Introduction:
External cardiac massage has been a basic CPR maneuver for years. The aim of the study was to assess the quality of chest compression during a real-time continuous cardiac compression simulation on a cardio-pulmonary resuscitation mannequin (considering medical rescuer experience and BMI).

Material and methods:
This was a prospective study involving 17 medical rescuers, and 21 Medical Rescue stu-dents and university lecturers. During the simulation the participants performed continuous external cardiac compression for 15 minutes or until the refusal to continue. The depth and rate were analyzed at 60-second periods, leading to average values of cardiopulmonary resuscitation effectiveness. The analysis covered complete research data gathered in real time (10 minute periods).

Results:
The average compression depth significantly decreased from the first (40.66 SE ± 0.80 mm) to the fourth minute of the study (38.21 SE ± 0.95 mm). The average compression rate was significantly different between the initial values (120.97 SE ± 2.83/min) and the sixth minute of the study (123.69 SE ± 2.55/min). The average compression depth amounted to n 36.03 SE ± 1.22 mm in non-professionals and 40.06 SE ± 1.37 mm in professionally active participants. In the participants with a BMI > 25, the only differentiating point in time was the beginning of the task when the average compression depth was 41.97 SE ± 1.12 mm. In the participants with a BMI < 25, there was a gradual decrease in the compression depth within the initial four minutes of the task.

Conclusions:
Rescuer body mass is an important factor influencing proper chest compression depth during continuous cardiac compression. Professional rescuers are capable of performing continuous cardiac compression longer than non-professionals, at the same time maintaining acceptable sternum deflection and compression rate.