Elsevier

Resuscitation

Volume 96, November 2015, Pages 220-225
Resuscitation

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

https://doi.org/10.1016/j.resuscitation.2015.07.051Get rights and content

Abstract

Aim

Recently 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.

Methods

We 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.

Results

A 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.

Conclusion

Even 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)

Introduction

The number of patients suffering cardiac arrest (CA) is continuously rising within the western society. Despite many efforts in the field of resuscitation science survival rates after out of hospital CA (OHCA) still remain unsatisfying low. However a large variety of factors improving outcome in patients suffering OHCA are well established. A prompt administration of sufficient chest compressions is known to be the most beneficial factor for outcome in patients suffering CA.1, 2, 3, 4, 5

Current guidelines recommend a target compression rate between 100 and 120 compressions per minute, a minimization of interruptions, constant compression depth of at least 5 cm and overall high compression ratios.6, 7 To assess these target guidelines, great hopes were recently set upon automated chest compression devices to support or even replace manual chest compression (cc). In the 2010 guidelines – of both, the American Heart Association and the European Resuscitation Council – LUCAS™ (Physio-Control Incorporation, Lund, Sweden) which is an automated mechanical piston device and AutoPulse® (ZOLL Medical Corporation; MA Chelmsford, USA), a load-distributing band device are specifically mentioned. Both guidelines pointed out that at the time the consensus was found that there was neither certain prove for these devices to improve nor to worsen outcome and that future study results were to be awaited.7, 8 A recent meta-analysis of Westfall et al. comprising eight studies about load distribution devices and four about piston driven devices concluded that mechanical chest compression devices achieved significantly more returns of spontaneous circulation (ROSC).9

Furthermore the mechanical versus manual cc for OOHCA (PARAMEDIC), Circulation Improving Resuscitation Care (CIRC) trial and LUCAS™ in CA study (LINC) study produced results depicting that mechanical cc deliver results comparable to manual cc but were not able to demonstrate superiority. However both devices are currently established and widely used although post-product placement data on outcome of the mentioned devices remain scare and inconclusive.2, 3, 10, 11, 12, 13, 14

Therefore we aimed to verify these results for the everyday use of mechanical cc devices by emergency medical technicians (EMT) and emergency medical physicians in an OHCA setting. Moreover we aimed analyzed whether mechanical cc impacts on 30-day survival with favorable neurological outcome.15, 16

Section snippets

Study population

Patients suffering OHCA and receiving resuscitative efforts by EMTs or physicians of the Municipal Ambulance Service of Vienna, between July 2013 and August 2014 were enrolled. To address the study goals, patients were stratified into two groups according to “mechanical cc” and “manual cc”. Mechanic cc was defined as actual chest compressions administrated by LUCAS or AutoPulse to the patients. If the device was brought to the scene, or prepared for use, but was not put in operation, it was not

Data acquisition and follow-up

Patient data were gathered from run-reports and written event recordings according to the Utstein criteria.4, 5, 6, 7, 8 ECG leads, thoracic impedance data as well as vital parameters were recorded from the moment the defibrillator-electrodes were placed at the patient. The aforementioned data were extracted from the EMS defibrillators used (LifePak 500, 12, or 15, Physio-Control, Redmond, WA, USA) by trained personal and forwarded for evaluation. Impedance data were analyzed using CODE-STAT™

Statistical analysis

Discrete data are shown as counts and percentages and were analyzed using Chi-Square test. Continuous variables are shown as mean and interquartile-range (IQR) and analyzed using Mann–Whitey-U test or Kruskal–Wallis test for comparison within the subgroups. Uni- and multivariable Cox-regression hazard analysis reflecting a multiplicatively association of covariates on the hazard were used to assess the influence of cc type on mortality. Results were presented as hazard ratio (HR) and the

Results

Overall 938 patients were enrolled. Patients were stratified into two groups according to “mechanical cc” (n = 283) and “manual cc” (n = 655; see Fig. 1), because of the very low number of cases with mechanical CPR only, a separation in three subgroups would not yield significance. The mean age of the total cohort was 68 ± 11 years and 343 (36.6%) of the patients were female.

The group that received manual cc was overall older with 70 ± 10 years compared to 63 ± 9 years (p  0.001). Significantly less

Outcome parameters

Any ROSC was achieved in 341 (36.3%) of all patients and sustained ROSC in 266 (28.3%) patients. There were 153 (16.3%) survivors at 30 days after the initial event of which 113 (73.4%) had a CPC of 1 or 2. The patients receiving manual resuscitation were more likely to attain sustained ROSC (n = 201, 30.6%) compared to those receiving mechanical cc (n = 65, 23.0%) (p = 0.017). Though the 30 day survival did not significantly differ between the groups, the neurological outcome did. There was a

Compression ratio and CPR duration

The compression ratios stayed high even in long (>20 min) resuscitation efforts. In the group with manual cc the compression ratio after 20 min was 83% (78–87) and the same as in the shorter resuscitations (82%(75–87) in resuscitations shorter than 10 min and 82% (77–87) in resuscitations that took between 10 and 20 min) and as high as in the group resuscitated with mechanical cc for more than 20 min with 82% (79–86) (Table 2, Table 3).

Comparing devices

Within the mechanical cc subgroup, ‘LUCAS™’ was used in 239 (84.5%) and ‘AutoPulse®’ in 44 (15.5%) cases. Comparing the two devices used for mechanical cc there was no difference in the quality of CPR or outcome. The mean compression ratio for the LUCAS™ group was 82% (79–86) and for the AutoPulse® group 82% [77–87] (p = 0.895). In patients receiving mechanical cc with ‘LUCAS™’ sustained ROSC was achieved in 82 (34.3%) patients as compared to 13 patients treated with ‘AutoPulse®’ (29.5%) (p = 

Survival analysis

A total of 785 (83.7%) patients – consisting of 538 (82.1%) patients who received manual and 247 (87.3%) patients who received mechanical cc – did not survive until hospital discharge. Mechanical cc had a strong, direct association with in-hospital mortality in the entire study cohort with an HR per one standard deviation (1-SD) of 1.59 (95% CI 1.21–2.09, p = 0.01). Moreover after adjustment for potential cofounders, within the multivariate model mechanical cc still remained significantly and

Discussion

Our prospective observational study revealed a significant difference in neurological outcome between manual only and manual cc followed by the administration of mechanical cc or automated cc only. Both, sustained ROSC as well as favorable neurological outcome were significantly more common in patients receiving only manual cc. In addition, we were able to demonstrate an overall satisfyingly high compression ratio, even for longer resuscitations. Surprisingly also in the group of resuscitations

Conclusion

Within the current study we were able to demonstrate, that there was a high quality of CPR in both manual and mechanical subgroup detectable. However the outcome in patients who received mechanical cc was significantly worse than in the manual cc subgroup. While 73.4% of the 30 day survivors reached a CPC 1/2 within the manual cc subgroup, only 56.8% of the patients within the mechanical cc subgroup had good neurological outcome. Maybe the indication for using a mechanical chest compression

Conflict of interest statement

Funding sources

None.

Disclosures

None.

Acknowledgements

We are indebted to the EMTs and physicians of the Vienna Ambulance Service for their support and indulgence.

References (31)

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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2015.07.051.

1

These authors are contributed equally in this work.

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