Deep Neural Networks for ECG-Based Pulse Detection during Out-of-Hospital Cardiac Arrest

The automatic detection of pulse during out-of-hospital cardiac arrest (OHCA) is necessary for the early recognition of the arrest and the detection of return of spontaneous circulation (end of the arrest). The only signal available in every single defibrillator and valid for the detection of pulse is the electrocardiogram (ECG). In this study we propose two deep neural network (DNN) architectures to detect pulse using short ECG segments (5 s), i.e., to classify the rhythm into pulseless electrical activity (PEA) or pulse-generating rhythm (PR). A total of 3914 5-s ECG segments, 2372 PR and 1542 PEA, were extracted from 279 OHCA episodes. Data were partitioned patient-wise into training (80%) and test (20%) sets. The first DNN architecture was a fully convolutional neural network, and the second architecture added a recurrent layer to learn temporal dependencies. Both DNN architectures were tuned using Bayesian optimization, and the results for the test set were compared to state-of-the art PR/PEA discrimination algorithms based on machine learning and hand crafted features. The PR/PEA classifiers were evaluated in terms of sensitivity (Se) for PR, specificity (Sp) for PEA, and the balanced accuracy (BAC), the average of Se and Sp. The Se/Sp/BAC of the DNN architectures were 94.1%/92.9%/93.5% for the first one, and 95.5%/91.6%/93.5% for the second one. Both architectures improved the performance of state of the art methods by more than 1.5 points in BAC.This work was supported by: The Spanish Ministerio de Economía y Competitividad, TEC2015-64678-R, jointly with the Fondo Europeo de Desarrollo Regional (FEDER), UPV/EHU via GIU17/031 and the Basque Government through the grant PRE_2018_2_0260

Reduction of CPR artifacts in the ventricular fibrillation ECG by coherent line removal

<p>Abstract</p> <p>Background</p> <p>Interruption of cardiopulmonary resuscitation (CPR) impairs the perfusion of the fibrillating heart, worsening the chance for successful defibrillation. Therefore ECG-analysis <it>during ongoing chest compression </it>could provide a considerable progress in comparison with standard analysis techniques working only during "hands-off" intervals.</p> <p>Methods</p> <p>For the reduction of CPR-related artifacts in ventricular fibrillation ECG we use a localized version of the <it>coherent line removal </it>algorithm developed by Sintes and Schutz. This method can be used for removal of periodic signals with sufficiently coupled harmonics, and can be adapted to specific situations by optimal choice of its parameters (e.g., the number of harmonics considered for analysis and reconstruction). Our testing was done with 14 different human ventricular fibrillation (VF) ECGs, whose fibrillation band lies in a frequency range of [1 Hz, 5 Hz]. The VF-ECGs were mixed with 12 different ECG-CPR-artifacts recorded in an animal experiment during asystole. The length of each of the ECG-data was chosen to be 20 sec, and testing was done for all 168 = 14 × 12 pairs of data. VF-to-CPR ratio was chosen as -20 dB, -15 dB, -10 dB, -5 dB, 0 dB, 5 dB and 10 dB. Here -20 dB corresponds to the highest level of CPR-artifacts.</p> <p>Results</p> <p>For non-optimized <it>coherent line removal </it>based on signals with a VF-to-CPR ratio of -20 dB, -15 dB, -10 dB, -5 dB and 0 dB, the signal-to-noise gains (SNR-gains) were 9.3 ± 2.4 dB, 9.4 ± 2.4 dB, 9.5 ± 2.5 dB, 9.3 ± 2.5 dB and 8.0 ± 2.7 (mean ± std, <it>n </it>= 168), respectively. Characteristically, an original VF-to-CPR ratio of -10 dB, corresponds to a variance ratio <it>var</it>(VF):<it>var</it>(CPR) = 1:10. An improvement by 9.5 dB results in a restored VF-to-CPR ratio of -0.5 dB, corresponding to a variance ratio <it>var</it>(VF):<it>var</it>(CPR) = 1:1.1, the variance of the CPR in the signal being reduced by a factor of 8.9.</p> <p>Discussion</p> <p>The <it>localized coherent line removal </it>algorithm uses the information of a single ECG channel. In contrast to multi-channel algorithms, no additional information such as thorax impedance, blood pressure, or pressure exerted on the sternum during CPR is required. Predictors of defibrillation success such as mean and median frequency of VF-ECGs containing CPR-artifacts are prone to being governed by the harmonics of the artifacts. Reduction of CPR-artifacts is therefore necessary for determining reliable values for estimators of defibrillation success.</p> <p>Conclusions</p> <p>The <it>localized coherent line removal </it>algorithm reduces CPR-artifacts in VF-ECG, but does not eliminate them. Our SNR-improvements are in the same range as offered by multichannel methods of Rheinberger et al., Husoy et al. and Aase et al. The latter two authors dealt with different ventricular rhythms (VF and VT), whereas here we dealt with VF, only. Additional developments are necessary before the algorithm can be tested in real CPR situations.</p

Optimal Dispatch of Volunteers to Out-of-hospital Cardiac Arrest Patients

Initiatives with mobile phone dispatched volunteers to out-of-hospital cardiac arrest (OHCA) cases, can be found today in some countries, e.g. Sweden, the Netherlands, Switzerland and Italy. When an OHCA case is reported, an alarm is sent to the registered volunteers’ phones. However, the allocation of which volunteers to send to the automatic external defibrillator (AED) and who to send directly to the patient, is today based on simple rules of thumb. In this paper, we propose a model to optimally select how many and which volunteers to send directly to the patient, and who should pick up and deliver an AED. The results show that the model can help increase the survivability of the patients, compared to simple decision rules

Operative versus non-operative management of rib fractures in flail chest after cardiopulmonary resuscitation manoeuvres

OBJECTIVES: Blunt chest trauma after mechanical resuscitation manoeuvres appears to have a significant impact on the often complicated course. Due to a lack of data in the literature, the purpose of this study was to investigate the feasibility and immediate outcome of chest wall stabilization for flail chest in this vulnerable patient population. METHODS: We retrospectively reviewed the medical records of patients after cardiopulmonary resuscitation between January 2014 and December 2018 who were diagnosed with flail chest. We attempted to compare patients after surgery with those after conservative treatment. RESULTS: Of a total of 56 patients with blunt chest trauma after mechanical resuscitation and after coronary angiography, 25 were diagnosed with flail chest. After the exclusion of 2 patients because of an initial decision to palliate, 13 patients after surgical stabilization could be compared with 10 patients after conservative therapy. Although there was no significant difference in the total duration of ventilatory support, there was a significant advantage when the time after stabilization to extubation was compared with the duration of ventilation in the conservative group. The presence of pulmonary contusion, poor Glasgow Coma Scale score or the development of pneumonia negatively affected the outcome, but additional sternal fracture did not. CONCLUSIONS: Surgical stabilization for chest wall instability is well tolerated even by this vulnerable patient population. Our results should be used for further randomized controlled approaches. It is necessary to evaluate the situation with all parameters in an interdisciplinary manner and to decide on a possible surgical therapy at an early stage if possible

Preclinical Optimization of Treatment with Inhaled Argon to Improve Neurological Outcome and Survival After Cardiac Arrest

Introduction. Treatment of post cardiac arrest (CA) syndrome represents a clinical priority. Inhalation of the noble gas Argon may represent an attractive option. The purpose of the current thesis is to determine the efficacy, safety and mechanisms of action of Argon in different experimental models. Methods. In order to assess the efficacy of argon treatment on post CA syndrome, a pig model of CA with underlying acute myocardial infarction and cardiopulmonary resuscitation (CPR) was used. Following resuscitation, animals were randomly assigned to receive ventilation with 70% Argon (Ar 70%) or 70% Nitrogen (N270%) in oxygen. Argon effects were studied in models of CA with different level of severity (i.e. short or long duration of untreated ventricular fibrillation). Furthermore, administration of low Argon concentration (i.e. 50%) was evaluated in a subset of animals. Hemodynamics, myocardial function, neurologic recovery, brain and cardiac histological injury and biomarkers together with survival were evaluated. The safety of Argon treatment was assessed in healthy pigs. In parallel, mechanisms of action were explored. Specifically, brain protection was investigated in a rat model of CA followed by CPR. After resuscitation, animals were randomized to receive Ar 70% or N270%. Brain glutamate, gamma-amino butyric acid, pyruvate and lactate were measured by in vivo micro-dialysis. In addition, myocardial protection by argon was explored in rats subjected to coronary artery occlusion followed by reperfusion and receiving Ar 70% or N270% during reperfusion. Six and 24 h after reperfusion, myocardial injury, plasma troponin T concentration and myocardial neutrophil infiltration were evaluated. Results. Efficacy of argon on preventing post CA brain injury has been demonstrated in swine. Indeed, a faster and complete neurologic recovery following CA and CPR was achieved in Argon-treated animals compared to controls, without detrimental effects on hemodynamics and respiratory gas exchanges. Beneficial effects of Argon tended to be higher at a concentration of 70% than of 50%. Results obtained in small rodents suggest that ventilation with Argon reduces brain lactate/ pyruvate level and troponin T release. However, further studies are needed in order explain the mechanism underpining Argon protective effects. Conclusion. The consistency of the results is highly suggestive to consider ventilation with Argon as a promising therapeutic approach after CA and CPR

Cardiac arrest in children preceding PICU admission: Aetiology and outcome in a developing country

Includes bibliographical referencesObjective: To describe the characteristics and outcomes of children admitted to PICU following cardiac arrest between January 2010 and December 2011. Methods: Retrospective descriptive study of routinely collected data. Results: Of 2501 PICU admissions, 110 (4.4%; 58.7% male) had preceding cardiac arrest, 80.6% of which occurred in hospital. Median (IQR) age was 7.2 (2.5 - 21.6) months; 30.8% had chronic underlying disease. Children presented most commonly with respiratory (n=28, 27.2%), cardiovascular (n= 22, 21.4%), and gastrointestinal disease (n= 20, 19.4%). Twenty-eight (27.2%) arrested while undergoing a procedure. Cardiopulmonary resuscitation (CPR) was given for median (IQR) 10 (5 - 20) minutes. Thirty-five (34%) patients received no adrenaline, 44 (42.7%) received up to 3 doses of adrenaline, and 24 (23.3%) received more than 3 doses of adrenaline during resuscitation. Duration of CPR and number of adrenaline doses did not significantly influence patient outcome. Survival to PICU discharge was 63 (61.2%), 57 (55.3%) survived to hospital discharge with half the deaths in PICU occurred within 24 hours of PICU admission. Out of 51 survivors whose neurological status were assessed 32 were normal, 6 had mild disability, 7 had moderate disability and 6 had severe disability. Standardized mortality ratio (actual/mean predicted) was 0.7. The median (IQR) length of stay in PICU and hospital were 3 (1 - 8) and 27 (9 -52) days respectively. Pediatric risk of mortality (PIM2) score was the only variable independently associated with mortality on multiple logistic regression (adjusted OR 1.05; 95% CI 1.02 - 1.07; p=0.0009)

Effect of thoracic venting on arterial pressure, and flow during external cardiopulmonary resuscitation in animals

To test the hypothesis that fluctuations in global intrathoracic pressure are the dominant cause of blood flow during external cardiopulmonary resuscitation (CPR) the authors studied the effects of open pneumothorax on experimental CPR in 7 domestic pigs and 12 mongrel dogs. Similar studies were conducted independently at three laboratories and are reported jointly. All studies were conducted during electrically induced ventricular fibrillation and with standard CPR technique, including ventral-dorsal chest compression at 60/min, 0.5 sec compression duration, 1:5ventilation:compression ratio. During alternate periods of CPR, intrathoracic pressure was vented through bilateral chest tubes, placed to create open pneumothorax and partial collapse of the lungs. During this maneuver, global intrathoracic pressure fluctuations were greatly attenuated, but direct but direct cardiac compression and adequate ventilation continued. In the three laboratories, systolic/diastolic arterial pressures during CPR with thoracic venting (± SE) averaged 68 ± 4.2/28 ± 3.3, 60 ± 10/18 ± 4.5, and 66 ± 6.3/23 ± 1.5 mm Hg. These values are compared to 68 ± 4.4/27 ± 3.0, 67 ± 12/17 ± 6.1, and 56± 6.2/22 ± 1.9 mm Hg with the thorax intact. Carotid artery mean flow, measured with an in-line flowmeter, was 13.0 ± 2.2 ml/min vented vs. 13.4 ± 2.6 intact in 7 pigs; 11.4 ± 3.8 ml/min vented vs. 11.2 ± 3.7 intact in 5 dogs. Cardiac output, determined by indicator dilution, was 25 ± 4.3 ml/min/kg vented vs. 20 ± 4.3 intact in 7 dogs. Thoracic venting did not decrease blood pressures and flows during CPR, as would be predicted from the hypothesis that generalized intrathoracic pressure fluctuations are the dominant hemodynamic mechanism. The results are consistent with the classical notion that CPR works by compression of the heart between the sternum and the spine. This mechanism should not be discounted in future attempts to improve CPR

The Role of Chest Compressions on Ventilation during Advanced Cardiopulmonary Resuscitation

There is growing interest in the quality of manual ventilation during cardiopulmonary resuscitation (CPR), but accurate assessment of ventilation parameters remains a challenge. Waveform capnography is currently the reference for monitoring ventilation rate in intubated patients, but fails to provide information on tidal volumes and inspiration–expiration timing. Moreover, the capnogram is often distorted when chest compressions (CCs) are performed during ventilation compromising its reliability during CPR. Our main purpose was to characterize manual ventilation during CPR and to assess how CCs may impact on ventilation quality. Methods: Retrospective analysis were performed of CPR recordings fromtwo databases of adult patients in cardiac arrest including capnogram, compression depth, and airway flow, pressure and volume signals. Using automated signal processing techniques followed by manual revision, individual ventilations were identified and ventilation parameters were measured. Oscillations on the capnogram plateau during CCs were characterized, and its correlation with compression depth and airway volume was assessed. Finally, we identified events of reversed airflow caused by CCs and their effect on volume and capnogram waveform. Results: Ventilation rates were higher than the recommended 10 breaths/min in 66.7% of the cases. Variability in ventilation rates correlated with the variability in tidal volumes and other ventilatory parameters. Oscillations caused by CCs on capnograms were of high amplitude (median above 74%) and were associated with low pseudo-volumes (median 26 mL). Correlation between the amplitude of those oscillations with either the CCs depth or the generated passive volumes was low, with correlation coefficients of −0.24 and 0.40, respectively. During inspiration and expiration, reversed airflow events caused opposed movement of gases in 80% of ventilations. Conclusions: Our study confirmed lack of adherence between measured ventilation rates and the guideline recommendations, and a substantial dispersion in manual ventilation parameters during CPR. Oscillations on the capnogram plateau caused by CCs did not correlate with compression depth or associated small tidal volumes. CCs caused reversed flow during inspiration, expiration and in the interval between ventilations, sufficient to generate volume changes and causing oscillations on capnogram. Further research is warranted to assess the impact of these findings on ventilation quality during CPR.This research was funded by the grant PID2021-126021OB-I00 by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe, and by the grant IT1590-22 by the Basque Government. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Consensus evidence evaluation in resuscitation research: analysis of Type I and Type II errors

Objective: This paper addresses the following statistical question: ‘if genuine improvements in cardiopulmonary resuscitation (CPR) were discovered that doubled the probability of resuscitation success in a series of randomized clinical trials, would they be recognized and incorporated into consensus guidelines?’ Methods: Statistical powers for hypothetical individual clinical trials comparing experimental and control CPR were computed as a function of the study N when the true probabilities for immediate survival, 24 h survival, and discharge survival in the experimental group were twice those in the control group. Next, the binomial distributions describing the numbers of statistically significant studies in a series of equally powered trials of the same intervention were determined. These were compared with varying criteria for consensus among expert reviewers, expressed in terms of the number of ‘positive’ studies showing a statistically significant difference that reviewers would require before approving the experimental method. Results: False-negative evaluations (i.e. failures to approve a technique that actually doubled survival) were extremely common under a wide range of realistic assumptions and consensus criteria, especially when simulated long-term survival data were considered. Similar methods showed that false-positive evaluations would be extremely rare, provided that at least two of the clinical trials in a series showed a statistically significant benefit of the experimental method. Conclusions: Optimization of evidence evaluation can and should be carried out to make better use of available data in creating resuscitation guidelines. One simple approach is the ‘two and one quarter test’: if at least two well-conducted studies in a series are significantly positive (P\u3c0.05) comprising at least one-quarter of all studies in the series, a positive effect can be inferred with small Type I and Type II errors. In addition, greater reliance on modern, unbiased methods such as cumulative meta-analysis is needed to increase the sensitivity of evidence evaluation for detecting useful innovations in resuscitation