Assessment of the Peripheral Blood Flow of Lower Limbs in Patients with Diabetes Mellitus with the Use of Digital Photoplethysmography

Introduction: The microcirculation of the lower limbs (LL) of diabetics is influenced by hyperglycemia and several factors (hypertension, obesity, dyslipidemia) leading to the functional and later the structural changes, manifesting as dysregulation of the peripheral blood flow.

Materials and Methods: The study included 39 patients with type 2 diabetes, and the same number of the control group. The digital photoplethysmography (PPG) was used for assessment of the peripheral circulation with reflectance mode, sensing from the 1st and 2nd toe of the LL after acclimatisation of the patient in the supine position. The subjects were also asked to refrain from smoking, to avoid drinks containing caffeine and using of medicaments with vasodilatator function at least 2 hours before examination.

Results: The pulse amplitudes and the peak times of the PPG curves were significantly higher in diabetic group than in the control group. The mean pulse amplitudes in diabetics were in the range of 0.69 % 0.86 %, the pulse peak time in the range of 140 - 154 ms. The mean pulse amplitudes in the control group were in the range of 0.37 0.54 %, the mean pulse peak time were in the range of 120 - 133 ms. The PPG findings of the LL were symmetrical (non-significant t-test). We have not found a correlation between the PPG records and duration, compensation of diabetes, age, glycemia, blood pressure, dyslipidemia, smoking and obesity.

Conclusion: This simple-to-use technique shows the increased total skin microcirculation in diabetic patients. Microvascular shunting of blood presenting in peripheral nerves and in the skin of diabetic feet are responsible for reduced hyperemia response to any inflammatory process with the increased susceptibility for inquiring the diabetic foot infection.