Respiratory Function in Ventilated Newborn Infants Nursed Prone and Supine.

OBJECTIVES

Prone positioning has been associated with improved oxygenation in ventilated newborn infants but the physiological basis of this improvement has not been previously studied. We aimed to test the hypothesis that respiratory function measured by composite physiological indices would be improved in the prone compared to the supine position.

STUDY

DESIGN

Prospective observational study of ventilated newborns in a tertiary neonatal unit studied prone and supine at random order.

METHODOLOGY: The ventilation to perfusion ratio (VA/Q) and right to left shunt were non-invasively calculated using the oxyhemoglobin dissociation curve method. The gradient of the arterial to end tidal carbon dioxide (PaCO2 - EtCO2 gradient) was calculated to describe changes in the alveolar dead space.

RESULTS

Forty-six (26 male) infants with a median (IQR) gestational age of 34.8 (33.1-36.3) weeks and birth weight of 2.34 (1.77-2.87) kg were studied after 5 (2-10) hours of invasive ventilation. The VA/Q was significantly higher in the prone position [0.57 (0.52-0.63)] compared to supine [0.53 (0.46-0.62), p = 0.001]. Right to left shunt was significantly lower in prone [7 (0-12) %] compared to supine [9 (1-16) %, p = 0.003]. The PaCO2 - EtCO2 gradient was significantly lower in prone [6.3 (3.8-8.4) mmHg] compared to supine [12.1 (7.1-16.0) mmHg].

CONCLUSIONS

The prone position in ventilated neonates was associated with improved ventilation to perfusion matching and lower intrapulmonary shunting and alveolar dead space compared to supine.