Distal skin vasodilation promotes rapid sleep onset in preterm neonates

Abstract

Although sleep is of paramount importance for preterm neonates, care of the latter in a neonatal intensive care unit does not favour sleep. Given that several studies in adults have described a 'vegetative preparedness to sleep' (in which distal skin vasodilation before lights-out promotes rapid sleep onset), we looked at whether or not this process operates in preterm neonates. Sleep propensity was assessed in terms of the duration of a spontaneous episode of wakefulness (W). Skin temperatures at six body sites (the abdomen, pectoral region, eye, hand, thigh and foot) were measured (using infrared thermography) during nocturnal polysomnography in 29 9-day-old preterm neonates (postmenstrual age: 209 ± 9 days). We then determined whether the duration of the W episode depended upon the local skin temperatures measured at the start, during and end of the episode. The W episode was shorter when distal skin temperatures (thigh, hand and foot) and the pectoral temperature were higher at the end of the episode (i.e. at sleep onset). The relationship with the duration of the W episode was not significant for temperatures measured at the start of the W episode. We observed gradual distal vasodilation at the pectoral region, the thigh, hand and foot (i.e. affecting most of the body's skin surface) during W episodes. Our results constitute initial evidence to show that distal vasodilation may have a key role in facilitating sleep onset in very preterm neonates.

Skin Temperatures of Back or Neck Are Better Than Abdomen for Indication of Average Proximal Skin Temperature During Sleep of School-Aged Children

“…when DPG = 0°C, i.e., disappearance of the thermoregulatory shell (12)]. This is consistent with the observation that in preterm neonates homogenization between proximal and distal skin Ts was related to more rapid sleep onset (13). DPG can therefore be considered as a marker for skin thermal homogenization between the distal and the proximal regions of the body.…”

“…Similar time patterns are also observed in preschool children (mean age: 4 years) (24), in 4 to 9 months old infants (25) and even in preterm neonates (13,26). Although the usability of DPG to predict rate of sleep onset is reported as limited in infants (25) results show that, as in studies of adults, the larger the distal vasodilation, the more rapid the sleep onset (13). Also consistent with those shown in adults, the results of these studies of infants and children show that proximal and distal skin Ts do not share the same time patterns.…”

“…Studies performed on school-aged children sleeping in their natural settings showed that DPG [T calf -T subclavicular (20), T feet -T subclavicular, abdomen (23)] increased before and after sleep onset. Similar time patterns are also observed in preschool children (mean age: 4 years) (24), in 4 to 9 months old infants (25) and even in preterm neonates (13,26). Although the usability of DPG to predict rate of sleep onset is reported as limited in infants (25) results show that, as in studies of adults, the larger the distal vasodilation, the more rapid the sleep onset (13).…”

“…Given the vast possibilities for determining proximal or distal T measurement, DPG (distal T minus proximal T) may be calculated in different ways. Using single Ts, calculations have included proximal T which is not located on the trunk (forehead, flank, limbs) even though they have been shown to show similar time pattern as hands or feet T ( 13 ). Unique DPGs have been calculated between upper (T ear lobe – T mastoid ), middle (T hand – T arm ) and lower body (T foot – T leg ) regions, and exhibit anti-correlated fluctuations in the hand-to-arm and foot-to-leg gradients ( 42 ).…”

“…Reported single and combined body sites for measures of distal skin T, proximal skin T and DPG.FootOne foot, or average value of the right and left feet(13,23,25,(32)(33)(34)(35)(36) HandMeasured variously at back of the hand(s), one or both middle fingers…”