Aim: To analyze the correlation of the Poincaré plot descriptors of RR intervals with standard measures of heart rate variability (HRV) and spontaneous baroreflex sensitivity (BRS). A physiological model of changing respiratory rates from 6 to 15 breaths/min provided a wide range of RR intervals for analysis.
Material and methods: Beat-to-beat finger blood pressure, ECG, and respiratory curves were recorded noninvasively in 15 young healthy volunteers (19-25 years old; 7 females) breathing for 5 min at 4 different respiratory rates of 6, 9, 12, and 15 breaths/min. Four descriptors of the Poincaré plot (SD1, SD2, S, and SD2/SD1), time and frequency domain HRV, and spontaneous BRS (cross-correlation method) were calculated for each 5-min recording.
Results: The values of SD1 characterizing short-term HRV, SD2 describing long-term HRV, and S measuring total HRV were significantly correlated with BRS and time and frequency domain measures of short, long, and total HRV. The LF/HF significantly correlated with SD2 and SD2/SD1 representing the balance between long- and short-term HRV. None of the Poincaré plot descriptors was correlated with the mean RR interval. The increased respiratory rate caused a significant reduction of BRS, measures of total and long-term HRV, and an increase of HF that peaked at 12 breaths/min.
Conclusions: The descriptors of the Poincaré plot of RR intervals are significantly correlated with measures of BRS and time and frequency domain HRV, but not with heart rate. A faster respiratory rate reduces long-term HRV measures and temporarily increases HF.