Figure 1: (a) Time series of heart beat interval (upper panel), time series of respiratory interval (middle panel), and ratio of heart beat frequency to respiratory frequency (lower panel) in a representative case during receiving routine bronchodilator test. Event mark (red line) denotes the start of the inhalation of Berotec. (b) Heart rate variability analysis at stage 4 (5-min segment), shortly before inhalation of Berotec, in a representative case. Upper panel: Cardiotachogram of RR intervals for the time-domain analysis. Lower panel: Power spectrum of the RR intervals for the frequency-domain analysis. Blue line denotes 0.04 Hz mark. Green line denotes 0.15 Hz mark. Red line denotes 0.4 Hz mark.