending on the gestational age at birth and post-menstrual age.Average transcutaneous carbon dioxide (TCO2) decreased over time as infants became more mature despite weaning respiratory support. This improvement was most significant in infants born at the lowest gestational ages.

Safety of conscious sedation in electroanatomical mapping procedures and cryoballoon pulmonary vein isolation

Immobilization of patients during electrophysiological procedures, to avoid complications by patients’ unexpected bodily motion, is achieved by moderate to deep conscious sedation using benzodiazepines and propofol for sedation and opioids for analgesia. Our aim was to compare respiratory and hemodynamic safety endpoints of cryoballoon pulmonary vein isolation (PVI) and electroanatomical mapping (EAM) procedures. Included patients underwent either cryoballoon PVI or EAM procedures. Sedation monitoring included non-invasive blood pressure measurements, transcutaneous oxygen saturation (tSpO2) and transcutaneous carbon-dioxide (tpCO2) measurements. We enrolled 125 consecutive patients, 67 patients underwent cryoballoon atrial fibrillation ablation and 58 patients had an EAM and radiofrequency ablation procedure. Mean procedure duration of EAM procedures was significantly longer (p < 0.001) and propofol doses as well as morphine equivalent doses of administered opioids were significantly higher in EAM patients compared to cryoballoon patients (p < 0.001). Cryoballoon patients display higher tpCO2 levels compared to EAM patients at 30 min (cryoballoon: 51.1 ± 7.0 mmHg vs. EAM: 48.6 ± 6.2 mmHg, p = 0.009) and at 60 min (cryoballoon: 51.4 ± 7.3 mmHg vs. EAM: 48.9 ± 6.6 mmHg, p = 0.07) procedure duration. Mean arterial pressure was significantly higher after 60 min (cryoballoon: 84.7 ± 16.7 mmHg vs. EAM: 76.7 ± 13.3 mmHg, p = 0.017) in cryoballoon PVI compared to EAM procedures. Regarding respiratory and hemodynamic safety endpoints, no significant difference was detected regarding hypercapnia, hypoxia and episodes of hypotension. Despite longer procedure duration and deeper sedation requirement, conscious sedation in EAM procedures appears to be as safe as conscious sedation in cryoballoon ablation procedures regarding hemodynamic and respiratory safety endpoints.

Transcutaneous Carbon Dioxide Measurement in Adult Patients with Neuromuscular Disorders: A quality Level Assessment

Carbon dioxide tension (PCO2) monitoring during sleep, is crucial to identify respiratory failure in patients with neuromuscular disorders (NMD). Transcutaneous PCO2 monitoring is an available technique to measure PCO2. To assess the quality level of transcutaneous blood gas measurements via SenTec monitor. A 12-month analysis of SenTec measurements was conducted in a Belgian Centre for Home Mechanical Ventilation (HMV). Over two consecutive nights; SpO2 and PCO2 measurements, the presence of PCO2 drift and drift correction with SenTec, were reviewed and scores (0, 1, 2 for poor, medium and high level) were assigned to estimate the quality of measurements. Sixty-nine NMD patients met the inclusion criteria, of which 48/69 used HMV. PCO2 drift and drift correction were present in 15% and 68% of the 138 recordings, respectively. The quality level of measurements throughout night 1, scored 1.55 (0-2). The relevance of our clinical findings from SenTec scoring 1.94 (1-2); was considered highly satisfactory. HMV was ineffective in 24/48 patients. Among 12 patients with hypercapnia, 8 patients improved PCO2 between night 1 and 2. Among 12 patients with hypocapnia, PCO2 improved in 4/12 patients, who reached the range of normal PCO2 (35-47 mmHg). The quality of SenTec measurements was acceptable in the majority of recordings and clinical findings were deemed satisfactory in all cases. A single SenTec measurement was sufficient to determine the need for NIV. However, two SenTec registrations were insufficient to both improve NIV effectiveness in 50% of cases, and, to ensure follow-up of our interventions.

P1386Continuous, transcutaneous carbon-dioxide monitoring in complex electrophysiological procedures in conscious sedation - is there a safer way to sleep?

Abstract Funding Acknowledgements Karolina Weinmann was supported by the Hertha-Nathorff fellowship from Ulm University Background – Ablation of cardiac arrhythmias by complex electrophysiological procedures is a growing field. A moderate to deep sedation is needed to immobilize the patient to warrant a safe and effective intervention. The administrated medication to obtain an adequate sedation has respiratory depressant side effects and could cause respiratory complications, like hypercapnia and hypoxia. Purpose – Our aim was to investigate the feasibility and accuracy of an additional, continuous transcutaneous carbon-dioxide (tpCO2) measurement during moderate to deep sedation in complex electrophysiological catheter ablations. Methods – Consecutive patients received an electrophysiological intervention with need for deep sedation. Routine hemodynamic monitoring was performed by the measurement of non-invasive blood-pressure, oxygen saturation and half-hourly venous blood gas analysis. Additionally, patients received a tpCO2 sensor on the forehead with an automated, continuous documentation of transcutaneous oxygen saturation and carbon-dioxide. A precise sedation protocol was performed and administrated drugs were registered. Results – We included 110 patients to the analysis. Fifty patients received cryoballoon pulmonary vein isolation, 58 patients 3D-mapping procedure and two patients ventricular tachycardia ablation. The mean procedure time was 135.1 ± 63.5 minutes and the fluoroscopy time was 21.5 ± 10.9 minutes. To achieve an adequate sedation a mean of 5.0 ± 0.8 mg midazolam, 583.8 ± 320.4 mg propofol, 72.0 ± 30.3 µg fentanyl and 0.2 ± 0.1 mg remifentanil were administrated. Hypercapnia (pCO2 &amp;gt; 70 mmHg) was detected in five patient by the tpCO2 monitoring and only in two patients using venous carbon-dioxide partial pressure (vpCO2) analysis. Correlation of tpCO2 and vpCO2 were analyzed half-hourly by Pearsons’ correlation coefficient. There was a good correlation during the investigated 120 minutes of procedure time (baseline: r = 0.65, p &amp;lt; 0.0001; 30 minutes: r = 0.75, p &amp;lt; 0.0001; 60 minutes: r = 0.77, p &amp;lt; 0.0001; 90 minutes: r = 0.78, p &amp;lt; 0.0001; 120 minutes: r = 0.85, p &amp;lt; 0.0001). The detected difference between tpCO2 and vpCO2 was at baseline &amp;lt;5 mmHg in 65% (79/110) and &amp;lt;10 mmHg in 96% (103/110), after 30 minutes the difference was &amp;lt;5 mmHg in 71% (78/110) and &amp;lt;10 mmHg in 96% (105/110), after 60 minutes the difference was &amp;lt;5 mmHg in 77% (60/78) and &amp;lt;10 mmHg in 96% (75/78) and after 90 minutes the difference between the two methods was &amp;lt;5 mmHg in 63% (30/48) and &amp;lt;10 mmHg in 98% (47/48) of the cohort. Conclusion – The continuous tpCO2 monitoring is a feasible and precise method with a good correlation to the venous blood gas carbon-dioxide analysis of the standard monitoring during complex catheter ablations in deep sedation. Randomized trials are required to further analyze if tpCO2 monitoring adds further safety to electrophysiological procedures in deep sedation.

Transcutaneous Carbon Dioxide Monitoring During Apnea Testing for Determination of Neurologic Death in Children: A Retrospective Case Series.

Determination of neurologic death in children is a clinical diagnosis based on absence of neurologic function with irreversible coma and apnea. Apnea testing during determination of neurologic death assesses spontaneous respiration when PaCO2 increases to greater than or equal to 60 and greater than or equal to 20 mm Hg above pre-apneic baseline. The utility of transcutaneous carbon dioxide measurements during apnea testing in children is unknown. We seek to determine the degree of correlation between paired transcutaneous carbon dioxide and PaCO2 values during apnea testing for determination of neurologic death. Single-center, retrospective case series. Twenty-eight bed PICU in a 259-bed, tertiary care, referral center. Children 0-18 years old undergoing determination of neurologic death between May 2017 and December 2018. None. Primary outcomes were paired transcutaneous carbon dioxide and PaCO2 values obtained during determination of neurologic death. Primary analyses included Pearson correlation coefficient, Bland-Altman bias and limits of agreement, and comparative statistics. Descriptive data included demographics, admission diagnoses, hemodynamics, Vasoactive Inotropic Scores, and arterial blood gas measurement. Eight children underwent 15 determination of neurologic death examinations resulting in 31 paired transcutaneous carbon dioxide and PaCO2 values for study. Transcutaneous carbon dioxide and PaCO2 correlated well (r = 0.94; p < 0.01). Bias between transcutaneous carbon dioxide and PaCO2 was -3.29 ± 7.14 mm Hg. Differences in means did not correlate with Vasoactive Inotropic Score (r = 0.2) or patient temperature (r = 0.11). Receiver operator characteristic curve of transcutaneous carbon dioxide after 3-10 minutes of apnea to discriminate positive apnea testing by the standard of PaCO2 yielded an area under the curve of 0.91 and threshold of greater than or equal to 64 mm Hg (sensitivity, 91.7%; specificity, 100%; positive predictive value, 100%; negative predictive value, 92.3%; accuracy, 95.9%). During apnea testing for determination of neurologic death in children, noninvasive transcutaneous carbon dioxide monitoring demonstrated high correlation, accuracy, and minimal bias when compared with PaCO2. Further validation is required before any recommendation to replace PaCO2 with noninvasive transcutaneous carbon dioxide monitoring can be proposed. However, concurrent transcutaneous carbon dioxide data may limit unnecessary apnea time and associated hemodynamic instability or respiratory decompensation by approximating goal arterial blood sampling to document target PaCO2.

Transcutaneous carbon dioxide measurements in fruits, vegetables and humans: A prospective observational study.

Transcutaneous carbon dioxide measurement (TcCO2) is frequently used as a surrogate for arterial blood gas sampling in adults and children with critical illness. Data from noninvasive TcCO2 monitoring assists with clinical decisions regarding mechanical ventilation settings, estimation of metabolic consumption and determination of adequate end-organ tissue perfusion. To report TcCO2 values obtained from various fruits, vegetables and elite critical care medicine specialists. Prospective, observational, nonblinded cohort study. Single-centre, tertiary paediatric referral centre and organic farmers' market. Vegetables and fruits included 10 samples of each of the following: red delicious apple (Malus domestica), manzano banana (Musa sapientum), key lime (Citrus aurantiifolia), miniature sweet bell pepper (Capsicum annuum), sweet potato (Ipomoea batatas) and avocado (Persea americana). Ten human controls were studied including a paediatric intensivist, a paediatric inpatient hospital physician, four paediatric resident physicians and four paediatric critical care nurses. None. TcCO2 values for each species and device response times. TcCO2 readings were measurable in all study species except the sweet potato. Mean ± SD values of TcCO2 for human controls [4.34 ± 0.37 kPa (32.6 ± 2.8 mmHg)] were greater than apples [3.09 ± 0.19 kPa (23.2 ± 1.4 mmHg), P < 0.01], bananas [2.73 ± 0.28 kPa (20.5 ± 2.1 mmHg), P < 0.01] and limes [2.76 ± 0.52 kPa (20.7 ± 3.9 mmHg), P < 0.01] but no different to those of avocados [4.29 ± 0.44 kPa (32.2 ± 3.3 mmHg), P = 0.77] and bell peppers [4.19 ± 1.13 kPa (31.4 ± 8.5 mmHg), P = 0.68]. Transcutaneous response times did not differ between research cohorts and human controls. We found nonroot, nontuberous vegetables to have TcCO2 values similar to that of healthy, human controls. Fruits yield TcCO2 readings, but substantially lower than human controls.

Novel transcutaneous sensor combining optical tcPO2 and electrochemical tcPCO2 monitoring with reflectance pulse oximetry.

This study investigated the accuracy, drift, and clinical usefulness of a new optical transcutaneous oxygen tension (tcPO2) measuring technique, combined with a conventional electrochemical transcutaneous carbon dioxide (tcPCO2) measurement and reflectance pulse oximetry in the novel transcutaneous OxiVenT™ Sensor. In vitro gas studies were performed to measure accuracy and drift of tcPO2 and tcPCO2. Clinical usefulness for tcPO2 and tcPCO2 monitoring was assessed in neonates. In healthy adult volunteers, measured oxygen saturation values (SpO2) were compared with arterially sampled oxygen saturation values (SaO2) during controlled hypoxemia. In vitro correlation and agreement with gas mixtures of tcPO2 (r = 0.999, bias 3.0 mm Hg, limits of agreement − 6.6 to 4.9 mm Hg) and tcPCO2 (r = 0.999, bias 0.8 mm Hg, limits of agreement − 0.7 to 2.2 mm Hg) were excellent. In vitro drift was negligible for tcPO2 (0.30 (0.63 SD) mm Hg/24 h) and highly acceptable for tcPCO2 (− 2.53 (1.04 SD) mm Hg/12 h). Clinical use in neonates showed good usability and feasibility. SpO2-SaO2 correlation (r = 0.979) and agreement (bias 0.13%, limits of agreement − 3.95 to 4.21%) in healthy adult volunteers were excellent. The investigated combined tcPO2, tcPCO2, and SpO2 sensor with a new oxygen fluorescence quenching technique is clinically usable and provides good overall accuracy and negligible tcPO2 drift. Accurate and low-drift tcPO2 monitoring offers improved measurement validity for long-term monitoring of blood and tissue oxygenation.Graphical abstract

Prevalencia de la hipoventilación relacionada con el sueño según diferentes criterios diagnósticos

INTRODUCCIÓN: la hipoventilación alveolar es una alteración que conduce a la re- tención de dióxido de carbono (CO2) y alteración en la presión arterial de CO2 (PaCO2) por múltiples causas (síndromes de hipoventilación). El diagnóstico es con gasometría arterial diurna en reposo con posible uso de subrogados, como la medición de dióxido de carbono transcutáneo (TcCO2).Todavía no está totalmente definida la estrategia diagnóstica, por lo cual nuestro objetivo fue evaluar la prevalencia de la hipoventilación durante el sueño utilizando diferentes crite- rios diagnósticos.MATERIALES Y MÉTODOS: estudio observacional, descriptivo, retrospectivo de corte transversal de pacientes que requirieron polisomnografía entre 2015 y 2016 con medi- ción de TcCO2 en el Instituto Nacional de Enfermedades Respiratorias Ismael Cosio Villegas de la Ciudad de México. Se les aplicó 6 diferentes criterios de hipoventilación durante el sueño. Se establecieron 3 grupos (sin trastornos respiratorios durante el sueño, pacientes con síndrome de hipoventilación-obesidad y pacientes con hipoventilación relacionada con alteración médica-neuromuscular). Se excluyeron pacientes que no tuvieran diagnóstico es- tablecido. Se utilizó el dispositivo SenTec Digital Monitoring System para la medición del TcCO2, con el que se obtuvo el CO2 basal, CO2 promedio, CO2 máximo y tiempo de CO2. Se utilizó el programa SPSS v23. La descripción se realizó con media, mediana, desviación estándar y porcentajes según el tipo de variable. Se realizaron pruebas de concordancia entre los diferentes criterios aplicados para cada distribución. Se aceptó la significancia estadística cuando p 0,05.RESULTADOS: una muestra total de 143 pacientes, 51 sin trastornos respiratorios du- rante el sueño, 63 con síndrome de hipoventilación-obesidad y 29 con hipoventilación rela- cionada con alteraciones médicas (neuromusculares). Predominó el sexo masculino y eran adultos jóvenes. Un TcCO2 38 mm Hg se diagnosticó al 68 % de los pacientes con síndro- me de hipoventilación-obesidad y el 69 % de los pacientes con hipoventilación alveolar por enfermedades neuromusculares (Kappa de Cohen = 0,40). Un TcCO2 49 mm Hg durante la noche diagnosticó al 82 % de los pacientes con síndrome de hipoventilación-obesidad y el 58% de los pacientes con hipoventilación alveolar por enfermedades neuromusculares (Kappa de Cohen = 0,63).CONCLUSIÓN: en la población estudiada, un pico de TcCO2 ≥49 mm Hg tiene un buen grado de acuerdo con el diagnóstico actual del paciente.

Transcutaneous Carbon Dioxide Measurements in Women Receiving Intrathecal Morphine for Cesarean Delivery: A Prospective Observational Study

(Anesth Analg. 2017;124(3):872–878) Neuraxial morphine, which is commonly used after cesarean delivery, has a favorable safety profile with a reported incidence of respiratory depression of only 0.07% to 0.9%. However, there is no standard definition of respiratory depression. The most sensitive measure may be hypercapnia (threshold of 50 mm Hg), which can be measured using the noninvasive, transcutaneous Topological Oscillation Search with Kinematical Analysis (TOSCA) monitor, which estimates arterial carbon dioxide levels (TcCO2). Thus, the authors of the present study estimated the incidence of respiratory depression as defined by hypercapnia events (TcCO2 &gt;50 mm Hg for ≥2 min) using the TOSCA monitor in women receiving 150 μg intrathecal morphine for postcesarean analgesia.

Randomized cross-over trial of ventilator modes during non-invasive ventilation titration in amyotrophic lateral sclerosis.

Non-invasive ventilation (NIV) improves survival, quality of life and sleep in patients with amyotrophic lateral sclerosis (ALS). Nevertheless, NIV titration is conducted in different ways. We aim to provide more insight into NIV titration by comparing the effects of a spontaneous (S) and spontaneous-timed (ST) modes on gas exchange, sleep architecture and patient-ventilator asynchronies (PVAs). After an initial night of NIV titration, patients were randomized to S or ST mode in a cross-over design. NIV was titrated using polysomnography, oximetry (oxygen saturation, SpO2 %) and transcutaneous carbon dioxide (PtcCO2 ) measurement. PVAs were analysed breath-by-breath. Thirteen patients were analysed after inclusion. ST mode showed better results in gas exchange (minimal SpO2 %: 83 (80-89)% vs 87 (84-89)%; oxygen desaturation index: 15 (5-28)/h sleep vs 7 (3-9)/h sleep; PtcCO2 >55 mm Hg: 20 (0-59)% vs 0 (0-27)% total sleep time for S and ST mode, respectively, all P < 0.05) and respiratory events (obstructive: 8.9 (1.2-18.3)/h sleep vs 1.8 (0.3-4.9)/h sleep and central: 2.6 (0.4-14.1)/h sleep vs 0.2 (0.0-1.1)/h sleep for S and ST mode, respectively, both P < 0.01). No differences in sleep architecture were found. Ineffective efforts and respiratory events were more frequently present in S mode. Nevertheless, four patients were discharged on S mode as these patients showed clinically better results for sleep architecture and PVA during the night on S mode. ST mode shows better results in gas exchange, respiratory events and PVA. Nevertheless, accurate NIV titration remains necessary as some patients show equal or better results when using the S mode.