Correlation structure of end-expiratory volume (EEV) in anesthetized rats with intact upper airway

The correlation structure of end-expiratory volume (EEV) was studied in anesthetized rats with intact airways subjected to lung inflation and deflation. The Hurst exponent H, was estimated from EEV fluctuations using modified dispersional analysis. The authors found that H for EEV was 0.5362/spl plusmn/0.0763 (mean/spl plusmn/std) and 0.6403/spl plusmn/0.0561 (mean/spl plusmn/std) with lung inflation and deflation, respectively. Both H were significantly different from those obtained after random shuffling of the original time series. Also H with lung deflation was significantly greater than that with lung inflation (P=0.029). The authors conclude that in rats breathing through the upper airway, a positive long-term correlation is present in EEV that is different between inflation and deflation.