Figure 1. Representative raw record from one animal demonstrating volume injections of 0.5, 0.4, 0.3, 0.2 and 0.1 ml and zero volume and subsequent application of a 60 Hz stimulus to the whole hypoglossal nerves.

Note that prior to volume injection the airway pressure was allowed to return to atmospheric pressure. In some instances this return was immediate but in most cases several minutes elapsed before the airway pressure returned to baseline. For this reason, only that part of the pressure record that coincides with the initial volume injection and subsequent application of the stimulus are shown.