Objective: Several studies have previously shown respiratory related evoked potentials (RREP) in humans elicited by mechanical stimuli applied on upper airways (UA). According to us, heterogeneous findings, concerning latencies and amplitudes, have been reported because of the different timing of stimuli application during the respiratory cycle and/or features of pressure stimuli. Therefore we evaluated the cortical response evoked by transmural pressure changes at the mouth induced by a negative expiratory pressure (NEP) device.
Methods: RREP were recorded in 22 healthy non-obese, non-snoring volunteers. The subjects were studied awake in seated position during quiet breathing. Three different pressure levels were applied, in a random order, 200 ms after the beginning of expiration. Cortical electrical responses were recorded from scalp electrodes at Fz, Cz, and Pz scalp location (international 10-20 system) referenced to the linked earlobes.
Results: RREP responses consisted of two negative (N45, N120) and two positive (P22, P85) waves. There was no significant effect of pressure or electrode on component latencies. The P22 wave (PRESSURE: F(df 2,42)=6.66, P<0.01), the N45 wave (PRESSURE: F(df 2,42)=16.51, P<0.001), and the P85 wave (PRESSURE: F(df2,42)=15.15, P<0.001) increased significantly theyr amplitude with increasing from pressure stimuli 1 to 10 cmH2O.
Conclusions: The present results suggest that the UA NEP application in humans is a reliable way of evoking cortical responses. The experimental features that we described allow us to minimize the confounding factors in evaluating RREPs. The NEP device appears to be a useful tool for investigation of the neurobiology of UA sensation in humans.