Predicting the lack of ROSC during pre-hospital CPR: should an end-tidal CO2 of 1.3 kPa be used as a cut-off value?

Temporal Trends in End-Tidal Capnography and Outcomes in Out-of-Hospital Cardiac Arrest: A Secondary Analysis of a Randomized Clinical Trial

Importance

While widely measured, the time-varying association between exhaled end-tidal carbon dioxide (EtCO2) and out-of-hospital cardiac arrest (OHCA) outcomes is unclear.

Objective

To evaluate temporal associations between EtCO2 and return of spontaneous circulation (ROSC) in the Pragmatic Airway Resuscitation Trial (PART).

Design, Setting, and Participants

This study was a secondary analysis of a cluster randomized trial performed at multicenter emergency medical services agencies from the Resuscitation Outcomes Consortium. PART enrolled 3004 adults (aged ≥18 years) with nontraumatic OHCA from December 1, 2015, to November 4, 2017. EtCO2 was available in 1172 cases for this analysis performed in June 2023.

Interventions

PART evaluated the effect of laryngeal tube vs endotracheal intubation on 72-hour survival. Emergency medical services agencies collected continuous EtCO2 recordings using standard monitors, and this secondary analysis identified maximal EtCO2 values per ventilation and determined mean EtCO2 in 1-minute epochs using previously validated automated signal processing. All advanced airway cases with greater than 50% interpretable EtCO2 signal were included, and the slope of EtCO2 change over resuscitation was calculated.

Main Outcomes and Measures

The primary outcome was ROSC determined by prehospital or emergency department palpable pulses. EtCO2 values were compared at discrete time points using Mann-Whitney test, and temporal trends in EtCO2 were compared using Cochran-Armitage test of trend. Multivariable logistic regression was performed, adjusting for Utstein criteria and EtCO2 slope.

Results

Among 1113 patients included in the study, 694 (62.4%) were male; 285 (25.6%) were Black or African American, 592 (53.2%) were White, and 236 (21.2%) were another race; and the median (IQR) age was 64 (52-75) years. Cardiac arrest was most commonly unwitnessed (n = 579 [52.0%]), nonshockable (n = 941 [84.6%]), and nonpublic (n = 999 [89.8%]). There were 198 patients (17.8%) with ROSC and 915 (82.2%) without ROSC. Median EtCO2 values between ROSC and non-ROSC cases were significantly different at 10 minutes (39.8 [IQR, 27.1-56.4] mm Hg vs 26.1 [IQR, 14.9-39.0] mm Hg; P < .001) and 5 minutes (43.0 [IQR, 28.1-55.8] mm Hg vs 25.0 [IQR, 13.3-37.4] mm Hg; P < .001) prior to end of resuscitation. In ROSC cases, median EtCO2 increased from 30.5 (IQR, 22.4-54.2) mm HG to 43.0 (IQR, 28.1-55.8) mm Hg (P for trend < .001). In non-ROSC cases, EtCO2 declined from 30.8 (IQR, 18.2-43.8) mm Hg to 22.5 (IQR, 12.8-35.4) mm Hg (P for trend < .001). Using adjusted multivariable logistic regression with slope of EtCO2, the temporal change in EtCO2 was associated with ROSC (odds ratio, 1.45 [95% CI, 1.31-1.61]).

Conclusions and Relevance

In this secondary analysis of the PART trial, temporal increases in EtCO2 were associated with increased odds of ROSC. These results suggest value in leveraging continuous waveform capnography during OHCA resuscitation.

Trial Registration

ClinicalTrials.gov Identifier: NCT02419573.

Prehospital monitoring of cerebral circulation during out of hospital cardiac arrest ? A feasibility study

BACKGROUND

About two-thirds of the in-hospital deaths after out-of-hospital cardiac arrests (OHCA) are a consequence of anoxic brain injuries, which are due to hypoperfusion of the brain during the cardiac arrests. Being able to monitor cerebral perfusion during cardiopulmonary resuscitation (CPR) is desirable to evaluate the effectiveness of the CPR and to guide further decision making and prognostication.

METHODS

Two different devices were used to measure regional cerebral oxygen saturation (rSO2): INVOS™ 5100 (Medtronic, Minneapolis, MN, USA) and Root® O3 (Masimo Corporation, Irvine, CA, USA). At the scene of the OHCA, advanced life support (ALS) was immediately initiated by the Emergency Medical Services (EMS) personnel. Sensors for measuring rSO2 were applied at the scene or during transportation to the hospital. rSO2 values were documented manually together with ETCO2 (end tidal carbon dioxide) on a worksheet specially designed for this study. The study worksheet also included a questionnaire for the EMS personnel with one statement on usability regarding potential interference with ALS.

RESULTS

Twenty-seven patients were included in the statistical analyses. In the INVOS™5100 group (n = 13), the mean rSO2 was 54% (95% CI 40.3-67.7) for patients achieving a return of spontaneous circulation (ROSC) and 28% (95% CI 12.3-43.7) for patients not achieving ROSC (p = 0.04). In the Root® O3 group (n = 14), the mean rSO2 was 50% (95% CI 46.5-53.5) and 41% (95% CI 36.3-45.7) (p = 0.02) for ROSC and no ROSC, respectively. ETCO2 values were not statistically different between the groups. The EMS personnel graded the statement of interference with ALS to a median of 2 (IQR 1-6) on a 10-point Numerical Rating Scale.

CONCLUSION

Our results suggest that both INVOS™5100 and ROOT® O3 can distinguish between ROSC and no ROSC in OHCA, and both could be used in the pre-hospital setting and during transport with minimal interference with ALS.

Clinical outcomes and safety of passive leg raising in out-of-hospital cardiac arrest: a randomized controlled trial

BACKGROUND

There are data suggesting that passive leg raising (PLR) improves hemodynamics during cardiopulmonary resuscitation (CPR). This trial aimed to determine the effectiveness and safety of PLR during CPR in out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a randomized controlled trial with blinded assessment of the outcomes that assigned adults OHCA to be treated with PLR or in the flat position. The trial was conducted in the Camp de Tarragona region. The main end point was survival to hospital discharge with good neurological outcome defined as cerebral performance category (CPC 1-2). To study possible adverse effects, we assessed the presence of pulmonary complications on the first chest X-rays, brain edema on the computerized tomography (CT) in survivors and brain and lungs weights from autopsies in non-survivors.

RESULTS

In total, 588 randomized cases were included, 301 were treated with PLR and 287 were controls. Overall, 67.8% were men and the median age was 72 (IQR 60-82) years. At hospital discharge, 3.3% in the PLR group and 3.5% in the control group were alive with CPC 1-2 (OR 0.9; 95% CI 0.4-2.3, p = 0.91). No significant differences in survival at hospital admission were found in all patients (OR 1.0; 95% CI 0.7-1.6, p = 0.95) and among patients with an initial shockable rhythm (OR 1.7; 95% CI 0.8-3.4, p = 0.15). There were no differences in pulmonary complication rates in chest X-rays [7 (25.9%) vs 5 (17.9%), p = 0.47] and brain edema on CT [5 (29.4%) vs 10 (32.6%), p = 0.84]. There were no differences in lung weight [1223 mg (IQR 909-1500) vs 1239 mg (IQR 900-1507), p = 0.82] or brain weight [1352 mg (IQR 1227-1457) vs 1380 mg (IQR 1255-1470), p = 0.43] among the 106 autopsies performed.

CONCLUSION

In this trial, PLR during CPR did not improve survival to hospital discharge with CPC 1-2. No evidence of adverse effects has been found. Clinical trial registration ClinicalTrials.gov: NCT01952197, registration date: September 27, 2013, https://clinicaltrials.gov/ct2/show/NCT01952197 .

Assessment of the evolution of end-tidal carbon dioxide within chest compression pauses to detect restoration of spontaneous circulation

Background

Measurement of end-tidal CO₂ (ETCO₂) can help to monitor circulation during cardiopulmonary resuscitation (CPR). However, early detection of restoration of spontaneous circulation (ROSC) during CPR using waveform capnography remains a challenge. The aim of the study was to investigate if the assessment of ETCO₂ variation during chest compression pauses could allow for ROSC detection. We hypothesized that a decay in ETCO₂ during a compression pause indicates no ROSC while a constant or increasing ETCO2 indicates ROSC.

Methods

We conducted a retrospective analysis of adult out-of-hospital cardiac arrest (OHCA) episodes treated by the advanced life support (ALS). Continuous chest compressions and ventilations were provided manually. Segments of capnography signal during pauses in chest compressions were selected, including at least three ventilations and with durations less than 20 s. Segments were classified as ROSC or non-ROSC according to case chart annotation and examination of the ECG and transthoracic impedance signals. The percentage variation of ETCO₂ between consecutive ventilations was computed and its average value, ΔET_avg, was used as a single feature to discriminate between ROSC and non-ROSC segments.

Results

A total of 384 segments (130 ROSC, 254 non-ROSC) from 205 OHCA patients (30.7% female, median age 66) were analyzed. Median (IQR) duration was 16.3 (12.9,18.1) s. ΔET_avg was 0.0 (-0.7, 0.9)% for ROSC segments and -11.0 (-14.1, -8.0)% for non-ROSC segments (p < 0.0001). Best performance for ROSC detection yielded a sensitivity of 95.4% (95% CI: 90.1%, 98.1%) and a specificity of 94.9% (91.4%, 97.1%) for all ventilations in the segment. For the first 2 ventilations, duration was 7.7 (6.0, 10.2) s, and sensitivity and specificity were 90.0% (83.5%, 94.2%) and 89.4 (84.9%, 92.6%), respectively. Our method allowed for ROSC detection during the first compression pause in 95.4% of the patients.

Conclusion

Average percent variation of ETCO₂ during pauses in chest compressions allowed for ROSC discrimination. This metric could help confirm ROSC during compression pauses in ALS settings.

The impact of ventilation rate on end-tidal carbon dioxide level during manual cardiopulmonary resuscitation

AIM

Ventilation rate is a confounding factor for interpretation of end-tidal carbon dioxide (ETCO₂) during cardiopulmonary resuscitation (CPR). The aim of our study was to model the effect of ventilation rate on ETCO₂ during manual CPR in adult out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a retrospective analysis of OHCA monitor-defibrillator files with concurrent capnogram, compression depth, transthoracic impedance and ECG. We annotated pairs of capnogram segments presenting differences in average ventilation rate and average ETCO₂ value but with other influencing factors (e.g. compression rate and depth) presenting similar values within the pair. ETCO₂ variation as a function of ventilation rate was adjusted through curve fitting using non-linear least squares as a measure of goodness of fit.

RESULTS

A total of 141 pairs of segments from 102 patients were annotated. Each pair provided a single data point for curve fitting. The best goodness of fit yielded a coefficient of determination R² of 0.93. Our model described that ETCO₂ decays exponentially with increasing ventilation rate. The model showed no differences attributable to the airway type (endotracheal tube or supraglottic King-LT-D).

CONCLUSION

Capnogram interpretation during CPR is challenging since many factors influence ETCO₂. For adequate interpretation, we need to know the effect of each factor on ETCO₂. Our model allows quantifying the effect of ventilation rate on ETCO₂ variation. Our findings could contribute to better interpretation of ETCO₂ during CPR.

Chest compressions induce errors in end-tidal carbon dioxide measurement

BACKGROUND

Real-time measurement of end-tidal carbon dioxide (ETCO₂) is used as a non-invasive estimate of cardiac output and perfusion during cardiopulmonary resuscitation (CPR). However, capnograms are often distorted by chest compressions (CCs) and this may affect ETCO₂ measurement. The aim of the study was to quantify the effect of CC-artefact on the accuracy of ETCO₂ measurements obtained during out-of-hospital manual CPR.

METHODS

We retrospectively analysed monitor-defibrillator recordings collected by two advanced life support agencies during out-of-hospital cardiac arrest. These two agencies, represented as A and B used different side-stream capnometers and monitor-defibrillators. One-minute capnogram segments were reviewed. Each ventilation within each segment was identified using the transthoracic impedance signal and the capnogram. ETCO₂ values per ventilation were manually annotated and compared to the corresponding capnometry values stored in the monitor-defibrillator. Ventilations were classified as distorted or non-distorted by CC-artefact.

RESULTS

A total of 407 1-min capnogram segments from 65 patients were analysed. Overall, 4095 ventilations were annotated, 2170 (32.4% distorted) and 1925 (31.8% distorted) for agency A and B, respectively. Median (IQR) unsigned error in ETCO₂ measurement increased from 1.5 (0.6-3.1)% for non-distorted to 5.5 (1.8-14.1)% for distorted ventilations; from 0.7 (0.3-1.2)% to 3.7 (1.0-9.9)% in agency A and from 2.3 (1.2-3.9)% to 8.3 (3.9-19.5)% in agency B (p < 0.001). Errors were higher than 10 mmHg in 9% and higher than 15 mmHg in 5% of the distorted ventilations.

CONCLUSION

CC-artefact causes ETCO₂ measurement errors in the two studied devices. This suggests that capnometer algorithms may need to be adapted to reliably perform in the presence of CC-artefact during CPR.

Modeling the impact of ventilations on the capnogram in out-of-hospital cardiac arrest

Aim

Current resuscitation guidelines recommend waveform capnography as an indirect indicator of perfusion during cardiopulmonary resuscitation (CPR). Chest compressions (CCs) and ventilations during CPR have opposing effects on the exhaled carbon dioxide (CO₂) concentration, which need to be better characterized. The purpose of this study was to model the impact of ventilations in the exhaled CO₂ measured from capnograms collected during out-of-hospital cardiac arrest (OHCA) resuscitation.

Methods

We retrospectively analyzed OHCA monitor-defibrillator files with concurrent capnogram, compression depth, transthoracic impedance and ECG signals. Segments with CC pauses, two or more ventilations, and with no pulse-generating rhythm were selected. Thus, only ventilations should have caused the decrease in CO₂ concentration. The variation in the exhaled CO₂ concentration with each ventilation was modeled with an exponential decay function using non-linear-least-squares curve fitting.

Results

Out of the original 1002 OHCA dataset (one per patient), 377 episodes had the required signals, and 196 segments from 96 patients met the inclusion criteria. Airway type was endotracheal tube in 64.8% of the segments, supraglottic King LT-D^™ in 30.1%, and unknown in 5.1%. Median (IQR) decay factor of the exhaled CO₂ concentration was 10.0% (7.8 − 12.9) with R² = 0.98(0.95 − 0.99). Differences in decay factor with airway type were not statistically significant (p = 0.17). From these results, we propose a model for estimating the contribution of CCs to the end-tidal CO₂ level between consecutive ventilations and for estimating the end-tidal CO₂ variation as a function of ventilation rate.

Conclusion

We have modeled the decrease in exhaled CO₂ concentration with ventilations during chest compression pauses in CPR. This finding allowed us to hypothesize a mathematical model for explaining the effect of chest compressions on ETCO₂ compensating for the influence of ventilation rate during CPR. However, further work is required to confirm the validity of this model during ongoing chest compressions.

Standardised data reporting from pre-hospital advanced airway management - a nominal group technique update of the Utstein-style airway template

Background

Pre-hospital advanced airway management with oxygenation and ventilation may be vital for managing critically ill or injured patients. To improve pre-hospital critical care and develop evidence-based guidelines, research on standardised high-quality data is important. We aimed to identify which airway data were most important to report today and to revise and update a previously reported Utstein-style airway management dataset.

Methods

We recruited sixteen international experts in pre-hospital airway management from Australia, United States of America, and Europe. We used a five-step modified nominal group technique to revise the dataset, and clinical study results from the original template were used to guide the process.

Results

The experts agreed on a key dataset of thirty-two operational variables with six additional system variables, organised in time, patient, airway management and system sections. Of the original variables, one remained unchanged, while nineteen were modified in name, category, definition or value. Sixteen new variables were added. The updated dataset covers risk factors for difficult intubation, checklist and standard operating procedure use, pre-oxygenation strategies, the use of drugs in airway management, airway currency training, developments in airway devices, airway management strategies, and patient safety issues not previously described.

Conclusions

Using a modified nominal group technique with international airway management experts, we have updated the Utstein-style dataset to report standardised data from pre-hospital advanced airway management. The dataset enables future airway management research to produce comparable high-quality data across emergency medical systems. We believe this approach will promote research and improve treatment strategies and outcomes for patients receiving pre-hospital advanced airway management.

Trial registration

The Regional Committee for Medical and Health Research Ethics in Western Norway exempted this study from ethical review (Reference: REK-Vest/2017/260).

Electronic supplementary material

The online version of this article (10.1186/s13049-018-0509-y) contains supplementary material, which is available to authorized users.

Data supporting the use of end-tidal carbon dioxide (ETCO2) measurement to guide management of cardiac arrest: A systematic review

The data presented in this article are related to the research article, "The Use of End-Tidal Carbon Dioxide (ETCO2) Measurement to Guide Management of Cardiac Arrest: A Systematic Review" [1]. This article is a systematic review and meta-analysis of existing data on the subject of whether any level of end-tidal carbon dioxide (ETCO2) measured during cardiopulmonary resuscitation (CPR) correlates with return of spontaneous circulation (ROSC) or survival in adult patients experiencing cardiac arrest in any setting. These data are made publicly available to enable critical or extended analyses.

Cerebral oximetry versus end tidal CO2 in predicting ROSC after cardiac arrest

STUDY OBJECTIVE

Both end tidal CO₂ (ETCO₂) and cerebral oxygen saturations (rSO₂) have been studied to determine their ability to monitor the effectiveness of CPR and predict return of spontaneous circulation (ROSC). We compared the accuracy of ETCO₂ and rSO₂ at predicting ROSC in ED patients with out-of-hospital cardiac arrest (OHCA).

METHODS

We performed a prospective, observational study of adult ED patients presenting in cardiac arrest. We collected demographic and clinical data including age, gender, presenting rhythm, rSO₂, and ETCO₂. We used receiver operating characteristic curves to compare how well rSO₂ and ETCO₂ predicted ROSC.

RESULTS

225 patients presented to the ED with cardiac arrest between 10/11 and 10/14 of which 100 had both rSO₂ and ETCO₂ measurements. Thirty three patients (33%) had sustained ROSC, only 2 survived to discharge. The AUCs for rSO₂ and ETCO₂ were similar (0.69 [95% CI, 0.59-0.80] and 0.77 [95% CI, 0.68-0.86], respectively), however, rSO₂ and ETCO₂ were poorly correlated (0.12, 95% CI, -0.08-0.31). The optimal cutoffs for rSO₂ and ETCO₂ were 50% and 20mm Hg respectively. At these cutoffs, ETCO₂ was more sensitive (100%, 95% CI 87-100 vs. 48%, 31-66) but rSO₂ was more specific (85%, 95% CI, 74-92 vs. 45%, 33-57).

CONCLUSIONS

While poorly correlated, rSO₂ and ETCO₂ have similar diagnostic characteristics. ETCO₂ is more sensitive and rSO₂ is more specific at predicting ROSC in OHCA.