Volume 132, November 2018, Pages 73-77  https://doi.org/10.1016/j.resuscitation.2018.08.018Get rights and content End-tidal carbon dioxide (ETCO2) is the partial pressure of carbon dioxide (PCO2) in the exhaled air measured at the end of expiration. CO2 is produced in perfused tissues by aerobic metabolism, it diffuses from the cells into the blood and is transported by the venous return to the lungs, where it is removed by ventilation. The major determinants of ETCO2 therefore include CO2 production, cardiac output (CO), lung perfusion and alveolar ventilation [1]. Capnography represents a continuous, non-invasive measurement of PCO2 in the exhaled air during the breathing cycle. The correspondent waveform is called a capnogram (Fig. 1). In the typical capnogram ETCO2 is the value recorded at the end of the plateau phase and it is the one which better reflects the alveolar PCO2. Normally, ETCO2 is around 5 mmHg lower than PCO2 in the arterial blood (PaCO2). This gradient increases when there is a ventilation/perfusion mismatch in the lung that may occur because of pulmonary embolism or lung hypoperfusion during cardiac arrest [2]. In patients with cardiac arrest, cardiopulmonary resuscitation (CPR) temporarily restores CO. Both experimental [3,4] and clinical [5] studies have shown that survival from cardiac arrest depends on provision of adequate perfusion to vital organs. However, direct measurement of organ blood flow during CPR is not clinically feasible. ETCO2 represents a non-invasive measurement of the effectiveness of CPR in terms of blood flow that is generated and the potential of successful resuscitation. In an Performing a rapid and successful endotracheal intubation during resuscitation from cardiac arrest is important. Detection of CO2 in exhaled air using waveform capnography is the most specific method for confirming endotracheal tube placement. A study [19] from Grmec et al. on 246 OHCAs who underwent prehospital intubation showed that capnography had 100[97–100]% specificity and 100[98–100]% sensitivity for detecting correct endotracheal tube placement. In a study [20] on 81 OHCAs who were ROSC is associated with a significant increase of ETCO2 (Fig. 2), which raises up to a level three times above the values during CPR and then slowly declines to a stable value in all patients that maintain ROSC [24]. ETCO2 monitoring can therefore help detect ROSC during resuscitation to avoid continuing unnecessary chest compression. On the other side, however, inappropriate interruptions of CPR should also be avoided, since they are detrimental to defibrillation success and survival [19,25,26 Since ETCO2 is expected to reflect organ perfusion during CPR, it may not only represent a target of resuscitation, but also a predictor indicating when prolonged CPR is futile. In 1997, Levine et al. [30] investigated on the association between ETCO2 measured after 20 min of ALS and survival to hospital admission in 150 adults with OHCA from primary cardiac cause associated to pulseless electrical activity (PEA). Results showed that no patient with ETCO2 ≤10 mmHg after 20 min of ALS survived When interpreting ETCO2 values during CPR a series of confounding factors need to be taken into account. As mentioned above, in patients with a respiratory cause of arrest, ETCO2 may initially be high [35,46] as a result of hypercapnia and may therefore not reflect cardiac output generated by CPR. Conversely, hyperventilation decreases ETCO2 levels during CPR. In a pig model of cardiac arrest Gazmuri et al. [47] demonstrated that increasing either respiratory rate from the recommended value of Measurement of ETCO2 is currently the only noninvasive clinical tool for estimating organ perfusion during CPR. During experimental CPR, ETCO2 has shown a significant positive correlation with cardiac index and with coronary and cerebral perfusion pressures. In observational studies on pre-hospital cardiac arrest, ETCO2 levels below 10 mmHg after 20 min of ALS were highly predictive of pre-hospital mortality. However, accuracy of ETCO2 as a predictor of ROSC is lower when it is measured earlier We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us. We confirm that we None.
The purpose of this study was to assess the effectiveness of an educational program about measuring ventilation using devices that assess carbon dioxide levels in patients recovering from a surgical procedure. A pre-post survey of knowledge attainment from an educational intervention about measuring ventilation using end-tidal carbon dioxide (EtCO2) and transcutaneous carbon dioxide (tcPCO2) devices in the postanesthesia care unit (PACU) was distributed to current members of the American Society of PeriAnesthesia Nurses. Participants received a 12-question pre-intervention (five were related to demographics) and a five-question post-intervention survey. Non-demographic survey questions used a one to five Likert scale to assess comfortability or confidence. The intervention created was a voice-over presentation designed to improve PACU RN's comfort and confidence with using and interpreting tcPCO2 or EtCO2 in the PACU. PACU RNs (N = 108) reported they ‘never’ or ‘rarely’ used EtCO2 (n = 57, 52.7%) monitoring or tcPCO2 (n = 93, 86.1%) monitoring in the PACU. A paired t test revealed statistically significant differences in the PACU RN's pre-survey and posttest comfortability of applying and interpreting EtCO2 or tcPCO2 monitors (P < .05). Capnography monitoring should be considered a standard of care for PACU patients. Education of registered nurses working in the PACU is critical before implementing EtCO2 or tcPCO2 monitoring. Characterise how changes in chest compression depth and rate affect variations in end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest (OHCA). Retrospective analysis of adult OHCA monitor-defibrillator recordings having concurrent capnogram, compression depth, transthoracic impedance and ECG, and with atleast 1,000 compressions. Within each patient, during no spontaneous circulation, nearby segments with changes in chest compression depth and rate were identified. Average ETCO2 within each segment was standardised to compensate for ventilation rate variability. Contributions of relative variations in depth and rate to relative variations in standardised ETCO2 were characterised using linear and non-linear models. Normalisation between paired segments removed intra and inter-patient variation and made coefficients of the model independent of the scale of measurement and therefore directly comparable. A total of 394 pairs of segments from 221 patients were analysed (33% female, median (IQR) age 66 (55–74) years). Chest compression depth and rate were 50.4 (43.2–57.0) mm and 111.1 (106.5–116.1) compressions per minute. ETCO2 before and after standardization was 32.1 (23.0–41.4) mmHg and 28.5 (19.4–38.7) mmHg. Linear model coefficient of determination was 0.89. Variation in compression depth mainly explained ETCO2 variation (coefficient 0.95, 95% confidence interval (CI): 0.93–0.98) while changes in compression rate did not (coefficient 0.04, 95% CI: 0.01–0.07). Non-linear trend analysis confirmed the results. This study quantified the relative importance of chest compression characteristics in terms of their impact on CO2 production during CPR. With ventilation rate standardised, variation in chest compression depth explained variations in ETCO2 better than variation in chest compression rate. We aimed to identify distinct trajectories of end-tidal carbon dioxide (EtCO2) during cardiopulmonary resuscitation in patients with out-of-hospital cardiac arrest (OHCA) and to investigate the association between EtCO2 trajectories and OHCA outcomes. This was a secondary analysis of a prospectively collected database on adult patients with OHCA who had been resuscitated in the emergency department of a tertiary medical center between 2015 and 2020. The primary outcome was the return of spontaneous circulation (ROSC). Group-based trajectory modelling was used to identify the EtCO2 trajectories. Multivariable logistic regression analysis was performed to evaluate the association between EtCO2 trajectories and ROSC. The predictive performance of the EtCO2 trajectories was assessed using the area under the receiver operating characteristic curve (AUC). The study comprised 655 patients with OHCA. In the primary analysis, three distinct EtCO2 trajectories, including 10-mmHg, 30-mmHg, and 50-mmHg trajectories, were identified. Compared with the 10-mmHg trajectory, both 30-mmHg (odds ratio [OR]: 4.66, 95% confidence interval [CI]: 3.15–6.90) and 50-mmHg (OR: 7.58, 95% CI: 4.30–13.35) trajectories were associated with a higher likelihood of ROSC. In a sensitivity analysis of excluding EtCO2 measured before tracheal intubation or after sodium bicarbonate administration, the predictive ability of the identified EtCO2 trajectories remained. As a single predictor of ROSC, EtCO2 trajectories had an acceptable discriminative performance (AUC: 0.69, 95% CI: 0.66–0.73). Three distinct EtCO2 trajectories during cardiopulmonary resuscitation were identified and significantly associated with outcomes. Early identification of these EtCO2 trajectories could potentially guide the ongoing resuscitation efforts. We sought to describe ventilation rates during out-of-hospital cardiac arrest (OHCA) resuscitation and their associations with airway management strategy and outcomes. We analyzed continuous end-tidal carbon dioxide capnography data from adult OHCA enrolled in the Pragmatic Airway Resuscitation Trial (PART). Using automated signal processing techniques, we determined continuous ventilation rates for consecutive 10-second epochs after airway insertion. We defined hypoventilation as a ventilation rate < 6 breaths/min. We defined hyperventilation as a ventilation rate > 12 breaths/min. We compared differences in total and percentage post-airway hyper- and hypoventilation between airway interventions (laryngeal tube (LT) vs. endotracheal intubation (ETI)). We also determined associations between hypo-/hyperventilation and OHCA outcomes (ROSC, 72-hour survival, hospital survival, hospital survival with favorable neurologic status). Adequate post-airway capnography were available for 1,010 (LT n = 714, ETI n = 296) of 3,004 patients. Median ventilation rates were: LT 8.0 (IQR 6.5–9.6) breaths/min, ETI 7.9 (6.5–9.7) breaths/min. Total duration and percentage of post-airway time with hypoventilation were similar between LT and ETI: median 1.8 vs. 1.7 minutes, p = 0.94; median 10.5% vs. 11.5%, p = 0.60. Total duration and percentage of post-airway time with hyperventilation were similar between LT and ETI: median 0.4 vs. 0.4 minutes, p = 0.91; median 2.1% vs. 1.9%, p = 0.99. Hypo- and hyperventilation exhibited limited associations with OHCA outcomes. In the PART Trial, EMS personnel delivered post-airway ventilations at rates satisfying international guidelines, with only limited hypo- or hyperventilation. Hypo- and hyperventilation durations did not differ between airway management strategy and exhibited uncertain associations with OCHA outcomes. Waveform capnography is considered the gold standard for verification of proper endotracheal tube placement, but current guidelines caution that it is unreliable in low-perfusion states such as cardiac arrest. Recent case reports found that long-deceased cadavers can produce capnographic waveforms. The purpose of this study was to determine the predictive value of waveform capnography for endotracheal tube placement verification and detection of misplacement using a cadaveric experimental model. We conducted a controlled experiment with two intubated cadavers. Tubes were placed within the trachea, esophagus, and hypopharynx utilizing video laryngoscopy. We recorded observations of capnographic waveforms and quantitative end-tidal carbon dioxide (ETCO2) values during tracheal versus extratracheal (i.e., esophageal and hypopharyngeal) ventilations. 106 and 89 tracheal ventilations delivered to cadavers one and two, respectively (n = 195) all produced characteristic alveolar waveforms (positive) with ETCO2 values ranging 2–113 mmHg. 42 esophageal ventilations (36 to cadaver one and 6 to cadaver two), and 6 hypopharyngeal ventilations (4 to cadaver one and 2 to cadaver two) all resulted in non-alveolar waveforms (negative) with ETCO2 values of 0 mmHg. Esophageal and hypopharyngeal measurements were categorized as extratracheal (n = 48). A binary classification test showed no false negatives or false positives, indicating 100% sensitivity (NPV 1.0, 95%CI 0.98–1.00) and 100% specificity (PPV 1.0, 95%CI 0.93–1.00). Though current guidelines question the reliability of waveform capnography for verifying endotracheal tube location during low-perfusion states such as cardiac arrest, our findings suggest that it is highly sensitive and specific. The rates of chest compressions (CCs) and ventilations are both important metrics to monitor the quality of cardiopulmonary resuscitation (CPR). Capnography permits monitoring ventilation, but the CCs provided during CPR corrupt the capnogram and compromise the accuracy of automatic ventilation detectors. The aim of this study was to evaluate the feasibility of an automatic algorithm based on the capnogram to detect ventilations and provide feedback on ventilation rate during CPR, specifically addressing intervals where CCs are delivered. The dataset used to develop and test the algorithm contained in-hospital and out-of-hospital cardiac arrest episodes. The method relies on adaptive thresholding to detect ventilations in the first derivative of the capnogram. The performance of the detector was reported in terms of sensitivity (SE) and Positive Predictive Value (PPV). The overall performance was reported in terms of the rate error and errors in the hyperventilation alarms. Results were given separately for the intervals with CCs. A total of 83 episodes were considered, resulting in 4880 min and 46,740 ventilations (8741 during CCs). The method showed an overall SE/PPV above 99% and 97% respectively, even in intervals with CCs. The error for the ventilation rate was below 1.8 min−1 in any group, and >99% of the ventilation alarms were correctly detected. A method to provide accurate feedback on ventilation rate using only the capnogram is proposed. Its accuracy was proven even in intervals where canpography signal was severely corrupted by CCs. This algorithm could be integrated into monitor/defibrillators to provide reliable feedback on ventilation rate during CPR. Airway complications occur more frequently outside the operating theatre and in emergency situations. Capnography remains the gold standard for confirming correct endotracheal tube placement, retaining high sensitivity and specificity in cardiac arrest. The 2010 European Resuscitation Council guidelines for adult advanced life support recommended waveform capnography in this setting. We investigated current UK practice relating to the availability and use of this technology during cardiac arrest. Between June and November 2014, a study was conducted of all UK acute hospitals with both a level three adult intensive care unit (ICU) and an emergency department (ED). A telephone questionnaire was administered examining intubation practice and utilisation of capnography within the ED, ICU and general wards. Two hundred and eleven hospitals met the inclusion criteria. The response rate was 100%. Arrests were mainly attended by anaesthesia (48%) and ICU physicians (38%) of registrar grade (56%). The ability to measure end tidal carbon dioxide (ETCO2) was available in all but 4 EDs; most used in waveform devices. Most ICUs were similar. However, in 67% of hospitals surveyed, it was not possible to measure ETCO2 in general wards. Where available, 87% used capnography to confirm ETT placement with less than 50% using ETCO2 to determine CPR effectiveness and 8% to prognosticate. We believe this is the first study of its kind to fully investigate the availability and use of capnography during cardiac arrest throughout the hospital. Whilst equipment provision appears adequate in critical care areas, it is insufficient in general wards. The use of capnography is recommended during resuscitation. By implementing the mnemonic “PQRST”, rescuers have a ready-made checklist to help them achieve the full potential of capnography. This approach can facilitate efforts to both reduce the hands-off time and individualize the treatment, which can lead to improved survival for our patients. Cardiac arrest is a common presentation to the emergency care system. The decision to terminate CPR is often challenging to heath care providers. An accurate, early predictor of the outcome of resuscitation is needed. The purpose of this systematic review is to evaluate the prognostic value of ETCO2 during cardiac arrest and to explore whether ETCO2 values could be utilised as a tool to predict the outcome of resuscitation. Literature search was performed using Medline and EMBASE databases to identify studies that evaluated the relationship between ETCO2 during cardiac arrest and outcome. Studies were thoroughly evaluated and appraised. Summary of evidence and conclusions were drawn from this systematic literature review. 23 observational studies were included. The majority of studies showed that ETCO2 values during CPR were significantly higher in patients who later developed ROSC compared to patients who did not. Several studies suggested that initial ETCO2 value of more than 1.33 kPa is 100% sensitive for predicting survival making ETCO2 value below 1.33 kPa a strong predictor of mortality. These studies however had several limitations and the 100% sensitivity for predicting survival was not consistent among all studies. ETCO2 values during CPR do correlate with the likelihood of ROSC and survival and therefore have prognostic value. Although certain ETCO2 cut-off values appears to be a strong predictor of mortality, the utility of ETCO2 cut-off values during CPR to accurately predict the outcome of resuscitation is not fully established. Therefore, ETCO2 values cannot be used as a mortality predictor in isolation. The American Heart Association (AHA) recommends monitoring cardiopulmonary resuscitation (CPR) quality using end tidal carbon dioxide (ETCO2) or invasive hemodynamic data. The objective of this study was to evaluate the association between clinician-reported physiologic monitoring of CPR quality and patient outcomes. Prospective observational study of index adult in-hospital CPR events using the AHA's Get With The Guidelines – Resuscitation Registry. Physiologic monitoring was defined using specific database questions regarding use of either ETCO2 or arterial diastolic blood pressure (DBP) to monitor CPR quality. Logistic regression was used to evaluate the association between physiologic monitoring and outcomes in a propensity score matched cohort. In the matched cohort, (monitored n = 3032; not monitored n = 6064), physiologic monitoring of CPR quality was associated with a higher rate of return of spontaneous circulation (ROSC; OR 1.22, CI95 1.04–1.43, p = 0.017) compared to no monitoring. Survival to hospital discharge (OR 1.04, CI95 0.91–1.18, p = 0.57) and survival with favorable neurological outcome (OR 0.97, CI95 0.75–1.26, p = 0.83) were not different between groups. Of index events with only ETCO2 monitoring indicated (n = 803), an ETCO2 >10 mmHg during CPR was reported in 520 (65%), and associated with improved survival to hospital discharge (OR 2.41, CI95 1.35–4.30, p = 0.003), and survival with favorable neurological outcome (OR 2.31, CI95 1.31–4.09, p = 0.004) compared to ETCO2 ≤10 mmHg. Clinician-reported use of either ETCO2 or DBP to monitor CPR quality was associated with improved ROSC. An ETCO2 >10 mmHg during CPR was associated with a higher rate of survival compared to events with ETCO2 ≤10 mmHg. |
What is the main determinant of ETCO2 during CPR
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