Introduction: In telephone assisted, advanced medical priority dispatch system (AMPDS) driven, lay-rescuer, compression-only cardiopulmonary resuscitation (COCPR) it remains unclear whether the instruction “push as hard as you can” improves compression depth.

Methods: This was a prospective, experimental, double-blinded, randomized, controlled, parallel group study to compare the depth of chest compressions achieved following the instruction “push as hard as you can” and the recommended guidelines. Primary outcome was defined as compression depth. Secondary outcomes were defined as drawn estimation of 5 cm by every participant, exertion measured by BORG scale, modified Nine Hole Peg Test (NHPT), provider’s systolic and diastolic blood pressure and the quality values measured by the Resusci® Anne skillmeter manikin.

Results: 13 participants were each allocated to control and intervention. 1 participant in the intervention group dropped out after 7 minutes due to exhaustion. Primary outcome showed a mean compression depth of 44.1 mm with an interindividual standard deviation (SDb) of 13.0 mm and an intraindividual standard deviation (SDw) of 6.7 mm for the control group versus 46.1 mm and a SDb of 9.0 mm and a SDw of 10.3 mm for the intervention group (Difference: 1.9 (-6.9 to 10.8), p=0.66). For secondary outcome participants estimated a mean of 43 ± 13 mm in control group versus 45 ± 15 mm in the intervention group (p=0.99). Secondary outcome investigating exhaustion and COCPR quality values did not show any difference.

Conclusion: There is no difference in compression depth, quality of COCPR or physical strain on lay-rescuers when advising “push as hard as you can” versus the standard AMPDS instruction “push down firmly 5 cm.”

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