Heart rate response to alarm tones in firefighters

Abstract

Objective: To examine cardiovascular responses to medical (MED) and fire (FIRE) alarm tones in firefighters.

Methods: Heart rate was collected throughout 24-h shifts (N = 41). Call logs were utilized post hoc to identify heart rate at the time the alarm sounded (TIME_TONE), peak heart rate following the alarm (TIME_PEAK), and heart rate at the time of station departure (TIME_DEPART) for MED and FIRE calls. A 2X3 (TONE x TIME) split-plot mixed-model repeated-measures analysis of variance (ANOVA) and least significant differences tests examined the influence of tone type on heart rate, expressed as a percent of age estimated maximum. Bivariate Pearson correlations examined the relationship between body mass index (BMI) and TIME_PEAK and TIME_DEPART. An alpha of 0.05 determined statistical significance and Bonferroni Corrections were applied to post hoc comparisons (p < 0.017).

Results: Follow-up analyses for the significant 2 × 3 repeated-measures ANOVA (p = 0.035) indicated differences in heart rate for MED (p < 0.001) and FIRE (p < 0.001) where TIME_TONE < TIME_PEAK, TIME_TONE < TIME_DEPART, and TIME_PEAK > TIME_DEPART. There was a non-significant simple effect of time for MED and FIRE at TIME_TONE (p = 0.259), but significant effects of tone type where FIRE > MED at TIME_PEAK (p < 0.001) and TIME_DEPART (p = 0.002). There was a significant small positive relationship between BMI and TIME_PEAK (p = 0.002) and TIME_DEPART (p < 0.001) for MED only.

Conclusions: Alarms increased heart rates to a greater extent in FIRE than MED calls. Higher BMI was related to greater heart rate responses in MED but was unrelated to FIRE response.

Keywords: Alarm tone; Autonomic nervous system; Body mass index; Firefighter; Heart rate; Work exposure.