Short and longer term repeatability of ballistocardiography in a sitting position with EMFi sensor.

Short and long-term alterations of ballistocardiographic parameters (BCG) were studied in a sitting position using Electromechanical Film (EMFi) sensors. Several physiological parameters were recorded from 48 men of middle age in consecutive recordings and after a 2-week interval. The duration and amplitudes of the signal components were studied. The repeatability index R, the Pearson correlation, and Bland-Altman (BA) repeatability methods were used to determine how repeatable the studied signals are. In consecutive and during 2 week recordings, the Pearson correlation rates for BCG systolic component values (from 0.88/0.83 (T(RJ)) to 0.97/0.78 (A(IJ)), PWV values for the left 0.97/0.67 and right ankle 0.98/0.76) were detected indicating excellent repeatability during consecutive recordings. Respectively BA T(RJ) was -0.002 ± 0.028/-0.004 ± 0.030. Corresponding R values were T(RJ) 0.90/0.82 and right ankle PWV 0.98/0.81. Quite modest blood pressure R values were obtained between 2 week recordings (systolic 0.63, diastolic 0.75, and heart rate 0.59). BCG and PWV measured with EMFi sensors are highly repeatable in consecutive recordings. In longer time interval recordings, BCG is influenced by hemodynamic instability, but in spite of this the reproducibility of the main parameters of the BCG and PWV were better than measured heart rate and blood pressure values.