Detect systolic peaks in PPG

Implements the Elgendi two event-related moving-average (TERMA) detector. The shipped windowed-sinc FIR is used in place of the original Butterworth filter. Its linear-phase group delay is explicitly undone by snapping each event-block candidate to the corresponding raw-signal maximum.

Usage

ppgDetectPulses(
  x,
  w1_ms = 111,
  w2_ms = 667,
  beta = 0.02,
  low = 0.5,
  high = 8,
  order = 65,
  refractory_ms = 300,
  assay_name = NULL
)

Arguments

x

A PPG PhysioExperiment.

w1_ms

Systolic event window in milliseconds.

w2_ms

Beat window in milliseconds.

beta

Moving-average threshold offset.

low, high

PPG band-pass cutoffs in Hz.

order

FIR order; even values are promoted to the next odd value.

refractory_ms

Minimum systolic-peak separation in milliseconds.

assay_name

Optional raw PPG assay name.

Value

A data frame with channel, sample, time_sec, and raw amplitude.

Details

This implementation uses the package's pure-R windowed-sinc FIR rather than the Butterworth filter in the original method. A strong late dicrotic wave may require increasing refractory_ms so that it is not counted as a second systolic pulse.

References

Elgendi M, Norton I, Brearley M, Abbott D, Schuurmans D (2013). Systolic peak detection in acceleration photoplethysmograms measured from emergency responders in tropical conditions. PLoS ONE, 8:e76585. doi:10.1371/journal.pone.0076585

Examples

set.seed(1)
simulation <- make_ppg(n_time = 3000)
head(ppgDetectPulses(simulation$pe))
#>   channel sample time_sec amplitude
#> 1       1    122    0.968  2.996094
#> 2       1    226    1.800  3.005296
#> 3       1    331    2.640  2.993458
#> 4       1    435    3.472  3.011860
#> 5       1    539    4.304  3.012044
#> 6       1    643    5.136  3.014261