Front-to-back defibrillator pad placement, called anterior-posterior (AP) in the study, took longer and was less often judged acceptable than anterior-lateral (AL) placement in a small simulation study. Mean AP application time was 14.19 seconds, compared with 10.62 seconds for AL, a gap of 3.57 seconds. The paired comparison reported a p-value of 0.0419.
The study examined two practical questions during simulated out-of-hospital cardiac arrest: whether AP and AL placement differed in anatomical accuracy and how quickly both pads could be applied. It linked an accuracy comparison under unguided and written-guidance conditions with a separate randomized crossover speed study, in which participants tried both positions.
A large gap in the accuracy test
The accuracy component involved 14 participants aged 21 to 56. They were convenience-recruited from clinical education settings and related events, and eligibility required basic-life-support training and fundamental knowledge of defibrillators or automated external defibrillators. Two independent assessors judged photographs as acceptable or unacceptable while blinded to participant identity, timing data and participant characteristics.
Without written guidance, 7 of 14 AL placements, or 50%, were acceptable, compared with 2 of 14 AP placements, or 14%. After written guidance, the AL figure was 13 of 14, or 93%, while AP stayed at 2 of 14, or 14%.
The errors followed a different pattern for the two positions. Unguided AL errors were mainly superior or lateral, meaning too high or too far to the side, and these errors were largely reduced after guidance. AP errors persisted, with lower or abdominal placement dominating guided AP attempts.
That sequence does not show that written guidance alone caused the observed AL change. The accuracy exercise used a fixed order, so practice, fatigue and familiarity could also have contributed to the difference.
AP placement took longer
The separate speed simulation included 9 EMS participants. Five were randomized to Group A, which applied AP then AL, and four to Group B, which applied AL then AP. Each participant served as their own control. Timing ran from a verbal start command to full adhesion of both pads.
Across the paired comparison, AP averaged 14.19 seconds and AL 10.62 seconds, making AP 3.57 seconds slower. The reported p-value was 0.0419. Order-specific means were 15.34 seconds for AP and 11.47 seconds for AL in Group A, and 12.76 seconds for AP and 9.56 seconds for AL in Group B.
Both pad configurations had longer mean times in the AP-first group than in the AL-first group. The authors treated the order breakdown as exploratory because the groups were small, and the study was not designed to settle how much of the timing difference would persist in a larger comparison.
A preliminary operational signal
The authors characterize the linked studies as feasibility and hypothesis-generating work. They say the design can identify large effects and operational issues, but is underpowered to exclude smaller or moderate differences between AP and AL placement.
These were pad-placement and timing exercises in simulation, not patient-outcome tests. The study did not measure defibrillation success, return of spontaneous circulation, survival or neurological outcomes.
The preprint has not been certified by peer review and says it should not be used to guide clinical practice. The simulation was registered as a service evaluation with the Welsh Ambulance Service University Trust, and participants consented after receiving study information.
The pre-protocol simulation was unfunded, while patient and public involvement was funded by Health and Care Research Wales.
The clinical importance of the 3.57-second delay remains uncertain, and the small exploratory design cannot rule out smaller or moderate differences. The findings therefore remain preliminary and should not be used to change clinical practice.
Paper data and sources
Original title: AnterioR-Posterior VErsuS Anterior-LaTeral defibrillator pAd position in out of hospital cardiac aRresT
Authors: Colbourne A, Dart T, Deakin CD et al.
Journal/Repository: Not provided
Status: Preprint, not yet peer-reviewed
First online: 2026-08-27
DOI: 10.64898/2026.08.24.26361176
Original paper · Full text