Introduction
Method
Participants
Procedure
Data recording
Data analysis—error identification
Type of error | Description | Correction for HRM data |
---|---|---|
T1 | A discrepancy greater than 20 ms at a single interval, either positive or negative | Error recorded, but not corrected |
T2 | A long interval, followed by a short interval. Whilst the two points either side were unaffected (<20 ms) | Two uncorrected R–R intervals averaged |
T3 | Short interval, followed by a long interval. Whilst the two points either side were unaffected (<20 ms) | Two uncorrected R–R intervals averaged |
T4 | Missed interval(s) on the HRM, equivalent to two or three ECG RR intervals | RR interval divided by the number of undetected R waves |
T5 | Extra, short, RR intervals from the HRM, in the space of one on the ECG | RR intervals combined to approach the corresponding ECG value |
T6-a | RR interval(s) entirely missed by the HRM, undetectable | Error recorded, but not corrected |
T6-b | RR interval(s) entirely missed by the HRM, detectable | Interpolated value from the two adjacent points inserted |
Data analysis—error correction
Data analysis—time and frequency domain and non-linear analysis
Time domain analysis
Frequency domain analysis
Non-linear analysis
Statistical analysis
Results
Type of error | Description of error | Supine | Standing |
---|---|---|---|
T1 | Single interval of discrepancy | 2 | 1 |
T2 | Long interval and short interval | 0 | 0 |
T3 | Short interval and long interval | 0 | 1 |
T4 | Too few intervals detected | 6 | 1 |
T5 | Too many intervals detected | 0 | 2 |
T6-a | Interval(s) missed entirely, undetectable | 1 | 5 |
T6-b | Interval(s) missed entirely, detectable | 1 | 0 |
ECG (mean ± SD) | Polar (mean ± SD) | Bias (LoA) | ICC (95 % CI) | Effect size (interpretation) | |
---|---|---|---|---|---|
Supine | |||||
SDNN (ms) | 61.37 ± 32.00 | 61.36 ± 32.03 | 0.01 (–0.22 to 0.24) | 1.00 (1.00–1.00) | 0.000 (small) |
RMSSD (ms) | 55.92 ± 37.76 | 55.92 ± 37.81 | 0.00 (–0.32 to 0.32) | 1.00 (1.00–1.00) | 0.000 (small) |
PNN50 (%) | 29.05 ± 23.05 | 29.30 ± 23.04 | –0.25 (–1.20 to 0.70) | 1.00 (1.00–1.00) | 0.011 (small) |
VLF power (ms2) | 819.17 ± 777.33 | 820.05 ± 779.10 | –0.88 (–7.52 to 5.76) | 1.00 (1.00–1.00) | 0.001 (small) |
LF power (ms2) | 1050.87 ± 994.29 | 1051.82 ± 994.94 | –0.95 (–6.25 to 4.36) | 1.00 (1.00–1.00) | 0.001 (small) |
HF power (ms2) | 182.97 ± 2212.28 | 1826.52 ± 2216.23 | 0.45 (–27.95 to 28.84) | 1.00 (1.00–1.00) | 0.000 (small) |
nuLF power | 40.97 ± 15.93 | 41.05 ± 16.07 | –0.08 (–0.72 to 0.56) | 1.00 (1.00–1.00) | 0.005 (small) |
nuHF power | 58.88 ± 15.88 | 58.81 ± 16.02 | 0.08 (–0.57 to 0.72) | 1.00 (1.00–1.00) | 0.005 (small) |
LF:HF ratio | 1.00 ± 1.43 | 1.05 ± 1.63 | –0.04 (–0.43 to 0.35) | 0.99 (0.98–1.00) | 0.029 (small) |
SD1 | 44.96 ± 33.54 | 44.95 ± 33.57 | 0.01 (–0.21 to 0.23) | 1.00 (1.00–1.00) | 0.000 (small) |
SD2 | 83.98 ± 46.25 | 83.96 ± 46.27 | 0.02 (–0.20 to 0.24) | 1.00 (1.00–1.00) | 0.000 (small) |
Sample entropy | 1.46 ± 0.31 | 1.46 ± 0.31 | –0.01 (–0.11 to 0.09) | 0.99 (0.97–1.00) | 0.021 (small) |
Standing | |||||
SDNN (ms) | 52.03 ± 16.67 | 52.00 ± 16.67 | 0.02 (–0.17 to 0.22) | 1.00 (1.00–1.00) | 0.001 (small) |
RMSSD (ms) | 30.09 ± 18.24 | 30.06 ± 18.14 | 0.03 (–0.28 to 0.34) | 1.00 (1.00–1.00) | 0.002 (small) |
PNN50 (%) | 7.23 ± 7.84 | 7.26 ± 7.99 | –0.04 (–1.42 to 1.34) | 1.00 (0.99–1.00) | 0.005 (small) |
VLF power (ms2) | 923.78 ± 766.72 | 923.99 ± 765.73 | –0.20 (–5.58 to 5.17) | 1.00 (1.00–1.00) | 0.000 (small) |
LF power (ms2) | 1371.91 ± 1132.93 | 1371.33 ± 1133.29 | 0.58 (–6.67 to 7.83) | 1.00 (1.00–1.00) | 0.001 (small) |
HF power (ms2) | 652.26 ± 753.96 | 647.93 ± 742.37 | 4.33 (–25.08 to 33.74) | 1.00 (1.00–1.00) | 0.006 (small) |
nuLF power | 70.14 ± 13.21 | 70.19 ± 13.13 | –0.05 (–0.83 to 0.74) | 1.00 (1.00–1.00) | 0.004 (small) |
nuHF power | 29.75 ± 13.14 | 29.70 ± 13.06 | 0.05 (–0.73 to 0.83) | 1.00 (1.00–1.00) | 0.004 (small) |
LF:HF ratio | 3.22 ± 2.39 | 3.23 ± 2.44 | –0.01 (–0.35 to 0.33) | 1.00 (0.99–1.00) | 0.004 (small) |
SD1 | 21.31 ± 12.92 | 21.29 ± 12.85 | 0.02 (–0.20 to 0.24) | 1.00 (1.00–1.00) | 0.002 (small) |
SD2 | 70.16 ± 20.85 | 70.13 ± 20.88 | 0.03 (–0.23 to 0.28) | 1.00 (1.00–1.00) | 0.001 (small) |
Sample entropy | 1.05 ± 0.28 | 1.05 ± 0.28 | 0.00 (–0.05 to 0.05) | 1.00 (0.99–1.00) | 0.012 (small) |