BACKGROUND:Although pad position influences current delivery, the relationship between transthoracic current, pad position, and shock efficacy during external defibrillation for refractory ventricular (VF) has not been examined. OBJECTIVE:To assess the relationship between pad position, current delivery and return of spontaneous circulation (ROSC) among patients enrolled in the Double Sequential External Defibrillation for Refractory VF (DOSE VF) trial. METHODS:We conducted a secondary, per-protocol analysis of patients enrolled in DOSE VF. Transthoracic current was calculated for the first six shocks using defibrillator-derived measures of shock energy and impedance, applying manufacturer-provided formulas. Current delivery was compared across standard anterolateral (AL), vector-change (VC) anteroposterior (AP), and double sequential external defibrillation (DSED; AL + AP) shocks. Multivariable logistic regression and generalized estimating equation (GEE) models were used to examine associations between current delivery, pad position and ROSC. RESULTS:342 patients were included (mean age 63.6 years; 85% male), contributing 849 interventional shocks (51.6% standard, 25.4% VC and 22.9% DSED). Mean current was significantly greater for AP shocks in both VC (19.6 A) and DSED (19.2 A), compared with standard AL (16.6 A) and DSED AL shocks (17.3 A) (P < 0.001). In GEE modeling, AP positioning was independently associated with ROSC compared to AL positioning (aOR 2.01; 95% CI: 1.12-3.59). Delivered current was not associated with ROSC. CONCLUSIONS:AP delivered higher current than AL positioning; however, pad position rather than delivered current was independently associated with ROSC. These findings suggest the additional AP pad position may be a key mechanistic contributor to the benefit of VC and DSED.

BACKGROUND:In patients with out-of-hospital cardiac arrest (OHCA) who receive multiple shocks, it is often unclear whether they are experiencing refractory or recurrent ventricular fibrillation (VF). Understanding into the cause of refractory VF is limited and the foundational evidence for alternative defibrillation strategies are lacking. To gain further insight into these patients we studied the incidence and possible predictors of refractory VF, and compared outcomes between patients with recurrent VF and those with refractory VF. METHODS:Using the ARREST registry, we included patients with VF at the first three rhythm checks between 2016 and 2019. ECG waveforms were analysed for successful termination of VF at five seconds after each shock delivered. Patients were classified as having refractory VF if all three shocks failed to terminate VF. The remaining patients were classified as having recurrent VF. Outcomes and possible predictors between both groups were compared. RESULTS:Out of 436 patients who met the inclusion criteria, 22 (5%) had refractory VF and 414 (95%) had recurrent VF. Rates of return of spontaneous circulation (ROSC) and 30-day survival were 9/22 (41%) vs 243/409 (59%) (RR 0.69 [95% CI, 0.41-1.15]) and 5/22 (23%) vs 187/408 (46%) (RR 0.49 [95% CI, 0.23-1.08]) in patients with refractory and recurrent VF, respectively. Predictors for refractory VF were absence of CPR and AED use before emergency medical services arrival, a longer delay to the first shock, and a lower amplitude spectral area value. CONCLUSIONS:The small group of refractory VF patients were characterised by unfavourable resuscitation characteristics. Clinical outcomes in refractory VF versus recurrent VF patients remain uncertain due to low patient numbers.

Background Time in ventricular fibrillation (VF) is associated with survival after out-of-hospital cardiac arrest (OHCA). The impact of vector change defibrillation (VC) and double sequential external defibrillation (DSED) on VF duration has not been explored. Objective To compare the effects of VC and DSED on VF duration and defibrillation outcomes. Methods We conducted a secondary analysis of patients enrolled in the Double Sequential External Defibrillation for Refractory VF RCT. We assessed the ECG after each shock, calculating VF time (median, IQR) and shock outcomes. The Kruskal-Wallis test was used to compare VF duration across groups, with post-hoc pairwise comparisons using Dunn’s test and Bonferroni correction. Chi-square tests compared shock outcomes. Results Among 342 patients, 1842 shocks were analyzed (834 after three failed standard shocks: 429 standard, 218 VC, 187 DSED). Median VF time was significantly shorter for DSED (83 [0, 120] s) and VC (98 [0, 120] s) compared to standard shocks (108 [38, 120] s) (P = 0.003). The proportion of shocks leading to return of spontaneous circulation (ROSC) and survival to hospital discharge respectively was higher for DSED (17.6%, 10.2% p < 0.001 ROSC, p = 0.002 survival) and VC (14.2%, 7.3% p < 0.002 ROSC, p = 0.049 survival) than for standard shocks (5.3%, 3.5%) The proportion of shocks in which VF was not terminated was significantly lower for DSED shocks (29.9%) than standard shocks (40.6%) (P = 0.013). Conclusions DSED and VC reduced VF duration and increased the likelihood of ROSC and survival compared to standard shocks. These findings may contribute to the improved survival noted in the trial.

Background and aims: Chest compressions generating good perfusion during cardiopulmonary resuscitation (CPR) in cardiac arrest patients are critical for positive patient outcomes. Conventional wisdom advises minimizing compression pauses because several compressions are required to recover arterial blood pressure (ABP) back to pre-pause values. Our study examines how compression pauses influence ABP recovery post-pause in out-of-hospital cardiac arrest. Methods: We analyzed data from a subset of a prospective, randomized LUCAS 2 Active Decompression trial. Patients were treated by an anesthesiologist-staffed rapid response car program in Oslo, Norway (2015-2017) with mechanical chest compressions using the LUCAS device at 102 compressions/min. Patients with an ABP signal during CPR and at least one compression pause >2 sec were included. Arterial cannulation, compression pauses, and ECG during the pause were verified by physician review of patient records and physiological signals. Pauses were excluded if return of spontaneous circulation occurred during the pause (pressure pulses associated with ECG complexes). Compression, mean, and decompression ABP for 10 compressions before/after each pause and the mean ABP during the pause were measured with custom MATLAB code. The relationship between pause duration and ABP recovery was investigated using linear regression. Results: We included 56 patients with a total of 271 pauses (pause duration: median = 11 sec, Q1 = 7 sec, Q3 = 18 sec). Mean ABP dropped from 53 +/- 10 mmHg for the last pre-pause compression to 33 +/- 7 mmHg during the pause. Compression and mean ABP recovered to >90% of pre-pause pressure within 2 compressions, or 1.7 sec. Pause duration did not affect the recovery of ABP post-pause (R2: 2 : 0.05, 0.03, 0.01 for compression, mean, and decompression ABP, respectively). Conclusions: ABP generated by mechanical CPR recovered quickly after pauses. Recovery of ABP after a pause was independent of pause duration.

Aim: The aim of this study was to evaluate chest compression rates (CCR) with and without the use of a metronome during treatment of out-of -hospital cardiac arrest (OHCA). Methods: We performed a retrospective cohort investigation of non-traumatic OHCA cases treated by Seattle Fire Department from January 1, 2013, to December 31, 2019. The exposure was a metronome running during CPR at a rate of 110 beats per minute. The primary outcome was the median CCR for all periods of CPR with a metronome compared to periods without a metronome. Results: We included 2,132 OHCA cases with 32,776 minutes of CPR data; 15,667 (48%) minutes had no metronome use, and 17,109 (52%) min-utes had a metronome used. Without a metronome, the median CCR was 112.8 per minute with an interquartile range of 108.4 - 119.1, and 27% of minutes were above 120 or less than 100. With a metronome, the median CCR was 110.5 per minute with an interquartile range of 110.0-112.0, and less than 4% of minutes were above 120 or less than 100. The compression rate was 109, 110, or 111 in 62% of minutes with a metronome com-pared to 18% of minutes with no metronome. Conclusion: The use of a metronome during CPR resulted in increased compliance to a predetermined compression rate. Metronomes are a sim-ple tool that improves achievement of a target compression rate with little variance from that target.

Introduction: Little is known about the impact of tidal volumes delivered by emergency medical services (EMS) to adult patients with out-of-hospital cardiac arrest (OHCA). A large urban EMS system changed from standard adult ventilation bags to small adult bags. We hypothesized that the incidence of return of spontaneous circulation (ROSC) at the end of EMS care would increase after this change.Methods: We performed a retrospective analysis evaluating adults treated with advanced airway placement for nontraumatic OHCA between January 1, 2015 and December 31, 2021. We compared rates of ROSC, ventilation rate, and mean end tidal carbon dioxide (ETCO2) by minute before and after the smaller ventilation bag implementation using linear and logistic regression.Results: Of the 1,994 patients included, 1,331 (67%) were treated with a small adult bag. ROSC at the end of EMS care was lower in the small bag cohort than the large bag cohort, 33% vs 40% (p = 0.003). After adjustment, small bag use was associated with lower odds of ROSC at the end of EMS care [OR 0.74, 95% CI 0.61 - 0.91]. Ventilation rates did not differ between cohorts. ETCO2 values were lower in the large bag cohort (33. 2 +/- 17.2 mmHg vs. 36.9 +/- 19.2 mmHg, p < 0.01).Conclusion: Use of a small adult bag during OHCA was associated with lower odds of ROSC at the end of EMS care. The effects on acid base status, hemodynamics, and delivered minute ventilation remain unclear and warrant additional study.

Introduction: Guidelines recommend monitoring end-tidal carbon dioxide (ETCO2) during out-of-hospital cardiac arrest (OHCA), though its prog-nostic value is poorly understood. This study investigated the relationship between ETCO2 and return of spontaneous circulation (ROSC) after defib-rillation in intubated non-traumatic OHCA patients.Methods: This retrospective, observational cohort analysis included adult OHCA patients who received a defibrillation shock during treatment by an urban EMS agency from 2015 to 2021. Peak ETCO2 values were determined for the 90-second periods before and after the first defibrillation in an intubated patient (shock of interest [SOI]). Values were analyzed for association between the change in ETCO2 from pre-to post-shock and the pres-ence of ROSC on the subsequent pulse check.Results: Of 518 eligible patients, mean age was 61, 72% were male, 50% had a bystander-witnessed arrest, and 62% had at least one episode of ROSC. The most common arrest etiology was medical (92%). Among all patients, peak ETCO2 during resuscitation prior to SOI was 36.8 mmHg (18.6). ETCO2 increased in patients who achieved ROSC immediately after SOI (from 38.3 to 47.6 mmHg; +9.3 CI: 6.5, 12.1); patients with sustained ROSC experienced the greatest increase in ETCO2 after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ETCO2 in patients who did not achieve ROSC after SOI rose (from 36.4 to 37.8 mmHg; +1.4 CI: -0.1, 2.8).Conclusions: ETCO2 rises after defibrillation in most patients during cardiac arrest. Patients with sustained ROSC experience larger rises, though the majority experience rises of less than 10 mmHg.

A 3 month old boy, with no known health conditions, suffered a sudden collapse at home. On first EMS arrival, ventricular fibrillation (VF) cardiac arrest was identified and resuscitation following UK national guidelines was initiated. He remained in cardiac arrest for over 25 min, during which he received 10 defibrillation shocks, each effective, but with VF reoccurring within a few seconds of each of the first 9. A return of spontaneous circulation (ROSC) was achieved after the 10th shock. The resuscitation was conducted fully in his home, with the early involvement of Advanced Paramedic Practitioners specialising in critical care (APP- CC). Throughout his resuscitation, there remained a strong focus on delivering quality resuscitation in situ, rather than a ‘load and go’ approach that would have resulted in very early conveyance to hospital with on-going CPR. The patient was subsequently discharged home and is making an excellent recovery. The arrest was later determined to have been caused by a primary arrhythmia as a result of a previously unidentified non-obstructive variant hypertrophic cardiomyopathy. We present data downloaded from the defibrillator used during the resuscitation that illustrates clearly the recurrent nature of his fibrillation.

Objective: Physiologic alterations during rapid sequence intubation (RSI) have been studied in several emergency airway management settings, but few data exist to describe physiologic alterations during prehospital RSI performed by ground-based paramedics. To address this evidence gap and provide guidance for future quality improvement initiatives in our EMS system, we collected electronic monitoring data to evaluate peri-intubation vital signs changes occurring during prehospital RSI. Methods: Electronic patient monitor data files from cases in which paramedic RSI was attempted were prospectively collected over a 15-month study period to supplement the standard EMS patient care documentation. Cases were analyzed to identify peri-intubation changes in oxygen saturation, heart rate, and blood pressure. Results: Data from 134 RSI cases were available for analysis. Paramedic-assigned prehospital diagnostic impression categories included neurologic (42%), respiratory (26%), toxicologic (22%), trauma (9%), and cardiac (1%). The overall intubation success rate (95%) and first-attempt success rate (82%) did not differ across diagnostic impression categories. Peri-intubation desaturation (SpO(2) decrease to below 90%) occurred in 43% of cases, and 70% of desaturation episodes occurred on first-attempt success. The incidence of desaturation varied among patient categories, with a respiratory diagnostic impression associated with more frequent, more severe, and more prolonged desaturations, as well as a higher incidence of accompanying cardiovascular instability. Bradycardia (HR decrease to below 60bpm) occurred in 13% of cases, and 60% of bradycardia episodes occurred on first-attempt success. Hypotension (systolic blood pressure decrease to below 90mmHg) occurred in 7% of cases, and 63% of hypotension episodes occurred on first-attempt success. Peri-intubation cardiac arrest occurred in 2 cases, one of which was on first-attempt success. Only 11% of desaturations and no instances of bradycardia were reflected in the standard EMS patient care documentation. Conclusions: In this study, the majority of peri-intubation physiologic alterations occurred on first-attempt success, highlighting that first-attempt success is an incomplete and potentially deceptive measure of intubation quality. Supplementing the standard patient care documentation with electronic monitoring data can identify unrecognized physiologic instability during prehospital RSI and provide valuable guidance for quality improvement interventions.

Background— Minimizing pauses in chest compressions during cardiopulmonary resuscitation is a focus of current guidelines. Prior analyses found that prolonged pauses for defibrillation (perishock pauses) are associated with worse survival. We analyzed resuscitations to characterize the association between pauses for all reasons and both ventricular fibrillation termination and patient survival. Methods and Results— In 319 patients with ventricular tachycardia/fibrillation out-of-hospital cardiac arrest, we analyzed recordings from all defibrillators used during resuscitation and measured durations of all cardiopulmonary resuscitation pauses. Median durations were 32 seconds (25th and 75th percentile, 22 and 52 seconds) for the longest pause for any reason, 23 seconds (25th and 75th percentile, 14 and 34 seconds) for the longest perishock pause, and 24 seconds (25th and 75th percentile, 11 and 38 seconds) for the longest nonshock pause. Multivariable regression models showed lower odds for survival per 5-second increase in the longest overall pause (odds ratio, 0.89; 95% confidence interval, 0.83–0.95), longest perishock pause (odds ratio, 0.85; 95% confidence interval, 0.77–0.93), and longest nonshock pause (odds ratio, 0.83; 95% confidence interval, 0.75–0.91). In 36% of cases, the longest pause was a nonshock pause; this subgroup had lower survival than the group in whom the longest pause was a perishock pause (27% versus 44%, respectively; P <0.01) despite a higher chest compression fraction. Preshock pauses were 8 seconds (25th and 75th percentile, 4 and 17 seconds) for shocks that terminated ventricular fibrillation and 7 seconds (25th and 75th percentile, 4 and 13 seconds) for shocks that did not ( P =0.18). Conclusions— Prolonged pauses have a negative association with survival not explained by chest compression fraction or decreased ventricular fibrillation termination rate. Ventricular fibrillation termination was not the mechanism linking pause duration and survival. Strategies shortening the longest pauses may improve outcome.

Background: Minimizing 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.Methods: We 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.Results: Compared 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).Conclusions: Our 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. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

Background: Minimizing the chest compression pause associated with application of a mechanical CPR (mCPR) device is a key component of optimal integration of mCPR into the overall resuscitation process. As part of a multi-agency implementation project, Anchorage Fire Department deployed LUCAS mCPR devices on BLS and ALS vehicles for initiation early in resuscitation efforts. A 2012 report from that project identified the pause interval for mCPR device application as a key opportunity for quality improvement (QI). In early 2013 we began a QI initiative to reduce device application time and optimize the overall CPR process, which included education on the importance of minimizing pauses, training on techniques for efficient device application, and a requirement for two manual CPR cycles prior to initiation of mCPR. To assess QI initiative effectiveness, we compared key CPR process metrics from before to during and after its implementation. Methods: We included all cases of EMS-treated out-of-hospital cardiac arrest during 2012 and 2013 in which mCPR 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. Results: Compared to cases from 2012 (n=61), median (25th, 75th percentile) duration of the pause prior to first mCPR compression for cases from 2013 (n=71) decreased from 21 (15, 31) to 7 (4, 12) seconds (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) seconds (p<0.001), while the proportion of cases where the longest pause was for mCPR device application decreased from 74% to 32% (p<0.001). Conclusions: Our QI initiative substantially reduced the duration of the pause prior to first mCPR 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 mCPR device application efficiency within an overall high-performance CPR process.

Background: Mechanical CPR (mCPR) devices enable defibrillation shock delivery during ongoing chest compressions, without the pause required during manual CPR. It is unknown whether shock delivery during ongoing mCPR, vs. during a pause, affects VF termination efficacy. Animal studies suggest that during ongoing mCPR, timing a shock to a specific phase of the compression cycle may significantly affect shock efficacy. Methods: We retrospectively analyzed electronic defibrillator recordings from the Amsterdam Resuscitation Study (ARREST), a prospective out-of-hospital cardiac arrest registry. We identified cases with LUCAS mCPR and at least one shock delivered after mCPR initiation. Shocks were sorted by energy level, and the most prevalent (360 J) was selected for the present analysis. Continuous ECG and impedance signals were analyzed to determine VF termination (defined as absence of VF at 5 sec after shock) for each shock after mCPR initiation, and whether the shock was delivered during a pause or during mCPR. For shocks delivered during a pause we measured pre-shock pause duration; for shocks delivered without pausing we measured the exact timing of the shock during the compression cycle. Results: In 153 cases meeting analysis criteria, 509 360J shocks occurred after mCPR initiation; VF termination outcome could be determined for 460. VF termination for first eligible shock during mCPR in each case was 84/97 (87%) during a pause, and 79/93 (85%; p=0.74) during ongoing mCPR; for all eligible shocks, VF termination was 203/242 (83.9%) and 155/196 (79.1%; p=0.20) respectively. For shocks during mCPR, there were no statistically significant differences in VF termination rate for shocks during four equal length phases beginning with LUCAS piston upstroke: 39/44 (89%), 39/49 (80%), 35/51 (69%), 40/50 (80%) (p = 0.12). For shocks during a pause, VF termination rate did not differ for pre-shock pauses ≤5 sec (75/91, 82.4%) vs. >5 sec (128/151, 84.8%; p=0.63). Conclusions: Our results indicate that shocks can be delivered during ongoing mCPR without reducing defibrillation efficacy. The exact shock timing during the mCPR compression cycle did not significantly alter shock efficacy. VF termination rate was not affected by pre-shock pause duration during mCPR.