Simple photoplethysmography pulse encoding technique for communicating the detection of peripheral arterial disease-a proof of concept study.

Objective: To assess the feasibility of novel photoplethysmography (PPG) Pulse Sounder/Pulse Visualizer communication techniques for alerting the presence (or absence) of peripheral arterial disease (PAD).

Approach: Proof of concept evaluation using our previously published multi-site PPG pulse data set (110 participants included; age  >  40 years; 44% PAD by ankle brachial pressure index (ABPI)). Two main pulse encoding rules using the risetime as an example feature to mark each heartbeat in a 6 s analysis study window: if risetime at both great toes  ⩽time threshold ('no PAD' state) then heartbeat marked with a single 5 kHz audio tone; if risetime from either great toe  >  threshold ('PAD') then heartbeat marked with a distinct train of 5 kHz audio tones. A simple spectrogram visual plot was also produced for each participant's audio signals. ROC curve analysis first determined an appropriate risetime threshold using the simple-to-evaluate PAD Visualizer and then re-tested at this level with PAD Sounder and classification performance summarized.

Main Results: The pulse encoding rules used were easy to learn. Visualizer best communication performance at risetime 0.27 s gave specificity 80.6%, sensitivity 95.8%, accuracy 87.3%, negative predictive value 96.2%, and Kappa statistic of 0.75. Classification performance for blinded assessment with audio PAD Sounder was identical.

Significance: Substantial agreements demonstrated between Sounder/Visualizer disease techniques and the ABPI PAD reference. These simple-to-use PAD communications methods when embedded into an appropriate device platform could offer significant benefits in PAD diagnosis for a range of clinical settings, including primary care where low-cost, portable and easy-to-use diagnostics can be desirable.