Transcutaneous Carbon Dioxide Monitoring Research Articles

Accuracy and Interpretation of Transcutaneous Carbon Dioxide Monitoring in Critically Ill Children

Accuracy and Interpretation of Transcutaneous Carbon Dioxide Monitoring in Critically Ill Children

Recent Technologies for Transcutaneous Oxygen and Carbon Dioxide Monitoring.

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

BackgroundBronchoscopy is a relatively invasive procedure where patients are often sedated. However, adequate sedation is not always achieved. Propofol is often used for difficult-to-sedate patients undergoing bronchoscopy despite a potential risk of respiratory depression. Transcutaneous carbon dioxide (tcpCO2) monitoring, introduced recently, is recognized as a convenient surrogate method for continuous monitoring of the partial pressure of arterial carbon dioxide (PaCO2). This study examined the safety of switching to propofol during bronchoscopy by using transcutaneous carbon dioxide monitoring. MethodsPatients in whom transcutaneous gas monitoring had been performed during bronchoscopy were included in this study. The participants were divided into two groups: 1) the midazolam + fentanyl group (MF group), and 2) the group in which midazolam was switched to propofol owing to inadequate sedation obtained with midazolam + fentanyl (MFP group). We retrospectively analyzed the transcutaneous gas measurement data collected in patients under propofol sedation for bronchoscopy. ResultsThis study included 61 (MF, n = 41; MFP, n = 20) patients. The duration of elevated tcpCO2 (>50 mm Hg) was greater in the MFP group (MF 8.5 min vs. MFP 22.1 min, p = 0.042). ConclusionSwitching midazolam to propofol during bronchoscopy was significantly associated with a higher risk of elevated tcpCO2, which is indicative of respiratory depression. Therefore, continuous tcpCO2 monitoring is required to ensure the safety of patients under propofol sedation for bronchoscopy.

A Transcutaneous Carbon Dioxide Monitor Based on Time-Domain Dual Lifetime Referencing.

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 Carbon Dioxide Monitoring More Accurately Detects Hypercapnia than End-Tidal Carbon Dioxide Monitoring during Non-Intubated Video-Assisted Thoracic Surgery: A Retrospective Cohort Study

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.

Transcutaneous carbon dioxide monitoring during prolonged apnoea with high-flow nasal oxygen.

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.

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

Abstract Introduction &amp; 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 &amp;gt;50mmHg for &amp;gt;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&amp;lt;0.05), slow wave sleep (132 vs. 99 minutes, p&amp;lt;0.05) and REM sleep (115 vs. 83 minutes, p&amp;lt;0.05) during HSS. Correlation was excellent between the percentage of total sleep time with pCO2 &amp;gt;50mmHg (κ=0.94, p&amp;lt;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.

Ambulatory transcutaneous carbon dioxide monitoring for children with neuromuscular disease

ObjectiveEarly screening and diagnosis of nocturnal hypoventilation can slow progression to diurnal hypercapnia and mortality in children with neuromuscular disease (NMD). However, gold standard, laboratory-based polysomnography (PSG) testing is a limited resource. Therefore, we evaluated the diagnostic accuracy of ambulatory transcutaneous carbon dioxide (tcCO2) monitoring used in the home compared to PSG in children with NMD. MethodsProspective, cross-sectional study in children 0–18 years old with a confirmed diagnosis of NMD and a clinically indicated need for PSG. Ambulatory tcCO2 was assessed by a respiratory therapist in participant's homes. Demographics, and PSG (including tcCO2). ResultsWe enrolled 39 children with NMD; 3 had unusable ambulatory tcCO2 data because of failure of drift correction on the machine (n = 2) or an air bubble (n = 1). The remaining 36 patients aged 11 months to 16 years (median (IQR) 12.5 years (6.0–15.8)) had ambulatory tcCO2 and outpatient level 1 PSG data. Ambulatory tcCO2 monitoring had a sensitivity of 20.0% (95% confidence interval [CI] 0.5–71.6%) and a specificity of 93.5% (95% CI 78.6–99.2%). Almost all children and/or parents (34/36, 94%) preferred ambulatory monitoring over in-hospital PSG. ConclusionsAmbulatory transcutaneous carbon dioxide monitoring was not sufficiently accurate as a clinical tool for the diagnosis of nocturnal hypoventilation our cohort of children with neuromuscular disease despite being preferred over PSG by both children and parents.

Impact of sleep-related hypoventilation in patients with pleuroparenchymal fibroelastosis

BackgroundPleuroparenchymal fibroelastosis (PPFE) is a rare fibrosing lung disease with a predilection for the upper lobe and its progression causes hypoventilation, resulting in hypercapnia. Even though the association between sleep-related hypoventilation (SRH) and chronic obstructive pulmonary disease was well documented, its impact in patients with PPFE was not evaluated. The aim of this study is to clarify the impact of SRH on prognosis in PPFE.MethodsA retrospective review of the medical records of 52 patients with PPFE who underwent transcutaneous carbon dioxide monitoring during sleep was done.Patients were stratified into SRH (n = 28) and non-SRH (n = 24) groups based on American Academy of Sleep Medicine criteria. The impact of SRH on the prognosis of PPFE, as well as the clinical factors and comorbidities of PPFE associated with SRH, were evaluated.ResultsForced expiratory volume in the first second (FEV1), forced vital capacity (FVC), total lung capacity (TLC), and carbon monoxide diffusing capacity (DLco) in the SRH group were significantly lower than the non-SRH group (P < .01). Chronic pulmonary aspergillosis (CPA) was found at a higher rate in the SRH group (P = .02). The median survival time for SRH patients was 330 days, whereas roughly 80% of non-SRH patients were alive during the 3-year observation period (P < .01). Body mass index was a significant prognostic factor in PPFE patients with SRH (HR .78; 95% CI; .64–.94; P < .01). Home oxygen therapy (HOT) during the day and noninvasive positive pressure ventilation (NPPV) at night while sleeping tended to improve prognosis in the SRH group, as indicated by HR of .25 (P = .07).ConclusionsSRH may be a poor prognostic factor for PPFE. Additionally, SRH may modify susceptibility to Aspergillosis in patients with PPFE. HOT plus NPPV may improve the disease outcomes in patients with SRH.

Hypoventilation and sleep hypercapnia in a case of congenital variant-like Rett syndrome

BackgroundBreathing disturbances are often a primary clinical concern especially during wakefulness of the classic form of Rett syndrome, but data for atypical forms are lacking.Case presentationWe report the case of a 20-month-old female affected by Rett syndrome with congenital variant-like onset, characterized by severe hypotonia and neurodevelopment impairment. She presented hypoventilation, persistent periodic breathing, and sustained desaturation during sleep, without obstructive or mixed events. Pulse oximetry and capnography during wakefulness were strictly normal. To the best of our knowledge, this is the first case of a patient affected by a congenital variant of Rett syndrome presenting sleep hypercapnia. Hypotonia may play a major role in the genesis of hypoventilation and hypoxemia in our patient. Non-invasive ventilation led to quality-of-life improvements.ConclusionsThus, we suggest screening patients with congenital-like Rett syndrome through transcutaneous bedtime carbon dioxide and oxygen monitoring. Moreover, assisted control mode was a breakthrough to achieve adequate ventilation in our case.

Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) as unique technique for airway management during operative hysteroscopy under general anesthesia: a registered feasibility pilot cohort study.

The term THRIVE refers to the delivery of 100% heated and humidified oxygen via a nasal cannula to maintain viable gas exchange during prolonged apnea. There are no reports of its application for Operative Hysteroscopy (OH) under general anesthesia (GA). The aim of the study is to investigate the success rate of THRIVE as unique airway management technique in this setting. The results will support the development of a randomized controlled trial (RCT) to demonstrate the non-inferiority of THRIVE compared to traditional techniques. Twenty consecutive ASA I-II women presenting for OH were enrolled. Standard anesthesia, as well as transcutaneous carbon dioxide (tcCO2) monitoring, was performed. After preoxygenation with 30 L∙min-1, GA was induced with propofol and fentanyl, then oxygen flow was increased to 70 L∙min-1 and anesthesia maintained with propofol infusion. The primary outcome was success rate of THRIVE defined as SpO2 > 94%, tcCO2 < 60 mmHg and no need for rescue airway intervention. Mean age was 47 ± 12 years. Mean duration of the procedure was 25 ± 9 minutes, and the success rate of the technique was 100%. Median SpO2 during the procedure was 100 (IQR 99-100) %. Mean maximum tcCO2 level was 51 ± 7 mmHg while mean tcCO2 level during the procedure was 45 ± 7 mmHg. At the end of the procedure, mean tcCO2 was 44 ± 5 mmHg. THRIVE allowed adequate gas exchange during OH under GA, without additional rescue airway interventions. The application of THRIVE in this setting may allow minimal airway manipulation and optimal comfort for the patient with low failure rate. We calculated the sample size for the planned non-inferiority RCT investigating the effectiveness of THRIVE versus laryngeal mask ventilation in OH: 82 is the minimal number of patients per group to test a non-inferiority limit of 10%.

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.

Clinical characteristics of patients with obstructive sleep apnea hypopnea syndrome combined with alveolar hypoventilation

Objective: To evaluate the clinical characteristics of patients with obstructive sleep apnea hypopnea syndrome (OSAHS) combined with alveolar hypoventilation. Methods: This retrospective study included patients who were diagnosed as OSAHS by polysomnography (PSG) and underwent daytime awake transcutaneous carbon dioxide (PtcCO2) monitoring from November 2019 to February 2021 at the Sleep Center of the Second Affiliated Hospital of Soochow University. A total of 177 patients were enrolled in the analysis, including 167 males and 10 females, aged (40±8) years old. Patients with daytime awake PtcCO2>45 mmHg (1 mmHg=0.133 kPa) were diagnosed as daytime alveolar hypoventilation, with which participants were divided into the daytime alveolar hypoventilation group and non-daytime alveolar hypoventilation group. Body mass index (BMI) cut-off value predicting daytime alveolar hypoventilation was calculated and the patients were divided into the high BMI group and low BMI group. The continuous nocturnal PtcCO2 data was available for a subset of 128 patients, and the patients were divided into two groups according the daytime alveolar hypoventilation or not. Across-group differences were compared, respectively. Results: Compared with the non-daytime alveolar hypoventilation group (n=125), the BMI [27.57 (26.55, 30.33) vs 26.60 (25.06, 28.09) kg/m2], Epworth sleepiness score(ESS) score [9.50 (6.25, 12.00) vs 7.00 (4.00, 10.75)], higher oxygen desaturation index (ODI) [38.00 (15.23, 64.93) vs 26.80 (11.30, 44.30) events/h] and percentage of total time with oxygen saturation level<90% (TS90%) [11.24% (1.88%, 32.44%) vs 4.35% (0.72%, 9.87%)] of the daytime alveolar hypoventilation group(n=52) were significantly higher (P<0.05), and lowest arterial oxygen saturation (LSaO2) [74.50% (60.25%, 82.00%) vs 79.00% (73.00%, 84.50%)], mean arterial oxygen saturation (MSaO2) [94.00% (91.00%, 95.00%) vs 95.00% (94.00%, 96.00%)] were significantly lower (P<0.05). The BMI cut-off value for predicting daytime alveolar hypoventilation was 27.04 kg/m2. Of the 177 enrolled patients, 90 were in the high BMI group and 87 were in low group. Compared with the low BMI group, the proportion of daytime sleepiness, the ESS score, the prevalence of hypertension, AHI and daytime awake PtcCO2 in the high BMI group were significantly higher (P<0.05). Among the subset of 128 patients with nocturnal PtcCO2 data available, the BMI, daytime PtcCO2 level, the nocturnal CO2 level and the prevalence of sleep related alveolar hypoventilation in the daytime alveolar hypoventilation group (n=40) were significantly higher than those in the non-daytime alveolar hypoventilation group (n=88) (P<0.05). Conclusions: The OSAHS patients with alveolar hypoventilation have higher BMI and more severe nocturnal hypoxia. OSAHS patients with BMI>27.04 kg/m2 are more likely to develop sleep related alveolar hypoventilation disorder.

Sleep-related hypoventilation and hypercapnia in multiple system atrophy detected by polysomnography with transcutaneous carbon dioxide monitoring.

PurposeWe aimed to evaluate sleep-related hypoventilation in multiple system atrophy (MSA) using polysomnography (PSG) with transcutaneous partial pressure of carbon dioxide (PtcCO2) monitoring.MethodsThis prospective study included 34 patients with MSA. Motor and autonomic function, neuropsychological tests, PSG with PtcCO2 monitoring, and pulmonary function tests were performed. Sleep-related hypoventilation disorder (SRHD) was defined according to the International Classification of Sleep Disorders, third edition.ResultsNine (27%) of the 34 patients met the diagnostic criteria of SRHD. Twenty-nine (85%) patients had sleep-related breathing disorders based on an Apnea–Hypopnea Index of ≥ 5/h. The patients with MSA and SRHD had a higher arousal index (p = 0.017) and obstructive apnea index (p = 0.041) than those without SRHD. There was no difference in the daytime partial pressure of carbon dioxide in arterial blood or respiratory function between MSA patients with and without SRHD.ConclusionSleep-related hypoventilation may occur in patients with MSA even with a normal daytime partial pressure of carbon dioxide. This can be noninvasively detected by PSG with PtcCO2 monitoring. SRBD and sleep-related hypoventilation are common among patients with MSA, and clinicians should take this into consideration while evaluating and treating this population.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11325-022-02568-4.

An Infra-Red-Based Prototype for a Miniaturized Transcutaneous Carbon Dioxide Monitor.

New types of miniaturized biomedical devices transform contemporary diagnostic and therapeutic techniques in medicine. This evolution has demonstrated exceptional promise in providing infrastructures for enabling precision health by creating diverse sensing modalities. To this end, this paper presents a prototype for transcutaneous carbon dioxide monitoring to diversify the measurable critical parameters for human health. Transcutaneous carbon dioxide monitoring is a noninvasive, surrogate method of assessing the partial pressure of carbon dioxide in the blood. The partial pressure of carbon dioxide is a vital index that can help understand momentarily changing ventilation trends. Therefore, it needs to be reported continuously to monitor the ventilatory status of critically ill patients. The proposed prototype employs an infrared LED as the excitation source. The infrared emission, which decreases in response to an increasing carbon dioxide concentration, is applied to a thermopile sensor that can detect the infrared intensity variations precisely. We have measured the changes in the partial pressure of carbon dioxide in the range of 0-120 mmHg, which covers humans' typical values, 35-45 mmHg. The prototype occupies an area of 25 cm2 (50 mm × 50 mm) and consumes 85 mW power.

Transcutaneous carbon dioxide monitoring could reduce physical contact with COVID-19 patients

Transcutaneous carbon dioxide monitoring could reduce physical contact with COVID-19 patients

Contribution of hypercapnia to cognitive impairment in severe sleep-disordered breathing.

Although cognitive impairment in obstructive sleep apnea (OSA) is primarily attributed to intermittent hypoxemia and sleep fragmentation, hypercapnia may also play a role in patients whose OSA is complicated by hypoventilation. This study investigated the impact of hypercapnia on cognitive function in severe sleep-disordered breathing (OSA accompanied by hypoventilation). Patients with severe OSA (apnea-hypopnea index >30 events/h; n = 246) underwent evaluation for accompanying hypoventilation with polysomnography that included continuous transcutaneous carbon dioxide (TcCO2) monitoring and awake arterial blood gas analysis. Patients were categorized as having no hypoventilation (n = 84), isolated sleep hypoventilation (n = 40), or awake hypoventilation (n = 122). Global cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA), memory with the Rey Auditory Verbal Learning Test (RAVLT), and processing speed with the Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV), Digit Symbol Coding subtest (DSC). Apnea-hypopnea index was similar across groups (P = .15), but the sleep and awake hypoventilation groups had greater nocturnal hypoxemia compared with the no-hypoventilation group (P < .01). Within all groups, mean MoCA scores were < 26, which is the validated threshold to indicate mild cognitive impairment; RAVLT scores were lower than age-matched norms only in the awake-hypoventilation group (P ≤ .01); and DSC scores were lower than age-matched norms within all groups (P < .01). In multivariable regression analyses, higher arterial partial pressure of carbon dioxide (PaCO2) and TcCO2 during wakefulness were associated with lower MoCA and DSC scores (P ≤ .03), independent of confounders including overlap syndrome (OSA + chronic obstructive pulmonary disease). Awake hypoventilation is associated with greater deficits in cognitive function in patients with severe sleep-disordered breathing. Beaudin AE, Raneri JK, Ayas NT, Skomro RP, Smith EE, Hanly PJ; on behalf of Canadian Sleep and Circadian Network. Contribution of hypercapnia to cognitive impairment in severe sleep-disordered breathing. J Clin Sleep Med. 2022;18(1):245-254.

Intraoperative Monitoring of the Obese Patient Undergoing Surgery: A Narrative Review.

With the increasing prevalence of obesity in the population, anaesthetists must confidently manage both the pathophysiological and technical challenges presented in bariatric and non-bariatric surgery. The intraoperative period represents an important opportunity to optimise and mitigate risk. However, there is little formal guidance on what intraoperative monitoring techniques should be used in this population. This narrative review collates the existing evidence for intraoperative monitoring devices in the obese patients. Although a number of non-invasive blood pressure monitors have been tested, an invasive arterial line remains the most reliable monitor if accurate, continuous monitoring is required. Goal-directed fluid therapy is recommended by clinical practice guidelines, but the methods tested to assess this had guarded applicability to the obese population. Transcutaneous carbon dioxide (CO2) monitoring may offer additional benefit to standard capnography in this population. Individually titrated positive end expiratory pressure (PEEP) and recruitment manoeuvres improved intraoperative mechanics but yielded no benefit in the immediate postoperative period. Depth of anaesthesia monitoring appears to be beneficial in the perioperative period regarding recovery times and complications. Objective confirmation of reversal of neuromuscular blockade continues to be a central tenet of anaesthesia practice, particularly relevant to this group who have been characterised as an “at risk” extubation group. Where deep neuromuscular blockade is used, continuous neuromuscular blockade is suggested. Both obesity and the intraoperative context represent somewhat unstable search terms, as the clinical implications of the obesity phenotype are not uniform, and the type and urgency of surgery have significant impact on the intraoperative setting. This renders the generation of summary conclusions around what intraoperative monitoring techniques are suitable in this population highly challenging.

Assessing Agreement of Transcutaneous Carbon Dioxide Monitoring and Blood Gas Analysis in a Neonatal Population

Objective: To assess agreement between transcutaneous carbon dioxide (TcCO2) monitoring and blood gas analysis in neonates. Study Design: This was a prospective observational study performed in a tertiary neonatal intensive care unit. 19 infants with a mean postmenstrual age of 35+3 weeks were included. Agreement was assessed by Bland-Altman analysis and concordance correlation coefficient. End-user feedback was collected from staff and infants were assessed for evidence of skin damage. Results: Overall bias from 698 paired samples was -0.30 (SD 1.21, p&lt;0.0001) with good concordance (CCC 0.80). 69% (95% CI 65%-72%, p=0.0003) of samples fell within the predefined clinically acceptable difference of 1kPa. Agreement was more favorable for non-invasively ventilated infants (bias -0.11, CCC 0.91). Staff feedback was positive, and no infants suffered skin damage. Conclusion: TcCO2 monitoring is a reliable assessment tool for both invasively and non-invasively ventilated neonates. It can be used as an adjunct to blood gas analysis, reducing the frequency of invasive blood tests.

Polysomnography parameters as predictors of respiratory adverse events following adenotonsillectomy in children

The first-line treatment of obstructive sleep apnea syndrome in children is adenotonsillectomy, but this may result in perioperative respiratory adverse events (PRAEs). The primary aim of this study is to examine whether the McGill oximetry score (MOS) and other polysomnography parameters can predict major PRAEs following adenotonsillectomy. We secondarily evaluated the MOS interrater reliability and correlation with other polysomnography parameters. This retrospective study included all children aged 0-18 years who underwent preoperative polysomnography between June 2010 and January 2016 prior to adenotonsillectomy at a tertiary pediatric institution. Oximetries from polysomnograms were assigned an MOS. Univariable and multivariable models for prediction of major PRAEs were constructed. MOS was correlated with polysomnography parameters and interrater reliability was evaluated. This study included 106 children; 15 had a major PRAE. A multivariable prediction model that combined MOS and age showed evidence for the ability to predict major PRAEs with an area under the receiver operating characteristic curve of 0.68 (95% confidence interval: 0.52, 0.84), whereby increased MOS and younger age were associated with PRAEs, but apnea-hypopnea index was not. MOS had excellent interrater reliability (κ = 0.95) and was highly correlated with oxygen saturation nadir and cumulative time percentage with oxygen saturation less than 90%. A prediction model including MOS and age may predict PRAEs following adenotonsillectomy. This suggests that nocturnal oximetry provides the most essential information of polysomnography measures to direct postoperative monitoring following adenotonsillectomy. Xiao L, Barrowman N, Momoli F, etal. Polysomnography parameters as predictors of respiratory adverse events following adenotonsillectomy in children. J Clin Sleep Med. 2021;17(11):2215-2223.