Avoiding involuntary sleep during civil air operations: validation of a wrist-worn alertness device

Fatigue and sleepiness may rise to unacceptably high levels during civil air operations as a result of relatively long duty periods that may coincide with the circadian low of alertness, and disruption of the circadian rhythm due to time zone shift. Previous studies investigated various measures to detect the presence of sleep. Of these, wrist inactivity was able to identify sleep lasting longer than 5 min, and an alertness device based on wrist inactivity was subsequently developed. The aim of the present study was to assess the effectiveness and utility of the device.

The alertness device was worn by 21 Air New Zealand pilots during flights between Auckland and Perth. The presence of sleepiness and sleep was determined using brain electrical activity (electroencephalogram - EEG) and eye movements (via the electrooculogram - EOG). The EEG and EOG were recorded over the entire flight and were used to validate the effectiveness of the alertness device by determining whether sleep was detected correctly. Also, the pilots assessed the effectiveness and utility of the device subjectively.

Of the 21 pilots, 10 showed sleepiness or sleep during the flights based on the EEG and EOG. The study demonstrated that the alertness device provides an effective method for preventing or inhibiting accidental sleep. Although some sleep episodes in excess of 5 min occurred due to brief movements resetting the alarm delay timer, the efficacy of the device can be increased by modifying the alarm software to ignore brief movements within a period of sleep. The majority of the aircrew found the device acceptable to use.

The study has shown that the alertness device can awaken pilots effectively during flight. Its anticipated use is to prevent accidental sleep during flight, and as part of cockpit napping procedures to ensure that the non-napping pilot remains awake. However, use of such a device is not intended to replace the development of rosters that minimize fatigue or to extend current duty times.