Biostrap measures respiratory rate with an algorithm combining the following: 

  1. Changes in amplitude of the PPG signal: As someone breathes in and breathes out, we review the signal changes
  2. Heart Rate Variability: We also look at the the inter beat variability captured through the device as someone breathes in and out.

Please also refer to this paper: http://iopscience.iop.org/article/10.1088/0967-3334/37/4/610/meta

Did this answer your question?