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.

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.

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.

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.

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.

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.

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 Fβ score with β = 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 Fβ score of 0.94 (with β = 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.

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.

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. .

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.

Monitoring persistent pulmonary hypertension of the newborn using the arterial to end tidal carbon dioxide gradient

Persistent pulmonary hypertension of the newborn (PPHN) can be monitored theoretically by the difference of the partial pressure of arterial (PaCO2) to end-tidal CO2 (EtCO2). We aimed to test the hypothesis that the PaCO2-EtCO2 gradient in infants with PPHN would be higher compared to infants without PPHN. Prospective, observational study of term-born ventilated infants with echocardiographically-confirmed PPHN with right-to-left shunting and term-born control infants without respiratory disease. The PaCO2-EtCO2 gradient was calculated as the difference between the PaCO2 measured from indwelling arterial sample lines and EtCO2 measured by continuous Microstream sidestream capnography. Twenty infants (9 with PPHN and 11 controls) were studied with a median (IQR) gestational age of 39.5 (38.7-40.4) weeks, a birthweight of 3.56 (3.15-3.93) kg and a birthweight z-score of 0.03 (- 0.91 to 1.08). The PaCO2-EtCO2 gradient was larger in the infants with PPHN compared to those without PPHN after adjusting for differences in the mean airway pressure and fraction of inspired oxygen (adjusted p = 0.037). In the infants with PPHN the median PaCO2-EtCO2 gradient decreased from 10.7 mmHg during the acute illness to 3.3 mmHg pre-extubation. The median difference in the gradient was significantly higher in infants with PPHN (6.2 mmHg) compared to infants without PPHN (-3.2 mmHg, p = 0.022). The PaCO2-EtCO2 gradient was higher in infants with PPHN compared to term born infants without PPHN and decreased over the first week of life in infants with PPHN. The gradient might be utilised to monitor the evolution and resolution of PPHN.

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.

Korean clinical practice guidelines for diagnostic and procedural sedation

Safe and effective sedation depends on various factors, such as the choice of sedatives, sedation techniques used, experience of the sedation provider, degree of sedation-related education and training, equipment and healthcare worker availability, the patient's underlying diseases, and the procedure being performed. The purpose of these evidence-based multidisciplinary clinical practice guidelines is to ensure the safety and efficacy of sedation, thereby contributing to patient safety and ultimately improving public health. These clinical practice guidelines comprise 15 key questions covering various topics related to the following: the sedation providers; medications and equipment available; appropriate patient selection; anesthesiologist referrals for high-risk patients; pre-sedation fasting; comparison of representative drugs used in adult and pediatric patients; respiratory system, cardiovascular system, and sedation depth monitoring during sedation; management of respiratory complications during pediatric sedation; and discharge criteria. The recommendations in these clinical practice guidelines were systematically developed to assist providers and patients in sedation-related decision making for diagnostic and therapeutic examinations or procedures. Depending on the characteristics of primary, secondary, and tertiary care institutions as well as the clinical needs and limitations, sedation providers at each medical institution may choose to apply the recommendations as they are, modify them appropriately, or reject them completely.

End-tidal carbon dioxide after sodium bicarbonate infusion during mechanical ventilation or ongoing cardiopulmonary resuscitation

PURPOSE

End-tidal CO2 is used to monitor the ventilation status or hemodynamic efficacy during mechanical ventilation or cardiopulmonary resuscitation (CPR), and it may be affected by various factors including sodium bicarbonate administration. This study investigated changes in end-tidal CO2 after sodium bicarbonate administration.

MATERIALS AND METHODS

This single-center, prospective observational study included adult patients who received sodium bicarbonate during mechanical ventilation or CPR. End-tidal CO2 elevation was defined as an increase of ≥20% from the baseline end-tidal CO2 value. The time to initial increase (lag time, Tlag), time to peak (Tpeak), and duration of the end-tidal CO2 rise (Tduration) were compared between the patients with spontaneous circulation (SC group) and those with ongoing resuscitation (CPR group).

RESULTS

Thirty-three patients, (SC group, n = 25; CPR group, n = 8), were included. Compared with the baseline value, the median values of peak end-tidal CO2 after sodium bicarbonate injection increased by 100% (from 21 to 41 mmHg) in all patients, 89.5% (from 21 to 39 mmHg) in the SC group, and 160.2% (from 15 to 41 mmHg) in the CPR group. The median Tlag was 17 s (IQR: 12-21) and the median Tpeak was 35 s (IQR: 27-52). The median Tduration was 420 s (IQR: 90-639). The median Tlag, Tpeak, and Tduration were not significantly different between the groups. Tduration was associated with the amount of sodium bicarbonate for SC group (correlation coefficient: 0.531, p = 0.006).

CONCLUSION

The administration of sodium bicarbonate may lead to a substantial increase in end-tidal CO2 for several minutes in patients with spontaneous circulation and in patients with ongoing CPR. After intravenous administration of sodium bicarbonate, the use of end-tidal CO2 pressure as a physiological indicator may be limited.

Indirect cardiac output assessment in a swine pediatric acute respiratory distress syndrome model

PURPOSE

To investigate the correlation between volume of carbon dioxide elimination (V̇CO2) and end-tidal carbon dioxide (PETCO2) with cardiac output (CO) in a swine pediatric acute respiratory distress syndrome (ARDS) model.

METHODS

Respiratory and hemodynamic variables were collected from twenty-six mechanically ventilated juvenile pigs under general anesthesia before and after inducing ARDS, using oleic acid infusion.

RESULTS

Prior to ARDS induction, mean (SD) CO, V̇CO2, PETCO2, and dead space to tidal volume ratio (Vd/Vt) were 4.16 (1.10) L/min, 103.69 (18.06) ml/min, 40.72 (3.88) mmHg and 0.25 (0.09) respectively. Partial correlation coefficients between average CO, V̇CO2, and PETCO2 were 0.44 (95% confidence interval: 0.18-0.69) and 0.50 (0.18-0.74), respectively. After ARDS induction, mean CO, V̇CO2, PETCO2, and Vd/Vt were 3.33 (0.97) L/min, 113.71 (22.97) ml/min, 50.17 (9.73) mmHg and 0.40 (0.08). Partial correlations between CO and V̇CO2 was 0.01 (-0.31 to 0.37) and between CO and PETCO2 was 0.35 (-0.002 to 0.65).

CONCLUSION

ARDS may limit the utility of volumetric capnography to monitor CO.

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.

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.

Incidence of postoperative opioid-induced respiratory depression episodes in patients on room air or supplemental oxygen: a post-hoc analysis of the PRODIGY trial

BACKGROUND

Supplemental oxygen (SO) potentiates opioid-induced respiratory depression (OIRD) in experiments on healthy volunteers. Our objective was to examine the relationship between SO and OIRD in patients on surgical units.

METHODS

This post-hoc analysis utilized a portion of the observational PRediction of Opioid-induced respiratory Depression In patients monitored by capnoGraphY (PRODIGY) trial dataset (202 patients, two trial sites), which involved blinded continuous pulse oximetry and capnography monitoring of postsurgical patients on surgical units. OIRD incidence was determined for patients receiving room air (RA), intermittent SO, or continuous SO. Generalized estimating equation (GEE) models, with a Poisson distribution, a log-link function and time of exposure as offset, were used to compare the incidence of OIRD when patients were receiving SO vs RA.

RESULTS

Within the analysis cohort, 74 patients were always on RA, 88 on intermittent and 40 on continuous SO. Compared with when on RA, when receiving SO patients had a higher risk for all OIRD episodes (incidence rate ratio [IRR] 2.7, 95% confidence interval [CI] 1.4-5.1), apnea episodes (IRR 2.8, 95% CI 1.5-5.2), and bradypnea episodes (IRR 3.0, 95% CI 1.2-7.9). Patients with high or intermediate PRODIGY scores had higher IRRs of OIRD episodes when receiving SO, compared with RA (IRR 4.5, 95% CI 2.2-9.6 and IRR 2.3, 95% CI 1.1-4.9, for high and intermediate scores, respectively).

CONCLUSIONS

Despite oxygen desaturation events not differing between SO and RA, SO may clinically promote OIRD. Clinicians should be aware that postoperative patients receiving SO therapy remain at increased risk for apnea and bradypnea.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02811302, registered June 23, 2016.

A neonatal in-vitro study on the effect of the inflation pressure on end-tidal carbon dioxide levels

BACKGROUND

Describing the association of the peak inflation pressure (PIP) with end-tidal carbon dioxide (ETCO2) is a prerequisite for the development of closed loop ventilation in neonatal intensive care. We aimed to develop an in-vitro system to study this relationship.

METHODS

A ventilator was connected to a test lung, supplied with a stable CO2 concentration from a cylinder. The PIP was altered and the change in ETCO2 per unit of PIP was calculated in three models mimicking respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) and viral bronchiolitis.

RESULTS

The median (IQR) change in ETCO2 per unit of PIP was 0.23(0.13-0.38) kPa/cmH2O, using 138 paired measurements of PIP and ETCO2. The median (IQR) change in ETCO2 per unit of PIP, was higher when starting at an ETCO2 > 6 kPa [0.43(0.33-0.58) kPa/cmH2O] compared to starting at an ETCO2 < 6 kPa [0.14(0.08-0.20) kPa/cmH2O, p < 0.001]. The median (IQR) change in ETCO2 per unit of PIP, was larger in the model of RDS [0.33(0.13-0.51) kPa/cmH2O] compared to the BPD [0.23(0.13-0.33) kPa/cmH2O, p = 0.043] and the bronchiolitis models [0.15(0.10-0.31) kPa/cmH2O, p = 0.017].

CONCLUSIONS

The change in ETCO2 in response to increasing PIP was larger for higher ETCO2 values and in a model simulating neonatal RDS, compared to BPD and bronchiolitis.

Deep learning classification of capnography waveforms: secondary analysis of the PRODIGY study

Capnography monitors trigger high priority 'no breath' alarms when CO2 measurements do not exceed a given threshold over a specified time-period. False alarms occur when the underlying breathing pattern is stable, but the alarm is triggered when the CO2 value reduces even slightly below the threshold. True 'no breath' events can be falsely classified as breathing if waveform artifact causes an aberrant spike in CO2 values above the threshold. The aim of this study was to determine the accuracy of a deep learning approach to classifying segments of capnography waveforms as either 'breath' or 'no breath'. A post hoc secondary analysis of data from 9 North American sites included in the PRediction of Opioid-induced Respiratory Depression In Patients Monitored by capnoGraphY (PRODIGY) study was conducted. We used a convolutional neural network to classify 15 s capnography waveform segments drawn from a random sample of 400 participants. Loss was calculated over batches of 32 using the binary cross-entropy loss function with weights updated using the Adam optimizer. Internal-external validation was performed by iteratively fitting the model using data from all but one hospital and then assessing its performance in the remaining hospital. The labelled dataset consisted of 10,391 capnography waveform segments. The neural network's accuracy was 0.97, precision was 0.97 and recall was 0.96. Performance was consistent across hospitals in internal-external validation. The neural network could reduce false capnography alarms. Further research is needed to compare the frequency of alarms derived from the neural network with the standard approach.

Capnography as a tool for triaging and diagnosis of diabetic ketoacidosis in the emergency department: A prospective observational study

OBJECTIVES

The cornerstone of management of acidosis in a patient with diabetic ketoacidosis (DKA) has traditionally been carried out by blood gas analysis, which is expensive and associated with significant risk. It is against this background that the correlation between end-tidal carbon dioxide (EtCO₂), blood pH, and EtCO₂ bicarbonate levels was analyzed. The predictive value of EtCO₂ was also analyzed in the diagnosis of DKA. Finally, we aimed to determine the value of EtCO₂ as a screening test for the exclusion of DKA.

MATERIALS AND METHODS

This was a prospective cohort study carried out in the emergency department of a tertiary care teaching hospital from September 2020 to September 2021. Patients with suspected DKA underwent simultaneous blood gas collection and EtCO₂ analysis.

RESULTS

A total of 123 patients with blood sugar levels >250 mg/dl and moderate-to-large (≥2+) urine ketones were studied. A cut-off value of EtCO₂ ≤24 was determined to rule in DKA with a sensitivity of 93.02% and specificity of 91.9%. EtCO₂ >26 could effectively rule out the diagnosis of DKA with sensitivity of 98.8% and specificity of 75.7%. A significant linear correlation between pH and EtCO₂ (P < 0.0001, r = 0.82) and HCO3 and EtCO₂ (r = 0.896, P < 0.0001) was found.

CONCLUSIONS

EtCO₂ values ≤24 can accurately identify patients with DKA in the presence of elevated blood sugar and urinary ketones and must be considered a valuable addition to the diagnostic criteria. EtCO₂ values >26 can be an effective triaging tool for ruling our DKA. A significant linear correlation between pH and EtCO₂ and pH and HCO3 was observed. EtCO₂ can be considered a surrogate marker for the degree of response to the treatment in DKA.

Technical validation of the EMMA capnometer under hyperbaric conditions

INTRODUCTION

End-tidal carbon dioxide (ETCO2) monitoring is essential for monitoring intubated critical care patients, yet its use in hyperbaric environments can be problematic. We postulated that the EMMA mainstream capnometer may function accurately under hyperbaric conditions.

METHODS

Stage 1. The EMMA mainstream capnometer was tested at 101 kPa against a reference side-stream capnometer, Philips IntelliVue M3015B microstream, using 10 customised reference gases of various carbon dioxide (CO₂) concentrations (2.47%-8.09%, or 18.5-60.7 mmHg at 101 kPa) in either air or oxygen. Stage 2. The functionality and accuracy of the EMMA capnometer was tested under hyperbaric conditions, 121-281 kPa, using the same test gases.

RESULTS

At 101 kPa, the EMMA capnometer measured CO₂ at levels lower than expected (mean of differences = -2.5 mmHg (95% CI -2.1 to -2.9, P < 0.001)). The Philips capnometer measured CO₂ more closely to expected CO₂ (mean of differences = -1.1 mmHg (95% CI -0.69 to -1.4, P < 0.001). Both devices demonstrated a significant linear relationship with expected CO₂. The EMMA capnometer functioned up to the maximum test pressure (281 kPa). The device over-read CO₂ measurements at pressures > 141 kPa. Although variance increased at pressures in the therapeutic range for hyperbaric treatments, a significant linear relationship between expected and EMMA measured CO₂ was demonstrated. The EMMA capnometer tolerated pressures to 281 kPa, but its display was limited to CO₂ < 99 mmHg.

CONCLUSIONS

This study validated EMMA capnometer function to 281 kPa in the hyperbaric environment. The device over-read CO₂ measurements at pressures >141 kPa, however there was a linear relationship between expected and measured CO₂. The EMMA capnometer may be clinically useful for monitoring expired CO₂ in patients undergoing hyperbaric oxygen treatment.

The effect of capnography on the incidence of hypoxia during sedation for EGD and colonoscopy in mildly obese patients: a randomized, controlled study

BACKGROUND

By continually monitoring end-tidal carbon dioxide concentrations, capnography can detect abnormal ventilation or apnoea early. This randomized, controlled study explored the effect of early intervention with capnography on the incidence of hypoxia in mildly obese patients undergoing sedation for esophagogastroduodenoscopy (EGD) and colonoscopy.

METHODS

This is a single-center, randomized, single-blind, parallel-assignment, controlled trial. Mildly obese patients (28 kg/m² ≤ BMI < 40 kg/m²) undergoing sedation for EGD and colonoscopy were randomly assigned to either the standard or capnography group. Standard cardiopulmonary monitoring equipment was used in both groups, and additional capnography was performed in the capnography group. In the event of inadequate alveolar ventilation during sedation, five interventions were administered in sequence (a-e) : a: increasing oxygen flow (5 L/min); b: a chin lift or jaw thrust maneuver; c: placement of the nasopharyngeal airway and chin lift; d: mask positive-pressure ventilation, and e: ventilator-assisted ventilation with tube insertion. The primary outcome was the incidence of hypoxia (SpO₂ < 90%, ≥ 10 s) in each group. The secondary outcomes included the incidence of severe hypoxia (SpO₂ ≤ 85%), subclinical respiratory depression (90% ≤ SpO₂ < 95%), interventions, minimum SpO₂ during operation, patient satisfaction, endoscopist satisfaction, and other adverse events of anesthesia sedation.

RESULTS

228 patients were included (capnography group = 112; standard group = 113; three patients were excluded) in this study. The incidence of hypoxia was significantly lower in the capnography group than in the standard group (13.4% vs. 30.1%, P = 0.002). Subclinical respiratory depression in the capnography group was higher than that of the standard group (30.4% vs. 17.7%, P = 0.026). There was only a 5.4% incidence of severe hypoxia in the capnography group compared with 14.2% in the standard group (P = 0.026). During sedation, 96 and 34 individuals in the capnography and standard groups, respectively, underwent the intervention. There was a statistically significant difference (P < 0.0001) in the number of the last intraoperative intervention between the two groups ( a:47 vs. 1, b:46 vs. 26, c:2 vs. 5, d:1 vs. 2, e:0 vs. 0 ). No significant differences were found between the two groups in terms of minimum SpO₂ during operation, patient satisfaction, or endoscopist satisfaction rating. There was no statistically significant difference in adverse events of anesthesia sedation between the two groups.

CONCLUSION

Capnography during sedation for EGD and colonoscopy allows for the detection of apnea and altered breathing patterns in mildly obese patients before SpO₂ is reduced. Effective intervention measures are given to patients within this time frame, which reduces the incidence of hypoxia and severe hypoxia in patients.

TRIAL REGISTRATION

Ethical approval was granted by the Medical Ethics Committee (Chairperson Professor Tian Hui) of Qilu Hospital, Shandong University ((Ke) Lun Audit 2021 (186)) on 15/07/2021. The study was registered ( https://www.chictr.org.cn ) on 23/10/2021(ChiCTR2100052234). Designed and reported using CONSORT statements.

Comparison of mainstream end tidal carbon dioxide on Y-piece side versus patient side of heat and moisture exchanger filters in critically ill adult patients: a prospective observational study

The purpose of the study was to investigate the accuracy of mainstream EtCO2 measurements on the Y-piece (filtered) side of the heat and moisture exchanger filter (HMEF) in adult critically ill patients, compared to that on the patient (unfiltered) side of HMEF. We conducted a prospective observational method comparison study between July 2019 and December 2019. Critically ill adult patients receiving mechanical ventilation with HMEF were included. We performed a noninferiority comparison of the accuracy of EtCO2 measurements on the two sides of HMEF. The accuracy was measured by the absolute difference between PaCO2 and EtCO2. We set the non-inferiority margin at + 1 mmHg in accuracy difference between the two sides of HMEF. We also assessed the agreement between PaCO2 and EtCO2 using Bland-Altman analysis. Among thirty-seven patients, the accuracy difference was - 0.14 mmHg (two-sided 90% CI - 0.58 to 0.29), and the upper limit of the CI did not exceed the predefined margin of + 1 mmHg, establishing non-inferiority of EtCO2 on the Y-piece side of HMEF (P for non-inferiority < 0.001). In the Bland-Altman analyses, 95% limits of agreement between PaCO2 and EtCO2 were similar on both sides of HMEF (Y-piece side, - 8.67 to  + 10.65 mmHg; patient side, - 8.93 to  + 10.67 mmHg). The accuracy of mainstream EtCO2 measurements on the Y-piece side of HMEF was noninferior to that on the patient side in critically ill adults. Mechanically ventilated adult patients could be accurately monitored with mainstream EtCO2 on the Y-piece side of the HMEF unless their tidal volume was extremely low.

Preventing unrecognised oesophageal intubation

Major harm from unrecognised oesophageal intubation continues, despite the 2018 Royal College of Anaesthetists' 'no trace, wrong place' campaign. It is likely that publicly reported cases represent a fraction of real occurrences. This article summarises a 2022 consensus guideline on the prevention of unrecognised oesophageal intubation from the Project for Universal Management of Airway and international airway societies. The guideline is written for all airway operators and assistants, in any clinical setting, and readers are advised to deepen their understanding by studying the original guideline. The recommendations include how to avoid and recognise oesophageal intubation as well as a set of logical actions to take when it is a plausible possibility, even if it is not suspected. The guideline emphasises the importance of videolaryngoscopy, capnography and oxygen saturation monitoring for all tracheal intubations, wherever performed. It introduces the concept of sustained exhaled carbon dioxide, which is central to identifying oesophageal intubation, and acting to prevent progression to unrecognised oesophageal intubation. In the absence of sustained exhaled carbon dioxide, the default action is to remove the tube. This will mean some tracheal placed tubes are removed but based on a risk-benefit analysis, this is desirable. The tube should only be left in place if there is clear danger in removing it and in this event, its position should be confirmed, using repeat videolaryngoscopy plus one other of bronchoscopy, skilled ultrasound or use of an oesophageal detector device. The importance of human factors is underlined; for instance, the value of a shared and vocalised report of videolaryngoscopy view and trained assistants working with the operator to confirm whether the criteria for sustained exhaled carbon dioxide are met, to minimise error and improve team working.

Comparing the Effect of Respiratory Physiotherapy and Positive End-Expiratory Pressure Changes on Capnography Results in Intensive Care Unit Patients with Ventilator-Associated Pneumonia

Background

While critically ill patients experience a life-threatening illness, they commonly develop ventilator-associated pneumonia (VAP) which can increase morbidity, mortality, and healthcare costs. The present study aimed to compare the effect of respiratory physiotherapy and increased positive endexpiratory pressure (PEEP) on capnography results.

Materials and Methods

This randomized control clinical trial was performed on 80 adult patients with VAP in the intensive care unit (ICU). The patients were randomized to receive either PEEP at 5 cm H2O, followed by a moderate increase in PEEP to 10 cm H2O, or PEEP at 5 cm H2O with respiratory physiotherapy for 15 min. The numerical values were recorded on the capnograph at minutes 1, 5, 10, 15, and 30 in both methods. Data collection instruments included a checklist and MASIMO capnograph.

Results

As evidenced by the obtained results, the two methods significantly differed in the excreted pCO2 (partial pressure of carbon dioxide) (P<0.0001). However, the average amount of excreted pCO2 was higher in the respiratory physiotherapy and PEEP intervention (38.151mmHg) in comparison with increasing PEEP alone method (36.184mmHg). Also, PEEP elevation method prolonged the time of the first phase (inhalation time) and the second phase while shortening the third phase (exhalation time) in capnography waves.

Conclusion

CO2 excretion in patients with VAP increased after respiratory physiotherapy. Further, physiotherapy demonstrated more acceptable results in CO2 excretion compared with PEEP changes in mechanically ventilated patients.

Videolaryngoscopy: Channelizing through Intensive Care Unit Intubations

How to cite this article: Kothekar AT, Wajekar AS, Joshi AV. Videolaryngoscopy: Channelizing through Intensive Care Unit Intubations. Indian J Crit Care Med 2023;27(2):85-86.

Ventilation rates measured by capnography during out-of-hospital cardiac arrest resuscitations and their association with return of spontaneous circulation

BACKGROUND

Clinical guidelines for adult out-of-hospital cardiac arrest (OHCA) recommend a ventilation rate of 8-10 per minute yet acknowledge that few data exist to guide recommendations. The goal of this study was to evaluate the utility of continuous capnography to measure ventilation rates and the association with return of spontaneous circulation (ROSC).

METHODS

This was a retrospective observational cohort study. We included all OHCA during a two-year period and excluded traumatic and pediatric patients. Ventilations were recorded using non-invasive continuous capnography. Blinded medically trained team members manually annotated all ventilations. Four techniques were used to analyze ventilation rate. The primary outcome was sustained prehospital ROSC. Secondary outcomes were vital status at the end of prehospital care and survival to hospital admission. Univariable and multivariable logistic regression models were constructed.

RESULTS

A total of 790 OHCA were analyzed. Only 386 (49%) had useable capnography data. After applying inclusion and exclusion criteria, the final study cohort was 314 patients. The median ventilation rate per minute was 7 (IQR 5.4-8.5). Only 70 (22%) received a guideline-compliant ventilation rate of 8-10 per minute. Sixty-two (20%) achieved the primary outcome. No statistically significant associations were observed between any of the ventilation parameters and patient outcomes in both univariable and multivariable logistic regression models.

CONCLUSIONS

We failed to detect an association between intra-arrest ventilation rates measured by continuous capnography and proximal patient outcomes after OHCA. Capnography has poor reliability as a measure of ventilation rate. Achieving guideline-compliant ventilation rates remains challenging.

Comparison of ultrasonography, clinical method and capnography for detecting correct endotracheal tube placement- A prospective, observational study

Background and Aims

In emergency airway management, unstable haemodynamics of the patients calls for the early need to detect correct endotracheal tube (ETT) placement. Ultrasonography has an advantage of being readily available along with being non-invasive and providing real time images. We aimed to study the usefulness of tracheal ultrasonography and use it as a tool to assess correct tracheal intubation in patients in the intensive care unit.

Methods

This was a hospital-based observational study. The study included 92 patients who needed and were taken up for endotracheal intubation. Tube placement was confirmed simultaneously by three different observers with their respective method, i.e., ultrasonography, clinical method and capnography.

Results

Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of ultrasonography against capnography were 100% each with P value of 1. However, for clinical method against capnography, the sensitivity was 96.5%, specificity 28.6%, PPV 94.3% and NPV 40% with P value of 0.727. Mean time taken to detect correct placement of the ETT by ultrasonography, capnography and clinical method was 4.93 s, 15.39s and 17.80s, respectively. Out of 92 intubations, 85 were tracheal and 7 were oesophageal. All intubations were detected accurately with ultrasonography and capnography, ultrasonography being faster. Clinical method correctly detected 82 out of 85 tracheal intubations and 2 out of 7 oesophageal intubations, and was therefore less accurate than the other two methods.

Conclusion

The study shows that ultrasonography is as reliable a method for confirmation of endotracheal intubation as capnography and is more reliable than clinical method. Besides, ultrasonography is faster than the other two methods.

Expiratory high-frequency percussive ventilation: a novel concept for improving gas exchange

Background

Although high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about tissue overdistension caused by the oscillations and consequent lung damage. We compared a modified percussive ventilation modality created by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) with conventional mechanical ventilation (CMV) and standard HFPV.

Methods

Hypoxia and hypercapnia were induced by decreasing the frequency of CMV in New Zealand White rabbits (n = 10). Following steady-state CMV periods, percussive modalities with oscillations randomly introduced to the entire breathing cycle (HFPV) or to the expiratory phase alone (eHFPV) with varying amplitudes (2 or 4 cmH₂O) and frequencies were used (5 or 10 Hz). The arterial partial pressures of oxygen (PaO₂) and carbon dioxide (PaCO₂) were determined. Volumetric capnography was used to evaluate the ventilation dead space fraction, phase 2 slope, and minute elimination of CO₂. Respiratory mechanics were characterized by forced oscillations.

Results

The use of eHFPV with 5 Hz superimposed oscillation frequency and an amplitude of 4 cmH₂O enhanced gas exchange similar to those observed after HFPV. These improvements in PaO₂ (47.3 ± 5.5 vs. 58.6 ± 7.2 mmHg) and PaCO₂ (54.7 ± 2.3 vs. 50.1 ± 2.9 mmHg) were associated with lower ventilation dead space and capnogram phase 2 slope, as well as enhanced minute CO₂ elimination without altering respiratory mechanics.

Conclusions

These findings demonstrated improved gas exchange using eHFPV as a novel mechanical ventilation modality that combines the benefits of conventional and small-amplitude high-frequency oscillatory ventilation, owing to improved longitudinal gas transport rather than increased lung surface area available for gas exchange.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02215-2.

Efficacy of capnographic and bispectral index monitoring on trans-oral therapeutic endoscopy: A prospective observational study

BACKGROUND AND AIM

Oral therapeutic and invasive endoscopy requires deep sedation to reduce patient distress due to prolonged examination and procedures. The usefulness of capnography and bispectral index (BIS) monitoring in the early hypoxia detection in oral therapeutic and invasive endoscopy has yet to be evaluated. This study aimed to investigate the clinical impact of capnography and BIS monitoring on hypoxic events during oral therapeutic and invasive endoscopic procedures.

METHODS

This is a prospective observational study. Trans-oral non-intubated therapeutic and/or invasive endoscopic procedures were performed with conventional monitoring (pulse oximetry, pulse, and blood pressure) as well as additional monitoring (BIS and end-tidal CO₂ concentration). Hypoxia is defined as oxygen saturation of <90% that lasts >15 s. The clinical impact of capnography and BIS monitoring on hypoxic events during oral therapeutic and invasive endoscopic procedures were investigated with the risk factors for hypoxia in each patient.

RESULTS

Patients with hypoxia had significantly more apneas detected using capnography than other patients. The multivariate analysis revealed the detected apnea by capnography as an independent risk factor for hypoxia (odds ratio: 3.48[95% confidence interval: 1.24-9.78], P = 0.02). The BIS was not significantly different as a risk factor for hypoxia; however, per-event analysis revealed significantly decreased BIS values over time in 3 min before hypoxic events.

CONCLUSIONS

Apnea detected by capnography was an independent predictor of hypoxia. The BIS value was not associated with hypoxia events; however, it showed a significant downward trend before hypoxia events.

Capnography in newborns under mechanical ventilation and its relationship with the measurement of CO2 in blood samples

INTRODUCTION

Monitoring the partial pressure of CO₂ (PCO₂) in newborns who require ventilation would allow avoiding hypocapnia and hypercapnia. The measurement of end-tidal carbon dioxide (ETCO₂) is an alternative rarely implemented in this population.

OBJECTIVE

To evaluate the relationship between ETCO₂ and PCO₂ in newborns.

METHODS

Cross-sectional study comparing two PCO₂ measurement methods, the conventional one by analysis of blood samples and the one estimated by ETCO₂. The study included hospitalized newborns that required conventional mechanical ventilation. The ETCO₂ was measured with a Tecme GraphNet® neo, a neonatal ventilator with an integrated capnograph, and we obtained the ETCO₂-PCO₂ gradient. We conducted correlation and Bland-Altman plot analyses to estimate the agreement.

RESULTS

A total of 277 samples (ETCO₂ / PCO₂) from 83 newborns were analyzed. The mean values ​​of ETCO₂ and PCO₂ were 41.36mmHg and 42.04mmHg. There was a positive and significant correlation between ETCO₂ and PCO₂ in the overall analysis (r=0.5402; P<.001) and in the analysis of each unit (P<.001). The mean difference was 0.68 mmHg (95% CI, -0.68 to 1.95) and was not significant. We observed a positive systematic error (PCO₂ > ETCO₂) in 2 of the units, and a negative difference in the third (PCO₂ < ETCO₂).

DISCUSSION

The correlation between ETCO and PCO₂ was significant, although the obtained values ​​were not equivalent, with differences ranging from 0.1mmHg and 20mmHg. Likewise, we found systematic errors that differed in sign (positive or negative) between institutions.

Capnography for Monitoring of the Critically Ill Patient

Capnography has been widely adopted in multiple clinical areas. The capnogram and end-tidal carbon dioxide offer a wealth of information, in the right clinical setting, and when properly interpreted. In this article, the authors aim to review the most common clinical scenarios during which capnography has been shown to be of benefit. This includes the areas of fluid responsiveness, cardiopulmonary resuscitation, and conscious sedation. They review the published literature, highlighting its pitfalls and identifying its limitations.

Proposals from a French expert panel for respiratory care in ALS patients

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive diaphragm weakness and deteriorating lung function. Bulbar involvement and cough weakness contribute to respiratory morbidity and mortality. ALS-related respiratory failure significantly affects quality of life and is the leading cause of death. Non-invasive ventilation (NIV), which is the main recognized treatment for alleviating the symptoms of respiratory failure, prolongs survival and improves quality of life. However, the optimal timing for the initiation of NIV is still a matter of debate. NIV is a complex intervention. Multiple factors influence the efficacy of NIV and patient adherence. The aim of this work was to develop practical evidence-based advices to standardize the respiratory care of ALS patients in French tertiary care centres.

METHODS

For each proposal, a French expert panel systematically searched an indexed bibliography and prepared a written literature review that was then shared and discussed. A combined draft was prepared by the chairman for further discussion. All of the proposals were unanimously approved by the expert panel.

RESULTS

The French expert panel updated the criteria for initiating NIV in ALS patients. The most recent criteria were established in 2005. Practical advice for NIV initiation were included and the value of each tool available for NIV monitoring was reviewed. A strategy to optimize NIV parameters was suggested. Revisions were also suggested for the use of mechanically assisted cough devices in ALS patients.

CONCLUSION

Our French expert panel proposes an evidence-based review to update the respiratory care recommendations for ALS patients in daily practice.

PaCO2-EtCO2 Gradient and D-dimer in the Diagnosis of Suspected Pulmonary Embolism

BACKGROUND

The diagnosis of pulmonary embolism (PE) because of nonspecific clinical presentation remains as a challenge for emergency physicians. Arterial to end-tidal partial pressure of carbon dioxide (P(a-Et) CO2) gradient may be useful in the evaluation of PE. This aimed to define the diagnostic role of P(a-Et)CO2 gradient by sidestream capnography, as a noninvasive method, and D-dimer in patients with PE.

MATERIALS AND METHODS

Two hundred and three patients with chest pain or dyspnea who attend the hospital emergency ward were enrolled over a study period at a single academic center. PE was confirmed by multidetector computed tomography (MDCT) scans. PaCO2, EtCO2, and D-dimer were measured within 24 h of MDCT by capnograph.

RESULTS

The combination of P(a-Et)CO2 gradient (cutoff >9.2 ng/ml) and D-dimer (cutoff >3011 ng/ml) with sensitivity and specificity of 30.2% and 87.2% showed a significant diagnostic value in detecting PE (area under the curve = 0.577, P = 0.045) but not alone (P > 0.05).

CONCLUSION

As the results show, the combination of P(a-Et)CO2 gradient and D-dimer can show an acceptable diagnostic value in detecting PE, although it suggests further research on evaluating the diagnostic value of P(a-Et)CO2 gradient and combining it with other diagnostic criteria to achieve a definite and generalizable result.

[I-Gel® laryngeal mask versus bag-valve-mask in instrumental cardiopulmonary resuscitation under capnographic monitoring: Cluster-randomized pilot clinical trial]

OBJECTIVE

To compare the basic airway and the advanced airway with the supraglottic device I-Gel®, by means of capnography during intermediate CPR.

DESIGN

Randomized experimental pilot study by groups.

SETTING

Out-hospital care basic life support units on the Island of Mallorca.

PARTICIPANTS

Adults attended after cardiorespiratory arrest of non-traumatic origin.

INTERVENTIONS

Advanced airway management during instrumental CPR with I-Gel® or basic CPR with bag-valve-mask, under capnographic monitoring.

MAIN MEASUREMENTS

Capnometric levels obtained according to the device used, number of insertions of the I-Gel®, cases without achieving correct insertion/ventilation by branches, achievement of ROSC in CPR and number of hospital live admissions.

RESULTS

Twenty-three cases were recruited for analysis. The insertion success rate of the I-Gel® was 92.9% at the first attempt, the mean capnometric values were 16.3mmHg in the control group and 27.4% in the intervention group. 34.8% (n=8) of the patients achieved spontaneous circulation recovery at some point and 26.1% (n=6) were admitted to hospital alive. The survival analysis, taking into account the arrival of the unit and the first minute of ventilations recorded together with the variable hospital admission, suggests a certain trend of greater survival in the intervention branch (P=.066).

CONCLUSIONS

The use of I-Gel® raises an improvement in the ventilation of the patients in PCR, evidenced by the mean capnometric values in the intervention group, finding no correlation with CPR outcome variables.

Mechanical active compression-decompression versus standard mechanical cardiopulmonary resuscitation: A randomised haemodynamic out-of-hospital cardiac arrest study

BACKGROUND

Active compression-decompression cardiopulmonary resuscitation (ACD-CPR) utilises a suction cup to lift the chest-wall actively during the decompression phase (AD). We hypothesised that mechanical ACD-CPR (Intervention), with AD up to 30 mm above the sternal resting position, would generate better haemodynamic results than standard mechanical CPR (Control).

METHODS

This out-of-hospital adult non-traumatic cardiac arrest trial was prospective, block-randomised and non-blinded. We included intubated patients with capnography recorded during mechanical CPR. Exclusion criteria were pregnancy, prisoners, and prior chest surgery. The primary endpoint was maximum tidal carbon dioxide partial pressure (p_MTCO₂) and secondary endpoints were oxygen saturation of cerebral tissue (SctO₂), invasive arterial blood pressures and CPR-related injuries. Intervention device lifting force performance was categorised as Complete AD (≥30 Newtons) or Incomplete AD (≤10 Newtons). Haemodynamic data, analysed as one measurement for each parameter per ventilation (Observation Unit, OU) with non-linear regression statistics are reported as mean (standard deviation). A two-sided p-value < 0.05 was considered as statistically significant.

RESULTS

Of 221 enrolled patients, 210 were deemed eligible (Control 109, Intervention 101). The Control vs. Intervention results showed no significant differences for p_MTCO₂: 29(17) vs 29(18) mmHg (p = 0.86), blood pressures during compressions: 111(45) vs. 101(68) mmHg (p = 0.93) and decompressions: 21(20) vs. 18(18) mmHg (p = 0.93) or for SctO₂%: 55(36) vs. 57(9) (p = 0.42). The 48 patients who received Complete AD in > 50% of their OUs had higher SctO₂ than Control patients: 58(11) vs. 55(36)% (p < 0.001).

CONCLUSIONS

Mechanical ACD-CPR provided similar haemodynamic results to standard mechanical CPR. The Intervention device did not consistently provide Complete AD.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier (NCT number): NCT02479152. The Haemodynamic Effects of Mechanical Standard and Active Chest Compression-decompression During Out-of-hospital CPR.

Evaluation of the Integrated Pulmonary Index® during non-anesthesiologist sedation for percutaneous endoscopic gastrostomy

Standard monitoring of heart rate, blood pressure and arterial oxygen saturation during endoscopy is recommended by current guidelines on procedural sedation. A number of studies indicated a reduction of hypoxic (art. oxygenation < 90% for > 15 s) and severe hypoxic events (art. oxygenation < 85%) by additional use of capnography. Therefore, U.S. and the European guidelines comment that additional capnography monitoring can be considered in long or deep sedation. Integrated Pulmonary Index® (IPI) is an algorithm-based monitoring parameter that combines oxygenation measured by pulse oximetry (art. oxygenation, heart rate) and ventilation measured by capnography (respiratory rate, apnea > 10 s, partial pressure of end-tidal carbon dioxide [PetCO2]). The aim of this paper was to analyze the value of IPI as parameter to monitor the respiratory status in patients receiving propofol sedation during PEG-procedure. Patients reporting for PEG-placement under sedation were randomized 1:1 in either standard monitoring group (SM) or capnography monitoring group including IPI (IM). Heart rate, blood pressure and arterial oxygen saturation were monitored in SM. In IM additional monitoring was performed measuring PetCO2, respiratory rate and IPI. Capnography and IPI values were recorded for all patients but were only visible to the endoscopic team for the IM-group. IPI values range between 1 and 10 (10 = normal; 8-9 = within normal range; 7 = close to normal range, requires attention; 5-6 = requires attention and may require intervention; 3-4 = requires intervention; 1-2 requires immediate intervention). Results on capnography versus standard monitoring of the same study population was published previously. A total of 147 patients (74 in SM and 73 in IM) were included in the present study. Hypoxic events occurred in 62 patients (42%) and severe hypoxic events in 44 patients (29%), respectively. Baseline characteristics were equally distributed in both groups. IPI = 1, IPI < 7 as well as the parameters PetCO2 = 0 mmHg and apnea > 10 s had a high sensitivity for hypoxic and severe hypoxic events, respectively (IPI = 1: 81%/81% [hypoxic/severe hypoxic event], IPI < 7: 82%/88%, PetCO2: 69%/68%, apnea > 10 s: 84%/84%). All four parameters had a low specificity for both hypoxic and severe hypoxic events (IPI = 1: 13%/12%, IPI < 7: 7%/7%, PetCO2: 29%/27%, apnea > 10 s: 7%/7%). In multivariate analysis, only SM and PetCO2 = 0 mmHg were independent risk factors for hypoxia. IPI (IPI = 1 and IPI < 7) as well as the individual parameters PetCO2 = 0 mmHg and apnea > 10 s allow a fast and convenient conclusion on patients' respiratory status in a morbid patient population. Sensitivity is good for most parameters, but specificity is poor. In conclusion, IPI can be a useful metric to assess respiratory status during propofol-sedation in PEG-placement. However, IPI was not superior to PetCO2 and apnea > 10 s.

Diagnostic accuracy of end-tidal carbon dioxide detection in determining correct placement of nasogastric tube: An updated systematic review with meta-analysis

BACKGROUND

Misplacement of the nasogastric tube in the respiratory tract could cause serious complications and even death. Thus, nasogastric tube verification is necessary for optimal patient safety and comfort. Although end-tidal carbon dioxide detection is considered an effective approach to determine nasogastric tube location, there is a paucity of up-to-date evidence.

OBJECTIVES

To review the diagnostic accuracy of end-tidal carbon dioxide detection in determining inadvertent airway intubation and verifying correct placement of nasogastric tubes.

DESIGN

A systematic review and meta-analysis.

METHODS

We searched clinical trials that evaluated the diagnostic accuracy of colorimetric capnometry or capnography in detecting nasogastric tubes located in the airway and differentiating between inadvertent airway intubation and correct nasogastric tube placement in any adult care setting. Four English language databases - Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and CINAHL - and four Chinese language databases - China Biomedical Literature Database, WanFang Data, China National Knowledge Infrastructure, and Airiti Library - were searched from July 2009 to March 2021. Clinical trial registration databases and reference lists of included studies and relevant reviews were also searched. Two reviewers extracted the data of all included studies using a data extraction form. Two reviewers assessed the methodological quality independently with the Quality Assessment of Diagnostic Accuracy Studies-2 tool. We conducted meta-analysis using the hierarchical bivariate model and estimated the pool sensitivity and specificity of capnography and colorimetric capnometry. Forest plots were generated to display the results. Heterogeneity was investigated by meta-regression. The certainty of evidence was evaluated with the Grading of Recommendations Assessment, Development and Evaluations framework.

RESULTS

Of 1,155 records identified, seven new studies were added to this update and a total of 16 studies were analysed in the systematic review. The total absolute number of true positive, false negative, true negative, and false positive observations were 142, 6, 1,500, and 65 respectively. Low to very low certainty of evidence indicated that the use of colorimetric capnometry or capnography is potentially an effective method in differentiating between respiratory and nasogastric tube placement for critically ill adult patients. Pooled results (13 studies, 1,541 intubations) for sensitivity and specificity were 0.96 (95% confidence interval [0.88, 0.99]) and 0.99 (95% confidence interval [0.96, 1.00]), respectively.

CONCLUSIONS

Colorimetric capnometry and capnography may have the potential to be of high sensitivity and specificity for the detection of inadvertent airway nasogastric tube placements in critically ill adults. More evidence is required to generalize the updated findings to different types of patients and settings.

Tension pneumothorax decompression with colorimetric capnography: pilot case series

Tension pneumothorax is a life-threatening condition that can develop when either the visceral pleura is disrupted, or with injury to the tracheobronchial tree. Rapid, accurate diagnosis and appropriate management are required to prevent significant atelectasis, hypoxia, circulatory arrest, and ultimate patient demise. Needle decompression is the current standard of care for the management of tension pneumothorax. Healthcare providers struggle to assess the success of decompression due to a lack of any immediate objective feedback. The gaseous composition of tension pneumothorax is similar to that of end respiratory gas. This includes an increased partial pressure of carbon dioxide in comparison to atmospheric air, which makes colorimetric capnography an ideal confirmatory test. This colorimetric capnography device may help the healthcare providers to make an objective and accurate assessment of the success of the needle decompression, in particular in prehospital environments.

Ventilation Monitoring

Ventilation or breathing is vital for life yet is not well monitored in hospital or at home. Respiratory rate is a neglected vital sign and tidal volumes together with breath sounds are checked infrequently in many patients. Medications with the potential to depress ventilation are frequently administered, and may be accentuated by obesity causing airway obstruction in the form of sleep apnea. Sepsis may adversely affect ventilation by causing an increase in respiratory rate, often a very early sign of infection. Changes in ventilation may be early signs of deterioration in the patient.

Modeling the Cost Savings of Continuous Pulse Oximetry and Capnography Monitoring of United States General Care Floor Patients Receiving Opioids Based on the PRODIGY Trial

INTRODUCTION

Despite the high incidence of respiratory depression on the general care floor and evidence that continuous monitoring improves patient outcomes, the cost-benefit of continuous pulse oximetry and capnography monitoring of general care floor patients remains unknown. This study modeled the cost and length of stay savings, investment break-even point, and likelihood of cost savings for continuous pulse oximetry and capnography monitoring of general care floor patients at risk for respiratory depression.

METHODS

A decision tree model was created to compare intermittent pulse oximetry versus continuous pulse oximetry and capnography monitoring. The model utilized costs and outcomes from the PRediction of Opioid-induced respiratory Depression In patients monitored by capnoGraphY (PRODIGY) trial, and was applied to a modeled cohort of 2447 patients receiving opioids per median-sized United States general care floor annually.

RESULTS

Continuous pulse oximetry and capnography monitoring of high-risk patients is projected to reduce annual hospital cost by $535,531 and cumulative patient length of stay by 103 days. A 1.5% reduction in respiratory depression would achieve a break-even investment point and justify the investment cost. The probability of cost saving is ≥ 80% if respiratory depression is decreased by ≥ 17%. Expansion of continuous monitoring to high- and intermediate-risk patients, or to all patients, is projected to reach a break-even point when respiratory depression is reduced by 2.5% and 3.5%, respectively, with a ≥ 80% probability of cost savings when respiratory depression decreases by ≥ 27% and ≥ 31%, respectively.

CONCLUSION

Compared to intermittent pulse oximetry, continuous pulse oximetry and capnography monitoring of general care floor patients receiving opioids has a high chance of being cost-effective.

TRIAL REGISTRATION

www.clinicaltrials.gov , Registration ID: NCT02811302.

Comparisons of the efficiency of respiratory rate monitoring devices and acoustic respiratory sound during endoscopic submucosal dissection

During moderate sedation for gastrointestinal endoscopic submucosal dissection (ESD), monitoring of ventilatory function is recommended. We compared the following techniques of respiratory rate (RR) measurement with respiratory sound (RRa): capnography (RRc), thoracic impedance (RRi), and plethysmograph (RRp). This study enrolled patients aged ≥ 20 years who underwent esophageal (n = 19) and colorectal (n = 5) ESDs. RRc, RRi, RRp, and RRa were measured by Capnostream™ 20P, BSM-2300, Nellcor™ PM1000N, and Radical-7^®, respectively. In total, 413 RR data were collected from the esophageal ESD group and 114 RR data were collected from the colorectal ESD group. Compared with RRa during colorectal ESD, that during esophageal ESD had larger bias [95% limit of agreement (LOA)] with RRc [1.9 (- 11.0-14.8) vs. - 0.4 (- 2.9-2.2)], RRi [9.4 (- 16.8-9.4) vs. - 1.5 (- 12.0-8.9)], and RRp [0.3 (- 5.7-6.4) vs. 0.2 (- 3.2-3.6)]. Of the correct RR values displayed during esophageal ESD, > 90% were measured as RRa and RRp. Moreover, RRc was a useful parameter during colorectal ESD. To maximize patient safety during ESD under sedation, endoscopists and medical staff should know the feature and principle of the devices used for RR measurement. During esophageal ESD, RRa and RRp may be a good parameter to detect bradypnea or apnea. RRc, RRa and RRp are useful for reliable during colorectal ESD.Trial registration UMIN-CTR (UMIN000025421).

Use of capnography for prediction of obstruction severity in non-intubated COPD and asthma patients

BACKGROUND

Capnography waveform contains essential information regarding physiological characteristics of the airway and thus indicative of the level of airway obstruction. Our aim was to develop a capnography-based, point-of-care tool that can estimate the level of obstruction in patients with asthma and COPD.

METHODS

Two prospective observational studies conducted between September 2016 and May 2018 at Rabin Medical Center, Israel, included healthy, asthma and COPD patient groups. Each patient underwent spirometry test and continuous capnography, as part of, either methacholine challenge test for asthma diagnosis or bronchodilator reversibility test for asthma and COPD routine evaluation. Continuous capnography signal, divided into single breaths waveforms, were analyzed to identify waveform features, to create a predictive model for FEV1 using an artificial neural network. The gold standard for comparison was FEV1 measured with spirometry.

MEASUREMENTS AND MAIN RESULTS

Overall 160 patients analyzed. Model prediction included 32/88 waveform features and three demographic features (age, gender and height). The model showed excellent correlation with FEV1 (R = 0.84), R² achieved was 0.7 with mean square error of 0.13.

CONCLUSION

In this study we have developed a model to evaluate FEV1 in asthma and COPD patients. Using this model, as a point-of-care tool, we can evaluate the airway obstruction level without reliance on patient cooperation. Moreover, continuous FEV1 monitoring can identify disease fluctuations, response to treatment and guide therapy.

TRIAL REGISTRATION

clinical trials.gov, NCT02805114. Registered 17 June 2016, https://clinicaltrials.gov/ct2/show/NCT02805114.

Use of supraglottic airway devices under capnography monitoring during cardiopulmonary resuscitation: A systematic review

BACKGROUND

Bag-valve-mask ventilation is the most commonly applied method during cardiopulmonary resuscitation. Globally, advanced airway management with blind insertion devices such as supraglottic airway devices has been implemented for years by different emergency services. The efficiency of ventilation via such devices could be measured by capnography.

OBJECTIVE

The objective of this study was to determine whether capnography is useful in patients undergoing cardiopulmonary resuscitation and to assess the effectiveness of ventilation via supraglottic airway devices.

REVIEW METHODS USED

This is a systematic review written following the steps of Preferred Reporting Items for Systematic Review and Meta-analyses protocols.

DATA SOURCES

A bibliographic search was carried out from the following databases: EBSCOhost, Scopus, EMBASE, Virtual Health Library, PubMed, Cochrane Library, Spanish Medical Index, Spanish Bibliographic Index in Health Sciences, and Latin American and Caribbean Health Sciences Literature, from inception until September 2019.

REVIEW METHODS

Studies describing the use of capnography with supraglottic airway devices during cardiopulmonary resuscitation manoeuvres were selected and evaluated using the Critical Appraisal Skills Programme.

RESULTS

Twenty-four articles were identified by title and abstract: six were randomised clinical trials, 11 were nonrandomised clinical trials, six were descriptive prospective studies, and one was a descriptive retrospective study. Nine primary research articles were selected for synthesis. Only one provided objective values of capnography obtained with ventilation with these devices, correlating them with the results of resuscitation.

CONCLUSIONS

The evidence published so far is scarce, mostly from observational studies with high risk of bias in general. Although a degree of recommendation cannot be established, some results indicate that capnography has the potential to facilitate advanced clinical practice of ventilation with supraglottic airway devices during cardiopulmonary resuscitation.

Capillary blood gas in infants with bronchiolitis: Can end-tidal capnography replace it?

OBJECTIVES

To explore the predictive ability of capillary blood gas (CBG) pCO₂ for respiratory decompensation in infants aged ≤6 months with bronchiolitis admitted from the emergency department; to determine whether end-tidal CO₂ (etCO₂) capnography can serve as a less invasive substitute for CBG pCO₂.

STUDY DESIGN

This was a prospective cohort study of previously healthy infants aged ≤6 months admitted for bronchiolitis from the emergency department (ED). Initial CBG pCO₂ and etCO₂ capnography were obtained in the ED prior to inpatient admission. Simple logistic regression modeling was used to examine the associations of CBG pCO₂ and etCO₂ capnography with respiratory decompensation. Pearson's correlation measured the relationship between CBG pCO₂ and etCO₂ capnography.

RESULTS

Of 134 patients, 61 had respiratory decompensation. There was a significant association between CBG pCO₂ and respiratory decompensation (OR = 1.07, p = 0.003), even after outlying values were excluded (OR = 1.06, p = 0.005). End tidal CO₂ capnography was not significantly associated with decompensation (OR = 1.02, p = 0.17), even after outlying values were excluded (OR = 1.02, p = 0.24). There was a moderate correlation between etCO₂ capnography and CBG pCO₂ (r = 0.39, p < 0.001).

CONCLUSION

In infants with bronchiolitis, CBG pCO₂ provides an objective measure for predicting respiratory decompensation, and a single etCO₂ measurement should not replace its use.

[The end-tidal carbon dioxide as an early sign and predictor of the return of spontaneous circulation during out-of-hospital cardiac arrest. A systematic review.]

BACKGROUND

There is no clear evidence on the maximum level of end-tidal carbon dioxide (ETCO₂) predictor of the return of spontaneous circulation (RSC) after an out-of-hospital cardiorespiratory arrest. The aims of this work was to synthesise and analyse the available evidence on the usefulness of monitoring values ETCO₂ in an out-of-hospital cardiorespiratory arrest as an early sign and prognostic indicator of the RSC.

METHODS

Systematic review, with narrative synthesis of the results, of primary studies published in English or Spanish was conducted in Medline, CINAHL, Web of Science, EMBASE, Proquest, Scopus, Cochrane, ÍnDICEs CSIC and CUIDEN of studies that analyse the usefulness of monitoring of the level of ETCO₂ as a sign of the RSC after an out-of-hospital cardiorespiratory arrest. PRISMA declaration was followed. The risk of bias was assessed with the Newcastle-Ottawa Scale.

RESULTS

1,011 studies were found, eight of which fulfilled the inclusion criteria. The studies reported an association between the abrupt increase in ETCO₂ and RSC to disagree on the predictive cut-off points (an increase than 10 mmHg and initial values or three minutes greater than 10 mmHg or 19 mmHg). The studies were of moderate to high methodological quality.

CONCLUSIONS

ETCO₂ values correlate with the RSC in adults with cardiorespiratory arrest and could predict non-survival, so they should be incorporated into advanced life support algorithms and Utstein-style reports.

Comparison of ETCO2 Value and Blood Gas PCO2 Value of Patients Receiving Non-invasive Mechanical Ventilation Treatment in Emergency Department

Capnography is the non-invasive measurement and graphic representation of the partial pressure of CO2 in expiration. Although there are many studies in the literature comparing the partial pressure of carbon dioxide (pCO2) and end-tidal CO2 (ETCO2) values in patients who underwent IMV (invasive mechanical ventilation), there are no studies showing their interchangeable applicability in patients who received NIMV (non-IMV). We aimed to evaluate whether the use of ETCO2 in the treatment process can replace pCO2 use in patients scheduled for NIMV treatment in the emergency department. Patients who applied to the emergency department with respiratory distress between March 2019 and January 2020, who were diagnosed with acute cardiogenic edema or acute chronic obstructive pulmonary disease (COPD) exacerbation, and who needed NIMV were included in the study. General characteristics of the patients and the pCO2 and ETCO2 values were measured in the blood gas 1 h after the NIMV application was started. 64.2% (99 patients) of the patients included in the study were male, and 35.8% (55 patients) were female. The mean age of the patients included in the study was 69.1 ± 12.2 years. The mean pCO2 values ​​were measured as 52.6 ± 13.2. The mean of ETCO2 values ​​measured simultaneously was 33.6 ± 10.1. There was a significant difference between the controlled pCO2 values ​​and ETCO2 values ​​at the first hour of NIMV treatment (Z: - 10.640, p < 0.001). The ETCO2 level was found to be different in our patients who received NIMV treatment, which could not be used instead of the pCO2 level.

Use of noninvasive volume assessment methods to predict acute blood loss in spontaneously breathing volunteers

OBJECTIVE

The use of noninvasive volume assessment methods to predict acute blood loss in spontaneously breathing patients remains unclear. We aimed to investigate changes in the pleth variability index (PVI), vena cava collapsibility index (VCCI), end-tidal carbon dioxide (EtCO2), pulse pressure (PP), and mean arterial pressure (MAP) in spontaneously breathing volunteers after acute loss of 450 mL blood and passive leg raise (PLR).

METHODS

This prospective observational study enrolled healthy volunteers in the blood donation center of an academic hospital. We measured the PVI, EtCO2, VCCI, MAP, and PP before blood donation; at the 0th and 10th minute of blood donation; and after PLR. The primary outcome was the changes in PVI, EtCO2, VCCI, MAP, and PP.

RESULTS

We enrolled thirty volunteers. There were significant differences among the four obtained measurements of the PVI, EtCO2, and MAP (P<0.001, P<0.001, P<0.001, respectively). Compared to the predonation values, post-hoc analysis revealed an increase in the PVI at the 0th min postdonation (mean difference [MD], 5.4±5.9; 95% confidence interval [CI], -7.6 to -3.1; P<0.001); a decrease in the EtCO2 and MAP at the 0th and 10th minute postdonation, respectively (MD, 2.4±4.6; 95% CI, 0.019 to 4.84; P=0.008 and MD, 6.4±6.4; 95% CI, 3 to 9.7; P<0.001, respectively). Compared with EtCO2 at the 10th minute, the value increased after PLR (MD, 1.8±3.2; 95% CI, 0.074 to 4.44; P=0.006).

CONCLUSION

The PVI and EtCO2 could detect early hemodynamic changes after acute blood loss. However, it remains unclear whether they can determine volume status in spontaneously breathing patients.

Arterial and end-tidal carbon dioxide partial pressure difference during prehospital anaesthesia in critically ill patients

BACKGROUND

Normoventilation is crucial for many critically ill patients. Ventilation is routinely guided by end-tidal capnography during prehospital anaesthesia, based on the assumption of the gap between arterial partial pressure of carbon dioxide (PaCO2 ) and end-tidal carbon dioxide partial pressure (PetCO2 ) of approximately 0.5 kPa (3.8 mmHg).

METHODS

We retrospectively analysed the airway registry and patient chart data of patients who had been anaesthetised and intubated endotracheally by the prehospital critical care team and had their prehospital arterial blood gases analysed. Bland-Altman analysis was used to estimate the bias and limits of agreement.

RESULTS

Altogether 502 patients were included in the study, with a median age of 58 years. The most common patient groups were post-resuscitation (155, 31%), neurological emergencies (96, 19%), intoxication (75, 15%) and trauma (68, 14%). The median of the gap between PaCO2 and PetCO2 was 1.3 kPa (interquartile range 0.7 to 2.2) (9.8 (5.3-16.5) mmHg). Mean bias of PetCO2 was -1.6 kPa/12.0 mmHg (standard deviation 1.7 kPa/12.8 mmHg) with 95% confidence limits of agreement -4.9 to 1.9 kPa (-36.8 to 14.3 mmHg). The gap was ≥ 1.0 kPa (>7.5 mmHg) in 297 (66%, 95% confidence interval 55 to 63) patients.

CONCLUSION

Our results suggest that end-tidal capnography alone might not be an adequate method to achieve normoventilation for critically ill patients intubated and mechanically ventilated in prehospital setting. Thus, an arterial blood gas analysis might be useful to recognize patients with an increased gap between PaCO2 and PetCO2 .