Value of integrated pulmonary index monitoring for the detection of adverse respiratory events in patients undergoing sedation for gastrointestinal system endoscopy.

Objectives: To determine if the integrated pulmonary index detects changes in ventilation status early in patients undergoing gastrointestinal endoscopy under sedation, and to determine the risk factors affecting hypoxia. METHODS: The retrospective study was conducted at the endoscopy unit of a tertiary university hospital in Turkey and comprised data between October 2018 and December 2019 related to patients of either gender aged >18 years who were assessed as American Society of Anaesthesiologists grade I-III and underwent elective lower and upper gastrointestinal endoscopy. Monitoring was done with capnography in addition to standard procedures. Data was analysed using SPSS 23. RESULTS: Of the 154 patients, 94(%) were females and 60(%) were males. The overall mean age was 50.88±11.8 years (range: 20-70 years). Mean time under anaesthesia was 23.58±4.91 minutes and mean endoscopy time was 21.73±5.06 minutes. During the procedure, hypoxia was observed in 42(27.3%) patients, severe hypoxia in 23(14.9%) and apnoea in 70(45.5%). Mean time between apnoea and hypoxia was 12.59±7.99 seconds, between apnoea and serious hypoxia 21.07±17.64 seconds, between integrated pulmonary index score 1 and hypoxia 12.91±8.17 sec, between integrated pulmonary index score 1 and serious hypoxia 21.59±14.13 seconds, between integrated pulmonary index score <7 and hypoxia 19.63±8.89 seconds, between integrated pulmonary index score <7 and serious hypoxia 28.39±12.66 seconds, between end-tidal carbon dioxide and hypoxia 12.95±8.33 seconds, and between end-tidal carbon dioxide and serious hypoxia 21.29±7.55 seconds. With integrated pulmonary index score 1, sensitivity value for predicting hypoxia and severe hypoxia was 88.1% and 95.7%, respectively, and specificity was 67% and 60.3%, respectively. With integrated pulmonary index score <7, the corresponding values were 100%, 100%, 42% and 64.1%, respectively. CONCLUSIONS: Capnographic monitoring, especially the follow-up integrated pulmonary index score, was found to be valuable and reliable in terms of finding both time and accuracy of the risk factor in the diagnosis of respiratory events.

Monitoring CO2 kinetics as a marker of cardiopulmonary efficiency.

PURPOSE OF REVIEW: To describe current and near future developments and applications of CO2 kinetics in clinical respiratory and cardiovascular monitoring. RECENT FINDINGS: In the last years, we have witnessed a renewed interest in CO2 kinetics in relation with a better understanding of volumetric capnography and its derived parameters. This together with technological advances and improved measurement systems have expanded the monitoring potential of CO2 kinetics including breath by breath continuous end-expiratory lung volume and continuous noninvasive cardiac output. Dead space has slowly been gaining relevance in clinical monitoring and prognostic evaluation. Easy to measure dead space surrogates such as the ventilatory ratio have demonstrated a strong prognostic value in patients with acute respiratory failure. SUMMARY: The kinetics of carbon dioxide describe many relevant physiological processes. The clinical introduction of new ways of assessing respiratory and circulatory efficiency based on advanced analysis of CO2 kinetics are paving the road to a long-desired goal in clinical monitoring of critically ill patients: the integration of respiratory and circulatory monitoring during mechanical ventilation.

Clinical validation of a capnodynamic method for measuring end-expiratory lung volume in critically ill patients.

RATIONALE: End-expiratory lung volume (EELV) is reduced in mechanically ventilated patients, especially in pathologic conditions. The resulting heterogeneous distribution of ventilation increases the risk for ventilation induced lung injury. Clinical measurement of EELV however, remains difficult. OBJECTIVE: Validation of a novel continuous capnodynamic method based on expired carbon dioxide (CO2) kinetics for measuring EELV in mechanically ventilated critically-ill patients. METHODS: Prospective study of mechanically ventilated patients scheduled for a diagnostic computed tomography exploration. Comparisons were made between absolute and corrected EELVCO2 values, the latter accounting for the amount of CO2 dissolved in lung tissue, with the reference EELV measured by computed tomography (EELVCT). Uncorrected and corrected EELVCO2 was compared with total CT volume (density compartments between - 1000 and 0 Hounsfield units (HU) and functional CT volume, including density compartments of - 1000 to - 200HU eliminating regions of increased shunt. We used comparative statistics including correlations and measurement of accuracy and precision by the Bland Altman method. MEASUREMENTS AND MAIN RESULTS: Of the 46 patients included in the final analysis, 25 had a diagnosis of ARDS (24 of which COVID-19). Both EELVCT and EELVCO2 were significantly reduced (39 and 40% respectively) when compared with theoretical values of functional residual capacity (p < 0.0001). Uncorrected EELVCO2 tended to overestimate EELVCT with a correlation r2 0.58; Bias - 285 and limits of agreement (LoA) (+ 513 to - 1083; 95% CI) ml. Agreement improved for the corrected EELVCO2 to a Bias of - 23 and LoA of (+ 763 to - 716; 95% CI) ml. The best agreement of the method was obtained by comparison of corrected EELVCO2 with functional EELVCT with a r2 of 0.59; Bias - 2.75 (+ 755 to - 761; 95% CI) ml. We did not observe major differences in the performance of the method between ARDS (most of them COVID related) and non-ARDS patients. CONCLUSION: In this first validation in critically ill patients, the capnodynamic method provided good estimates of both total and functional EELV. Bias improved after correcting EELVCO2 for extra-alveolar CO2 content when compared with CT estimated volume. If confirmed in further validations EELVCO2 may become an attractive monitoring option for continuously monitor EELV in critically ill mechanically ventilated patients. TRIAL REGISTRATION: clinicaltrials.gov (NCT04045262).

Diagnosis and Severity Assessment of COPD Using a Novel Fast-Response Capnometer and Interpretable Machine Learning.

INTRODUCTION: Spirometry is the gold standard for COPD diagnosis and severity determination, but is technique-dependent, nonspecific, and requires administration by a trained healthcare professional. There is a need for a fast, reliable, and precise alternative diagnostic test. This study's aim was to use interpretable machine learning to diagnose COPD and assess severity using 75-second carbon dioxide (CO2) breath records captured with TidalSense's N-TidalTM capnometer. METHOD: For COPD diagnosis, machine learning algorithms were trained and evaluated on 294 COPD (including GOLD stages 1-4) and 705 non-COPD participants. A logistic regression model was also trained to distinguish GOLD 1 from GOLD 4 COPD with the output probability used as an index of severity. RESULTS: The best diagnostic model achieved an AUROC of 0.890, sensitivity of 0.771, specificity of 0.850 and positive predictive value (PPV) of 0.834. Evaluating performance on all test capnograms that were confidently ruled in or out yielded PPV of 0.930 and NPV of 0.890. The severity determination model yielded an AUROC of 0.980, sensitivity of 0.958, specificity of 0.961 and PPV of 0.958 in distinguishing GOLD 1 from GOLD 4. Output probabilities from the severity determination model produced a correlation of 0.71 with percentage predicted FEV1. CONCLUSION: The N-TidalTM device could be used alongside interpretable machine learning as an accurate, point-of-care diagnostic test for COPD, particularly in primary care as a rapid rule-in or rule-out test. N-TidalTM also could be effective in monitoring disease progression, providing a possible alternative to spirometry for disease monitoring.

Individualized estimation of arterial carbon dioxide partial pressure using machine learning in children receiving mechanical ventilation.

BACKGROUND: Measuring arterial partial pressure of carbon dioxide (PaCO2) is crucial for proper mechanical ventilation, but the current sampling method is invasive. End-tidal carbon dioxide (EtCO2) has been used as a surrogate, which can be measured non-invasively, but its limited accuracy is due to ventilation-perfusion mismatch. This study aimed to develop a non-invasive PaCO2 estimation model using machine learning. METHODS: This retrospective observational study included pediatric patients (< 18 years) admitted to the pediatric intensive care unit of a tertiary children's hospital and received mechanical ventilation between January 2021 and June 2022. Clinical information, including mechanical ventilation parameters and laboratory test results, was used for machine learning. Linear regression, multilayer perceptron, and extreme gradient boosting were implemented. The dataset was divided into 7:3 ratios for training and testing. Model performance was assessed using the R2 value. RESULTS: We analyzed total 2,427 measurements from 32 patients. The median (interquartile range) age was 16 (12-19.5) months, and 74.1% were female. The PaCO2 and EtCO2 were 63 (50-83) mmHg and 43 (35-54) mmHg, respectively. A significant discrepancy of 19 (12-31) mmHg existed between EtCO2 and the measured PaCO2. The R2 coefficient of determination for the developed models was 0.799 for the linear regression model, 0.851 for the multilayer perceptron model, and 0.877 for the extreme gradient boosting model. The correlations with PaCO2 were higher in all three models compared to EtCO2. CONCLUSIONS: We developed machine learning models to non-invasively estimate PaCO2 in pediatric patients receiving mechanical ventilation, demonstrating acceptable performance. Further research is needed to improve reliability and external validation.

Application of End-Tidal CO2 Monitoring to ICU Management.

Waveform capnography is a noninvasive measurement of ventilation and perfusion commonly employed in the prehospital setting. It is easy to apply, and modern cardiac monitors are equipped with the necessary ports and capability to display results. Despite its ease of use, end-tidal CO2 monitoring has not yet achieved widespread adoption within the hospital setting. It is routinely used in the emergency department and by anesthesiologists, but its application could support ICU management in critically ill patients. Its use is routinely supported by multiple professional societies, and it has been recommended as a requirement in all cardiac arrests. Careful analysis of the waveform and expired carbon dioxide can guide therapy for patients experiencing respiratory emergencies, hemodynamic compromise, metabolic acidosis, and shock due to trauma, hypovolemia, or sepsis. Use of capnography throughout the hospital could improve patient outcomes and prevent unidentified deterioration.

Prehospital Use of Waveform Capnography in Intubated Neonates.

INTRODUCTION: Routine continuous monitoring of endotracheal tube placement with waveform capnography is considered standard of care in the prehospital setting. However, maintaining this standard in neonatal patients remains a challenge due to low tidal volumes that do not tolerate the additional dead space ETCO2 attachments add. Additionally, continuous ETCO2 can increase the risk of ETT dislodgement or kinking because of the weight and size of the capnography attachments relative to the patient and tube size. We hypothesize that there is a gap in care of intubated neonates when compared to adults in the prehospital setting in terms of continuous monitoring of ETT placement. METHODS: Data were obtained from a single air medical agency. Through a retrospective chart review, records of intubated neonates (<28 days), children (≥28 days-12 years), adolescents (13-18 years), and adults (aged ≥18 years) were analyzed. Records were available from 11/21/13-1/21/22. The number of intubation attempts, whether an intubation was successful, and the use of capnography were recorded in RedCap. Statistical analysis was performed in Microsoft Excel via Chi Square Goodness of Fit Tests. RESULTS: During the study period, 674 intubation attempts were identified, and 28 charts were excluded due to missing patient age. Continuous waveform ETCO2 monitoring was used on 62%, 94%, 95%, and 97% of successfully intubated neonates, children, adolescents, and adults, respectively. There was a statistically significant difference between use of continuous waveform capnography in adults and neonates (p-value = 0.013). There was also a statistically significant difference between use of continuous waveform capnography in intubated neonates, children, and adolescents (p-value = 0.049). CONCLUSION: Continuous ETCO2 monitoring is underutilized in intubated neonates compared to children, adolescents, and adults in the prehospital setting in this study population. This suggests a gap in the standard of care provided to neonates. Additional studies are needed to determine if these results are consistent around the industry and if there is a higher rate of undetected tube displacement in neonates who are transported without waveform capnography.

Role of continuous pulse oximetry and capnography monitoring in the prevention of postoperative respiratory failure, postoperative opioid-induced respiratory depression and adverse outcomes on hospital wards: A systematic review and meta-analysis.

OBJECTIVE: The current standards of postoperative respiratory monitoring on medical-surgical floors involve spot-pulse oximetry checks every 4-8 h, which can miss the opportunity to detect prolonged hypoxia and acute hypercapnia. Continuous respiratory monitoring can recognize acute respiratory depression episodes; however, the existing evidence is limited. We sought to review the current evidence on the effectiveness of continuous pulse oximetry (CPOX) with and without capnography versus routine monitoring and their effectiveness for detecting postoperative respiratory failure, opioid-induced respiratory depression, and preventing downstream adverse events. METHODS: We performed a systematic literature search on Ovid Medline, Embase, and Cochrane Library databases for articles published between 1990 and April 2023. The study protocol was registered in Prospero (ID: 439467), and PRISMA guidelines were followed. The NIH quality assessment tool was used to assess the quality of the studies. Pooled analysis was conducted using the software R version 4.1.1 and the package meta. The stability of the results was assessed using sensitivity analysis. DESIGN: Systematic Review and Meta-Analysis. SETTING: Postoperative recovery area. PATIENTS: 56,538 patients, ASA class II to IV, non-invasive respiratory monitoring, and post-operative respiratory depression. INTERVENTIONS: Continuous pulse oximetry with or without capnography versus routine monitoring. MEASUREMENTS: Respiratory rate, oxygen saturation, adverse events, and rescue events. RESULTS: 23 studies (17 examined CPOX without capnography and 5 examined CPOX with capnography) were included in this systematic review. CPOX was better at recognizing desaturation (SpO2 < 90%) OR: 11.94 (95% CI: 6.85, 20.82; p < 0.01) compared to standard monitoring. No significant differences were reported for ICU transfer, reintubation, and non-invasive ventilation between the two groups. CONCLUSIONS: Oxygen desaturation was the only outcome better detected with CPOX in postoperative patients in hospital wards. These comparisons were limited by the small number of studies that could be pooled for each outcome and the heterogeneity between the studies.

Trending Ability of End-Tidal Capnography Monitoring During Mechanical Ventilation to Track Changes in Arterial Partial Pressure of Carbon Dioxide in Critically Ill Patients With Acute Brain Injury: A Monocenter Retrospective Study.

BACKGROUND: Changes in arterial partial pressure of carbon dioxide (Pa co2 ) may alter cerebral perfusion in critically ill patients with acute brain injury. Consequently, international guidelines recommend normocapnia in mechanically ventilated patients with acute brain injury. The measurement of end-tidal capnography (Et co2 ) allows its approximation. Our objective was to report the agreement between trends in Et co2 and Pa co2 during mechanical ventilation in patients with acute brain injury. METHODS: Retrospective monocenter study was conducted for 2 years. Critically ill patients with acute brain injury who required mechanical ventilation with continuous Et co2 monitoring and with 2 or more arterial gas were included. The agreement was evaluated according to the Bland and Altman analysis for repeated measurements with calculation of bias, and upper and lower limits of agreement. The directional concordance rate of changes between Et co2 and Pa co2 was evaluated with a 4-quadrant plot. A polar plot analysis was performed using the Critchley methods. RESULTS: We analyzed the data of 255 patients with a total of 3923 paired ΔEt co2 and ΔPa co2 (9 values per patient in median). Mean bias by Bland and Altman analysis was -8.1 (95 CI, -7.9 to -8.3) mm Hg. The directional concordance rate between Et co2 and Pa co2 was 55.8%. The mean radial bias by polar plot analysis was -4.4° (95% CI, -5.5 to -3.3) with radial limit of agreement (LOA) of ±62.8° with radial LOA 95% CI of ±1.9°. CONCLUSIONS: Our results question the performance of trending ability of Et co2 to track changes in Pa co2 in a population of critically ill patients with acute brain injury. Changes in Et co2 largely failed to follow changes in Pa co2 in both direction (ie, low concordance rate) and magnitude (ie, large radial LOA). These results need to be confirmed in prospective studies to minimize the risk of bias.

Measurement accuracy of a microwave doppler sensor beneath the mattress as a continuous respiratory rate monitor: a method comparison study.

PURPOSE: Non-contact continuous respiratory rate monitoring is preferred for early detection of patient deterioration. However, this technique is under development; a gold standard respiratory monitor has not been established. Therefore, this prospective observational method comparison study aimed to compare the measurement accuracy of a non-contact continuous respiratory rate monitor, a microwave Doppler sensor positioned beneath the mattress, with that of other monitors. METHODS: The respiratory rate of intensive care unit patients was simultaneously measured using a microwave Doppler sensor, capnography, thoracic impedance pneumography, and a piezoelectric sensor beneath the mattress. Bias and 95% limits of agreement between the respiratory rate measured using capnography (standard reference) and that measured using the other three methods were calculated using Bland-Altman analysis for repeated measures. Clarke error grid (CEG) analysis evaluated the sensor's ability to assist in correct clinical decision-making. RESULTS: Eighteen participants were included, and 2,307 data points were analyzed. The bias values (95% limits of agreement) of the microwave Doppler sensor, thoracic impedance pneumography, and piezoelectric sensor were 0.2 (- 4.8 to 5.2), 1.5 (- 4.4 to 7.4), and 0.4 (- 4.0 to 4.8) breaths per minute, respectively. Clinical decisions evaluated using CEG analyses were correct 98.1% of the time for the microwave Doppler sensor, which was similar to the performance of the other devices. CONCLUSION: The microwave Doppler sensor had a small bias but relatively low precision, similar to other devices. In CEG analyses, the risk of each monitor leading to inadequate clinical decision-making was low. TRIAL REGISTRATION NUMBER: UMIN000038900, February 1, 2020.

Capnography access and use in Kenya and Ethiopia.

PURPOSE: Lack of access to safe and affordable anesthesia and monitoring equipment may contribute to higher rates of morbidity and mortality in low- and middle-income countries (LMICs). While capnography is standard in high-income countries, use in LMICs is not well studied. We evaluated the association of capnography use with patient and procedure-related characteristics, as well as the association of capnography use and mortality in a cohort of patients from Kenya and Ethiopia. METHODS: For this retrospective observational study, we used historical cohort data from Kenya and Ethiopia from 2014 to 2020. Logistic regression was used to study the association of capnography use (primary outcome) with patient/procedure factors, and the adjusted association of intraoperative, 24-hr, and seven-day mortality (secondary outcomes) with capnography use. RESULTS: A total of 61,792 anesthetic cases were included in this study. Tertiary or secondary hospital type (compared with primary) was strongly associated with use of capnography (odds ratio [OR], 6.27; 95% confidence interval [CI], 5.67 to 6.93 and OR, 6.88; 95% CI, 6.40 to 7.40, respectively), as was general (vs regional) anesthesia (OR, 4.83; 95% CI, 4.41 to 5.28). Capnography use was significantly associated with lower odds of intraoperative mortality in patients who underwent general anesthesia (OR, 0.31; 95% CI, 0.17 to 0.48). Nevertheless, fully-adjusted models for 24-hr and seven-day mortality showed no evidence of association with capnography. CONCLUSION: Capnography use in LMICs is substantially lower compared with other standard anesthesia monitors. Capnography was used at higher rates in tertiary centres and with patients undergoing general anesthesia. While this study revealed decreased odds of intraoperative mortality with capnography use, further studies need to confirm these findings.

RéSUMé: OBJECTIF: Le manque d'accès à des équipements d'anesthésie et de monitorage sécuritaires et abordables peut contribuer à des taux plus élevés de morbidité et de mortalité dans les pays à revenu faible et intermédiaire (PRFI). Alors que la capnographie est une modalité standard dans les pays à revenu élevé, son utilisation dans les PRFI n'est pas bien étudiée. Nous avons évalué l'association de l'utilisation de la capnographie avec les caractéristiques des patient·es et des interventions, ainsi que l'association de l'utilisation de la capnographie et de la mortalité dans une cohorte de patient·es du Kenya et d'Éthiopie. MéTHODE: Pour cette étude observationnelle rétrospective, nous avons utilisé des données de cohortes historiques du Kenya et de l'Éthiopie de 2014 à 2020. Une régression logistique a été utilisée pour étudier l'association entre l'utilisation de la capnographie (critère d'évaluation principal) et les facteurs patient·es/interventions, ainsi que pour étudier l'association ajustée entre la mortalité peropératoire, à 24 h et à sept jours (critères d'évaluation secondaires) et l'utilisation de la capnographie. RéSULTATS: Au total, 61 792 cas d'anesthésie ont été inclus dans cette étude. Le type d'hôpital tertiaire ou secondaire (par rapport à un établissement primaire) était fortement associé à l'utilisation de la capnographie (rapport de cotes [RC], 6,27; intervalle de confiance [IC] à 95 %, 5,67 à 6,93 et RC, 6,88; IC 95 %, 6,40 à 7,40, respectivement), tout comme l'était l'anesthésie générale (vs régionale) (RC, 4,83; IC 95 %, 4,41 à 5,28). L'utilisation de la capnographie était significativement associée à une probabilité plus faible de mortalité peropératoire chez les patient·es ayant reçu une anesthésie générale (RC, 0,31; IC 95 %, 0,17 à 0,48). Néanmoins, les modèles entièrement ajustés pour la mortalité à 24 heures et à sept jours n'ont montré aucune donnée probante d'association avec la capnographie. CONCLUSION: L'utilisation de la capnographie dans les PRFI est considérablement moins répandue que celle d'autres moniteurs d'anesthésie standard. La capnographie a été utilisée à des taux plus élevés dans les centres tertiaires et chez des patient·es sous anesthésie générale. Bien que cette étude ait révélé une diminution de la probabilité de mortalité peropératoire avec l'utilisation de la capnographie, d'autres études doivent confirmer ces résultats.

Large animal ventilator-integrated volumetric capnography generates clinically acceptable values of physiologic dead space in anesthetized healthy adult horses.

OBJECTIVE: To evaluate the agreement between the Tafonius large animal ventilator-integrated volumetric capnography (vCap) software and the Respironics NICO noninvasive cardiac output monitor reference system. ANIMALS: Data were collected from 56 healthy adult horses undergoing general anesthesia. METHODS: Animals were placed under general anesthesia and connected to the Tafonius large animal ventilator circle system. A flow partitioning device with CO2 and flow sensors was utilized to couple the endotracheal tube to the NICO monitor. Tafonius CO2 and flow sensors are incorporated into the Y-piece of the breathing circuit. Arterial blood samples were collected to determine the partial pressure of arterial carbon dioxide (PaCO2) immediately before data collection. The PaCO2 was input into the Tafonius and NICO monitor, and dead space ventilation (%Vd), end-tidal CO2 partial pressure (ETco2), mixed-expired CO2 partial pressure (Peco2), and expired tidal volume (Vt) were calculated over a single breath. Multiple measurements were completed for each patient, with a total of 200 paired data points collected for analysis. Data were assessed for normality, and Bland-Altman analysis was performed. Bias and 95% limits of agreement were calculated. RESULTS: The limits of agreement for %Vd of the ventilator-derived measurements fell within ± 10% of the NICO monitor reference method. CLINICAL RELEVANCE: Our results indicate that, when compared to the NICO monitor method, the Tafonius-integrated vCap software provides clinically acceptable values of Peco2, Vt, and %Vd in healthy adult horses.

Comparing the EMMA capnograph with sidestream capnography and arterial carbon dioxide pressure at 284 kPa.

Introduction: Capnography aids assessment of the adequacy of mechanical patient ventilation. Physical and physiological changes in hyperbaric environments create ventilation challenges which make end-tidal carbon dioxide (ETCO2) measurement particularly important. However, obtaining accurate capnography in hyperbaric environments is widely considered difficult. This study investigated the EMMA capnograph for hyperbaric use. Methods: We compared the EMMA capnograph to sidestream capnography and the gold standard arterial carbon dioxide blood gas analysis in a hyperbaric chamber. In 12 resting subjects breathing air at 284 kPa, we recorded ETCO2 readings simultaneously derived from the EMMA and sidestream capnographs during two series of five breaths (total 24 measurements). An arterial blood gas sample was also taken simultaneously in five participants. Results: Across all measurements there was a difference of about 0.1 kPa between the EMMA and sidestream capnographs indicating a very slight over-estimation of ETCO2 by the EMMA capnograph, but fundamentally good agreement between the two end-tidal measurement methods. Compared to arterial blood gas pressure the non-significant difference was about 0.3 and 0.4 kPa for the EMMA and sidestream capnographs respectively. Conclusions: In this study, the EMMA capnograph performed equally to the sidestream capnograph when compared directly, and both capnography measures gave clinically acceptable estimates of arterial PCO2.

SAMAY S24: a novel wireless 'online' device for real-time monitoring and analysis of volumetric capnography.

Volumetric capnography (VCap) provides information about CO2 exhaled per breath (VCO2br) and physiologic dead space (VDphys). A novel wireless device with a high response time CO2 mainstream sensor coupled with a digital flowmeter was designed to monitor all VCap parameters online in rabbits (SAMAY S24).Ten New Zealand rabbits were anesthetized and mechanically ventilated. VCO2br corresponds to the area under the VCap curve. We used the modified Langley method to assess the airway VD (VDaw) and the alveolar CO2 pressure. VDphys was estimated using Bohr's formula, and the alveolar VD was calculated by subtracting VDaw from VDphys. We compared (Bland-Altman) the critical VCap parameters obtained by SAMAY S24 (Langley) with the Functional Approximation based on the Levenberg-Marquardt Algorithm (FA-LMA) approach during closed and opened chest conditions.SAMAY S24 could assess dead space volumes and VCap shape in real time with similar accuracy and precision compared to the 'offline' FA-LMA approach. The opened chest condition impaired CO2 kinetics, decreasing the phase II slope, which was correlated with the volume of CO2 exhaled per minute.

Diagnostic accuracy of using capnography in verification of nasogastric tube placement among adult patients in hospital settings: Protocol of a diagnostic study.

OBJECTIVE: To determine the diagnostic accuracy of end-tidal carbon dioxide (ETCO2) detection using capnography for verifying the correct placement of nasogastric tubes (NGTs) among adult patients in hospital settings. MATERIALS AND METHODS: A prospective observational diagnostic study will be conducted. Patients ≥ 18-year-old and requiring the insertion of an NGT will be recruited using a convenience sampling method from 39 general medical and geriatric wards, intensive care units, accident and emergency departments, and subacute/rehabilitation/infirmary wards in 21 acute or subacute/convalescent/extended care hospitals. ETCO2 detection by sidestream capnography, which indicates an airway intubation of an NGT when a capnogram waveform or an ETCO2 level > 10mmHg (1.33 kPa) occurs, will serve as the index test. The reference standards will be the X-ray performed and pH value of gastric aspiration (pH ≤ 5.5) after the index test. Each participant will be included only once. Sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic curve of capnography will be calculated to assess the diagnostic performance of capnography. The variability in diagnostic accuracy in participants with different characteristics will be explored by using chi-squared or Fisher's exact tests. The time spent and the cost of the tests will be compared using the paired t-test. All statistical tests will be two-sided with a level of significance set at 0.05. DISCUSSION: This study will provide evidence on the diagnostic accuracy of capnography in verifying NGT placement and its applicability to patients in hospitals settings, since this evidence is limited in the current literature. In addition, it will help identify the optimal combination of tests in verifying the correct placement of NGTs and inform the update of clinical practice guidelines and stakeholders' decisions on the adoption of ETCO2 detection as a routine method for verifying NGT placement. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT05817864.

Comparison of 4 point-of-care techniques to detect correct positioning of nasogastric tubes in dogs (2020-2021).

OBJECTIVE: To compare 4 point-of-care (POC) techniques to assess nasogastric (NG) tube placement versus radiographs as a reference standard. POC methods included air inflation with auscultation, fluid aspiration with pH measurement, ultrasonography, and capnography. DESIGN: Prospective observational study in hospitalized dogs between 2020 and 2021. SETTING: University teaching hospital. ANIMALS: Fifty-one dogs requiring NG tube placement as part of their normal care. INTERVENTIONS: After standard blind NG tube placement, each POC method was performed following standardized instructions. All POC methods were scored as to whether the investigator believed the tube to be in the gastrointestinal tract (as indicated by positive auscultation of borborygmus during insufflation, positive fluid aspiration with pH ≤5, presence of hyperechoic shadow in the esophagus, or absence of capnographic waveform). Subsequently, radiographs were taken to determine NG tube position as a gold standard. The sensitivity, specificity, and accuracy of each test as compared to 2-view thoracic radiographs were determined. MEASUREMENTS AND MAIN RESULTS: Sensitivity, specificity, and accuracy for each POC technique were as follows: air auscultation (84.4%, 50.5%, and 80.4%, respectively), neck ultrasound (95.6%, 83.3%, and 94.1%, respectively), capnography (91.1%, 33.3%, and 84.3%, respectively), and fluid aspiration with pH measurement (22.2%, 100%, and 31.4%, respectively). CONCLUSIONS: Among the 4 techniques evaluated, neck ultrasound had the best overall performance for assessing NG tube placement. Fluid aspiration with pH measurement might also have potential due to perfect specificity, but its clinical utility may be limited by low sensitivity and accuracy. Nonetheless, 2-view thoracic radiography should still be considered the standard method for confirmation of NG tube placement as none of the 4 POC techniques investigated showed both high sensitivity and perfect specificity.

Identifying Early Opioid-Induced Respiratory Depression and Rapid Response Team Activation.

BACKGROUND: Opioids can cause respiratory depression, which could lead to patient harm. The project site noted a gap in identifying and monitoring postsurgical thoracic patients at risk for opioid-induced respiratory depression (OIRD), so an evidence-based solution was sought. AIMS: The purpose of this quality improvement project was to determine if translating the research by Khanna et al. (2020) on implementing the prediction of opioid-induced respiratory depression in patients monitored by capnography (PRODIGY) risk prediction tool would affect rapid response team (RRT) activation among postsurgical thoracic patients in a cardiovascular and thoracic care unit (CVTCU) at John Muir Medical Center, Concord Campus over four weeks. METHODS: The four-week quantitative quasi-experimental project had a total sample size of 29 participants. Pulse oximetry was used to identify OIRD in the comparison group (n = 12). The implementation group consisted of patients identified as at-risk for OIRD by the PRODIGY risk prediction tool and were monitored with pulse oximetry and capnography (n = 17). RESULTS: A χ2 analysis showed χ2 (1, n = 29) = .73, p = .393 for activation of the RRT using the PRODIGY risk prediction tool, which was not statistically significant. However, clinical significance was supported by a 5.9% increase in RRT activations. CONCLUSION: Based on the results, implementing the PRODIGY risk prediction tool and capnography monitoring on at-risk patients may affect RRT activation in this population.

Machine diagnosis of chronic obstructive pulmonary disease using a novel fast-response capnometer.

BACKGROUND: Although currently most widely used in mechanical ventilation and cardiopulmonary resuscitation, features of the carbon dioxide (CO2) waveform produced through capnometry have been shown to correlate with V/Q mismatch, dead space volume, type of breathing pattern, and small airway obstruction. This study applied feature engineering and machine learning techniques to capnography data collected by the N-Tidal™ device across four clinical studies to build a classifier that could distinguish CO2 recordings (capnograms) of patients with COPD from those without COPD. METHODS: Capnography data from four longitudinal observational studies (CBRS, GBRS, CBRS2 and ABRS) was analysed from 295 patients, generating a total of 88,186 capnograms. CO2 sensor data was processed using TidalSense's regulated cloud platform, performing real-time geometric analysis on CO2 waveforms to generate 82 physiologic features per capnogram. These features were used to train machine learning classifiers to discriminate COPD from 'non-COPD' (a group that included healthy participants and those with other cardiorespiratory conditions); model performance was validated on independent test sets. RESULTS: The best machine learning model (XGBoost) performance provided a class-balanced AUROC of 0.985 ± 0.013, positive predictive value (PPV) of 0.914 ± 0.039 and sensitivity of 0.915 ± 0.066 for a diagnosis of COPD. The waveform features that are most important for driving classification are related to the alpha angle and expiratory plateau regions. These features correlated with spirometry readings, supporting their proposed properties as markers of COPD. CONCLUSION: The N-Tidal™ device can be used to accurately diagnose COPD in near-real-time, lending support to future use in a clinical setting. TRIAL REGISTRATION: Please see NCT03615365, NCT02814253, NCT04504838 and NCT03356288.

Effect of external dead space removal on CO2 homeostasis in mechanically ventilated adult Covid-19 patients.

BACKGROUND: Patients with Covid-19 respiratory failure present with hypoxemia, often in combination with hypercapnia. In this prospective, observational study we examined the effect of removing external dead space (DS) on CO2 -homeostasis in mechanically ventilated Covid-19 patients. In addition, volumetric capnography was validated for its ability to estimate external DS volume using in vitro measured DS volumes as reference. METHODS: In total, 10 patients with acute respiratory distress syndrome from Covid-19 were included. Volumetric capnography, mechanical ventilation, and arterial blood gas data were analyzed before and after removal of external DS and analyzed for potentially significant changes in response to DS removal. Measurements of external DS were obtained in circuit using volumetric capnography and compared to actual measured DS volumes off the circuit. RESULTS: After the removal of external DS, the alveolar minute ventilation and CO2 elimination improved, notwithstanding unchanged respiratory rate and tidal volumes. The increase in CO2 elimination was associated with a decrease in arterial CO2 partial pressure (PaCO2 ). The volumetric capnography method for assessment of external DS showed a low bias of -9 mL (lower limit of agreement -40, 95% CI -60 to -20 mL, upper limit of agreement 21 mL, 95% CI: 1-40 mL) and a percentage error of 48% compared to absolute values measured in vitro. CONCLUSION: Removal of external DS increased alveolar minute ventilation and CO2 elimination in Covid-19 patients with respiratory failure in the current study. This was associated with a decrease in PaCO2 . This may indicate a decreased CO2 production due to decreased work of breathing and more effective gas-exchange in response to DS removal. In addition, volumetric capnography appears to be a clinically feasible method for continuous measurement of external DS in the current study and may be of value in optimizing ventilator treatment.

Medic and Portable Pulse Oximeter Respiratory Rate Measurement Comparison to Waveform Capnography: A Prospective, Observational Study.

BACKGROUND: The second leading cause of preventable battlefield death involves airway management. Tactical combat casualty care (TCCC) guidelines emphasize combat casualty airway, breathing and respiratory evaluation, including respiratory rate (RR) measurement. The current standard of practice for the US Army medics is to measure the RR by manual counting. Manual counting methods are operator-dependent, and medics face situational stressors limiting accurate measurement of RR in combat settings. To date, no published studies evaluate alternate methods of RR measurement by medics. The purpose of this study is to compare RR assessment by medics against waveform capnography and commercial finger pulse oximeters with continuous plethysmography. MATERIALS AND METHODS: We conducted a prospective, observational study to compare Army medic RR assessments against plethysmography and waveform capnography RR. Assessments were performed prior to and following exertion at 30 and 60 seconds with both the pulse oximeter (NSN 6515-01-655-9412) and defibrillator monitor (NSN 6515-01-607-8629), followed by end-user surveys. RESULTS: Of the 40 medics enrolled over a 4-month period, most were male (85%), and reported between less than 5 years of military and medical experience. The mean manual RR reported by medics at rest did not significantly differ from waveform capnography (14.05 versus 13.98, p is equal to 0.523); however, mean manual RR reported by medics on post-exertional subjects was significantly lower than waveform capnography (25.62 versus 29.77, p is less than 0.001). Time to medic-obtained RR was slower than the pulse oximeter (NSN 6515-01-655-9412) both at rest (-7.37 seconds, p is less than 0.001) and at exertion (-6.50 seconds, p is less than 0.001). While the mean difference in RR between the pulse oximeter (NSN 6515-01-655-9412) and waveform capnography in models at rest at 30 seconds was statistically significant (-1.38, p is less than 0.001). There was no overall statistically significant differences in RR between the pulse oximeter (NSN 6515-01-655-9412) and waveform capnography in models at exertion at 30 seconds and at rest and exertion at 60 seconds. CONCLUSION: Resting RR measurement did not differ significantly; however, medic-obtained RR considerably deviated from both pulse oximeters and waveform capnography at elevated rates. Existing commercial pulse oximeters with RR plethysmography do not differ significantly from waveform capnography and should be investigated further for consideration in fielding across the force for RR assessment.