Quality assessment of defribrillation and advanced life support using data from the medical control module of the defibrillator

Extracting physiologic and clinical data from defibrillators for research purposes to improve treatment for patients in cardiac arrest

Background

A defibrillator should be connected to all patients receiving cardiopulmonary resuscitation (CPR) to allow early defibrillation. The defibrillator will collect signal data such as the electrocardiogram (ECG), thoracic impedance and end-tidal CO2, which allows for research on how patients demonstrate different responses to CPR. The aim of this review is to give an overview of methodological challenges and opportunities in using defibrillator data for research.

Methods

The successful collection of defibrillator files has several challenges. There is no scientific standard on how to store such data, which have resulted in several proprietary industrial solutions. The data needs to be exported to a software environment where signal filtering and classifications of ECG rhythms can be performed. This may be automated using different algorithms and artificial intelligence (AI). The patient can be classified being in ventricular fibrillation or -tachycardia, asystole, pulseless electrical activity or having obtained return of spontaneous circulation. How this dynamic response is time-dependent and related to covariates can be handled in several ways. These include Aalen's linear model, Weibull regression and joint models.

Conclusions

The vast amount of signal data from defibrillator represents promising opportunities for the use of AI and statistical analysis to assess patient response to CPR. This may provide an epidemiologic basis to improve resuscitation guidelines and give more individualized care. We suggest that an international working party is initiated to facilitate a discussion on how open formats for defibrillator data can be accomplished, that obligates industrial partners to further develop their current technological solutions.

Do cardiopulmonary resuscitation real-time audiovisual feedback devices improve patient outcomes? A systematic review and meta-analysis

BACKGROUND

Cardiac arrest is a leading cause of mortality in America and has increased in the incidence of cases over the last several years. Cardiopulmonary resuscitation (CPR) increases survival outcomes in cases of cardiac arrest; however, healthcare workers often do not perform CPR within recommended guidelines. Real-time audiovisual feedback (RTAVF) devices improve the quality of CPR performed. This systematic review and meta-analysis aims to compare the effect of RTAVF-assisted CPR with conventional CPR and to evaluate whether the use of these devices improved outcomes in both in-hospital cardiac arrest (IHCA) and out-of-hospital cardiac arrest (OHCA) patients.

AIM

To identify the effect of RTAVF-assisted CPR on patient outcomes and CPR quality with in- and OHCA.

METHODS

We searched PubMed, SCOPUS, the Cochrane Library, and EMBASE from inception to July 27, 2020, for studies comparing patient outcomes and/or CPR quality metrics between RTAVF-assisted CPR and conventional CPR in cases of IHCA or OHCA. The primary outcomes of interest were return of spontaneous circulation (ROSC) and survival to hospital discharge (SHD), with secondary outcomes of chest compression rate and chest compression depth. The methodological quality of the included studies was assessed using the Newcastle-Ottawa scale and Cochrane Collaboration's "risk of bias" tool. Data was analyzed using R statistical software 4.2.0. results were statistically significant if P < 0.05.

RESULTS

Thirteen studies (n = 17600) were included. Patients were on average 69 ± 17.5 years old, with 7022 (39.8%) female patients. Overall pooled ROSC in patients in this study was 37% (95% confidence interval = 23%-54%). RTAVF-assisted CPR significantly improved ROSC, both overall [risk ratio (RR) 1.17 (1.001-1.362); P = 0.048] and in cases of IHCA [RR 1.36 (1.06-1.80); P = 0.002]. There was no significant improvement in ROSC for OHCA (RR 1.04; 0.91-1.19; P = 0.47). No significant effect was seen in SHD [RR 1.04 (0.91-1.19); P = 0.47] or chest compression rate [standardized mean difference (SMD) -2.1; (-4.6-0.5)]; P = 0.09]. A significant improvement was seen in chest compression depth [SMD 1.6; (0.02-3.1); P = 0.047].

CONCLUSION

RTAVF-assisted CPR increases ROSC in cases of IHCA and chest compression depth but has no significant effect on ROSC in cases of OHCA, SHD, or chest compression rate.

Long-term outcomes after out-of-hospital cardiac arrest: a systematic review and meta-analysis

AIMS

Long term outcomes after out-of-hospital cardiac arrest (OHCA) are not well understood. This study aimed to evaluate the long-term (1-year and beyond) survival outcomes, including overall survival and survival with favorable neurological status and the quality-of-life (QOL) outcomes, among patients who survived the initial OHCA event (30 days or till hospital discharge).

METHODS

Embase, Medline and PubMed were searched for primary studies (randomized controlled trials, cohort and cross-sectional studies) which reported the long-term survival outcomes of OHCA patients. Data abstraction and quality assessment was conducted, and survival at predetermined timepoints were assessed via single-arm meta-analyses of proportions, using generalized linear mixed models. Comparative meta-analyses were conducted using the Mantel-Haenszel Risk Ratio (RR) estimates, using the DerSimonian and Laird model.

RESULTS

67 studies were included, and among patients that survived to hospital discharge or 30-days, 77.3% (CI=71.2-82.4), 69.6% (CI=54.5-70.3), 62.7% (CI=54.5-70.3), 46.5% (CI=32.0-61.6), and 20.8% (CI=7.8-44.9) survived to 1-, 3-, 5-, 10- and 15-years respectively. Compared to Asia, the probability of 1-year survival was greater in Europe (RR=2.1, CI=1.8-2.3), North America (RR=2.0, CI=1.7-2.2) and Oceania (RR=1.9,CI=1.6-2.1). Males had a higher 1-year survival (RR:1.41, CI=1.25-1.59), and patients with initial shockable rhythm had improved 1-year (RR=3.07, CI=1.78-5.30) and 3-year survival (RR=1.45, CI=1.19-1.77). OHCA occurring in residential locations had worse 1-year survival (RR=0.42, CI=0.25-0.73).

CONCLUSION

Our study found that up to 20.8% of OHCA patients survived to 15-years, and survival was lower in Asia compared to the other regions. Further analysis on the differences in survival between the regions are needed to direct future long-term treatment of OHCA patients.

[Adult advanced life support]

These European Resuscitation Council Advanced Life Support guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the prevention of and ALS treatments for both in-hospital cardiac arrest and out-of-hospital cardiac arrest.

European Resuscitation Council Guidelines 2021: Adult advanced life support

These European Resuscitation Council Advanced Life Support guidelines, are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the prevention of and ALS treatments for both in-hospital cardiac arrest and out-of-hospital cardiac arrest.

An automatic system for the comprehensive retrospective analysis of cardiac rhythms in resuscitation episodes

AIM

An automatic resuscitation rhythm annotator (ARA) would facilitate and enhance retrospective analysis of resuscitation data, contributing to a better understanding of the interplay between therapy and patient response. The objective of this study was to define, implement, and demonstrate an ARA architecture for complete resuscitation episodes, including chest compression pauses (CC-pauses) and chest compression intervals (CC-intervals).

METHODS

We analyzed 126.5h of ECG and accelerometer-based chest-compression depth data from 281 out-of-hospital cardiac arrest (OHCA) patients. Data were annotated by expert reviewers into asystole (AS), pulseless electrical activity (PEA), pulse-generating rhythm (PR), ventricular fibrillation (VF), and ventricular tachycardia (VT). Clinical pulse annotations were based on patient-charts and impedance measurements. An ARA was developed for CC-pauses, and was used in combination with a chest compression artefact removal filter during CC-intervals. The performance of the ARA was assessed in terms of the unweighted mean of sensitivities (UMS).

RESULTS

The UMS of the ARA were 75.0% during CC-pauses and 52.5% during CC-intervals, 55-points and 32.5-points over a random guess (20% for five categories). Filtering increased the UMS during CC-intervals by 5.2-points. Sensitivities for AS, PEA, PR, VF, and VT were 66.8%, 55.8%, 86.5%, 82.1% and 83.8% during CC-pauses; and 51.1%, 34.1%, 58.7%, 86.4%, and 32.1% during CC-intervals.

CONCLUSIONS

A general ARA architecture was defined and demonstrated on a comprehensive OHCA dataset. Results showed that semi-automatic resuscitation rhythm annotation, which may involve further revision/correction by clinicians for quality assurance, is feasible. The performance (UMS) dropped significantly during CC-intervals and sensitivity was lowest for PEA.

Comparative performance assessment of commercially available automatic external defibrillators: A simulation and real-life measurement study of hands-off time

PURPOSE

Early and good quality cardiopulmonary resuscitation (CPR) and the use of automated external defibrillators (AEDs) improve cardiac arrest patients' survival. However, AED peri- and post-shock/analysis pauses may reduce CPR effectiveness.

METHODS

The time performance of 12 different commercially available AEDs was tested in a manikin based scenario; then the AEDs recordings from the same tested models following the clinical use both in Pavia and Ticino were analyzed to evaluate the post-shock and post-analysis time.

RESULTS

None of the AEDs was able to complete the analysis and to charge the capacitors in less than 10s and the mean post-shock pause was 6.7±2.4s. For non-shockable rhythms, the mean analysis time was 10.3±2s and the mean post-analysis time was 6.2±2.2s. We analyzed 154 AED records [104 by Emergency Medical Service (EMS) rescuers; 50 by lay rescuers]. EMS rescuers were faster in resuming CPR than lay rescuers [5.3s (95%CI 5-5.7) vs 8.6s (95%CI 7.3-10).

CONCLUSIONS

AEDs showed different performances that may reduce CPR quality mostly for those rescuers following AED instructions. Both technological improvements and better lay rescuers training might be needed.

Providers with Limited Experience Perform Better in Advanced Life Support with Assistance Using an Interactive Device with an Automated External Defibrillator Linked to a Ventilator

BACKGROUND

Medical teams with limited experience in performing advanced life support (ALS) or with a low frequency of cardiopulmonary resuscitation (CPR) while on duty, often have difficulty complying with CPR guidelines.

OBJECTIVE

This study evaluated whether the quality of CPR of trained medical students, who served as an example of teams with limited experience in ALS, could be improved with device assistance. The primary outcome was the hands-off time (i.e., the percentage of the entire CPR time without chest compressions). The secondary outcome was seven time intervals, which should be as short as possible, and the quality of ventilations and chest compressions on the mannequin.

METHODS

We compared standard CPR equipment to an interactive device with visual and acoustic instructions for ALS workflow measures to guide briefly trained medical students through the ALS algorithm in a full-scale mannequin simulation study with a randomized crossover study design. The study equipment consisted of an automatic external defibrillator and ventilator that were electronically linked and communicating as a single system. Included were regular medical students in the third to sixth years of medical school of one class who provided written informed consent for voluntary participation and for the analysis of their CPR performance data. No exclusion criteria were applied. For statistical measures of evaluation we used an analysis of variance for crossover trials accounting for treatment effect, sequence effect, and carry-over effect, with adjustment for prior practical experience of the participants.

RESULTS

Forty-two medical students participated in 21 CPR sessions, each using the standard and study equipment. Regarding the primary end point, the study equipment reduced the hands-off time from 40.1% (95% confidence interval [CI] 36.9-43.4%) to 35.6% (95% CI 32.4-38.9%, p = 0.031) compared with the standard equipment. Within the prespecified secondary end points, study equipment reduced the time interval until the first rescuer changeover from 273 s (95% CI 244-302 s) to 223 s (95% CI 194-253 s, p = 0.001) and increased the percentage of ventilations with a correct tidal volume of 400-600 mL from 34.3% (95% CI 19.0-49.6%) to 60.9% (95% CI 45.6-76.2%, p = 0.018).

CONCLUSIONS

The assist device increased the rescuers' CPR quality. CPR providers with limited experience or a limited frequency of CPR performance (i.e., rural Emergency Medical Services crew) may potentially benefit from this assist device.

Advanced life support therapy on out-of-hospital cardiac arrest patients: an engineering perspective

In the USA alone, several hundred thousand people die of sudden cardiac arrests each year. Basic life support, defined as chest compressions and ventilations, and early defibrillation are the only factors proven to increase the survival of patients with out-of-hospital cardiac arrest and are key elements in the chain of survival defined by the American Heart Association. The current cardiopulmonary resuscitation guidelines treat all patients the same but studies show a need for more individualization of treatment. This review focusses on ideas on how to strengthen the weak parts of the chain of survival including the ability to measure the effects of therapy, improve time efficiency and optimize the sequence and quality of the various components of cardiopulmonary resuscitation.

Optimizing the duration of CPR prior to defibrillation improves the outcome of CPR in a rat model of prolonged cardiac arrest

AIMS

This study was to investigate whether optimal duration of CPR prior to defibrillation could be guided by Amplitude Spectrum Analysis (AMSA) in the setting of prolonged VF on outcome of CPR.

METHODS

VF was induced in thirty Sprague-Dawley rats and untreated for 8 minutes. Animals were then randomized into 3 groups prior to CPR: The duration of CPR prior to defibrillation was guided by AMSA (CC+AMSA); guidelines-based with delayed defibrillation that simulated the AED algorithm (GL+AED); and guidelines-based with immediate shock (GL+shock ready).

RESULTS

Regardless of groups, the majority of the animals (85%) required over 5 min of CPR to achieve restoration of spontaneous circulation (ROSC). Significantly greater rate of ROSC after first defibrillation (70% vs 0%, p < 0.01), lesser CPR interruptions and the number of defibrillations were observed in the CC+AMSA group when compared to both guidelines-based groups (p < 0.001). This was associated with a significantly better post-resuscitation myocardial and neurological function and longer durations of survival.

CONCLUSIONS

After prolonged VF, optimal duration of CPR prior to defibrillation guided by AMSA improves the outcome of CPR.

Data management in automated external defibrillators: a call for a standardised solution

BACKGROUND

The ECG data stored in automated external defibrillators (AEDs) may be valuable for establishing a final diagnosis and deciding further diagnostics and treatment. Different data management systems are used and this may create significant problems for data storage and access for physicians treating victims in whom an AED has been used.

METHODS

In this descriptive study, we collected information (number, manufacturer and model) on 17 December 2010 from a web page used for the voluntary registration of AEDs in Denmark. The manufacturers were contacted and asked to provide information about data downloading.

RESULTS

There were 12 different manufactures and 20 different AED models. Five models were registered in a quantity <5. We report data from the remaining 15 models (3603 AEDs). Several models stored only one case or 15 min of ECG data. All models had a data transfer option, but most had outdated 'hardware': Seven had infrared transfer; one had a cable with a serial port. Four had a removable memory device, but only one was a USB. The software was available as freeware only in a few cases. Otherwise, a CD ROM was needed, some even with a licence. The software for the second most common AED could not be installed.

CONCLUSION

The development of data management solutions is not a high priority. We encourage the manufacturers to collaborate with researchers to develop a simple data transfer solution in order to improve patient care and facilitate research.

Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis

BACKGROUND

Prior studies have identified key predictors of out-of-hospital cardiac arrest (OHCA), but differences exist in the magnitude of these findings. In this meta-analysis, we evaluated the strength of associations between OHCA and key factors (event witnessed by a bystander or emergency medical services [EMS], provision of bystander cardiopulmonary resuscitation [CPR], initial cardiac rhythm, or the return of spontaneous circulation). We also examined trends in OHCA survival over time.

METHODS AND RESULTS

An electronic search of PubMed, EMBASE, Web of Science, CINAHL, Cochrane DSR, DARE, ACP Journal Club, and CCTR was conducted (January 1, 1950 to August 21, 2008) for studies reporting OHCA of presumed cardiac etiology in adults. Data were extracted from 79 studies involving 142 740 patients. The pooled survival rate to hospital admission was 23.8% (95% CI, 21.1 to 26.6) and to hospital discharge was 7.6% (95% CI, 6.7 to 8.4). Stratified by baseline rates, survival to hospital discharge was more likely among those: witnessed by a bystander (6.4% to 13.5%), witnessed by EMS (4.9% to 18.2%), who received bystander CPR (3.9% to 16.1%), were found in ventricular fibrillation/ventricular tachycardia (14.8% to 23.0%), or achieved return of spontaneous circulation (15.5% to 33.6%). Although 53% (95% CI, 45.0% to 59.9%) of events were witnessed by a bystander, only 32% (95% CI, 26.7% to 37.8%) received bystander CPR. The number needed to treat to save 1 life ranged from 16 to 23 for EMS-witnessed arrests, 17 to 71 for bystander-witnessed, and 24 to 36 for those receiving bystander CPR, depending on baseline survival rates. The aggregate survival rate of OHCA (7.6%) has not significantly changed in almost 3 decades.

CONCLUSIONS

Overall survival from OHCA has been stable for almost 30 years, as have the strong associations between key predictors and survival. Because most OHCA events are witnessed, efforts to improve survival should focus on prompt delivery of interventions of known effectiveness by those who witness the event.

Using ontologies to integrate and share resuscitation data from diverse medical devices

OBJECTIVE

To propose a method for standardised data representation and demonstrate a technology that makes it possible to translate data from device dependent formats to this standard representation format.

METHODS AND RESULTS

Outcome statistics vary between emergency medical systems organising resuscitation services. Such differences indicate a potential for improvement by identifying factors affecting outcome, but data subject to analysis have to be comparable. Modern technology for communicating information makes it possible to structure, store and transfer data flexibly. Ontologies describe entities in the world and how they relate. Letting different computer systems refer to the same ontology results in a common understanding on data content. Information on therapy such as shock delivery, chest compressions and ventilation should be defined and described in a standardised ontology to enable comparison and combining data from diverse sources. By adding rules and logic data can be merged and combined in new ways to produce new information. An example ontology is designed to demonstrate the feasibility and value of such a standardised structure.

CONCLUSIONS

The proposed technology makes possible capturing and storing of data from different devices in a structured and standardised format. Data can easily be transformed to this standardised format, compared and combined independent of the original structure.

Improving cardiopulmonary resuscitation quality to ensure survival

PURPOSE OF REVIEW

There is correlation between quality of bystander cardiopulmonary resuscitation and patient survival. Recent developments in defibrillator technology enable recording of cardiopulmonary resuscitation quality, and have shown quality of professional cardiopulmonary resuscitation far from guidelines' levels for factors such as chest compression depth and rate, ventilation rate, and pauses in chest compressions. The effects of cardiopulmonary resuscitation quality factors on patient survival are presently under scrutiny.

RECENT FINDINGS

Factors such as depth of and pauses in chest compressions immediately before defibrillation attempts affect outcome. Both immediate automated feedback on cardiopulmonary resuscitation quality and use of the same quality data during postevent debriefing improve cardiopulmonary resuscitation quality, and the combination appears to improve outcome. The increased awareness of quality problems, particularly unwanted pauses in chest compressions, has caused more emphasis on chest compressions in cardiopulmonary resuscitation protocols including the 2005 Guidelines. There is a growing number of reports of increased survival with these new protocols.

SUMMARY

Cardiopulmonary resuscitation quality affects survival after cardiac arrest. Reporting cardiopulmonary resuscitation quality data should be standard in all studies of cardiac arrest as effects of studied interventions can depend on or influence cardiopulmonary resuscitation quality. These data are also valuable in quality improvement processes both in-hospital and out-of-hospital.

Automatic identification of return of spontaneous circulation during cardiopulmonary resuscitation

The main problem during pulse check in out-of-hospital cardiac arrest is the discrimination between normal pulse-generating rhythm (PR) and pulseless electrical activity (PEA). It has been suggested that circulatory information can be acquired by measuring the thoracic impedance via the defibrillator pads. To investigate this, we performed an experimental study where we retrospectively analyzed 127 PEA segments and 91 PR segments out of 219 and 113 segments. A PEA versus PR classification framework was developed, that uses short segments (< 10 s) of ECG and impedance measurements to discriminate between the two rhythms. Using realistic data analyzed over a duration of 3 s, our system correctly identifies 90.0% of the segments with rhythm being pulseless electrical activity, and 91.5% of the normal pulse rhythm segments. Automatic identification of pulse could avoid unnecessary pulse checks and thereby reduce no-flow time and potentially increase the chance of survival.

Quality of cardiopulmonary resuscitation before and during transport in out-of-hospital cardiac arrest

AIM OF THE STUDY

To evaluate quality of cardiopulmonary resuscitation (CPR) performed during transport after out-of-hospital cardiac arrest.

MATERIALS AND METHODS

Retrospective, observational study of all non-traumatic cardiac arrest patients older than 18 years who received CPR both before and during transport between May 2003 and December 2006 from the community run EMS system in Oslo. Chest compressions and ventilations were detected from impedance changes in routinely collected ECG signals, and hands-off ratio calculated as time without chest compressions divided by total CPR time.

RESULTS

Seventy-five of 787 consecutive out-of-hospital cardiac arrest patients met the inclusion criteria. Quality data were available from 36 of 66 patients receiving manual CPR and 7 of 9 receiving mechanical CPR. CPR was performed for mean 21+/-11 min before and 12+/-8 min during transport. With manual CPR hands-off ratio increased from 0.19+/-0.09 on-scene to 0.27+/-0.15 (p=0.002) during transport. Compression and ventilation rates were unchanged causing a reduction in compressions per minute from 94+/-14 min(-1) to 82+/-19 min(-1) (p=0.001). Quality was significantly better with mechanical than manual CPR. Four patients (5%) survived to hospital discharge; two with manual CPR (Cerebral performance categories (CPC) 1 and 2), and two with mechanical CPR (CPC scores 3 and 4). No discharged patients had any spontaneous circulation during transport.

CONCLUSIONS

The fraction of time without chest compressions increased during transport of out-of-hospital cardiac arrest patients. Every effort should therefore be made to stabilise patients on-scene before transport to hospital, but all transport with ongoing CPR is not futile.

Is CPR quality improving? A retrospective study of out-of-hospital cardiac arrest

AIM OF THE STUDY

To evaluate the quality of cardiopulmonary resuscitation (CPR) performed by a physician-manned ambulance, and assess whether it changed with time influenced by developing scientific evidence and guideline changes.

MATERIALS AND METHODS

A retrospective, observational study of all cardiac arrest patients (except trauma) older than 18 years treated between May 2003 and December 2006 by the physician-manned ambulance in Oslo. CPR quality was assessed from continuous electronic recordings from the defibrillators (LIFEPAK 12, Physio-Control or a modified Heartstart 4000, Philips Medical Systems). Ventilations were assessed from changes in transthoracic impedance, chest compressions from transthoracic impedance for LIFEPAK 12 and from an accelerometer for Heartstart 4000 (nine patients). Values are given as mean+/-S.D. and differences analysed with ANOVA and unpaired Student's t-test with Bonferroni correction.

RESULTS

Forty-eight of 169 consecutive cases were excluded from CPR quality analysis, 47 due to missing defibrillator data and one due to a short arrest time (<1min). Hands-off intervals (fraction of time without spontaneous circulation where no chest compressions are given) were reduced from 0.18+/-0.11 in 2003 to 0.10+/-0.06 in 2006 (p=0.03). Compression and ventilation rates were significantly reduced from 122+/-12 and 16+/-3min(-1), respectively in 2003 to 111+/-10 and 12+/-3 in 2006 (p<0.0001 and p=0.001). In 2003-2004 10% were discharged alive versus 16% in 2005-2006 (p=0.3, Chi-square test).

CONCLUSION

High quality CPR is achievable out-of-hospital, and the improvement with time could reflect developing scientific evidence focusing on reducing hands-off intervals and hyperventilation.

Shock outcome is related to prior rhythm and duration of ventricular fibrillation

BACKGROUND

Several different ventricular fibrillation (VF) analysis features based on ECG have been reported for shock outcome prediction. In this study we investigated the influence of the time from VF onset to shock delivery (VF duration) and the rhythm before onset of VF, on the probability of return of spontaneous circulation (ROSC). We also analysed how these factors relate to the VF analysis feature median slope.

METHODS

ECG recordings from 221 cardiac arrest patients from previously published prospective studies on the quality of CPR were used. VF duration and prior rhythm were determined when VF occurred during the episode. Median slope before each shock was calculated.

RESULTS

The median VF duration was shorter in shocks producing ROSC, 24 seconds (s) versus 70s (P<0.001). VF duration shorter than 30s resulted in 27% ROSC versus 10% for those longer than 30s (OR=3.5 [95% CI: 2.2-5.4]). The prior rhythm influenced the probability of ROSC, with perfusing rhythm being superior, followed by PEA, asystole, and "poor" PEA (broad complexes and/or irregular/very slow rate), respectively. The probability of ROSC corresponded well with the average median slope value for each group, but the correlation between median slope and VF duration was very poor (r2=0.05).

CONCLUSIONS

Based on our findings, detection of VF during ongoing chest compressions might be valuable because VF of short duration was associated with ROSC. Further, the rhythm before VF affects shock outcome with a perfusing rhythm giving the best prospect. The median slope can be used for shock outcome prediction, but not for determining VF duration. A combination could be beneficial and warrants further studies.

Uniform reporting of measured quality of cardiopulmonary resuscitation (CPR)

BACKGROUND

CPR quality is an important determinant of cardiac arrest outcome. Recent investigations have demonstrated that quality of clinical CPR is variable and often not in compliance with international consensus guidelines. The 2005 update of these guidelines included new recommendations for the measurement of resuscitation and CPR performance and the institution of measures to improve resuscitation care. Common definitions and reporting templates need to be established for the variables of CPR quality. This will allow for meaningful comparisons between treatment groups in clinical trials as well as a common system for quality improvement and documentation of this improvement.

METHODS/RESULTS

In this report, we present the results from an international consensus working group to propose common definitions and criteria for reporting variables of CPR quality, based on the best available data for the importance of various CPR variables. The recommendations are discussed in light of the different purposes outlined above.

Comparison of hands-off time during CPR with manual and semi-automatic defibrillation in a manikin model

BACKGROUND

Rhythm analysis with current semi-automatic external defibrillators (AEDs) requires mandatory interruptions of chest compressions that may compromise the outcome after cardiopulmonary resuscitation (CPR). We hypothesised that interruptions would be shorter when the defibrillator was operated in manual mode by trained and certified ambulance personnel.

MATERIALS AND METHODS

Sixteen pairs of ambulance personnel operated the defibrillator (Lifepak((R))12) in both semi-automatic (AED) and manual (MED) mode in a randomised, cross-over manikin CPR study, following the ERC 2000 Guidelines.

RESULTS

Median time from last chest compression to shock delivery (with interquartile range) was 17s (13, 18) versus 11s (6, 15) (mean difference (95% CI) 6s (2, 10), p=0.004). Similarly, median time from shock delivery to resumed chest compressions was 25s (22, 26) versus 8s (7, 12) (median difference 13s, p=0.001) in the AED and MED groups, respectively. While sensitivity for identifying ventricular fibrillation (VF) in both modes and specificity in the AED mode were 100%, specificity was 89% in manual mode. Thus, some unwarranted shocks resulting in hands-off time (time without chest compressions) were given in manual mode. However, mean hands-off-ratio (time without chest compressions divided by total resuscitation time) was still lower, 0.2s (0.1, 0.3) versus 0.3s (0.28, 0.32) in manual mode, mean difference 0.10s (0.05, 0.15), p=0.001.

CONCLUSION

Paramedics performed CPR with less hands-off time before and after shocks on a manikin with manual compared to semi-automatic defibrillation following the 2000 Guidelines. However, 12% of the shocks given manually were inappropriate.

Implementation of a standardised treatment protocol for post resuscitation care after out-of-hospital cardiac arrest

BACKGROUND

Mortality among patients admitted to hospital after out-of-hospital cardiac arrest (OHCA) is high. Based on recent scientific evidence with a main goal of improving survival, we introduced and implemented a standardised post resuscitation protocol focusing on vital organ function including therapeutic hypothermia, percutaneous coronary intervention (PCI), control of haemodynamics, blood glucose, ventilation and seizures.

METHODS

All patients with OHCA of cardiac aetiology admitted to the ICU from September 2003 to May 2005 (intervention period) were included in a prospective, observational study and compared to controls from February 1996 to February 1998.

RESULTS

In the control period 15/58 (26%) survived to hospital discharge with a favourable neurological outcome versus 34 of 61 (56%) in the intervention period (OR 3.61, CI 1.66-7.84, p=0.001). All survivors with a favourable neurological outcome in both groups were still alive 1 year after discharge. Two patients from the control period were revascularised with thrombolytics versus 30 (49%) receiving PCI treatment in the intervention period (47 patients (77%) underwent cardiac angiography). Therapeutic hypothermia was not used in the control period, but 40 of 52 (77%) comatose patients received this treatment in the intervention period.

CONCLUSIONS

Discharge rate from hospital, neurological outcome and 1-year survival improved after standardisation of post resuscitation care. Based on a multivariate logistic analysis, hospital treatment in the intervention period was the most important independent predictor of survival.

Who is reviewing the data review systems of automated external defibrillators? Implications of flawed time lines for clinicians and researchers

The unintentional print-out by two different software programmes of the same resuscitation-related events stored on a data card of a Laerdal FR2-automated external defibrillator (AED), led to the discovery of flaws in the registration of the time line by one of the commercially available Laerdal software programmes. This observation stresses the need for a continuation of the medical supervision of AED projects, the close co-operation between clinicians and AED manufacturers, the well-controlled introduction of new devices and strict postmarket surveillance programmes.

Difficulty of cardiac arrest rhythm identification does not correlate with length of chest compression pause before defibrillation

OBJECTIVE

Performing high-quality cardiopulmonary resuscitation immediately before electrical defibrillation serves as an important predictor of shock success. Long preshock pauses in cardiopulmonary resuscitation frequently occur, as noted by recent clinical investigations. We sought to determine whether these long pauses were due to difficulties in identifying shockable rhythms or rather due to local factors during resuscitation attempts.

DESIGN

Prospective in-hospital study of cardiac arrest resuscitation attempts coupled with a retrospective review of preshock pause rhythms by 12 trained providers. Reviewers scored rhythms by ease of identification using a discrete Likert scale from 1 (most difficult to identify) to 5 (easiest to identify). The resuscitation cohort was organized into preshock pause-duration quartiles for statistical analysis. Resident physicians were then surveyed regarding human factors affecting preshock pauses.

RESULTS

A total of 118 preshock pauses from 45 resuscitation episodes were collected. When evaluated by quartiles of preshock pause duration, difficulty of rhythm identification did not correlate with increasing pause time. In fact, the opposite was found (longest preshock pause quartile of 23.8-60.2 secs vs. shortest pause quartile of 1.1-7.9 secs; rhythm difficulty scores, 3.2 vs. 3.0; p = .20). When 29 resident physicians who recently served on resuscitation teams were surveyed, 18 of 29 (62.1%) attributed long pauses to lack of time sense during resuscitation, and 16 of 29 (55.2%) thought that room crowding prevented rapid defibrillation.

CONCLUSIONS

Long cardiopulmonary resuscitation pauses before defibrillation are likely due to human factors during the resuscitation and not due to inherent difficulties with rhythm identification. This preliminary work highlights the need for more research and training in the area of team performance and human factors during resuscitation.

Haemodynamic effects of adrenaline (epinephrine) depend on chest compression quality during cardiopulmonary resuscitation in pigs

BACKGROUND

Adrenaline (epinephrine) is used during cardiopulmonary resuscitation (CPR) based on animal experiments without supportive clinical data. Clinically CPR was reported recently to have much poorer quality than expected from international guidelines and what is generally done in laboratory experiments. We have studied the haemodynamic effects of adrenaline during CPR with good laboratory quality and with quality simulating clinical findings and the feasibility of monitoring these effects through VF waveform analysis.

METHODS AND RESULTS

After 4 min of cardiac arrest, followed by 4 min of basic life support, 14 pigs were randomised to ClinicalCPR (intermittent manual chest compressions, compression-to-ventilation ratio 15:2, compression depth 30-38 mm) or LabCPR (continuous mechanical chest compressions, 12 ventilations/min, compression depth 45 mm). Adrenaline 0.02 mg/kg was administered 30 s thereafter. Plasma adrenaline concentration peaked earlier with LabCPR than with ClinicalCPR, median (range), 90 (30, 150) versus 150 (90, 270) s (p = 0.007), respectively. Coronary perfusion pressure (CPP) and cortical cerebral blood flow (CCBF) increased and femoral blood flow (FBF) decreased after adrenaline during LabCPR (mean differences (95% CI) CPP 17 (6, 29) mmHg (p = 0.01), FBF -5.0 (-8.8, -1.2) ml min(-1) (p = 0.02) and median difference CCBF 12% of baseline (p = 0.04)). There were no significant effects during ClinicalCPR (mean differences (95% CI) CPP 4.7 (-3.2, 13) mmHg (p = 0.2), FBF -0.2 (-4.6, 4.2) ml min(-1)(p = 0.9) and CCBF 3.6 (-1.8, 9.0)% of baseline (p = 0.15)). Slope VF waveform analysis reflected changes in CPP.

CONCLUSION

Adrenaline improved haemodynamics during laboratory quality CPR in pigs, but not with quality simulating clinically reported CPR performance.

Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: A prospective interventional study

AIMS

To compare quality of CPR during out-of-hospital cardiac arrest with and without automated feedback.

MATERIALS AND METHODS

Consecutive adult, out-of-hospital cardiac arrests of all causes were studied. One hundred and seventy-six episodes (March 2002-October 2003) without feedback were compared to 108 episodes (October 2003-September 2004) where automatic feedback on CPR was given. Automated verbal and visual feedback was based on measured quality with a prototype defibrillator. Quality of CPR was the main outcome measure and survival was reported as specified in the protocol.

RESULTS

Average compression depth increased from (mean +/- S.D.) 34 +/- 9 to 38 +/- 6 mm (mean difference (95% CI) 4 (2, 6), P < 0.001), and median percentage of compressions with adequate depth (38-51 mm) increased from 24% to 53% (P < 0.001, Mann-Whitney U-test) with feedback. Mean compression rate decreased from 121 +/- 18 to 109 +/- 12 min(-1) (difference -12 (-16, -9), P = 0.001). There were no changes in the mean number of ventilations per minute; 11 +/- 5 min(-1) versus 11 +/- 4 min(-1) (difference 0 (-1, 1), P = 0.8) or the fraction of time without chest compressions; 0.48 +/- 0.18 versus 0.45 +/- 0.17 (difference -0.03 (-0.08, 0.01), P = 0.08). With intention to treat analysis 7/241 control patients were discharged alive (2.9%) versus 5/117 with feedback (4.3%) (OR 1.5 (95% CI; 0.8, 3), P = 0.2). In a logistic regression analysis of all cases, witnessed arrest (OR 4.2 (95% CI; 1.6, 11), P = 0.004) and average compression depth (per mm increase) (OR 1.05 (95% CI; 1.01, 1.09), P = 0.02) were associated with rate of hospital admission.

CONCLUSIONS

Automatic feedback improved CPR quality in this prospective non-randomised study of out-of-hospital cardiac arrest. Increased compression depth was associated with increased short-term survival.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT00138996), http://www.clinicaltrials.gov/.

Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest

BACKGROUND

Cardiopulmonary resuscitation (CPR) and electrical defibrillation are the primary treatment options for ventricular fibrillation (VF). While recent studies have shown that providing CPR prior to defibrillation may improve outcomes, the effects of CPR quality remain unclear. Specifically, the clinical effects of compression depth and pauses in chest compression prior to defibrillation (pre-shock pauses) are unknown.

METHODS

A prospective, multi-center, observational study of adult in-hospital and out-of-hospital cardiac resuscitations was conducted between March 2002 and December 2005. An investigational monitor/defibrillator equipped to measure compression characteristics during CPR was used.

RESULTS

Data were analyzed from 60 consecutive resuscitations in which a first shock was administered for VF. The primary outcome was first shock success defined as removal of VF for at least 5s following defibrillation. A logistic regression analysis demonstrated that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio 1.86 for every 5s decrease; 95% confidence interval 1.10-3.15) and higher mean compression depth during the 30s of CPR preceding the pre-shock pause (adjusted odds ratio 1.99 for every 5mm increase; 95% confidence interval 1.08-3.66).

CONCLUSIONS

The quality of CPR prior to defibrillation directly affects clinical outcomes. Specifically, longer pre-shock pauses and shallow chest compressions are associated with defibrillation failure. Strategies to correct these deficiencies should be developed and consideration should be made to replacing current-generation automated external defibrillators that require long pre-shock pauses for rhythm analysis.

Practical issues in the evaluation of methods for the prediction of shock outcome success in out-of-hospital cardiac arrest patients

There is a need for robust, effective predictors of the outcome from shock for out-of-hospital cardiac arrest patients. Such technology would enable the emergency responder to provide a therapy tailored to the patient's needs. Here we report our most recent findings while dwelling intentionally on the rationale behind the decisions taken during system development. Specifically, we illustrate the need for sensible data selection, fully cross-validated results and the care necessary when evaluating system performance. We analyze 878 pre-shock ECG traces, all of at least 10 s duration from 110 patients with cardiac arrest of cardiac aetiology. The continuous wavelet transform was applied to preshock segments of ECG trace. Time-frequency markers are extracted from the transform and a linear threshold derived from a training set to provide high sensitivity prediction of successful defibrillation. These systems are then evaluated on a withheld test set. All experiments are cross-validated. When compared to popular Fourier-based techniques our wavelet transform method, COP (Cardioversion Outcome Predictor), provides a 10-20% improvement in performance with values of 66 +/- 4 specificity at 95 +/- 4 sensitivity, 61 +/- 4 specificity at 97 +/- 2 sensitivity and 56 +/- 1 specificity at 98 +/- 2 sensitivity achieved for datasets limited to 3, 6, and 9 shocks per patient, respectively. Thus, the assessment of the wavelet marker was associated with a high specificity value at or above 95% sensitivity in comparison to previously reported methods. Therefore, COP could provide an optimal index for the identification of patients for whom shocking would be futile, and for whom an alternative therapy could be considered.