Standardisation facilitates reliable interpretation of ETCO2 during manual cardiopulmonary resuscitation.

BACKGROUND: Interpretation of end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) is affected by variations in ventilation and chest compressions. This study investigates the impact of standardising ETCO2 to constant ventilation rate (VR) and compression depth (CD) on absolute values and trends METHODS: Retrospective study of out-of-hospital cardiac arrest cases with manual CPR, including defibrillator and clinical data. ETCO2, VR and CD values were averaged by minute. ETCO2 was standardised to 10 vpm and 50 mm. We compared standardised (ETs) and measured (ETm) values and trends during resuscitation. RESULTS: Of 1,036 cases, 287 met the inclusion criteria. VR was mostly lower than recommended, 8.8 vpm, and highly variable within and among patients. CD was mostly within guidelines, 49.8 mm, and less varied. ETs was lower than ETm by 7.3 mmHg. ETs emphasized differences by sex (22.4 females vs. 25.6 mmHg males), initial rhythm (29.1 shockable vs. 22.7 mmHg not), intubation type (25.6 supraglottic vs. 22.4 mmHg endotracheal) and return of spontaneous circulation (ROSC) achieved (34.5 mmHg) vs. not (20.1 mmHg). Trends were different between non-ROSC and ROSC patients before ROSC (-0.3 vs. +0.2 mmHg/min), and between sustained and rearrest after ROSC (-0.7 vs. -2.1 mmHg/min). Peak ETs was higher for sustained than for rearrest (53.0 vs. 42.5 mmHg). CONCLUSION: Standardising ETCO2 eliminates effects of VR and CD variations during manual CPR and facilitates comparison of values and trends among and within patients. Its clinical application for guidance of resuscitation warrants further investigation.

Assessment of respiratory rate monitoring in the emergency department.

Objectives: This study aimed to compare the different respiratory rate (RR) monitoring methods used in the emergency department (ED): manual documentation, telemetry, and capnography. Methods: This is a retrospective study using recorded patient monitoring data. The study population includes patients who presented to a tertiary care ED between January 2020 and December 2022. Inclusion and exclusion criteria were patients with simultaneous recorded RR data from all three methods and less than 10 min of recording, respectively. Linear regression and Bland-Altman analysis were performed between different methods. Results: A total of 351 patient encounters met study criteria. Linear regression yielded an R-value of 0.06 (95% confidence interval [CI] 0.00-0.12) between manual documentation and telemetry, 0.07 (95% CI 0.01-0.13) between manual documentation and capnography, and 0.82 (95% CI 0.79-0.85) between telemetry and capnography. The Bland-Altman analysis yielded a bias of -0.8 (95% limits of agreement [LOA] -12.2 to 10.6) between manual documentation and telemetry, bias of -0.6 (95% LOA -13.5 to 12.3) between manual documentation and capnography, and bias of 0.2 (95% LOA -6.2 to 6.6) between telemetry and capnography. Conclusion: There is a poor correlation between manual documentation and both automated methods, while there is relatively good agreement between the automated methods. This finding highlights the need to further investigate the methodology used by the ED staff in monitoring and documenting RR and ways to improve its reliability given that many important clinical decisions are made based on these assessments.

The Theatre Recovery and Anaesthetic nurse Capnography Education (TRACE) project.

The Theatre Recovery and Anaesthetic Nurse Capnography Education (TRACE) project is a multidisciplinary quality improvement project. The overall aim is to educate anaesthetic and recovery nurses on the correct use of capnography and educate non-consultant hospital doctors on the guidelines on Preventing Unrecognised Oesophageal Intubation from the Project for Universal Management of Airways group. This project addresses technical aspects of task performance such as correct waveform identification and interpretation, troubleshooting abnormal waveforms and establishing routine checks of capnography both pre-induction and post-intubation. The pre-induction verification of the correct function of capnography is an essential component of this project. In addition, the project focuses on team aspects of task performance with an emphasis on team psychological safety, empowering nurses to speak up using graded assertiveness and flattening hierarchies. As a result of the project, our nurses' knowledge about capnography and waveform identification improved to over 80% correct answers six months after completion of the project. In addition, over 90% of participants reported feeling confident in speaking up to both consultants and non-consultant hospital doctors when a waveform was not present before induction of anaesthesia or after attempted tracheal intubation.

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).

Respiratory rate monitoring in ICU patients and healthy volunteers using electrical impedance tomography: a validation study.

OBJECTIVE: The respiratory rate (RR) is considered one of the most informative vital signals. A well-validated standard for RR measurement in mechanically ventilated patient is capnography; a noninvasive technique for expiratory CO2 measurements. Reliable RR measurements in spontaneously breathing patients remains a challenge as continuous mainstream capnography measurements are not available. This study aimed to assess the accuracy of RR measurement using electrical impedance tomography (EIT) in healthy volunteers and intensive care unit (ICU) patients on mechanical ventilation and spontaneously breathing post-extubation. Comparator methods included RR derived from both capnography and bioimpedance electrocardiogram (ECG) measurements. Approach: Twenty healthy volunteers wore an EIT belt and ECG electrodes while breathing through a capnometer within a 10 - 40 breaths per minute (BPM) range. Nineteen ICU patients underwent similar measurements during pressure support ventilation and spontaneously breathing after extubation from mechanical ventilation. Stable periods with regular breathing and no artefacts were selected, and agreement between measurement methods was assessed using Bland-Altman analysis for repeated measurements. Main Result: Bland-Altman analysis revealed a bias less than 0.2 BPM, with tight limits of agreement (LOA) 1.5 BPM in healthy volunteers and ventilated ICU patients when comparing EIT to capnography. Spontaneously breathing ICU patients had wider LOA (2.5 BPM) when comparing EIT to ECG bioimpedance, but gold standard comparison was unavailable. RR measurements were stable for 91% of the time for capnography, 68% for EIT, and 64% of the ECG bioimpedance signals. After extubation, the percentage of stable periods decreased to 48% for EIT signals and to 55% for ECG bioimpedance. Significance: In periods of stable breathing, EIT demonstrated excellent RR measurement accuracy in healthy volunteers and ICU patients. However, stability of both EIT and ECG bioimpedance RR measurements declined in spontaneously breathing patients to approximately 50% of the time. .

Capnography waveforms: basic interpretation in neonatal intensive care.

End-tidal capnography can provide useful clinical information displayed on the ventilator screen or bedside monitor. It is important that clinicians can assess and utilise this information to assist in identifying underlying complications and pulmonary pathology. Sudden change or loss of the CO2 waveform can act as a safety measure in alerting clinicians of a dislodged or blocked endotracheal tube, considering the concurrent flow and volume waveforms. Visual pattern recognition by the clinicians of commonly seen waveform traces may act as an adjunct to other modes of ventilatory monitoring techniques. Waveforms traces can aid clinical management, help identify cases of ventilation asynchrony between the infant and the ventilator. We present some common clinical scenarios where tidal capnography can be useful in the timely identification of pulmonary complication and for practical troubleshooting at the cot-side.

Is chest tube capnography effective in differentiating between true and false air leaks after minimally invasive thoracic surgery?

OBJECTIVE: Air leak (AL) is the most frequent adverse event after thoracic surgery. When AL occurs, the concentration of the principal gas in the pleural space should be similar to that of air exhaled. Accordingly, we tried to develop a new method to identify AL by analyzing pCO2 levels in the air flow from the chest drainage using capnography. METHODS: This is a prospective observational study of 104 patients who underwent VATS surgery between January 2020 and July 2021. Digital drainage systems were used to detect AL. RESULTS: Eighty-two patients (79%) had lung resection. Among them, 19 had post-operative day 1 air leaks (median 67 ml/min). AL patients had higher intrapleural CO2 levels (median 24 mmHg) (p < 0.001). Median chest drainage duration was 2 days (range 1.0-3.0). Univariable logistic regression showed a linear and significant association between intrapleural CO2 levels and AL risk (OR 1.26, 95% CI 1.17-1.36, p < 0.001, C index: 0.94). The Univariable Gamma model demonstrated that an elevation in CO2 levels was linked to AL on POD1 (with an adjusted mean effect of 7.006, 95% CI 1.59-12.41, p = 0.011) and extended duration of drainage placement (p < 0.001). CONCLUSIONS: Intrapleural CO2 could be an effective tool to assess AL. The linear association between variables allows us to hypothesize the role of CO2 in the identification of AL. Further studies should be performed to identify a CO2 cutoff that will standardize the management of chest drainage.

A machine learning algorithm for detecting abnormal patterns in continuous capnography and pulse oximetry monitoring.

Continuous capnography monitors patient ventilation but can be susceptible to artifact, resulting in alarm fatigue. Development of smart algorithms may facilitate accurate detection of abnormal ventilation, allowing intervention before patient deterioration. The objective of this analysis was to use machine learning (ML) to classify combined waveforms of continuous capnography and pulse oximetry as normal or abnormal. We used data collected during the observational, prospective PRODIGY trial, in which patients receiving parenteral opioids underwent continuous capnography and pulse oximetry monitoring while on the general care floor [1]. Abnormal ventilation segments in the data stream were reviewed by nine experts and inter-rater agreement was assessed. Abnormal segments were defined as the time series 60s before and 30s after an abnormal pattern was detected. Normal segments (90s continuous monitoring) were randomly sampled and filtered to discard sequences with missing values. Five ML models were trained on extracted features and optimized towards an Fß score with ß = 2. The results show a high inter-rater agreement (> 87%), allowing 7,858 sequences (2,944 abnormal) to be used for model development. Data were divided into 80% training and 20% test sequences. The XGBoost model had the highest Fß score of 0.94 (with ß = 2), showcasing an impressive recall of 0.98 against a precision of 0.83. This study presents a promising advancement in respiratory monitoring, focusing on reducing false alarms and enhancing accuracy of alarm systems. Our algorithm reliably distinguishes normal from abnormal waveforms. More research is needed to define patterns to distinguish abnormal ventilation from artifacts.

Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study.

BACKGROUND: Capnography is a quantitative and reliable method of determining the ventilatory status of patients. We describe the test characteristics of capnography obtained during Emergency Department triage for screening acidemia. RESULTS: We performed an observational, pilot study of adult patients presenting to Emergency Department (ED) triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and acidemia ([Formula: see text] or [Formula: see text]) was identified in 28 patients. The measured respiratory rate (20.3 ± 6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51-0.75, p = 0.03). A low end-tidal CO2 (EtCO2 < 32 mmHg) had positive (LR+) and negative (LR-) likelihood ratios of 4.68 (95% CI 2.59-8.45) and 0.34 (95% CI 0.19-0.61) for acidemia, respectively-corresponding to sensitivity 71.4% (95% CI 51.3-86.8) and specificity 84.7% (95% CI 74.3-92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76-0.94, p = 0.00). Waveform analysis further revealed characteristically abnormal capnograms that were associated with underlying pathophysiology. CONCLUSIONS: Capnography is a quantitative method of screening acidemia in patients and can be implemented feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes such as sepsis or can serve as an early indicator of clinical deterioration.

Ultrasonography Imaging versus Waveform Capnography in Detecting Endotracheal Tube Placement during Intubation at a Tertiary Hospital.

Background: There is continued research to find new faster, highly accurate, easily accessible, and portable methods of confirming endotracheal tube position during intubation. A newer modality for visualizing endotracheal tube location is transtracheal or transcricothyroid ultrasonography. The aim of this study was to see if ultrasound machine can also be routinely used for the confirmation of endotracheal tube position in operating theaters along with capnograph. Methods: The study was observational and prospective, conducted from January 2017 to July 2017. Study locations were at the Tribhuvan University Teaching Hospital and Manmohan Cardiothoracic Vascular and Transplant Center operating rooms. Sample size taken was 95. Results: In the study, 11 patients had esophageal intubation out of the 95. The accuracy of both ultrasonography and capnography was found to be 96.84%. For ultrasonography, the sensitivity, specificity, along with positive predictive value and negative predictive value were 97.62%, 90.91%, 98.80%, and 83.33%, respectively, while that for capnography were found to be 96.43%, 100%, 100%, and 78.57%, respectively. The kappa value was calculated to be 0.749, which suggested the degree of agreement of result between the methods to be good. Compared to capnography, ultrasonography was found to be significantly faster for the confirmation of endotracheal tube location by 16.36 s (15.70-17.02) (P = 0.011). Conclusion: Both waveform capnography and ultrasonography were found to be accurate and reliable in confirming endotracheal tube location. The use of ultrasound during intubation can help confirm endotracheal tube location faster and also aid in precision when used along with capnography. Manual bag ventilations are not necessary when confirming endotracheal tube position by ultrasonography and thus may help in preventing aspiration of gastric contents into the lungs of the patient.

Navigating Pediatric Capnography: A Comprehensive Review of Scope and Limitations.

This review comprehensively explores pediatric capnography, a vital tool in contemporary respiratory monitoring. The overview encompasses the foundational principles of capnography, elucidating its real-time measurement of carbon dioxide (CO2) in respiratory gases. The review emphasizes its paramount role in pediatric care and underscores capnography's significance in detecting respiratory abnormalities and guiding timely interventions. The distinctions between mainstream and sidestream capnography, the key to understanding their applications, are meticulously outlined. Addressing the importance of ongoing research and education, the review advocates for a dynamic approach to refine guidelines and optimize capnography utilization in pediatric settings. The conclusion reflects on the scope and limitations of pediatric capnography, acknowledging its transformative impact while advocating for a judicious recognition of constraints. As we navigate the future of pediatric respiratory care, the synergy of research, education, and clinical application emerges as the cornerstone for advancing pediatric capnography to new horizons.

Assessing the cost-effectiveness of capnography for end-tidal CO2 monitoring during in-hospital cardiac arrest: A middle-income country perspective analysis.

Study objective: To evaluate the cost-effectiveness of EtCO2 monitoring during in-hospital cardiorespiratory arrest (CA) care outside the intensive care unit (ICU) and emergency room department. Design: We performed a cost-effectiveness analysis based on a simple decision model cost analysis and reported the study using the CHEERS checklist. Model inputs were derived from a retrospective Brazilian cohort study, complemented by information obtained through a literature review. Cost inputs were gathered from both literature sources and contacts with hospital suppliers. Setting: The analysis was carried out from the perspective of a tertiary referral hospital in a middle-income country. Participants: The study population comprised individuals experiencing in-hospital CA who received cardiopulmonary resuscitation (CPR) by rapid response team (RRT) in a hospital ward, not in the ICU or emergency room department. Interventions: Two strategies were assumed for comparison: one with an RRT delivering care without capnography during CPR and the other guiding CPR according to the EtCO2 waveform. Main outcome measures: Incremental cost-effectiveness rate (ICER) to return of spontaneous circulation (ROSC), hospital discharge, and hospital discharge with good neurological outcomes. Results: The ICER for EtCO2 monitoring during CPR, resulting in an absolute increase of one more case with ROSC, hospital discharge, and hospital discharge with good neurological outcome, was calculated at Int$ 515.78 (361.57-1201.12), Int$ 165.74 (119.29-248.4), and Int$ 240.55, respectively. Conclusion: In managing in-hospital CA in the hospital ward, incorporating EtCO2 monitoring is likely a cost-effective measure within the context of a middle-income country hospital with an RRT.

An Individual Barrier Enclosure Actively Removing Aerosols for Airborne Isolation: A Vacuum Tent.

BACKGROUND: Aerosol barrier enclosure systems have been designed to prevent airborne contamination, but their safety has been questioned. A vacuum tent was designed with active continuous suctioning to minimize risks of aerosol dispersion. We tested its efficacy, risk of rebreathing, and usability on a bench, in healthy volunteers, and in an ergonomic clinical assessment study. METHODS: First, a manikin with airway connected to a breathing simulator was placed inside the vacuum tent to generate active breathing, cough, and CO2 production; high-flow nasal cannula (HFNC) was applied in the manikin's nares. Negative pressure was applied in the vacuum tent's apex port using wall suction. Fluorescent microparticles were aerosolized in the vacuum tent for qualitative assessment. To quantify particles inside and around vacuum tent (aerosol retention), an airtight aerosol chamber with aerosolized latex microparticles was used. The vacuum tent was tested on healthy volunteers breathing with and without HFNC. Last, its usability was assessed in 5 subjects by 5 different anesthesiologists for delivery of full anesthesia, including intubation and extubation. RESULTS: The vacuum tent was adjusted until no leak was visualized using fluorescent particles. The efficacy in retaining microparticles was confirmed quantitatively. CO2 accumulation inside the vacuum tent showed an inverse correlation with the suction flow in all conditions (normal breathing and HFNC 30 or 60 L/min) in bench and healthy volunteers. Particle removal efficacy and safe breathing conditions (CO2, temperature) were reached when suctioning was at least 60 L/min or 20 L/min > HFNC flow. Five subjects were successfully intubated and anesthetized without ergonomic difficulties and with minimal interference with workflow and an excellent overall assessment by the anesthesiologists. CONCLUSIONS: The vacuum tent effectively minimized aerosol dispersion. Its continuous suction system set at a high suction flow was crucial to avoid the spread of aerosol particles and CO2 rebreathing.

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.

Assessing the prediction of arterial CO2 from end tidal CO2 in adult blunt trauma patients.

BACKGROUND: The control of PaCO2 in ventilated patients is known to be of particular importance in the management and prognosis of trauma patients. Although EtCO2 is often used as a continuous, non-invasive, surrogate marker for PaCO2 in ventilated trauma patients in the emergency department (ED), previous studies suggest a poor correlation in this cohort. However, previous data has predominantly been collected retrospectively, raising the possibility that the elapsed time between PaCO2 sampling and EtCO2 recording may contribute to the poor correlation. As such this study aimed to analyse the correlation of PaCO2 to EtCO2 in the ventilated blunt trauma patient presenting to the ED through contemporaneous sampling. METHODS: This study was conducted as a prospective observational study analysing the near simultaneous recording of EtCO2 and Arterial Blood Gas sampling of ventilated adult trauma patients in the ED of a Level 1 trauma centre over a 12-month period. Data was analysed using linear regression and subgroup analysis by Injury Severity Score (ISS) and Abbreviated Injury Score (AIS) of the Chest. RESULTS: Linear regression of EtCO2 vs PaCO2 demonstrated a moderate correlation with r = 0.54 (p < 0.01, n = 51, 95 % CI 0.31-0.71). Subgroup analysis by ISS, revealed a stronger correlation in those with minor ISS (0-11) (r = 0.76, p < 0.01, n = 13, 95 % CI 0.36-0.92) compared to those more severely injured patients (ISS > 15) (r = 0.44, P < 0.01, n = 38, 95 % CI 0.14-0.67). Analysis by AIS Chest demonstrated similar correlation between patients without chest injuries (AIS 0) (r = 0.55, n = 29, p < 0.01, 95 % CI 0.23-0.76) and those with an AIS >1 (r = 0.51, n = 22, p = 0.02, 95 % CI 0.11-0.77). In patients with traumatic head injuries who had an EtCO2 between 30 and 39 mmHg, only 57 % had a measured PaCO2 within 5 mmHg. CONCLUSIONS: As patients transition from minor to seriously injured, a decreasing strength of PaCO2 to EtCO2 correlation is observed, decreasing the reliability of EtCO2 as a surrogate marker of PaCO2 in this patient group. This inconsistency cannot be accounted for by the presence of chest injuries and worryingly is frequently seen in those with traumatic brain injuries.

Utility of non-invasive monitoring of exhaled carbon dioxide and perfusion index in adult patients in the emergency department.

BACKGROUND: Several noninvasive solutions are available for the assessment of patients at risk of deterioration. Capnography, in the form of end-tidal exhaled CO2 (ETCO2) and perfusion index (PI), could provide relevant information about patient prognosis. The aim of the present project was to determine the association of ETCO2 and PI with mortality of patients admitted to the emergency department (ED). METHODS: Multicenter, prospective, cohort study of adult patients with acute disease who needed continuous monitoring in the ED. The study included two tertiary hospitals in Spain between October 2022 and June 2023. The primary outcome of the study was in-hospital mortality (all-cause). Demographics, vital signs, ETCO2 and PI were collected. RESULTS: A total of 687 patients were included in the study. The in-hospital mortality rate was 6.8%. The median age was 79 years (IQR: 69-86), and 63.3% were males. The median ETCO2 value was 30 mmHg (26-35) in survivors and 23 mmHg (16-30) in nonsurvivors (p = 0.001). For the PI, the medians were 4.7% (2.8-8.1) for survivors and 2.5% (0.98-4-4) for nonsurvivors (p < 0.001). The model that presented the best AUC was age (odds ratio (OR): 1.02 (1.00-1.05)), the respiratory rate (OR: 1.06 (1.02-1.11)), and the PI (OR: 0.83 (0.75-0.91)), with a result of 0.840 (95% CI: 0.795-0.886); the model with the respiratory rate (OR: 1.05 (1.01-1.10)), the PI (OR: 0.84 (0.76-0.93)), and the ETCO2 (no statistically significant OR), with an AUC of 0.838 (95% CI: 0.787-0.889). CONCLUSIONS: The present study showed that the PI and respiratory rate are independently associated with in-hospital mortality. Both the PI and ETCO2 are predictive parameters with improved prognostic performance compared with that of standard vital signs.

Thoracic impedance pneumography in propofol-sedated patients undergoing percutaneous endoscopic gastrostomy (PEG) placement in gastrointestinal endoscopy: A prospective, randomized trial.

STUDY OBJECTIVE: To assess the efficacy of an ECG-based method called thoracic impedance pneumography to reduce hypoxic events in endoscopy. DESIGN: This was a single center, 1:1 randomized controlled trial. SETTING: The trial was conducted during the placement of percutaneous endoscopic gastrostomy (PEG). PATIENTS: 173 patients who underwent PEG placement were enrolled in the present trial. Indication was oncological in most patients (89%). 58% of patients were ASA class II and 42% of patients ASA class III. INTERVENTIONS: Patients were randomized in the standard monitoring group (SM) with pulse oximetry and automatic blood pressure measurement or in the intervention group with additional thoracic impedance pneumography (TIM). Sedation was performed with propofol by gastroenterologists or trained nurses. MEASUREMENTS: Hypoxic episodes defined as SpO2 < 90% for >15 s were the primary endpoint. Secondary endpoints were minimal SpO2, apnea >10s/>30s and incurred costs. MAIN RESULTS: Additional use of thoracic impedance pneumography reduced hypoxic episodes (TIM: 31% vs SM: 49%; p = 0.016; OR 0.47; NNT 5.6) and elevated minimal SpO2 per procedure (TIM: 90.0% ± 8.9; SM: 84.0% ± 17.6; p = 0.007) significantly. Apnea events >10s and > 30s were significantly more often detected in TIM (43%; 7%) compared to SM (1%; 0%; p < 0.001; p = 0.014) resulting in a time advantage of 17 s before the occurrence of hypoxic events. As a result, adjustments of oxygen flow were significantly more often necessary in SM than in TIM (p = 0.034) and assisted ventilation was less often needed in TIM (2%) compared with SM (9%; p = 0.053). Calculated costs for the additional use of thoracic impedance pneumography were 0.13$ (0.12 €/0.11 £) per procedure. CONCLUSIONS: Additional thoracic impedance pneumography reduced the quantity and extent of hypoxic events with less need of assisted ventilation. Supplemental costs per procedure were negligible. KEY WORDS: thoracic impedance pneumography, capnography, sedation, monitoring, gastrointestinal endoscopy, percutaneous endoscopic gastrostomy.

Comparison of Upper Airway Ultrasonography Against Quantitative Waveform Capnography for Validating Endotracheal Tube Position in a South Indian Population.

INTRODUCTION: The utilization of ultrasonography (USG) is progressively growing to verify the accurate positioning of the endotracheal tube (ETT). Non-detection of the esophageal intubation can be fatal. Various techniques are employed to confirm the placement of the ETT, but none of them are considered optimal. Quantitative waveform capnography (qWC) is often regarded as the most reliable method for this purpose; however, it may not necessarily be accessible and can be expensive. Hence, this investigation was carried out to contrast the use of bedside upper airway USG with qWC in order to confirm the accurate positioning of the ETT following intubation.  Methods: A prospective validation study was undertaken in the emergency department (ED) of Lourdes Hospital, Kochi. This study includes subjects who are of the age group >18 years of either sex requiring intubation in the ED for causes like respiratory failure, cardiac arrest, coma, head injury, and poisoning and cases in which intubation was achieved in the first attempt. The sample size calculated was 77. Intubation in our ED includes both elective and emergency. For all the patients undergoing intubation, consent was taken before the procedure (from close relatives of the patients) by another staff after explaining the procedure to be conducted by the doctor. Following the acquisition of consent, the intubation procedure was executed in accordance with the established hospital protocol. This protocol included verifying the intubation's success as well as employing clinical techniques such as observing bilateral chest expansion, conducting a five-point auscultation, and monitoring pulse oximetry. Furthermore, USG was employed to assess the positioning of the ETT placement. The time taken by each of these methods to confirm tube placement was noted, and the findings were assessed for the sensitivity (SN) and specificity (SP) of USG against the gold standard qWC to confirm endotracheal intubation. RESULTS: Eighty patients were enrolled in the study. All 80 patients were subjected to both ultrasound and end-tidal carbon dioxide (EtCO2). Of the 80 patients, six subjects (7.5%) underwent esophageal intubation, which was observed through the use of USG. Four patients had esophageal intubations and were correctly detected by EtCO2. All four esophageal intubations were correctly confirmed by EtCO2. Additionally, USG detected six intubations, out of which four were true and two were tracheal which was correctly confirmed by EtCO2. The bedside upper airway USG demonstrated an SN of 78 subjects at 97.4% (95% CI: 90.8-99.7%), an SP of 80 subjects at 100% (95% CI: 39.7-100%), a positive predictive value of 80 subjects at 100% (95% CI: 93.8-100%), and a negative predictive value of 53 subjects at 66.7% (95% CI: 33.7-88.7%). A positive test had an infinite likelihood ratio, whereas a negative test had a likelihood ratio of 0.03 (95% CI: 0.01-0.10). The average duration for confirmation by USG was 10.10 seconds.  Conclusion: The study's outcomes highlight the importance of incorporating USG into the clinical toolkit of ED physicians, ultimately contributing to enhanced patient safety and the optimization of endotracheal intubation procedures in the ED.

A dose-ranging study of the physiological and self-reported effects of repeated, rapid infusion of remifentanil in people with opioid use disorder and physical dependence on fentanyl.

RATIONALE: Understanding mechanisms of drug use decisions will inform the development of treatments for opioid use disorder (OUD). Decision-making experiments using neurobehavioral approaches require many trials or events of interest for statistical analysis, but the pharmacokinetics of most opioids limit dosing in humans. OBJECTIVES: This experiment characterized the effects of repeated infusions of the ultra-short acting opioid remifentanil in people with OUD and physical opioid dependence. METHODS: An inpatient study using a within-subjects, single-blind, escalating, within-session, pre-post design was conducted. Seven (3 female) subjects were maintained on oral oxycodone (40-60 mg, 4x/day = 160-240 total mg/day) for seven days prior to the dose-ranging session. Subjects received infusions of three ascending remifentanil doses (0.03, 0.1, 0.3 mcg/kg/infusion in 2 subjects; 0.1, 0.3, 1.0 mcg/kg/infusion in 5 subjects) every minute for 40 min per dose, with infusions administered over 5 s to model naturalistic delivery rates. End tidal carbon dioxide, respiration rate, oxygen saturation (SpO2) and heart rate were measured continuously. Blood pressure (BP), pupil diameter and self-reported drug effects were measured every 5 min. RESULTS: Pupil diameter, SpO2 and systolic BP decreased, and ratings on prototypic subjective effects questionnaire items increased, as a function of remifentanil dose. The number of infusions held because of sedation or physiological parameters exceeding predetermined cutoffs also increased with dose. CONCLUSIONS: This experiment established doses and procedures for the safe delivery of rapid, repeated remifentanil infusions to individuals with OUD and physical fentanyl dependence, which can be applied to the mechanistic study of opioid use decisions.

Changes in lung mechanics and ventilation-perfusion match: comparison of pulmonary air- and thromboembolism in rats.

BACKGROUND: Pulmonary air embolism (AE) and thromboembolism lead to severe ventilation-perfusion defects. The spatial distribution of pulmonary perfusion dysfunctions differs substantially in the two pulmonary embolism pathologies, and the effects on respiratory mechanics, gas exchange, and ventilation-perfusion match have not been compared within a study. Therefore, we compared changes in indices reflecting airway and respiratory tissue mechanics, gas exchange, and capnography when pulmonary embolism was induced by venous injection of air as a model of gas embolism or by clamping the main pulmonary artery to mimic severe thromboembolism. METHODS: Anesthetized and mechanically ventilated rats (n = 9) were measured under baseline conditions after inducing pulmonary AE by injecting 0.1 mL air into the femoral vein and after occluding the left pulmonary artery (LPAO). Changes in mechanical parameters were assessed by forced oscillations to measure airway resistance, lung tissue damping, and elastance. The arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were determined by blood gas analyses. Gas exchange indices were also assessed by measuring end-tidal CO2 concentration (ETCO2), shape factors, and dead space parameters by volumetric capnography. RESULTS: In the presence of a uniform decrease in ETCO2 in the two embolism models, marked elevations in the bronchial tone and compromised lung tissue mechanics were noted after LPAO, whereas AE did not affect lung mechanics. Conversely, only AE deteriorated PaO2, and PaCO2, while LPAO did not affect these outcomes. Neither AE nor LPAO caused changes in the anatomical or physiological dead space, while both embolism models resulted in elevated alveolar dead space indices incorporating intrapulmonary shunting. CONCLUSIONS: Our findings indicate that severe focal hypocapnia following LPAO triggers bronchoconstriction redirecting airflow to well-perfused lung areas, thereby maintaining normal oxygenation, and the CO2 elimination ability of the lungs. However, hypocapnia in diffuse pulmonary perfusion after AE may not reach the threshold level to induce lung mechanical changes; thus, the compensatory mechanisms to match ventilation to perfusion are activated less effectively.