Table 1.

Sleep-Wake State Definitions

Variable	Definitions
Quiet Sleep	Respiration is relatively regular (very regular or regular). No more than 20 seconds of continuous movement occurs in quiet sleep.
Active Sleep	Respirations are irregular. Sporadic motor movements may occur, but are not continuous. Rapid eye movements occur intermittently.
Sleep-Wake Transition	Behaviors of both wakefulness and sleep. Respirations are very irregular. Forty seconds of continuous movement in the middle of sleep is scored as sleep-wake transition.
Waking	Includes alert, non-alert waking and crying. Respirations are very irregular. Three minutes of continuous movement is scored as waking.
Very Regular Respiration	The smallest breath during a 10-second period is at least 80% of the height of the largest breath, and the narrowest peak-to-peak interval is at least 67% of the widest peak-to-peak interval.
Regular Respiration	Respiration during a 10-second period does not meet the criteria for very regular respiration but there is no more than one breath between 20–50% of the height of the largest breath, and the narrowest peak-to-peak interval is at least 50% of the widest peak-to-peak interval.
Irregular Respiration	Respiration is too irregular to qualify as regular respiration but does not meet the criteria for very irregular respiration.
Very Irregular Respiration	Scored when a 10-second period includes periodic respiration, continuous movement, and apneic pause defined as: (1) an absence of respiratory activity for an interval of more than 2 seconds between the end of expiration and the beginning of the next inspiration; (2) the presence of a detectable cardiac rhythm within the tracing of the respiratory pause; and (3) an obvious disruption of the ongoing respiratory pattern.