A clinical audit on maintenance of optimal peripheral oxygen saturation in preterm neonates needing mechanical ventilation at a level III neonatal intensive care unit

Introduction: With increasing survival of preterm neonates, oxygen therapy has become an integral part of neonatal respiratory support. In Sri Lanka survival rate of extremely preterm babies is nearly 70%. Most recent studies show oxygen saturations (SpO₂) of 91-95% in preterm neonates maximize survival while minimizing side effects such as retinopathy of prematurity. Oxygenation can be optimized by controlling ventilator settings- i.e. fraction of inspired oxygen (FiO₂), inspiratory time and mean airway pressure.

Objective: To study the SpO₂ trend maintained in ventilated (both invasive and non-invasive) preterm babies at the neonatal intensive care unit of Sri Jayewardenepura General Hospital.

Method: Study was done in March 2018 on ventilated preterm babies <34 weeks gestation and birth weight <1.5kg. Neonates with pulmonary hypertension, bronchopulmonary dysplasia, cyanotic heart disease, major congenital anomalies and neonates on palliative care were excluded. SpO₂ trend and related ventilator settings i.e. FiO₂, peak inspiratory pressure / pressure support, and positive end expiratory pressure, were recorded daily at 8am and 2pm. SpO₂ trend was observed for 10 minutes and the most persisting value taken to minimize observation bias. Data were analysed using SPSS 20.  

Results: Ten preterm neonates with 211 observations were studied. Maturity ranged from 27-33 weeks. Mean birth weight was 1.24 kg (SD=0.43) and 5 (50%) babies were extremely low birth weight. In 158 (74.9%) observations, SpO₂ was >95%. Optimal SpO₂ was noted only in 52/211 (24.6%) observations. In observations with SpO₂ >95% where invasive ventilation was used, 35/120 (29.1%) had minimum ventilator settings i.e. PiP-14H₂Ocm and FiO₂-21%. Among babies with non-invasive modes, 68.4% of observations had a FiO₂ of 21% with a PEEP of 5. Therefore, in 59.5% there was no room to reduce FiO₂ further and in 29.1% of the instances with invasive ventilation there was no room for reducing ventilator settings. SpO₂ was <89% only on 1 occasion.

Conclusions: Even though in most of the instances minimum ventilator settings were used still there was room for further reduction.