<<I remember learning in neonatal assessment once upon a time that babies
are obligatory nose breathers.  My eyes 'tell' me otherwise!>>

Since my book took a direct hit on this very topic in the recent JHL review,
it's time for me to chime in.
The discussion of obligatory nose breathing for infants is perhaps more a
problem of semantics than of anatomy.  It appears that  the term "obligate" is
causing us the most difficulty: (from the random house dictionary)1.  to
oblige or bind  legally or morally 2.  pledge commit or bind  3 necessary,
essential 4.  biol.  restricted to a particular condition of life
[in the case we are discussing, it seems the term "obligatory" is defined by
#4 restricted to a particular condition of life; rather than #'s 1-3 meaning
necessary or essential.]

Every pediatric text book I've reviewed states that babies are obligate nose
breathers.  Congenital plugs in the nares, for example, causes respiratory
distress.  Nose breathing for an infant is natural, while mouth breathing is
not and is tiring for a baby because it requires greater inspiratory effort
(Avery & First) .  It doesn't mean babies CAN'T breathe through their mouth,
it only means it is more difficult for them to do so.

It all boils down to anatomy.  According to Suzanne Evans Morris (The Normal
Acquisition of Oral feeding Skills) pg.  20
"...the oral space in the newborn is relatively small, partly due to the
comparative smallness of the mandible, or lower jaw.  The lower jaw is small
and some what pulled back in the newborn and the tongue in relation to the
cavity size is large.  In fact, in most instances not much oral space is
visible since the tongue is usually in constant contact with all the borders
of this cavity so that it completely fills the space....   In addition,
newborn are obligate nose breathers and do not breathe through their mouthes.
This has to do in part, with the positioning of the soft palate, but also with
the fact that there is no space in the mouth for air to be traveling in and
out.  This particular method of function in the newborn has a built-in
protective component.  When the system is not very sophisticated, it is much
safer breathing through one area and eating through another, thus not
requiring the system to share responsibilities for function.  We already know,
in the adult, respiratory function and feeding function share the same
channel.  In order to do this successfully, the sophisticated adult system has
to provide a valve so that the food does not travel through the larynx and
into the lungs.  One of the differences, then, in the newborn anatomy is the
very small oral space.
A second difference is that structurally the epiglottis and soft palate are in
approximation. . . .   Respiration does not have to be inhibited in order to
swallow.


It is remarkable how nature has provided the infant with this protective
mechanism so that the structure allows the infant to survive with a little
less function and coordination . . ."
The section is quite lengthy. Morris later goes on to say, that major changes
in this "valving system" occur at about 3-4 months of age including an
increase in the oral space.  If there are changes at 3-4 months, it stands to
reason that oral breathing becomes easier at that time.
Marie Davis, RN, IBCLC