Diabetes-Associated Changes in the Toe Photoplethysmogram During Local Heating Test.

We investigated changes in the pulse waveform recorded by photoplethysmography (PPG) during a local heating test in patients with diabetes. The following groups of subjects were studied: healthy individuals (n = 15), patients with Type 2 diabetes accompanied by diabetic retinopathy (n = 14), patients with Type 2 diabetes and diabetic foot syndrome (n = 16). Measurements were taken from the big toes of both limbs while the skin was heated from 32°C to 42°C. We found statistically significant changes in PPG waveform after heating between all three groups. The main change is that the dicrotic notch becomes more pronounced during the heating period. This effect is strongest in Group 1, slightly less pronounced in Group 2, and practically absent in Group 3. Thus, monitoring of the PPG waveform during the heating test may be an effective means of assessing microvascular lesions in diabetes.