IMPROVED UPPER AIRWAY PATENCY ELICITED BY ELECTRICAL-STIMULATION OF THE HYPOGLOSSUS NERVES

The present study evaluated the mechanisms by which upper airway (UAW) -dilating muscle contraction, elicited by hypoglossus nerve (HGN) stim ulation, improved UAW patency. Pressure-flow (P-V) relationships of th e isolated UAW as well as the negative intraluminal pressures required to cause UAW collapse were assessed before and during electrical stim ulation of the HGN in 8 anesthetized, ventilated dogs. Sectioning of t he HGN shifted the P-V relationship to the left, while electrical stim ulation resulted in a substantial shift of the curve to the right, ind icating UAW dilatation. UAW resistance decreased from 9.0 +/- 1.5 to 0 .3 +/- 0.1 cm H2O . l(-1). s during HGN stimulation (p < 0.01). The ma gnitude of negative intraluminal pressure at which UAW collapse occurr ed (the critical pressure) increased from -2.7 +/- 0.7 to -13.2 +/- 2. 1 cm H2O (p < 0.002). The increase in UAW conductance and stability ra ised the maximal flow which could be sustained without collapse from 0 .28 +/- 0.07 to 2.07 +/- 0.35 Vs during HGN stimulation (p < 0.001). T hese findings indicate that in the anesthetized dog, UAW muscle contra ction improves UAW patency both by dilating the UAW and by stiffening its walls.