Objective: Sudden Infant Death Syndrome (SIDS) is associated with prone sleeping and circulatory failure has been hypothesised as 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 mo of life.
Subjects: Term infants (N=20) were studied longitudinally at 2-4 wk, 2-3 mo and 5-6 mo with daytime polysomnography.
Main outcome measures:A photoplethysmographic cuff (FinometerTM) on the infant's wrist measured (MAP), systolic (SAP), diastolic (DAP) arterial pressure 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 mo 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 PNA on BP was identified (ANOVA) with MAP and DAP consistently averaging less (by 1-9 mmHg) at 2-3 mo 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, except at 2-3 mo in QS. An uncompensated fall in BP in the prone position at 2-3 mo (when SIDS risk is greatest) could increase the possibility of circulatory failure and SIDS in vulnerable infants.