New York - Research suggests that healthy newborn infants do not have what doctors call "nasoaxillary reflex" - a protective reflex that helps keep their nasal passages open.
In adults lying on their side, the nasoaxillary reflex ensures that the uppermost nasal airway is open, Dr Christopher O'Callaghan of the University of Leicester, United Kingdom, and colleagues explain in the journal Archives of Diseases of Childhood.
The researchers used acoustic rhinometry to see whether the nasoaxillary reflex is present in 11 healthy term newborns.
Acoustic rhinometry emits wide band noise into the nose and analyses the reflected sound in order to measure cross sectional area/distance mapping of the nasal cavity. The measurements were made while the infants were lying on their back (the supine position) and on their side (the lateral position).
When the newborns were turned from a back position to a side position, the team observed a significant decrease in the total minimum cross-sectional area of the nasal cavity. This was associated with a decrease in the total nasal volume.
"The finding that the total minimal cross-sectional area decreases when infants move from a supine to a lateral (side) sleeping position is of interest," O'Callaghan's team contends.
"As newborns tend to be obligate nose breathers, a decrease in the minimal cross-sectional area of the nasal cavity is likely to be linked to an increase in nasal resistance and in the work of breathing."
They note that the side sleeping position has been associated in one study with a slightly greater risk of SIDS (Sudden Infant Death Syndrome, or cot death) than in the back sleeping position, and that the back sleeping position "has unequivocally been recommended as being preferred to any other position to prevent SIDS."
SOURCE: Archives of Diseases in Childhood September 2006.