Duration of Ventilations During Cardiopulmonary Resuscitation by Lay Rescuers and First Responders

Ventilation during cardiopulmonary resuscitation: A narrative review

Ventilation during cardiopulmonary resuscitation is vital to achieve optimal oxygenation but continues to be a subject of ongoing debate. This narrative review aims to provide an overview of various components and challenges of ventilation during cardiopulmonary resuscitation, highlighting key areas of uncertainty in the current understanding of ventilation management. It addresses the pulmonary pathophysiology during cardiac arrest, the importance of adequate alveolar ventilation, recommendations concerning the maintenance of airway patency, tidal volumes and ventilation rates in both synchronous and asynchronous ventilation. Additionally, it discusses ventilation adjuncts such as the impedance threshold device, the role of positive end-expiratory pressure ventilation, and passive oxygenation. Finally, this review offers directions for future research.

Ventilation during cardiopulmonary resuscitation with mechanical chest compressions: How often are two insufflations being given during the 3-second ventilation pauses?

BACKGROUND

Mechanical chest compression devices in 30:2 mode provide 3-second pauses to allow for two insufflations. We aimed to determine how often two insufflations are provided in these ventilation pauses, in order to assess if prehospital providers are able to ventilate out-of-hospital cardiac arrest (OHCA) patients successfully during mechanical chest compressions.

METHODS

Data from OHCA cases of the regional ambulance service of Utrecht, The Netherlands, were prospectively collected in the UTrecht studygroup for OPtimal registry of cardIAc arrest database (UTOPIA). Compression pauses and insufflations were visualized on thoracic impedance and waveform capnography signals recorded by manual defibrillators. Ventilation pauses were analyzed for number of insufflations, duration of the subintervals of the ventilation cycles, and ratio of successfully providing two insufflations over the course of the resuscitation. Generalized linear mixed effects models were used to accurately estimate proportions and means.

RESULTS

In 250 cases, 8473 ventilation pauses were identified, of which 4305 (51%) included two insufflations. When corrected for non-independence of the data across repeated measures within the same subjects with a mixed effects analysis, two insufflations were successfully provided in 45% of ventilation pauses (95% CI: 40-50%). In 19% (95% CI: 16-22%) none were given.

CONCLUSION

Providing two insufflations during pauses in mechanical chest compressions is mostly unsuccessful. We recommend developing strategies to improve giving insufflations when using mechanical chest compression devices. Increasing the pause duration might help to improve insufflation success.

Feasibility of Mouth-to-Mouth Ventilation through FPP2 Respirator in BLS Training during COVID-19 Pandemic (MOVERESP Study): Simulation-Based Study

Background: Due to the COVID-19 pandemic, Basic Life Support (BLS) training has been limited to compression-only or bag–mask ventilation. The most breathable nanofiber respirators carry the technical possibility for inflation of the mannequin. The aim of this study was to assess the efficacy of mouth-to-mouth breathing through a FFP2 respirator during BLS. Methods: In the cross-over simulation-based study, the medical students performed BLS using a breathable nanofiber respirator for 2 min on three mannequins. The quantitative and qualitative efficacy of mouth-to-mouth ventilation through the respirator in BLS training was analyzed. The primary aim was the effectivity of mouth-to-mouth ventilation through a breathable respirator. The secondary aims were mean pause, longest pause, success in achieving the optimal breath volume, technique of ventilation, and incidence of adverse events. Results: In 104 students, effective breath was reached in 951 of 981 (96.9%) attempts in Adult BLS mannequin (Prestan), 822 of 906 (90.7%) in Resusci Anne, and 1777 of 1857 (95.7%) in Resusci Baby. In Resusci Anne and Resusci Baby, 28.9%/15.9% of visible chest rises were evaluated as low-, 33.0%/44.0% as optimal-, and 28.8%/35.8% as high-volume breaths. Conclusions: Mouth-to-mouth ventilation through a breathable respirator had an effectivity greater than 90%.

Manual chest compression pause duration for ventilations during prehospital advanced life support - An observational study to explore optimal ventilation pause duration for mechanical chest compression devices

AIM

Mechanical chest compression devices in the 30:2 mode generally provide a pause of three seconds to give two insufflations without evidence supporting this pause duration. We aimed to explore the optimal pause duration by measuring the time needed for two insufflations, during advanced life support with manual compressions.

METHODS

Prospectively collected data in the AmsteRdam REsuscitation STudies (ARREST) registry were analysed, including thoracic impedance signal and waveform capnography from manual defibrillators of the Amsterdam ambulance service. Compression pauses were analysed for number of insufflations, time interval from start of the compression pause to the end of the second insufflation, chest compression pause duration and ventilation subintervals.

RESULTS

During 132 out-of-hospital cardiac arrests, 1619 manual chest compression pauses to ventilate were identified. In 1364 (84%) pauses, two insufflations were given. In 28% of these pauses, giving two insufflations took more than three seconds. The second insufflation is completed within 3.8 seconds in 90% and within 5 seconds in 97.5% of these pauses. An increasing likelihood of achieving two insufflations is seen with increasing compression pause duration up to five seconds.

CONCLUSION

The optimal chest compression pause duration for mechanical chest compression devices in the 30:2 mode to provide two insufflations, appears to be five seconds, warranting further studies in the context of mechanical chest compression. A 5-second pause will allow providers to give two insufflations with a very high success rate. In addition, a 5-second pause can also be used for other interventions like rhythm checks and endotracheal intubation.

Implementation and Evaluation of Resuscitation Training for Childcare Workers

Background and Objective

Children spend a large amount of time in daycare centers or schools. Therefore, it makes sense to train caregivers well in first-aid measures in children. The aim of this study is to evaluate whether a multimodal resuscitation training for childcare workers can teach adherence to resuscitation guidelines in a sustainable way.

Materials and Methods

Caregivers at a daycare center who had previously completed a first-aid course received a newly developed multimodal resuscitation training in small groups of 7-8 participants by 3 AHA certified PALS instructors and providers. The 4-h focused retraining consisted of a theoretical component, expert modeling, resuscitation exercises on pediatric manikins (Laerdal Resusci Baby QCPR), and simulated emergency scenarios. Adherence to resuscitation guidelines was compared before retraining, immediately after training, and after 6 months. This included evaluation of chest compressions per round, chest compression rate, compression depth, full chest recoil, no-flow time, and success of rescue breaths. For better comparability and interpretation of the results, the parameters were evaluated both separately and summarized in a resuscitation score reflecting the overall adherence to the guidelines.

Results

A total of 101 simulated cardiopulmonary resuscitations were evaluated in 39 participants. In comparison to pre-retraining, chest compressions per round (15.0 [10.0-29.0] vs. 30.0 [30.0-30.0], p < 0.001), chest compression rate (100.0 [75.0-120.0] vs. 112.5 [105-120.0], p < 0.001), correct compression depth (6.7% [0.0-100.0] vs. 100.0% [100.0-100.0], p < 0.001), no-flow time (7.0 s. [5.0-9.0] vs. 4.0 s. [3.0-5.0], p < 0.001), success of rescue breaths (0.0% [0.0-0.0] vs. 100.0% [100.0-100.0], p < 0.001), and resuscitation score were significantly improved immediately after training (3.9 [3.2-4.9] vs. 6.3 [5.6-6.7], p < 0.001). At follow-up, there was no significant change in chest compression rate and success of rescue breaths. Chest compressions per round (30.0 [15.0-30.0], p < 0.001), no-flow time (5.0 s. [4.0-8.0], p < 0.001), compression depths (100.0% [96.7-100.0], p < 0.001), and resuscitation score worsened again after 6 months (5.7 [4.7-6.4], p = 0.03). However, the results were still significantly better compared to pre-retraining.

Conclusion

Our multimodal cardiopulmonary resuscitation training program for caregivers is effective to increase the resuscitation performance immediately after training. Although the effect diminishes after 6 months, adherence to resuscitation guidelines was significantly better than before retraining.

Effects of Bag Mask Ventilation and Advanced Airway Management on Adherence to Ventilation Recommendations and Chest Compression Fraction: A Prospective Randomized Simulator-Based Trial

The role of advanced airway management (AAM) in cardiopulmonary resuscitation (CPR) is currently debated as observational studies reported better outcomes after bag-mask ventilation (BMV), and the only prospective randomized trial was inconclusive. Adherence to CPR guidelines ventilation recommendations is unknown and difficult to assess in clinical trials. This study compared AAM and BMV with regard to adherence to ventilation recommendations and chest compression fractions in simulated cardiac arrests. A total of 154 teams of 3–4 physicians were randomized to perform CPR with resuscitation equipment restricting airway management to BMV only or equipment allowing for all forms of AAM. BMV teams ventilated 6 ± 6/min and AAM teams 19 ± 8/min (range 3–42/min; p < 0.0001 vs. BMV). 68/78 BMV teams and 23/71 AAM teams adhered to the ventilation recommendations (p < 0.0001). BMV teams had lower compression fractions than AAM teams (78 ± 7% vs. 86 ± 6%, p < 0.0001) resulting entirely from higher no-flow times for ventilation (9 ± 4% vs. 3 ± 3 %; p < 0.0001). Compared to BMV, AAM leads to significant hyperventilation and lower adherence to ventilation recommendations but favourable compression fractions. The cumulative effect of deviations from ventilation recommendations has the potential to blur findings in clinical trials.

Evaluation of a Multimodal Resuscitation Program and Comparison of Mouth-to-Mouth and Bag-Mask Ventilation by Relatives of Children With Chronic Diseases

OBJECTIVES

Children with chronic critical illness are at higher risk for cardiopulmonary arrests. Before chronically ill children are discharged from hospital, family members receive training in basic life support at many institutions. We evaluated whether a multimodal training program is able to teach adherence to current resuscitation guidelines and whether laypersons can be trained to perform both bag-mask ventilation and mouth-to-mouth ventilation equally effective in infants.

DESIGN

Prospective observational study.

SETTING

Pediatric critical care unit of a tertiary referral center.

SUBJECTS

Relatives of children with chronic illness prior to discharge from hospital.

INTERVENTIONS

Multimodal emergency and cardiopulmonary resuscitation training program.

MEASUREMENTS AND MAIN RESULTS

Following participation in our cardiopulmonary resuscitation training program 56 participants performed 112 simulated cardiopulmonary resuscitations (56 with mouth-to-mouth ventilation, 56 with bag-mask ventilation). Nearly all participants checked for consciousness and breathing. Shouting for help and activation of the emergency response system was only performed in half of the cases. There was almost full adherence to the resuscitation guidelines regarding number of chest compressions, chest compression rate, compression depth, full chest recoil, and duration of interruption of chest compression for rescue breaths. The comparison of mouth-to-mouth ventilation and bag-mask ventilation revealed no significant differences regarding the rate of successful ventilation (mouth-to-mouth ventilation: 77.1% ± 39.6%, bag-mask ventilation: 80.4% ± 38.0%; p = 0.39) and the cardiopulmonary resuscitation performance.

CONCLUSIONS

A standardized multimodal cardiopulmonary resuscitation training program for family members of chronically ill children is effective to teach good cardiopulmonary resuscitation performance and adherence to resuscitation guidelines. Laypersons could be successfully trained to equally perform mouth-to-mouth and bag-mask ventilation technique.

Combination of problem-based learning with high-fidelity simulation in CPR training improves short and long-term CPR skills: a randomised single blinded trial

BACKGROUND

Performance of sufficient cardiopulmonary resuscitation (CPR) by medical personnel is critical to improve outcomes during cardiac arrest. It has however been shown that even health care professionals possess a lack of knowledge and skills in CPR performance. The optimal method for teaching CPR remains unclear, and data that compares traditional CPR instructional methods with newer modalities of CPR instruction are needed. We therefore conducted a single blinded, randomised study involving medical students in order to evaluate the short- and long-term effects of a classical CPR education compared with a bilateral approach to CPR training, consisting of problem-based learning (PBL) plus high fidelity simulation.

METHODS

One hundred twelve medical students were randomized during a curricular anaesthesiology course to a control (n = 54) and an intervention (n = 58) group. All participants were blinded to group assignment and partook in a 30-min-lecture on CPR basics. Subsequently, the control group participated in a 90-min tutor-guided CPR hands-on-training. The intervention group took part in a 45-min theoretical PBL module followed by 45 min of high fidelity simulated CPR training. The rate of participants recognizing clinical cardiac arrest followed by sufficiently performed CPR was the primary outcome parameter of this study. CPR performance was evaluated after the intervention. In addition, a follow-up evaluation was conducted after 6 months.

RESULTS

51.9% of the intervention group met the criteria of sufficiently performed CPR as compared to only 12.5% in the control group on the day of the intervention (p = 0.007). Hands-off-time as a marker for CPR continuity was significantly less in the intervention group (24.0%) as compared to the control group (28.3%, p = 0.007, Hedges' g = 1.55). At the six-month follow-up, hands-off-time was still significantly lower in the intervention group (23.7% vs. control group: 31.0%, p = 0.006, Hedges' g = 1.88) but no significant difference in sufficiently performed CPR was detected (intervention group: 71.4% vs. control group: 54.5%, p = 0.55).

CONCLUSION

PBL combined with high fidelity simulation training leads to a measurable short-term increase in initiating sufficient CPR by medical students immediately after training as compared to classical education. At six month post instruction, these differences remained only partially.

Transthoracic Impedance Measured with Defibrillator Pads-New Interpretations of Signal Change Induced by Ventilations

Compressions during the insufflation phase of ventilations may cause severe pulmonary injury during cardiopulmonary resuscitation (CPR). Transthoracic impedance (TTI) could be used to evaluate how chest compressions are aligned with ventilations if the insufflation phase could be identified in the TTI waveform without chest compression artifacts. Therefore, the aim of this study was to determine whether and how the insufflation phase could be precisely identified during TTI. We synchronously measured TTI and airway pressure (Paw) in 21 consenting anaesthetised patients, TTI through the defibrillator pads and Paw by connecting the monitor-defibrillator’s pressure-line to the endotracheal tube filter. Volume control mode with seventeen different settings were used (5–10 ventilations/setting): Six volumes (150–800 mL) with 12 min⁻¹ frequency, four frequencies (10, 12, 22 and 30 min⁻¹) with 400 mL volume, and seven inspiratory times (0.5–3.5 s) with 400 mL/10 min⁻¹ volume/frequency. Median time differences (quartile range) between timing of expiration onset in the Paw-line (Paw_EO) and the TTI peak and TTI maximum downslope were measured. TTI peak and Paw_EO time difference was 579 (432–723) ms for 12 min⁻¹, independent of volume, with a negative relation to frequency, and it increased linearly with inspiratory time (slope 0.47, R2 = 0.72). Paw_EO and TTI maximum downslope time difference was between −69 and 84 ms for any ventilation setting (time aligned). It was independent (R2 < 0.01) of volume, frequency and inspiratory time, with global median values of −47 (−153–65) ms, −40 (−168–68) ms and 20 (−93–128) ms, for varying volume, frequency and inspiratory time, respectively. The TTI peak is not aligned with the start of exhalation, but the TTI maximum downslope is. This knowledge could help with identifying the ideal ventilation pattern during CPR.

Manikin study showed that counting inflation breaths out loud improved the speed of resuming chest compressions during two-person paediatric cardiopulmonary resuscitation

AIM

We investigated whether counting inflation breaths out loud during cardiopulmonary resuscitation (CPR) led to an earlier resumption of chest compressions.

METHODS

In this randomised controlled manikin simulation study, conducted from February 2015 to April 2015, 32 fourth-year Korean medical students, equally divided into study and control groups, performed 10 cycles of 15:2 CPR while administering inflation breaths using a bag mask. The first study participant counted the number of inflation breaths out loud, and the second study participant was told to perform chest compressions as soon as they heard their colleague say two. The control group did not count out loud. The groups were blinded to the study outcomes and put in separate rooms.

RESULTS

The median chest compression interruption time was shorter in the study group than the control group (40 vs 46 seconds, p < 0.01, r = 0.70), and the median chest compression fraction (CCF) was higher (68 vs 62%, p < 0.01, r = 0.71). Other quality outcomes related chest compressions and ventilation did not differ between the groups.

CONCLUSION

Counting the number of inflation breaths out loud was a simple method that improved the speed of resuming chest compressions and increased CCFs in 15:2 CPR.

Quality of bystander cardiopulmonary resuscitation during real-life out-of-hospital cardiac arrest

BACKGROUND

Cardiopulmonary resuscitation (CPR) can increase survival in out-of-hospital cardiac arrest (OHCA). However, little is known about bystander CPR quality in real-life OHCA.

AIM

To describe bystander CPR quality based on automated external defibrillator (AED) CPR process data during OHCA and compare it with the European Resuscitation Council 2010 and 2015 Guidelines.

METHODS

We included OHCA cases from the Capital Region, Denmark, (2012-2016) where a Zoll AED was used before ambulance arrival. For cases with at least one minute of continuous data, the initial 10min of CPR data were analysed for compression rate, depth, fraction and compressions delivered for each minute of CPR. Data are presented as median [25th;75th percentile].

RESULTS

We included 136 cases. Bystander median compression rate was 101min^-1 [94;113], compression depth was 4.8cm [3.9;5.8] and compressions per minute were 62 [48;73]. Of all cases, the median compression rate was 100-120min^-1 in 42%, compression depth was 5-6cm in 26%, compression fraction≥60% in 51% and compressions delivered per minute exceeded 60 in 54%. In a minute-to-minute analysis, we found no evidence of deterioration in CPR quality over time. The median peri-shock pause was 27s [23;31] and the pre-shock pause was 19s [17;22].

CONCLUSIONS

The median CPR performed by bystanders using AEDs with audio-feedback in OHCA was within guideline recommendations without deterioration over time. Compression depth had poorer quality compared with other parameters. To improve bystander CPR quality, focus should be on proper compression depth and minimizing pauses.

Mild Hypothermia Protects Pigs' Gastric Mucosa After Cardiopulmonary Resuscitation via Inhibiting Interleukin 6 (IL-6) Production

Background

The purpose of this study was to determine the effect of mild hypothermia therapy on gastric mucosa after cardiopulmonary resuscitation (CPR) and the underlying mechanism.

Material/Methods

Ventricular fibrillation was induced in pigs. After CPR, the surviving pigs were divided into mild hypothermia-treated and control groups. The changes in vital signs and hemodynamic parameters were monitored before cardiac arrest and at intervals of 0.5, 1, 2, 4, 6, 12, and 24 h after restoration of spontaneous circulation. Serum IL-6 was determined at the same time, and gastroscopy was performed. The pathologic changes were noted, and the expression of IL-6 was determined by hematoxylin and eosin (HE) staining and immunohistochemistry under light.

Results

The heart rate, mean arterial blood pressure, and cardiac output in both groups did not differ significantly. The gastric mucosa ulcer index evaluated by gastroscopy 2 h and 24 h after restoration of spontaneous circulation (ROSC) in the mild hypothermic group was lower than that the control group (P<0.05). The inflammatory pathologic score of gastric mucosa in the mild hypothermic group 6–24 h after ROSC was lower than that in the control group (P<0.05). Serum and gastric mucosa IL-6 expression 0.5–4 h and 6, 12, and 24 h after ROSC was lower in the mild hypothermic group than in the control group (P<0.05).

Conclusions

Mild hypothermia treatment protects gastric mucosa after ROSC via inhibiting IL-6 production and relieving the inflammatory reaction.

A novel protocol for dispatcher assisted CPR improves CPR quality and motivation among rescuers-A randomized controlled simulation study

BACKGROUND

Emergency dispatchers use protocols to instruct bystanders in cardiopulmonary resuscitation (CPR). Studies changing one element in the dispatcher's protocol report improved CPR quality. Whether several changes interact is unknown and the effect of combining multiple changes previously reported to improve CPR quality into one protocol remains to be investigated. We hypothesize that a novel dispatch protocol, combining multiple beneficial elements improves CPR quality compared with a standard protocol.

METHODS

A novel dispatch protocol was designed including wording on chest compressions, using a metronome, regular encouragements and a 10-s rest each minute. In a simulated cardiac arrest scenario, laypersons were randomized to perform single-rescuer CPR guided with the novel or the standard protocol.

PRIMARY OUTCOME

a composite endpoint of time to first compression, hand position, compression depth and rate and hands-off time (maximum score: 22 points). Afterwards participants answered a questionnaire evaluating the dispatcher assistance.

RESULTS

The novel protocol (n=61) improved CPR quality score compared with the standard protocol (n=64) (mean (SD): 18.6 (1.4)) points vs. 17.5 (1.7) points, p<0.001. The novel protocol resulted in deeper chest compressions (mean (SD): 58 (12)mm vs. 52 (13)mm, p=0.02) and improved rate of correct hand position (61% vs. 36%, p=0.01) compared with the standard protocol. In both protocols hands-off time was short. The novel protocol improved motivation among rescuers compared with the standard protocol (p=0.002).

CONCLUSIONS

Participants guided with a standard dispatch protocol performed high quality CPR. A novel bundle of care protocol improved CPR quality score and motivation among rescuers.

Part 3: Adult Basic Life Support and Automated External Defibrillation: 2015 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

This review comprises the most extensive literature search and evidence evaluation to date on the most important international BLS interventions, diagnostics, and prognostic factors for cardiac arrest victims. It reemphasizes that the critical lifesaving steps of BLS are (1) prevention, (2) immediate recognition and activation of the emergency response system, (3) early high-quality CPR, and (4) rapid defibrillation for shockable rhythms. Highlights in prevention indicate the rational and judicious deployment of search-and-rescue operations in drowning victims and the importance of education on opioid-associated emergencies. Other 2015 highlights in recognition and activation include the critical role of dispatcher recognition and dispatch-assisted chest compressions, which has been demonstrated in multiple international jurisdictions with consistent improvements in cardiac arrest survival. Similar to the 2010 ILCOR BLS treatment recommendations, the importance of high quality was reemphasized across all measures of CPR quality: rate, depth, recoil, and minimal chest compression pauses, with a universal understanding that we all should be providing chest compressions to all victims of cardiac arrest. This review continued to focus on the interface of BLS sequencing and ensuring high-quality CPR with other important BLS interventions, such as ventilation and defibrillation. In addition, this consensus statement highlights the importance of EMS systems, which employ bundles of care focusing on providing high-quality chest compressions while extricating the patient from the scene to the next level of care. Highlights in defibrillation indicate the global importance of increasing the number of sites with public-access defibrillation programs. Whereas the 2010 ILCOR Consensus on Science provided important direction for the “what” in resuscitation (ie, what to do), the 2015 consensus has begun with the GRADE methodology to provide direction for the quality of resuscitation. We hope that resuscitation councils and other stakeholders will be able to translate this body of knowledge of international consensus statements to build their own effective resuscitation guidelines.

Cardiopulmonary resuscitation quality and patient survival outcome in cardiac arrest: A systematic review and meta-analysis

AIM

To conduct a systematic review and meta-analysis to determine whether cardiopulmonary resuscitation (CPR) quality, as indicated by parameters such as chest compression depth, compression rate and compression fraction, is associated with patient survival from cardiac arrest.

METHODS

Five databases were searched (MEDLINE, Embase, CINAHL, Scopus and Cochrane) as well as the grey literature (MedNar). To satisfy inclusion criteria, studies had to document human cases of in- or out-of hospital cardiac arrest where CPR quality had been recorded using an automated device and linked to patient survival. Where indicated (I(2)<75%), meta-analysis was undertaken to examine the relationship between individual CPR quality parameters and either survival to hospital discharge (STHD) or return of spontaneous circulation (ROSC).

RESULTS

Database searching yielded 8,842 unique citations, resulting in the inclusion of 22 relevant articles. Thirteen were included in the meta-analysis. Chest compression depth was significantly associated with STHD (mean difference (MD) between survivors and non-survivors 2.59 mm, 95% CI: 0.71, 4.47); and with ROSC (MD 0.99 mm, 95% CI: 0.04, 1.93). Within the range of approximately 100-120 compressions per minute (cpm), compression rate was significantly associated with STHD; survivors demonstrated a lower mean compression rate than non-survivors (MD -1.17 cpm, 95% CI: -2.21, -0.14). Compression fraction could not be examined by meta-analysis due to high heterogeneity, however a higher fraction appeared to be associated with survival in cases with a shockable initial rhythm.

CONCLUSIONS

Chest compression depth and rate were associated with survival outcomes. More studies with consistent reporting of data are required for other quality parameters.

Fully automatic rhythm analysis during chest compression pauses

AIM

Chest compression artefacts impede a reliable rhythm analysis during cardiopulmonary resuscitation (CPR). These artefacts are not present during ventilations in 30:2 CPR. The aim of this study is to prove that a fully automatic method for rhythm analysis during ventilation pauses in 30:2 CPR is reliable an accurate.

METHODS

For this study 1414min of 30:2 CPR from 135 out-of-hospital cardiac arrest cases were analysed. The data contained 1942 pauses in compressions longer than 3.5s. An automatic pause detector identified the pauses using the transthoracic impedance, and a shock advice algorithm (SAA) diagnosed the rhythm during the detected pauses. The SAA analysed 3-s of the ECG during each pause for an accurate shock/no-shock decision.

RESULTS

The sensitivity and PPV of the pause detector were 93.5% and 97.3%, respectively. The sensitivity and specificity of the SAA in the detected pauses were 93.8% (90% low CI, 90.0%) and 95.9% (90% low CI, 94.7%), respectively. Using the method, shocks would have been advanced in 97% of occasions. For patients in nonshockable rhythms, rhythm reassessment pauses would be avoided in 95.2% (95% CI, 91.6-98.8) of occasions, thus increasing the overall chest compression fraction (CCF).

CONCLUSION

An automatic method could be used to safely analyse the rhythm during ventilation pauses. This would contribute to an early detection of refibrillation, and to increase CCF in patients with nonshockable rhythms.

Rhythm analysis during cardiopulmonary resuscitation: past, present, and future

Survival from out-of-hospital cardiac arrest depends largely on two factors: early cardiopulmonary resuscitation (CPR) and early defibrillation. CPR must be interrupted for a reliable automated rhythm analysis because chest compressions induce artifacts in the ECG. Unfortunately, interrupting CPR adversely affects survival. In the last twenty years, research has been focused on designing methods for analysis of ECG during chest compressions. Most approaches are based either on adaptive filters to remove the CPR artifact or on robust algorithms which directly diagnose the corrupted ECG. In general, all the methods report low specificity values when tested on short ECG segments, but how to evaluate the real impact on CPR delivery of continuous rhythm analysis during CPR is still unknown. Recently, researchers have proposed a new methodology to measure this impact. Moreover, new strategies for fast rhythm analysis during ventilation pauses or high-specificity algorithms have been reported. Our objective is to present a thorough review of the field as the starting point for these late developments and to underline the open questions and future lines of research to be explored in the following years.