Respiratory function parameters in ventilated newborn infants undergoing whole body hypothermia

Whole body hypothermia (WBH) exerts proven neuroprotective effects in infants with hypoxic-ischaemic encephalopathy (HIE). Our aim was to describe how WBH could impact on respiratory function in mechanically ventilated newborn infants, by recording primary and composite indices of oxygenation and ventilation before, during and after WBH.

The medical notes of 31 mechanically ventilated full-term newborn infants who underwent WBH for HIE were retrospectively reviewed. Fraction of inspired oxygen (FiO2), tidal volume (TV), mean airway Pressure (MAP), minute ventilation (MV), static compliance of the respiratory system (C(statRS)), ventilation efficiency index (VEI), alveolar-arterial gradient (A-a gradient) and oxygenation index (OI) were documented before and during hypothermic treatment, as well as during and after rewarming.

Fraction of inspired oxygen, MAP, OI and A-a gradient decreased during induction of hypothermia and tended to increase during rewarming. C(statRS), VEI and TV increased during induction of hypothermia and tended to decrease during rewarming. None of the changes achieved statistical significance.

These results suggest that WBH might affect respiratory function in mechanically ventilated infants with HIE. Oxygenation might be enhanced by hypothermia, probably as a result of decreased metabolism, while ventilation might also be facilitated as a result of the effect of hypothermia on lung mechanics.