Effects of sleeping position on development of infant cardiovascular control.

OBJECTIVE

Sudden Infant Death Syndrome (SIDS) is associated with prone sleeping, and circulatory failure has been hypothesised to be a factor in the fatal event. We aimed to determine the effect of prone sleeping on heart rate (HR) and blood pressure (BP) control over the first 6 months of life.

SUBJECTS: Term infants (n = 20) were studied longitudinally at 2-4 weeks, 2-3 months and 5-6 months with daytime polysomnography.

MAIN OUTCOME MEASURES: A photoplethysmographic cuff (Finometer, FMS, Finapres Medical Systems, Amsterdam, The Netherlands) on the infant's wrist measured mean, systolic, and diastolic arterial pressure (MAP, SAP, DAP) and HR during quiet sleep (QS) and active sleep (AS) in both the supine and prone positions.

RESULTS

BP in QS was lower compared to AS (by 3-9 mmHg) in both positions and at all three ages (p<0.05). At 2-3 months, a change from supine to prone in QS induced a fall in SAP (6 mmHg, p<0.05) and a rise in HR (4 bpm, p<0.05). An overall effect of postnatal age (PNA) on BP was identified (ANOVA) with MAP and DAP consistently averaging less (by 1-9 mmHg) at 2-3 months in both sleep states and sleeping positions compared with both other ages.

CONCLUSIONS

Infant BP is modified by sleep state and sleeping position. A tendency for BP to fall in the prone position appears to be prevented by elevated HR at 2-4 weeks and 5-6 months, but not at 2-3 months, coincident with the age of greatest risk for SIDS. An uncompensated fall in BP in the prone position at this age could increase the possibility of circulatory failure and SIDS in vulnerable infants.