Evaluation of fatigue, load and the quality of chest compressions by bystanders in hot and humid environments

Background

This study aimed to investigate the physiological load on bystanders during cardiopulmonary resuscitation (CPR) and the quality of chest compressions in hot and humid environments.

Methods

This prospective experimental study compared the physical load and quality of chest compressions among healthy volunteers who performed 10 min chest compression in a climate chamber under normal conditions (for Tokyo) (Wet Bulb Globe Temperature [WBGT] 21 °C) and hot and humid conditions (WBGT 31 °C). The primary outcome was the depth of chest compressions over a 10-minute period. Secondary outcomes included the volunteer’s heart rate (HR), core body temperature (BT), Borg scale for assessing fatigue, and blood lactate levels. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) and paired t-tests.

Results

Out of 31 participants, 29 participants (mean [SD] age: 21[0.7], male: 21 [70.5 %]) were included in the analysis. For WBGT 21 °C and 31 °C, the mean chest compression depth at 10 min was not statistically difference (the depth of chest compression: 52.2 mm and 51.5 mm (p = 0.52)). At 10 min, heart rate and core temperature were 126 vs. 143 bpm, and 37.4℃ vs. 37.5℃ for WBGT 21℃ vs. WBGT 31℃ (mean differences: 17 bpm [95 % CI: 7.7–26.3], 0.1℃ [95 % CI: −0.1–0.3]). At the end, Borg scale was 16 vs. 18 and lactate levels were 3.9 vs. 5.1 mmol/L (mean differences: 2 [95 % CI: 1–3], 1.2 mmol/L [95 % CI: 0.1–2.3]).

Conclusion

there was no significant difference in the depth of chest compression of paramedic students under the conditions between WBGT 31℃ and WBGT 21℃. For secondary outcomes, the lactate and fatigue of bystanders increased under WBGT 31℃ compared to WBGT 21℃. Further research is needed on CPR in hot and humid environments.