Interindividual variability in heart rate variability (HRV) and complexity (HRC) measurements

Abstract

Indices of HRV and HRC have been suggested as potential tools for assisting triage decisions in trauma patients (Aviat Space Environ Med 77:1107, 2007; J Trauma 63:512, 2007). Determination of intersubject variability in these measurements in normal individuals has not been performed. We hypothesized that common indices of HRV and HRC are not highly variable in healthy human subjects, thereby allowing the establishment of “normal” values. ECG was collected for 5 min in 31 supine, resting subjects. Time domain variables included RRISD, RMSSD, pNN50, and SD1 and SD2 from Poincaré plot analysis. Frequency domain variables (LF, 0.04–0.15 Hz; HF, 0.15–0.4Hz) were calculated using Fourier transform. HRC analyses included entropy (SampEn), fractal nature (FD‐L and FD‐DA), stationarity (StatAv), symbol dynamics (SymDyn) and detrended fluctuation analysis (DFA). Data are below:Against expectations, many parameters demonstrated high interindividual variability. Since application of clinical vital signs depends on comparison to a “normal” value, a single measurement of HRV or HRC may not be beneficial for determining patient status. However, tracking changes in continuously‐measured HRV or HRC parameters over time might be more useful.