 Multiple studies, most performed decades ago in larger infants, found that short onoff cycles of PT e.g. 15 min on60 min off, 1 h on3 h off, or 1 h on1 h off are as effective as uninterrupted PT to reduce TSB. Cycles with 6 h off PT do not appear to be as effective as uninterrupted PT. The clinical use of uninterrupted rather than cycled PT appears to be based largely on the assumption that PT is safe for all infants. 