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 1st and 2nd order autocorrelation models and estimation of the same parameters on the residuals following subtraction of the 1st or 2nd order models. All power spectra showed the highest power at the lowest frequencies; correspondingly the 1st order autocorrelation coefficients were significant at the 5% level except for T(E) (p = 0.12). The 2nd order coefficients were non-significant for all series. The 1st order autocorrelation coefficients of the residuals (after subtraction of the 1st order autocorrelation component) were all non-significant. With 1st order autocorrelation coefficients averaging between .12 and .37 the non-random part of the variation explained by the 1st order autocorrelation structure is between 1.4% and 13.7% and independent of stimulation of breathing by thermal or mental stimuli.