Delayed blood pressure recovery after head-up tilting during sleep in preterm infants

Dramatic changes in cardiovascular control occur in sleep during infancy, when sleep time is at a lifetime maximum. In infants born preterm there are significant cardiovascular complications later in life, and also an increased risk for sudden infant death syndrome (SIDS), possibly a result of inadequate compensation to a cardiorespiratory challenge in sleep. We aimed to examine the consequences of preterm birth on heart rate (HR) and blood pressure (BP) responses to head-up tilting (HUT) during sleep in infants. Preterm (n = 25) and term (n = 20) infants were studied using daytime polysomnography at 2-4 weeks', 2-3 months' and 5-6 months' term-corrected age (CA). BP was recorded using a photoplethysmographic cuff (Finometer); 15 degrees HUTs were performed during both quiet and active sleep. Preterm infants responded to HUT with increased HR and BP, followed by a bradycardia and a subsequent return of HR and BP to baseline. Overall, HUT responses were similar between term and preterm infants at matched ages. Notably, however, return of BP to baseline was considerably delayed in preterm infants ( approximately 37 beats post-tilt) compared with term infants ( approximately 23 beats post-tilt) at both 2-4 weeks' and 2-3 months' CA (P < 0.05). Our study has demonstrated that preterm infants respond to a BP perturbation with changes in HR that match those of term infants. However, delayed recovery of BP during sleep in the preterm infant may be indicative of underlying deficits or immaturity in vascular function or control, which may contribute to their vulnerability to SIDS and cardiovascular complications later in life.