We examined whether topical upper airway anesthesia leads to a reduction in
genioglossal (GG) electromyogram (EMG) in patients with obstructive sleep
apnea (OSA). Airway mechanics were also evaluated. In 13 patients with OSA,
we monitored GG EMG during tidal breathing and during the application of p
ulses of negative airway pressure (-10 to -12 cmH(2)O). Airflow resistance
and airway collapsibility were determined. All measurements were performed
with and without topical anesthesia (lidocaine). Anesthesia led to a signif
icant fall in the peak GG EMG response to negative pressure from 36.1 +/- 4
.7 to 24.8 +/- 5.3% (SE) of maximum (P < 0.01). This was associated with a
fall in phasic and tonic EMG during tidal breathing (phasic from 24.4 +/- 4
.1 to 16.4 +/- 3.4% of maximum and tonic from 10.9 +/- 1.6 to 8.0 +/- 1.3%
of maximum, P < 0.01). A significant rise in pharyngeal airflow resistance
was also observed. Our results demonstrate that topical receptor mechanisms
in the nasopharynx importantly influence dilator muscle activity and are l
ikely important in driving the augmented dilator muscle activity seen in th
e apnea patient.