Name

Synopsis

Description

These programs derive pNNx, time domain measures of heart rate variability defined for any time interval x as the fraction of consecutive normal sinus (NN) intervals that differ by more than x. Conventionally, such measures have been applied to assess parasympathetic activity using x = 50 milliseconds (yielding the widely-cited pNN50 statistic).

pnnlist

This program takes as standard input an annotation interval list, containing intervals in seconds and the (beat and non-beat) annotations that terminate each interval; and outputs on standard output each unique NN increment (x) in milliseconds, and the percentage of NN interval increments (pNNx) greater than x.

Options for pnnlist may include:

-h

Print this usage summary.

-i inc

Compute and output pNNx for x = 0, inc, 2*inc, ... milliseconds.

-p

Compute and output increments as percentage of initial intervals.

-s

Compute and output separate distributions of positive and negative intervals.

pNNx

This shell script invokes ann2rr(1) and pnnlist to obtain pNNx statistics using a beat annotation file as input. The input file must be specified using the -r record and -a annotator arguments.

Options for pNNx may include any of those usable with pnnlist, as well as:

-f time

Begin at the specified time. By default, pNNx starts at the beginning of the record.

-t time

Stop at the specified time.

Examples

These commands are functionally identical:
   ann2rr -r nsrdb/16265 -a atr -A -i s8 -w | pnnlist

   pNNx -r nsrdb/16265 -a atr

Each of these commands reads the atr (reference) annotations for MIT-BIH Normal Sinus Rhythm Database (nsrdb) record 16265 (downloading them directly from PhysioNet if the annotation file has not previously been downloaded into a local nsrdb directory. These commands will then print each unique NN interval increment in milliseconds along with the percentage of intervals greater than that value. Both of the examples above produce the same output; the first few lines are shown below:
   0 89.2738

   7.8125 69.4564

   15.625 53.3662

   23.4375 40.8539

   31.25 31.4265

   39.0625 24.1817

   46.875 18.4763

   54.6875 14.1261

   62.5 10.7312

   70.3125 8.06025

   78.125 6.09401

   85.9375 4.56975

   93.75 3.47841

   101.562 2.66896

    .

    .

    .

Environment

It may be necessary to set and export the shell variable WFDB (see setwfdb(1) ).

See Also

Author

Source

Table of Contents

• Name
• Synopsis
• Description
• pnnlist
• pNNx
• Examples
• Environment
• See Also
• Author
• Source

Up: WFDB Applications Guide

Updated 10 June 2022