The association between chest compression release velocity and outcomes from out-of-hospital cardiac arrest

BackgroundPrevious studies have demonstrated significant relationships between cardiopulmonary resuscitation (CPR) quality metrics and survival to hospital discharge from out-of-hospital cardiac arrest (OHCA). Recently, it has been suggested that a new metric, chest compression release velocity (CCRV), may be associated with improved survival from OHCA.Methods and resultsWe performed a retrospective review of all treated adult OHCA occurring over a two year period beginning January 1, 2012. CPR metrics were abstracted from accelerometer measurements during each resuscitation. Multivariable regression analysis was used to examine the impact of CCRV on survival to hospital discharge. Secondary outcome measures were the impact of CCRV on return of spontaneous circulation (ROSC) and neurologically intact survival (MRS ≤ 3). Among 1800 treated OHCA, 1137 met inclusion criteria. The median (IQR) age was 71.6 (60.6, 82.3) with 724 (64%) being male. The median (IQR) CCRV (mm/s) amongst 96 survivors was 334.5 (300.0, 383.2) compared to 304.0 (262.6, 354.1) in 1041 non survivors (p < 0.001). When adjusted for Utstein variables, the odds of survival to hospital discharge for each 10 mm/s increase in CCRV was 1.02 (95% CI: 0.98, 1.06). Similarly the odds of ROSC and neurologically intact survival were 1.01 (95% CI: 0.99, 1.03) and 1.02 (95% CI: 0.98, 1.06), respectively.ConclusionsWhen adjusted for Utstein variables, CCRV was not significantly associated with outcomes from OHCA. Further research in other EMS systems is required to clarify the potential impact of this variable on OHCA survival.     

The effect of transport on quality of cardiopulmonary resuscitation in out-of-hospital cardiac arrest

IntroductionMost manikin and clinical studies have found decreased quality of CPR during transport to hospital. We wanted to study quality of CPR before and during transport for out-of-hospital cardiac arrest patients and also whether quality of CPR before initiation of transport was different from the quality in patients only receiving CPR on scene.Materials and methodsQuality of CPR was prospectively registered with a modified defibrillator for consecutive cases of out-of-hospital cardiac arrest in three ambulance services during 2002–2005. Ventilations were registered via changes in transthoracic impedance and chest compressions were measured with an extra chest compression pad placed on the patients’ sternum. Paired t-tests were used to analyse quality of CPR before vs. during transport with ongoing CPR. Unpaired t-tests were used to compare CPR quality prior to transport to CPR quality in patients with CPR terminated on site.ResultsQuality of CPR did not deteriorate during transport, but as previously reported overall quality of CPR was substandard. Quality of CPR performed on site was significantly better when transport was not initiated with ongoing CPR compared to episodes with initiation of transport during CPR: fraction of time without chest compressions was 0.45 and 0.53 (p < 0.001), compression depth 37 mm and 34 mm (p = 0.04), and number of chest compressions per minute 61 and 56 (p = 0.01), respectively.ConclusionCPR quality was sub-standard both before and during transport. Early decision to transport might have negatively affected CPR quality from the early stages of resuscitation.     

Assessment of CPR interruptions from transthoracic impedance during use of the LUCAS™ mechanical chest compression system

BackgroundQuality of cardiopulmonary resuscitation (CPR) is a key determinant of outcome following out-of-hospital cardiac arrest (OHCA). Recent evidence shows manual chest compressions are typically too shallow, interruptions are frequent and prolonged, and incomplete release between compressions is common. Mechanical chest compression systems have been developed as adjuncts for CPR but interruption of CPR during their use is not well documented.AimAnalyze interruptions of CPR during application and use of the LUCAS? chest compression system.Methods54 LUCAS 1 devices operated on compressed air, deployed in 3 major US emergency medical services systems, were used to treat patients with OHCA. Electrocardiogram and transthoracic impedance data from defibrillator/monitors were analyzed to evaluate timing of CPR. Separately, providers estimated their CPR interruption time during application of LUCAS, for comparison to measured application time.ResultsIn the 32 cases analyzed, compressions were paused a median of 32.5 s (IQR 25–61) to apply LUCAS. Providers’ estimates correlated poorly with measured pause length; pauses were often more than twice as long as estimated. The average device compression rate was 104/min (SD 4) and the average compression fraction (percent of time compressions were occurring) during mechanical CPR was 0.88 (SD 0.09).ConclusionsInterruptions in chest compressions to apply LUCAS can be <20 s but are often much longer, and users do not perceive pause time accurately. Therefore, we recommend better training on application technique, and implementation of systems using impedance data to give users objective feedback on their mechanical chest compression device use.     

Mechanical active compression–decompression cardiopulmonary resuscitation (ACD-CPR) versus manual CPR according to pressure of end tidal carbon dioxide (PETCO2) during CPR in out-of-hospital cardiac arrest (OHCA)

AimIn animal and human studies, measuring the pressure of end tidal carbon dioxide (P_ETCO₂) has been shown to be a practical non-invasive method that correlates well with the pulmonary blood flow and cardiac output (CO) generated during cardiopulmonary resuscitation (CPR). This study aims to compare mechanical active compression–decompression (ACD) CPR with standard CPR according to P_ETCO₂ among patients with out-of-hospital cardiac arrest (OHCA), during CPR and with standardised ventilation.MethodsThis prospective, on a cluster level, pseudo-randomised pilot trial took place in the Municipality of Göteborg. During a 2-year period, all patients aged >18 years suffering an out-of-hospital cardiac arrest (OHCA) of presumed cardiac etiology were enrolled. The present analysis included only tracheally intubated patients in whom P_ETCO₂ was measured for 15 min or until the detection of a pulse-giving rhythm.ResultsIn all, 126 patients participated in the evaluation, 64 patients in the mechanical chest compression group and 62 patients in the control group. The group receiving mechanical ACD-CPR obtained the significantly highest P_ETCO₂ values according to the average (p = 0.04), initial (p = 0.01) and minimum (p = 0.01) values. We found no significant difference according to the maximum value between groups.ConclusionIn this hypothesis generating study mechanical ACD-CPR compared with manual CPR generated the highest initial, minimum and average value of P_ETCO₂. Whether these data can be repeated and furthermore be associated with an improved outcome after OHCA need to be confirmed in a large prospective randomised trial.     

Advanced life support performance with manual and mechanical chest compressions in a randomized,multicentre manikin study

Aim of the studyClinical mechanical chest compression studies report diverging outcomes. Confounding effects of variability in hands-off fraction (HOF) and timing of necessary tasks during advanced life support (ALS) may contribute to this divergence. Study site variability in these factors coupled to randomization of cardiopulmonary resuscitation (CPR) method was studied during simulated cardiac arrest prior to a multicentre clinical trial.MethodAmbulance personnel from four sites were tested in randomized, simulated cardiac arrest scenarios with manual CPR or load-distributing band CPR (LDB-CPR) on manikins. Primary emphasis was on HOF and time spent before necessary predefined ALS task (ALS milestones). Results are presented as mean differences (confidence interval).ResultsAt the site with lowest HOF during manual CPR, HOF deteriorated with LDB-CPR by 0.06 (0.005, 0.118, p = 0.04), while it improved at the two sites with highest HOF during manual CPR by 0.07 (0.019, 0.112, p = 0.007) and 0.08 (0.004, 0.165, p = 0.042). Initial defibrillation was 29 (3, 55, p = 0.032) s delayed for LDB-CPR vs. manual CPR. Other ALS milestones trended toward earlier completion with LDB-CPR; only significant for intravenous access, mean difference 70 (24, 115, p = 0.003) s.ConclusionIn this manikin study, HOF for manual vs. mechanical chest compressions varied between sites. Study protocol implementation should be simulation tested before launching multicentre trials, to optimize performance and improve reliability and scientific interpretation.     

A quality improvement initiative to optimize use of a mechanical chest compression device within a high-performance CPR approach to out-of-hospital cardiac arrest resuscitation

BackgroundMinimizing the chest compression pause associated with application of a mechanical CPR device is a key component of optimal integration into the overall resuscitation process. As part of a multi-agency implementation project, Anchorage Fire Department deployed LUCAS CPR devices on BLS and ALS fire apparatus for initiation early in resuscitation efforts. A 2012 report identified the pause interval for device application as a key opportunity for quality improvement (QI). In early 2013 we began a QI initiative to reduce device application time interval and optimize the overall CPR process. To assess QI initiative effectiveness, we compared key CPR process metrics from before to during and after its implementation.MethodsWe included all cases of EMS-treated out-of-hospital cardiac arrest during 2012 and 2013 in which a mechanical CPR device was used and the defibrillator electronic record was available. Continuous ECG and impedance data were analyzed to measure chest compression fraction, duration of the pause from last manual to first mechanical compression, and duration of the longest overall pause in the resuscitation effort.ResultsCompared to cases from 2012 (n = 61), median duration of the pause prior to first mechanical compression for cases from 2013 (n = 71) decreased from 21 (15, 31) to 7 (4, 12) s (p < 0.001), while median chest compression fraction increased from 0.90 (0.88, 0.93) to 0.95 (0.93, 0.96) (p < 0.001). Median duration of the longest pause decreased from 25 (20, 35) to 13 (10, 20) s (p < 0.001), while the proportion of cases where the longest pause was for mechanical CPR application decreased from 74% to 31% (p < 0.001).ConclusionsOur QI initiative substantially reduced the duration of the pause prior to first mechanical compression. Combined with the simultaneous significant increase in compression fraction and significant decrease in duration of the longest pause, this finding strongly suggests a large improvement in mechanical CPR device application efficiency within an overall high-performance CPR process.     

Outcome of avalanche victims with out-of-hospital cardiac arrest

Study backgroundPrevious studies focused on the outcome of avalanche victims with out-of-hospital cardiac arrest (OHCA) after long duration of burial (>35 min); the outcome of victims with short duration (≤35 min) remains obscure.Aim of the studyTo investigate outcome of avalanche victims with OHCA.MethodsRetrospective analysis of avalanche victims with OHCA between 2008 and 2013 in the Tyrolean Alps.Results55 avalanche victims were identified, 32 of whom were declared dead after extrication without cardiopulmonary resuscitation (CPR), all with long duration of burial. In the remaining 23 CPR was initiated at scene; three were partially and 20 completely buried, nine of whom suffered short and 11 long duration of burial. All nine victims with short duration of burial underwent restoration of spontaneous circulation (ROSC) at scene, four of them after bystander CPR, five after advanced life support by the emergency physician. Two patients with ROSC after short duration of burial and bystander CPR survived to hospital discharge with cerebral performance category 1. None of the 11 victims with long duration of burial survived to hospital discharge, although six were transported to hospital with ongoing CPR and three were supported with extracorporeal circulation.ConclusionsIn this case series survival with favourable neurological outcome was observed in avalanche victims with short duration of burial only if bystander CPR was immediately performed and ROSC achieved. Strategies for reducing avalanche mortality should focus on prompt extrication from the snow and immediate bystander CPR by uninjured companions.     

“Rolling Refreshers”: A novel approach to maintain CPR psychomotor skill competence

ObjectivesHigh quality CPR skill retention is poor. We hypothesized that “just-in-time” and “just-in-place” training programs would be effective and well-accepted to maintain CPR skills among PICU staff.Methods“Rolling Refreshers”, a portable manikin/defibrillator system with chest compression sensor providing automated corrective feedback to optimize CPR skills, were conducted daily in the PICU with multidisciplinary healthcare providers. Providers practiced CPR until skill success was attained, prospectively defined as <3 corrective prompts within 30 s targeting chest compression (CC) rate 90–120/min, CC depth >38 mm during continuous CPR. Providers completing ≥2 refreshers/month (Frequent Refreshers [FR]) were compared to providers completing <2 refreshers/month (Infrequent Refreshers [IR]) for time to achieve CPR skill success. Univariate analysis performed using non-parametric methods. Following actual cardiac arrests, CPR providers were surveyed for subjective feedback on training approach efficacy (5-point Likert scale; 1 = poor to 5 = excellent).ResultsOver 15 weeks, 420 PICU staff were “refreshed”: 340 nurses, 34 physicians, 46 respiratory therapists. A consecutive sample of 20 PICU staff was assessed before subsequent refresher sessions (FREQ n = 10, INFREQ n = 10). Time to achieve CPR skill success was significantly less in FREQ (median 21 s, IQR: 15.75–30 s) than in INFREQ (median 67 s, IQR: 41.5–84 s; p < 0.001). Following actual resuscitations, CPR providers (n = 9) rated “Rolling Refresher” training as effective (mean = 4.2; Likert scale 1–5; standard deviation 0.67).ConclusionsA novel “Rolling Refresher” CPR skill training approach using “just-in-time” and “just-in-place” simulation is effective and well received by PICU staff. More frequent refreshers resulted in significantly shorter times to achieve proficient CPR skills.     

An investigation of thrust,depth and the impedance cardiogram as measures of cardiopulmonary resuscitation efficacy in a porcine model of cardiac arrest

ObjectiveOptimising the depth and rate of applied chest compressions following out of hospital cardiac arrest is crucial in maintaining end organ perfusion and improving survival. The impedance cardiogram (ICG) measured via defibrillator pads produces a characteristic waveform during chest compressions with the potential to provide feedback on cardiopulmonary resuscitation (CPR) and enhance performance. The objective of this pre-clinical study was to investigate the relationship between mechanical and physiological markers of CPR efficacy in a porcine model and examine the strength of correlation between the ICG amplitude, compression depth and end-tidal CO₂ (ETCO₂).MethodsTwo experiments were performed using 24 swine (12 per experiment). For experiment 1, ventricular fibrillation (VF) was induced and mechanical CPR commenced at varying thrusts (0–60 kg) for 2 min intervals. Chest compression depth was recorded using a Philips QCPR device with additional recording of invasive physiological parameters: systolic blood pressure, ETCO2, cardiac output and carotid flow. For experiment 2, VF was induced and mechanical CPR commenced at varying depths (0–5 cm) for 2 min intervals. The ICG was recorded via defibrillator pads attached to the animal's sternum and connected to a Heartsine 500P defibrillator. ICG amplitude, chest compression depth, systolic blood pressure and ETCO₂ were recorded during each cycle. In both experiments the within-animal correlation between the measured parameters was assessed using a mixed effect model.ResultsIn experiment 1 moderate within-animal correlations were observed between physiological parameters and compression depth (r = 0.69–0.77) and thrust (r = 0.66–0.82). A moderate correlation was observed between compression depth and thrust (r = 0.75). In experiment 2 a strong within-animal correlation and moderate overall correlations were observed between ICG amplitude and compression depth (r = 0.89, r = 0.79) and ETCO₂ (r = 0.85, r = 0.64).ConclusionIn this porcine model of induced cardiac arrest moderate within animal correlations were observed between mechanical and physiological markers of chest compression efficacy demonstrating the challenge in utilising a single mechanical metric to quantify chest compression efficacy. ICG amplitude demonstrated strong within animal correlations with compression depth and ETCO₂ suggesting its potential utility to provide CPR feedback in the out of hospital setting to improve performance.     

Public Access Defibrillation: Great benefit and potential but infrequently used

BackgroundIn Copenhagen, a volunteer-based Automated External Defibrillator (AED) network provides a unique opportunity to assess AED use.We aimed to determine the proportion of Out-of-Hospital Cardiac Arrest (OHCA) where an AED was applied before arrival of the ambulance, and the proportion of OHCA-cases where an accessible AED was located within 100 m. In addition, we assessed 30-day survival.MethodsUsing data from the Mobile Emergency Care Unit and the Danish Cardiac Arrest Registry, we identified 521 patients with OHCA between October 1, 2011 and September 31, 2013 in Copenhagen, Denmark.ResultsAn AED was applied in 20 cases (3.8%, 95% CI [2.4 to 5.9]). Irrespective of AED accessibility, an AED was located within 100 m of a cardiac arrest in 23.4% (n = 102, 95% CI [19.5 to 27.7]) of all OHCAs. However, at the time of OHCA, an AED was located within 100 m and accessible in only 15.1% (n = 66, 95% CI [11.9 to 18.9]) of all cases.The 30-day survival for OHCA with an initial shockable rhythm was 64% for patients where an AED was applied prior to ambulance arrival and 47% for patients where an AED was not applied.ConclusionsWe found that 3.8% of all OHCAs had an AED applied prior to ambulance arrival, but 15.1% of all OHCAs occurred within 100 m of an accessible AED. This indicates the potential of utilising AED networks by improving strategies for AED accessibility and referring bystanders of OHCA to existing AEDs.     

Influence of chest compression rate guidance on the quality of cardiopulmonary resuscitation performed on manikins

AimsThe adequate chest compression rate during CPR is associated with improved haemodynamics and primary survival. To explore whether the use of a metronome would affect also chest compression depth beside the rate, we evaluated CPR quality using a metronome in a simulated CPR scenario.MethodsForty-four experienced intensive care unit nurses participated in two-rescuer basic life support given to manikins in 10 min scenarios. The target chest compression to ventilation ratio was 30:2 performed with bag and mask ventilation. The rescuer performing the compressions was changed every 2 min. CPR was performed first without and then with a metronome that beeped 100 times per minute. The quality of CPR was analysed with manikin software. The effect of rescuer fatigue on CPR quality was analysed separately.ResultsThe mean compression rate between ventilation pauses was 137 ± 18 compressions per minute (cpm) without and 98 ± 2 cpm with metronome guidance (p < 0.001). The mean number of chest compressions actually performed was 104 ± 12 cpm without and 79 ± 3 cpm with the metronome (p < 0.001). The mean compression depth during the scenario was 46.9 ± 7.7 mm without and 43.2 ± 6.3 mm with metronome guidance (p = 0.09). The total number of chest compressions performed was 1022 without metronome guidance, 42% at the correct depth; and 780 with metronome guidance, 61% at the correct depth (p = 0.09 for difference for percentage of compression with correct depth).ConclusionsMetronome guidance corrected chest compression rates for each compression cycle to within guideline recommendations, but did not affect chest compression quality or rescuer fatigue.     

Comparison of mechanical characteristics of the human and porcine chest during cardiopulmonary resuscitation

BackgroundMost studies investigating cardiopulmonary resuscitation (CPR) interventions or functionality of mechanical CPR devices have been performed using porcine models. The purpose of this study was to identify differences between mechanical characteristics of the human and porcine chest during CPR.Material and methodsCPR data of 90 cardiac arrest patients was compared to data of 14 porcine from two animal studies. Chest stiffness k and viscosity μ were calculated from acceleration and pressure data recorded using a Laerdal Heartstart 4000SP defibrillator during CPR. K and μ were calculated at chest compression depths of 15, 30 and 50 mm for three different time periods.ResultsAt a depth of 15 mm porcine chest stiffness was comparable to human chest stiffness at the beginning of resuscitation (4.8 vs. 4.5 N/mm) and clearly lower after 200 chest compressions (2.9 vs. 4.5 N/mm) (p < 0.05). At 30 and 50 mm porcine chest stiffness was higher at the beginning and comparable to human chest stiffness after 200 chest compressions. After 200 chest compressions porcine chest viscosity was similar to human chest viscosity at 15 mm (108 vs. 110 Ns/m), higher for 30 mm (240 vs. 188 Ns/m) and clearly higher for 50 mm chest compression depth (672 vs. 339 Ns/m) (p < 0.05).ConclusionIn conclusion, human and porcine chest behave relatively similarly during CPR with respect to chest stiffness, but differences in chest viscosity at medium and deep chest compression depth should at least be kept in mind when extrapolating porcine results to humans.     

The duration of cardiopulmonary resuscitation in emergency departments after out-of-hospital cardiac arrest is associated with the outcome: A nationwide observational study

Aim of the studyThe appropriate duration of cardiopulmonary resuscitation (CPR) for patients who experience out-of-hospital cardiac arrest (OHCA) remains unknown. This study aimed to evaluate the duration of CPR in emergency departments (EDs) and to determine whether the institutions’ median duration of CPR was associated with survival-to-discharge rate.MethodsA cohort of adult patients from a nationwide OHCA registry was retrospectively evaluated. The main variable was the median duration of CPR for each ED (institutional duration), and the main outcome was survival to discharge. Multivariable logistic regression analysis was performed to adjust for individual and aggregated confounders.ResultsAmong the 107,736 patients who experienced OHCA between 2006 and 2010, 30,716 (28.5%) were selected for analysis. The median age was 65 years, and 67.1% were men. The median duration of CPR for all EDs was 28 min, ranging from 11 to 45 min. EDs were categorized into 3 groups according to their institutional duration of CPR: groups A (<20 min), B (20–29 min), C (≥30 min). The observed survival rates of the 3 groups were 2.11%, 5.20%, and 5.62%, respectively. Compared with group B, the adjusted difference (95% confidence interval) for survival to discharge was 3.01% (1.90–4.11, P < 0.001) for group A, and 0.33% (−0.64 to 1.30, P = 0.51) for group C.ConclusionThe duration of CPR varied widely among hospitals. The institutional duration of CPR less than 20 min was significantly associated with lower survival-to-discharge rate.     

Comparison of out-of-hospital cardiac arrest occurring before and after paramedic arrival: Epidemiology,survival to hospital discharge and 12-month functional recovery

BackgroundDespite immediate resuscitation, survival rates following out-of-hospital cardiac arrests (OHCA) witnessed by emergency medical service (EMS) are reportedly low. We sought to compare survival and 12-month functional recovery outcomes for OHCA occurring before and after EMS arrival.MethodsBetween 1st July 2008 and 30th June 2013, we included 8648 adult OHCA cases receiving an EMS attempted resuscitation from the Victorian Ambulance Cardiac Arrest Registry, and categorised them into five groups: bystander witnessed cases ± bystander CPR, unwitnessed cases ± bystander CPR, and EMS witnessed cases. The main outcomes were survival to hospital and survival to hospital discharge. Twelve-month survival with good functional recovery was measured in a sub-group of patients using the Extended Glasgow Outcome Scale (GOSE).ResultsBaseline and arrest characteristics differed significantly across groups. Unadjusted survival outcomes were highest among bystander witnessed cases receiving bystander CPR and EMS witnessed cases, however outcomes differed significantly between these groups: survival to hospital (46.0% vs. 53.4% respectively, p < 0.001); survival to hospital discharge (21.1% vs. 34.9% respectively, p < 0.001). When compared to bystander witnessed cases receiving bystander CPR, EMS witnessed cases were associated with a significant improvement in the risk adjusted odds of survival to hospital (OR 2.02, 95% CI: 1.75–2.35), survival to hospital discharge (OR 6.16, 95% CI: 5.04–7.52) and survival to 12 months with good functional recovery (OR 5.56, 95% CI: 4.18–7.40).ConclusionWhen compared to OHCA occurring prior to EMS arrival, EMS witnessed arrests were associated with significantly higher survival to hospital discharge rates and favourable neurological recovery at 12-month post-arrest.     

The impact of a pre-hospital critical care team on survival from out-of-hospital cardiac arrest

AimTo assess the impact of a pre-hospital critical care team (CCT) on survival from out-of-hospital cardiac arrest (OHCA).MethodsWe undertook a retrospective observational study, comparing OHCA patients attended by advanced life support (ALS) paramedics with OHCA patients attended by ALS paramedics and a CCT between April 2011 and April 2013 in a single ambulance service in Southwest England. We used multiple logistic regression to control for an anticipated imbalance of prognostic factors between the groups. The primary outcome was survival to hospital discharge. All data were collected independently of the research.Results1851 cases of OHCA were included in the analysis, of which 1686 received ALS paramedic treatment and 165 were attended by both ALS paramedics and a CCT. Unadjusted rates of survival to hospital discharge were significantly higher in the CCT group, compared to the ALS paramedic group (15.8% and 6.5%, respectively, p < 0.001). After adjustment using multiple logistic regression, the effect of CCT treatment was no longer statistically significant (OR 1.54, 95% CI 0.89–2.67, p = 0.13). Subgroup analysis of OHCA with first monitored rhythm of ventricular fibrillation or pulseless ventricular tachycardia showed similar results.ConclusionPre-hospital critical care for OHCA was not associated with significantly improved rates of survival to hospital discharge. These results are in keeping with previously published studies. Further research with a larger sample size is required to determine whether CCTs can improve outcome in OHCA.     

Video-recording and time-motion analyses of manual versus mechanical cardiopulmonary resuscitation during ambulance transport

INTRODUCTION: The quality of cardiopulmonary resuscitation (CPR) plays a crucial role in saving lives from out-of-hospital cardiac arrest (OHCA). Previous studies have identified sub-optimal CPR quality in the prehospital settings, but the causes leading to such deficiencies were not fully elucidated. OBJECTIVE: This prospective study was conducted to identify operator- and ambulance-related factors affecting CPR quality during ambulance transport; and to assess the effectiveness of mechanical CPR device in such environment. MATERIALS AND METHODS: A digital video-recording system was set up in two ambulances in Taipei City to study CPR practice for adult, non-traumatic OHCAs from January 2005 to March 2006. Enrolled patients received either manual CPR or CPR by a mechanical device (Thumper). Quality of CPR in terms of (1) adequacy of chest compressions, (2) instantaneous compression rates, and (3) unnecessary no-chest compression interval, was assessed by time-motion analysis of the videos. RESULTS: A total of 20 ambulance resuscitations were included. Compared to the manual group (n=12), the Thumper group (n=8) had similar no-chest compression interval (33.40% versus 31.63%, P=0.16); significantly lower average chest compression rate (113.3+/-47.1 min(-1) versus 52.3+/-14.2 min(-1), P<0.05), average chest compression rate excluding no-chest compression interval (164.2+/-43.3 min(-1) versus 77.2+/-6.9 min(-1), P<0.05), average ventilation rate (16.1+/-4.9 min(-1) versus 11.7+/-3.5 min(-1), P<0.05); and longer no-chest compression interval before getting off the ambulance (5.7+/-9.9s versus 18.7+/-9.1s, P<0.05). The majority of the no-chest compression interval was considered operator-related; only 15.3% was caused by ambulance related factors. CONCLUSIONS: Many unnecessary no-chest compression intervals were identified during ambulance CPR, and most of this was operator, rather than ambulance related. Though a mechanical device could minimise the no-chest compression intervals after activation, it took considerable time to deploy in a system with short transport time. Human factors remained the most important cause of poor CPR quality. Ways to improve the CPR quality in the ambulance warrant further study.     

Resuscitation feedback and targeted education improves quality of pre-hospital resuscitation in Scotland

Background

Out-of-hospital cardiac arrest (OHCA) is a leading cause of mortality and serious neurological morbidity in Europe. Recent studies have demonstrated the adverse physiological consequences of poor resuscitation technique and have shown that quality of cardiopulmonary resuscitation (CPR) is a critical determinant of outcome from OHCA. Telemetry of the defibrillator transthoracic impedance (TTI) trace can objectively measure quality of pre-hospital resuscitation. This study aims to analyse the impact of targeted resuscitation feedback and training on quality of pre-hospital resuscitation.

Methods

Prospective, single centre, cohort study over 13 months (1st December 2009-31st December 2010). Baseline pre-hospital resuscitation data was gathered over a 3-month period. Modems (n = 40) were fitted to defibrillators on ambulance vehicles. Following a resuscitation attempt, the event was sent via telemetry and the TTI trace analysed. Outcome measures were time spent performing chest compressions, compression rate, the interval required to deliver a defibrillator shock and use of automatic or manual cardiac rhythm analysis. Targeted resuscitation classes were introduced and all ambulance crews received feedback following a resuscitation attempt. Pre-hospital resuscitation quality pre and post intervention were compared.

Results

111 resuscitation traces were analysed. Mean hands-on-chest time improved significantly following feedback and targeted resuscitation training (73.0% vs 79.3%, p = 0.007). There was no significant change in compression rate during the study period. There was a significant reduction in median time-to-shock interval from 20.25 s (IQR 15.50-25.50 s) to 13.45 s (IQR 2.25-22.00 s) (p = 0.006). Automatic rhythm recognition fell from 50% to 28.6% (p = 0.03) following intervention.

Conclusion

Telemetry and analysis of the TTI trace following OHCA allows objective evaluation of the quality of pre-hospital resuscitation. Targeted resuscitation training and ambulance feedback improves the quality of pre-hospital resuscitation. Further studies are required to establish possible survival benefit from this technique.     

A tourniquet assisted cardiopulmonary resuscitation augments myocardial perfusion in a porcine model of cardiac arrest

ObjectiveDuring cardiopulmonary resuscitation (CPR), myocardial blood flow generated by chest compression rarely exceeds 35% of its normal level. Cardiac output generated by chest compression decreases gradually with the prolongation of cardiac arrest and resuscitation. Early studies have demonstrated that myocardial blood flow during CPR is largely dependent on peripheral vascular resistance. In this study, we investigated the effects of chest compression in combination with physical control of peripheral vascular resistance assisted by tourniquets on myocardial blood flow during CPR.MethodsVentricular fibrillation was induced and untreated for 7 min in ten male domestic pigs weighing between 33 and 37 kg. The animals were then randomized to receive CPR alone or a tourniquet assisted CPR (T-CPR). In the CPR alone group, chest compression was performed by a miniaturized mechanical chest compressor. In the T-CPR group, coincident with the start of resuscitation, the thin elastic tourniquets were wrapped around the four limbs from the distal end to the proximal part. After 2 min of CPR, epinephrine (20 μg/kg) was administered via the femoral vein. After 5 min of CPR, defibrillation was attempted by a single 150 J shock. If resuscitation was not successful, CPR was resumed for 2 min before the next defibrillation. The protocol was continued until successful resuscitation or for a total of 15 min. Five minutes after resuscitation, the elastic tourniquets were removed. The resuscitated animals were observed for 2 h.ResultsT-CPR generated significantly greater coronary perfusion pressure, end-tidal carbon dioxide and carotid blood flow. There was no difference in both intrathoracic positive and negative pressures between the two groups. All animals were successfully resuscitated with a single shock in both groups. There were no significant changes in hemodynamics observed in the animals treated in the T-CPR group before-and-after the release of tourniquets at post-resuscitation 5 min.ConclusionsT-CPR improves myocardial and cerebral perfusion during CPR. It may provide a new and convenient method for augmenting myocardial and cerebral blood flow during CPR.     

Estimating the impact of off-balancing forces upon cardiopulmonary resuscitation during ambulance transport

IntroductionSurvival from out-of-hospital cardiac arrest (OOH-CA) remains poor, especially when patients are transported with CPR in progress. Previous investigations suggest that CPR quality erodes during transport due to the austere environment. We sought to determine how frequently ambulance personnel are exposed to off-balancing forces during transport of OOH-CA patients and to estimate the potential impact on CPR and coronary perfusion pressure (CPP).MethodsAn onboard monitoring system was utilized to record acceleration data during the transport of 50 OOH-CA patients. Acceleration vectors were calculated for every second of drive time (speed >0 m/s). A model was constructed to estimate the potential impact of these vectors upon CPR and CPP. These data were then compared to a case-control cohort of 102 matched non-urgent transports.ResultsA total of 5.8 h of drive time was analyzed in the cardiac arrest cohort. Mean transport time was 8 min 53 s with a mean drive time of 6 min 58 s. Critical acceleration threshold was exceeded 60% of transport time (202.42 min, mean 4.05 min/transport) yielding a potential hands-off ratio of 0.42 with a CPP < 15 mmHg 62% of drive time. Ambulance speed was inversely related to the magnitude of off-balancing forces. Comparison to 14.1 h of control cohort yielded similar off-balancing forces and relationships despite lower speeds and no “lights and siren” use.ConclusionCritical acceleration forces occur frequently during transport of OOH-CA patients and may directly effect CPR quality and thereby CPP. These force vectors are stronger and more frequent at slower speeds, comprising the majority of ambulance drive time. Reducing speed or transporting OOH-CA patients without lights and sirens does little to mitigate these forces.     

Mechanical chest compression does not seem to improve outcome after out-of hospital cardiac arrest. A single center observational trial

AimRecently three large post product placement studies, comparing mechanical chest compression (cc) devices to those who received manual cc, found equivalent outcome results for both groups. Thus the question arises whether those results could be replicated using the devices on a daily routine.MethodsWe prospectively enrolled 948 patients over a 12 months period. Chi-Square test and Mann–Whitney-U test were used to assess differences between “manual” and “mechanical” cc subgroups. Uni- and multivariate Cox regression hazard analysis were used to assess the influence of cc type on survival.ResultsA mechanical cc device was used in 30.1% (n = 283) cases. Patients who received mechanical cc had a significantly worse neurological outcome – measured in cerebral performance category (CPC) – than the manual cc group (56.8% vs. 78.6%, p = 0.009). Patients receiving mechanical cc were significantly younger, more were male and were more likely to have bystander CPR and an initially shock-able ECG rhythm. There was no difference in the quality of CPR that might explain the worse outcome in mechanical cc patients.ConclusionEven with high quality CPR in both, manual and mechanical cc groups, outcome in patients who received mechanical cc was significantly worse. The anticipated benefits of a higher compression ratio and a steadier compression depth of a mechanical cc device remain uncertain. In this study selection for mechanical cc was not standardized, and was non-random. This merits further investigation. Further research on how mechanical cc is chosen and used should be considered.Clinical trial registration: https://ekmeduniwien.at/core/catalog/2013/ (EK-Nr:1221/2013)