Background High-quality cardiopulmonary resuscitation (CPR) could improve survival of drowning victims. The purpose of the study is to assess the impact of fatigue caused by water rescue on subsequent CPR quality and the influence of a bystander’s participation on CPR quality in a lifeguard rescue.

Methods This was a simulated quasi-experimental study with a sample of 14 lifeguards and 13 laypersons. Each lifeguard performed 2 min single-rescuer CPR as baseline measurement. In three separate trials, a single lifeguard swam 50 m to perform a water rescue in a pool and returned with the manikin another 50 m. After each rescue, 10 min of CPR was performed by a single lifeguard, two lifeguards or a lifeguard with a layperson with no CPR training. Paired t-test and repeated analysis of variance were used to analyse CPR quality variables.

Results Baseline CPR quality was adequate for most measures except compression depth and re-expansion. After water rescue, the single lifeguard trial showed no significant differences compared with baseline. CPR score and ventilation score of the single-lifeguard trial was higher than that of the lifeguard-bystander trial (p=0.027, p<0.001). Both the two-lifeguard trial (p=0.025), and lifeguard-bystander trial (p=0.010) had a lower percentage of breaths with correct ventilation volume and higher percentage of breaths with excessive ventilation volume (p=0.007, p=0.011, respectively) than the single-lifeguard trial. No-flow time of the lifeguard-bystander trial was longer than other trials (p<0.001).

Conclusions Although CPR given by the lifeguard was not optimal, fatigue generated by a water rescue has no impact on the quality of subsequent CPR performed by a trained lifeguard for 10 min. Untrained bystanders assisting in CPR in a drowning event is unlikely to be helpful.