# Effectiveness of combinations of active compression-decompression cardiopulmonary resuscitation, impedance threshold devices and head-up cardiopulmonary resuscitation in adult out-of-hospital cardiac arrest: A systematic review

## TL;DR

This review examines how combining specific CPR techniques may improve survival and brain function after cardiac arrest outside hospitals.

## Contribution

The study evaluates the combined effectiveness of three neuroprotective CPR methods in adult out-of-hospital cardiac arrest.

## Key findings

- One trial found better neurological survival with impedance threshold devices and active compression-decompression CPR compared to standard CPR.
- Observational studies showed conflicting results when comparing the full neuroprotective bundle to standard CPR.
- Limited data suggests potential benefits of combining CPR adjuncts, but more research is needed.

## Abstract

This review summarises the current evidence base for combinations of neuroprotective CPR adjuncts (active compression-decompression chest compressions, impedance threshold devices, and head-up positioning) during out-of-hospital cardiac arrest.

A systematic search (PROSPERO registration CRD42023432302) was performed in English on MEDLINE, EMBASE, and the Cochrane Library in August 2023, and repeated in February 2024. All randomised and observational studies (not abstracts) reporting on any combination of the aforementioned CPR adjuncts were included. Papers were screened independently by two researchers, with a third reviewer acting as tiebreaker. Out-of-hospital, non-traumatic, cardiac arrests in patients >18 years were eligible for inclusion. Risk of bias was assessed using the Risk of Bias 2 tool and the Newcastle-Ottawa scale.

Eight of 1172 unique articles identified in the initial searches were included, with five randomised controlled trials and three observational studies. No randomised trial investigated a bundle of all three interventions. All randomised controlled trials were at intermediate or high risk of bias. Neurologically favourable survival was greater in patients treated with an impedance threshold device and active compression-decompression CPR when compared to standard CPR (8.9% vs 5.8%, p = 0.019) in the largest existing randomised trial. Conflicting results were found in observational studies comparing the complete neuroprotective bundle to standard CPR.

This review was limited by small study numbers and overlapping samples, which precluded a meta-analysis. Limited data suggests that combinations of adjuncts to improve cerebral perfusion during CPR may improve survival with favourable neurological outcome. A randomised controlled trial is required to establish whether combining all three together results in improved outcomes.