|Schipke JD et al.|
Effect of respiration rate on short-term heart rate variability
Journal of Clinical and Basic Cardiology 1999; 2 (1): 92-95
Keywords: Herzfrequenzvariabilität, kurzfristig, respiration, respiratorische Sinusarrhythmie, heart rate variability, respiration, respiratory sinus arrhythmia, short-term
Heart rate variability (HRV) is the consequence of various influences of the autonomic nervous system on heart rate. The influence of the respiration rate on HRV is well accepted (respiratory sinus arrhythmia: RSA). The extent of different respiration rates on HRV however, is not greatly appreciated. In our study, we stored a modified chest wall electrocardiogram on magnetic tape (Tracker, Reynolds) for later analysis (Pathfinder IV, RR-tools, Reynolds). 15 volunteers performed controlled respiration at six different 6 min-intervals: below the low-frequency range (LF) of the power spectrum (0.03 Hz), within LF (0.08, 0.10 and 0.13 Hz), within the high-frequency range (HF; 0.25 Hz), and above HF (0.50 Hz). HRV was expressed in the time domain in terms of standard deviation (SDNN), root mean square successive difference (RMSSD) and the percentage of differences between adjacent normal RR intervals that are > 50 ms (pNN50). After fast Fourier transformation, HRV was expressed in the frequency domain in terms of LF power (0.05-0.15 Hz), HF power (0.15-0.45 Hz), and the ratio (R) of LF to HF. Heart rate (72 ± 11 min-1) remained unchanged throughout the protocol, indicating a steady haemodynamic state. HRV differed up to 33 % in SDNN, 37 % in RMSSD and 75 % in pNN50 between the different respiration rates. LF power differed up to 72 % (p < 0.10), HF power up to 36 % and R up to 48 % (p < 0.10). Reproducibility seems satisfactory for the short-term analysis. Respiration rate-induced changes in the time domain measurements were not significant. Because of the large scatter of RMSSD and pNN50, we suggest SDNN as a reliable, easily accessible, and illustrative measurement for assessment of HRV. Respiration clearly affected the frequency domain measurements of HRV via shifts in the respiratory sinus arrhythmia. If major changes in respiration rate are to be expected, these should be interpreted with caution. On the other hand, the characteristic RSA-induced shifts in the frequency range could possibly be useful to determine respiration rate in freely moving individuals. J Clin Basic Cardiol 1999; 2: 92-5.