title: Breath-to-breath relationships between respiratory cycle variables in humans at fixed end-tidal PCO2 and PO2.
abstract: This study examined the statistical properties of breath-to-breath variations in the inspiratory and expiratory volumes and times during rest and light exercise. Sixty data sets were analyzed. Initial data and residuals after fitting time-series models were examined for 1) sustained periodicities with use of spectral analysis, 2) temporal changes in signal power with use of evolutionary spectral analysis, and 3) auto- and cross correlations with use of a portmanteau test. The major findings were as follows: 1) no sustained periodic components were detected; 2) temporal changes in signal power were normally present, but these did not affect significantly the results from time-series modeling; 3) for all variables, a simple autoregressive moving average (ARMA) AR1MA1 model generally described the autocorrelation; 4) considerable cross correlation remained between residuals from the AR1MA1 model; 5) relationships between variables could be described by using a multivariate time-series model; 6) residual fluctuations in end-tidal PCO2 had little influence; and 7) responses were broadly similar between rest and exercise, although some quantitative differences were found. The multivariate model provides a description of the structure of the interrelationships between cycle variables in a quantitative and a qualitative form.
authors.affiliation: University Laboratory of Physiology, Oxford, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Busso
authors.forename: P J
authors.initials: PJ
authors.lastname: Liang
authors.forename: P A
authors.initials: PA
authors.lastname: Robbins
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D003627:Data Interpretation, Statistical; D006801:Humans; D008954:Models, Biological; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology*; D012044:Regression Analysis; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide