The Effects of Wakefulness State on the Temporal Characteristics of Ventilatory Variables in Man

The effects of audiovisual stimulation on the temporal patterns of V_T, T_I, T_E were studied in 11 healthy subjects. 75 datasets of steady-state breathing each of eight minutes in duration were obtained during low wakefulness (lying still, eyes closed), low wakefulness with calibrated thermal pain stimulation and high wakefulness (playing a computer game). The analysis included removal of trend and mean, interpolation and re-sampling of the data to provide an equi-spaced time basis, test for normal distribution of datasets, power spectral estimation, estimation of the parameters of 1^st and 2^nd order autocorrelation models and estimation of the same parameters on the residuals following subtraction of the 1^st or 2^nd order models. All power spectra showed the highest power at the lowest frequencies; correspondingly the 1^st order autocorrelation coefficients were significant at the 5% level except for T_E (p = 0.12). The 2^nd order coefficients were non-significant for all series. The 1^st order autocorrelation coefficients of the residuals (after subtraction of the 1^st order autocorrelation component) were all non-significant. With 1^st order autocorrelation coefficients averaging between .12 and .37 the non-random part of the variation explained by the 1^st order autocorrelation structure is between 1.4% and 13.7% and independent of stimulation of breathing by thermal or mental stimuli.