Short Note Introduction Being Asleep at the Time of Residual Fire Is an Important Risk Factor for Fire-related Death.1 Conventional Residential Smoke

BEING ASLEEP AT THE TIME OF RESIDUAL FIRE IS AN IMPORTANT RISK FACTOR FOR FIRE-RELATED DEATH.1 CONVENTIONAL RESIDENTIAL SMOKE ALARMS generally produce a tone of 85 dB, which will awaken most sleeping adults.2,3 However, studies of auditory arousal thresholds during sleep have shown that a much higher average stimulus intensity is required to elicit arousals in children than in adults, and that many children do not awaken in certain sleep stages, even to extremely loud sounds. A small study of preadolescent boys showed that the frequency of even short-lived EEG arousals was only 25% with no sustained awakening elicited during the first cycle of stage 4 sleep (S4S) with auditory stimuli at intensities up to 123 dB.4 A later study from the same investigators showed that the frequency of awakening in boys aged 8-12 years was only 4.5% during slow wave sleep, 34% during stage 2 sleep, and 50% during rapid eye movement sleep with sound intensities up to 123 dB, i.e. 90-100 dB above background noise.5 A final study by this group examined the maturational changes between age and awakening to tone stimuli and found that while all young adults (20-24 years) could be awakened during S4S, only about 25% of children and adolescents (5-16 years) were awakened during S4S with a maximum intensity of 120 dB.6 A second problem inherent in escaping from a fire occurring during sleep is that many adults have sleep inertia or a transient impairment in cognitive and motor performance that occurs immediately upon awakening.7 Reaction time (RT) is a motor response that has been found to be sensitive to the degree of sleep inertia in adults. In adults, sleep inertia has been found to be worse after awakening from slow wave sleep than any other sleep stage.8 The combination of increased auditory arousal threshold during sleep, especially S4S, and sleep inertia upon awakening from sleep could be expected to impair a child’s ability to awaken to a home smoke alarm and successfully escape in the event of a residential fire. To our knowledge, the quantitative effects of sleep inertia or decrement in performance upon awakening from sleep have not been previously reported among children. As part of a study evaluating the effects of different types of alarms on awakening children from S4S,9 we measured reaction times (RT) of children upon awakening from the first two cycles of S4S compared with measurements about 90 minutes before bedtime. We were interested in whether changes in RT paralleled the ability of a child to be awakened from S4S and also correctly perform a self-rescue sequence (SRS) after awakening to an alarm.