An approach to define newborns´ sniffing position using an angle based on reproducible facial landmarks

The neutral or sniffing position is advised for mask ventilation in neonates to avoid airway obstruction. As definitions are manifold and often unspecific, we wanted to investigate the reliability and reproducibility of angle measurements based on facial landmarks that may be used in future clinical trials to determine a hypothetical head position with minimal airway obstruction during mask ventilation.

In a prospective single-center observational study, 2D sagittal photographs of 24 near-term and term infants were taken, with five raters marking facial landmarks to assess interobserver agreement of those landmarks and angle δ, defined as the angle between the line parallel to the lying surface and the line crossing Subnasale (Sn) and Porion' (P'). Angle δ was assessed in sniffing (δ^sniff ) and physiologic (δ^phys ) head position, the former based on a published, yet poorly defined head position where the tip of the nose aligns to the ceiling with the head in a supine, relaxed mid-position.

Infants had a mean (SD) gestational age of 37.3 (2.3) weeks. Angle δ could be determined in all 48 images taken in either the sniffing or the physiological head position. Interobserver correlation coefficient was 98.6 for all measurements independent of head position. Angle δ^sniff was 90.5° (5.7) in the sniffing position.

This study provides a new measuring technique using an angle that is reproducible and reliable and may be used in future studies to correlate head position with airway obstruction.