Fig. 2.

A: an example of the RR detection, using the root-mean-squared (RMS) signal ratio of coronary sinus lead 1 and electrocardiographic lead II (CS1/ECG II). The blue curve represents the estimated RR using our algorithm through the time course of this study. The red lines represent the RR reported by the respiratory monitor during each interval (indicated by the length of the red line) employed for the estimation of the RR. B: normalized power spectrum (in cycles/beat) as a function of time during the step down transition of the ventilation rate, from 13 to 7 breaths/min, for the data from A. There is a clear peak in the spectrum at a rate that decreases as a function of time as the ventilation rate decreases from 13 to 7 breaths/min.