Physiological vital sign reference ranges for well late preterm newborns calculated during a typical 2 h newborn period between 2 h and 7 days of life

Abstract

Objectives. To calculate 95% reference ranges for heart rate, respiratory rate, oxygen saturation, temperature and blood pressure for well late preterm newborns between 34^+0/7and 36^+6/7weeks of gestation during typical neonatal behaviour.Approach.A single-site, prospective cohort study in a major Australian quaternary hospital between February and September 2019. A total of 120 late preterm newborns had their heart rate, respiratory rate and oxygen saturation measurements recorded every 2 s for up to 2 h with unconditional 95% reference ranges determined using a linear mixed effects model with random intercept for total standard deviation calculation including repeated measures. Temperature and blood pressure measurements were collected twice-at the start and conclusion of the data recording period-with weighted 2.5th and 97.5th percentiles calculated using the mean value.Main results.A total of 364 577 heart rate, 365 208 respiratory rate, 360 494 peripheral oxygen saturation and 240 temperature and blood pressure values were obtained. The 95% reference ranges were: heart rate 102-164 bpm; respiratory rate 15-67 rpm; oxygen saturation 94%-100%; temperature 36.4 °C-37.6 °C; systolic blood pressure 51-86 mmHg; diastolic blood pressure 28-61 mmHg; mean arterial pressure 35-68 mmHg.Significance.Seven vital sign reference ranges were reported for the late preterm population during a typical newborn period (such as crying, sleeping, feeding, awake and alert, and during nappy hygiene cares); internal and external validation should be completed prior to clinical use. Cut off points for escalation of care have previously been generalised to all newborns irrespective of gestational age, which may result in over-treatment or a delay in recognising subtle signs of deterioration.

Keywords: newborn; physiological monitoring; reference range; vital sign.