NEW YORK (Reuters Health) – 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, UK, and
colleagues explain in the journal Archives of Diseases of
Childhood.
The researchers used acoustic rhinometry, a technique that
measures nasal patency, to see whether the nasoaxillary reflex
is present in 11 healthy term newborns.
Acoustic rhinometry emits wide band noise into the nose and
analyzes 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).
The investigators were unable to show a protective
nasoaxillary reflex in the infants.
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
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.
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