Pulse respiration quotient as a measure sensitive to changes in dynamic behavior of cardiorespiratory coupling such as body posture and breathing regime

FIGURE 1. (A) A segment of simultaneously recorded signals (8 s selected from a total of 1200 s): breathing and ECG in one subject in a supine position with spontaneous breathing; where: RRI—time interval between two adjacent R peaks of the ECG signal, BBI—breathing interval, calculated as the time difference between onsets of two successive inspirations (respiratory cycle), PRQ—pulse respiration quotient (number of heartbeats per respiratory cycle). (B) Obtaining PRQ from signals derived as rr and intervals. Gray line with crosses: rr intervals (ordinates) vs. rr onset time (abscissa). Black line with circles: BB intervals (ordinate) vs. BB onset time (abscissa). Black vertical lines and text boxes with parameter values are added for better explaining the principle behind obtaining PRQ from rr (RRI) and BB (BBI) intervals. Each PRQ value is a sum of the integer number of whole rr intervals (bint) and the non-integer parts of rr intervals (b1 and b2) that fall within one BBinterval (breathing cycle). Thus, PRQ = bint + b1+b2.

FIGURE 2. One-minute PRQ mean values and variabilities for 20 subjects. Supin—supine position with spontaneous breathing, Stand—standing with spontaneous breathing, Supin01—supine position with slow (0.1 Hz) breathing, Stand01—standing with slow (0.1 Hz) breathing.

FIGURE 3. Plot of PRQmean versus PRQsd minute values in time in four physiological states in 20 subjects. Supin—supine position with spontaneous breathing, Stand—standing with spontaneous breathing, Supin01—supine position with slow (0.1 Hz) breathing, Stand01—standing with slow (0.1 Hz) breathing.

FIGURE 4. (A) PDE distribution profiles of the PRQ parameter for 20 subjects in four physiological states: Supin—supine position with spontaneous breathing, Stand—standing with spontaneous breathing, Supin01—supine position with slow (0.1 Hz) breathing, Stand01—standing with slow (0.1 Hz) breathing; fact—fineness factor. Quantization around integer PRQ values is visible in most local maxima; (B) PDE distribution of PRQ parameter for 20 subjects that was calculated from artificial RR intervals (RRI) with uniform distribution (random values within the physiological limits of the RRI parameter) and real BB intervals.

FIGURE 5. Overlapping PDE distribution profiles of PRQ parameter for 20 subjects in 3 comparison of physiological states: (A) Supin-Stand, (B) Supin-Supin01, (C) Supin-Stand01; Supin—supine position with spontaneous breathing, Stand—standing with spontaneous breathing, Supin01—supine position with slow (0.1 Hz) breathing, Stand01—standing with slow (0.1 Hz) breathing; fact—fineness factor; DKL—Kullback-Leibler divergence (relative entropy).