That's actually the point of the Dying Gasp feature in OAM. It tells you as the device is dying. Hence dying gasp. If the device detects that the PSU(s) have lost input power, it can send a syslog, SNMP trap, or EOAM message before the device's control-plane fails, alerting an NMS or in the case of EOAM or OAM, the upstream device.