The use of nitrous oxide requires a nasal mask (inhaler) and
depends on the child’s understanding and willingness to
breathe through the nose. When children are able to cooperate in
the inhalation process, nitrous oxide/oxygen is an excellent,
safe, and effective technique to reduce anxiety and enhance effective
communication in children with anxiety. Administered by nasal mask,
its onset and recovery is rapid, and the effects are easily titrated
and reversible. By raising the pain threshold, increasing the tolerance
for the procedure and longer appointments, reducing the gag reflex,
and potentiating the effect of other sedatives (if utilized), nitrous
oxide analgesia has a predictable effect among the majority of the
pediatric population.12 But the use of nitrous
oxide/oxygen alone in children who are severely disruptive
may prove futile. Precooperative or noncooperative children (or
adults with disabilities) often breathe through their mouth, crying
or moving about in the dental chair, thus negating the effects of
any nitrous oxide/oxygen administered through a nasal inhaler.
Children with compulsive personalities or “take-charge” children
may not like the feeling of loss of control associated with nitrous
oxide, and they may unilaterally terminate the procedure. In addition,
nitrous oxide/oxygen inhalation will have a very low success
rate in children who have upper respiratory tract or other acute
respiratory infections. Any respiratory problem that prevents the
use of the nasal inhaler as the route of entry for the gases (ie,
common cold, acute or chronic sinusitis, chronic mouth breathing,
enlarged tonsils and/or adenoids, allergic rhinitis, tuberculosis,
bronchitis, cough, chronic obstructive pulmonary disease (COPD),
emphysema) represents a situation in which the technique of inhalation
anxiolysis would be ineffective and should be avoided. The use of
nitrous oxide/oxygen analgesia is also best avoided in
the pregnant patient during the first trimester to avoid increasing the
possibility of spontaneous abortion.15 Medical
consultation between the dentist and obstetrician is always advisable
for the pregnant patient. Additionally, air spaces in the maxillary
sinus, vestibulocochlear complex, and bowel can be displaced by
nitrous oxide. These nonrigid spaces can enlarge and cause discomfort
as a result of high concentration and prolonged use of nitrous oxide/oxygen
analgesia. The avoidance of hypoxia is especially important in children
with congenital methemoglobinemia.16