AbstractIn this study, the relation between the measurement duration and accuracy of pulse-counting was quantitatively examined with special reference to low-frequency fluctuations in heart rate variability. The interbeat intervals of 70 healthy male subjects were measured in standing, sitting and supine positions. Pulse rates for various durations were calculated by objective-scoring simulation based on the heartbeat recordings of the subjects. The duration of pulse-counting continuously varied from 6 to 60 s in the simulation. Simulated pulse rates were compared with the rate calculated from the 60 s that includes the given duration, and the absolute difference between the two rates was defined as the error. Average errors of pulse-counting for 15 s were 1.89, 1.89 and 1.80 bpm for standing, sitting and supine positions, respectively. No difference in error was observed between standing and sitting positions; however, smaller errors were observed in the supine position.by Hiromitsu Kobayashi
Mean SD Min Max 75.79 12.60 53.73 110.42 4.42 1.25 0.38 7.24 5.33 1.33 1.82 8.04 4.78 1.26 2.26 7.58 ) 4 standing sitting supine m p b ( 3 r o r r e d e n g s n U i 2 1 0 0 10 20 30 40 50 60 Measurement duration (s) Figure 2. Continuous plot of the simulated error and duration of pulse-counting. Note: The error increased hyperbolically with decreasing duration. No signicant difference was found between the errors in sitting and standing positions; however, smaller errors were observed in the supine position. Table 2 shows the average values and distribution characteristics of the error in standing, sitting and supine positions. For instance, the average error was 1.89 bpm with a measurement duration of 15 s in the sitting position. In this case, the probability of the error being greater than 4 and 7 bpm was 10% and 1%, respectively.
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Correlations of error with age, heart rate and frequency components of HRV in the sitting position are shown in Figure 3. A negative correlation was observed between the error and subjects age (r 2 0.12). No relationship was found between the error and heart rate. Although a correlation was observed between the error and both LF and VLF components (r 2 0.39 and 0.57, respectively), it was more apparent with VLF than with LF. Similar tendencies were observed in the standing and supine positions. Table 2. Simulated errors in sitting, standing and supine positions (bpm). 6 s 10 s 15 s 20 s Standing Sitting
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Supine Mean 10% 5% 1% Mean 10% 5% 1% Mean 10% 5% 1% 4.03 8 10 13 3.88 8 9 13 3.64 8 9 11 2.65 5 6 9 2.52 5 6 8 2.44 5 6 8 1.89 4 5 7 1.89 4 5 7 1.80 4 4 6 1.55 3 4 5 1.52 3 4 5 1.39 3 4 5 Note: 10%, 5% and 1% indicate the percentile values of the error. For example, for a 15 s counting in standing position, the probability that the error is larger than 5 bpm is estimated to be 5%. lnTP (ln-ms2) 6.14 1.21 2.84 8.29 30 s 1.10 2 3 4 1.03 2 3 4 0.99 2 3 4 Ergonomics A 5 B 5 C 5 ) ) ) m p b ( 4 r2=0.04 m p b ( 4 r2=0.28 m p b ( 4 r2=0.39 r o r r e 3 r o r r e 3 r o r r e 3 d e n g s n u i 2 1 d e n g s n u i 2 1 d e n g s n u i 2 1 0 40 60 80 HR (bpm) 100 120 0 0 2 8 lnHF (ln-ms2) 4 6 10 0 0 2 8 lnLF (ln-ms2) 4 6 10 D ) 5 E ) 5 F ) 5 m p b ( 4 r2=0.57 m p b ( 4 r2=0.49 m p b ( 4 r2=0.12 r o r r e 3 r o r r e 3 r o r r e 3 d e n g s n u i 2 1 d e n g s n u i 2 1 d e n g s n u i 2 1 0 0
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2 8 lnVLF (ln-ms2) 4 6 10 0 0 2 8 lnTP (ln-ms2) 4 6 10 0 10 20 30 40 50 60 age (year) Figure 3. Correlations of the simulated error for a 15 s measurement in the sitting position with heart rate (A), high-frequency component (B), low-frequency component (C), very low-frequency component (D), total-power component (E) and age (F). Note: The errors did not correlate with heart rate (A). Correlations were observed between simulated errors and frequency components of heart rate variability (B E). Smaller errors were observed in older compared with younger subjects (F).
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