Effect of supraglottic mechanoreceptors on spatial mapping of respiratory related evoked responses using wavelet and Laplacian methods

Respiratory related evoked potentials (RREPs) were recorded from eight norm al subjects in response to brief pressure pulses of -10 cm H2O with a durat ion of 200 ms to identify the contribution of supralaryngeal mechanorecepto rs to the evoked responses by constraining application of the stimulus to t he larynx and sublarvngeal regions through insertion of a larvngeal mask ai rway (LMA). Wavelet decomposition of RREP responses from 30 electrodes on t he right side of the scalp was performed for eight frequency scales in time . The RREPs at each wavelet scale were enhanced by eliminating the wavelet coefficients due to artifacts and noise. After denoising, the third (125-15 0 Hz), fourth (62.5-125 Hz), fifth (31.25-62.5 Hz) and sixth (13.62-31.25 H z) wavelet scales were used fnr estimation of the Laplacian. In addition, t he global field power was calculated to quantify the wavelet-filtered RREP activity and to extract features for statistical analysis, Our results show that estimates of the global field power at the fourth and fifth wavelet s cales are more significantly decreased after the insertion of the LMA than was true for scales 3 and 6. Further, after the LMA was inserted, the Lapla cian showed reduced activity in the posterior-lateral region in four subjec ts and reductions in other places in the rest. (C) 2000 Biomedical Engineer ing Society. [S0090-6964(00)00811-0].