The effects of a mixture of surface-active agents (Sonarex) on upper airways resistance and snoring in anaesthetized dogs.

We measured upper airways resistance from the trachea and from the pharynx to the atmosphere, EMG of the genioglossus muscle and the sound of snoring, in anaesthetized greyhounds, breathing spontaneously through the upper airways. Using extra-corporeally produced continuous flow we determined flow/pressure curves for the upper airways and resistances from the trachea and from the pharynx. We tested the effects of 0.9% saline and of Sonarex (a proprietary mixture containing sodium chloride, glycerol, polysorbate 80 and benzalkonium chloride). Both saline and Sonarex decreased upper airways resistance, but the latter did so more consistently. With Sonarex, genioglossus activity increased and the sound of snoring decreased. Flow/pressure curves 5-20 min after Sonarex showed a decrease in upper airways resistance and a smoother curve, whereas those with saline showed an increase in resistance. The sound produced by continuous flow through the upper airways was decreased by Sonarex but increased by saline. Thus, both Sonarex and saline decrease upper airways resistance, but Sonarex also reduces the sound of snoring and the resistance and sound of continuous airflow through the upper airways.