Detection of the single sweat glands activity via the macro thermography techniques and its relation with skin temperature and peripheral hemodynamics

Background and Objectives: Interest in the study of the human's sweat glands activity is due to the close relationship of their activity with human body's peripheral regions sympathetic innervation. The increased activity of sweat glands and secretion occurs not only due to thermoregulation, but also is a response to the psychoemotional load and the physiological and drug tests. Sweat gland activity's disruption manifests itself in pathologies such as diabetes mellitus, chronic heart failure, hyperhidrosis, thyrotoxicosis, and Parkinson's disease. Thus, the search for a method for quantifying the sweat glands activity on the surface of a human body based on physical methods is relevant for biomedical diagnosis. Materials and Methods: The primary thermographic data were recorded using a ThermaCam SC 3000 thermal imaging camera, FLIR Systems (Sweden) with a 34/100 macro lens, in the spectral range of 8-9 $\mu$m with a temperature sensitivity of 0.02$^{\circ}$C and a resolution of 320$\times$240 pixels with a frequency 5 frames per second. The measurements were performed in laboratory conditions with a stable ambient temperature of 23 $\pm$ 0.2$^{\circ}$C and the absence of forced convection. Simultaneously with temperature measurements, the volumetric blood flow was monitored using a KL-72001 photoplethysmographic sensor (Taiwan) at a wavelength of 800 nm. Results: The both hands reaction to a breathing test was observed. The dynamics of changes in the active sweat pore count, temperature and blood flow was analyzed. Using an algorithm for processing thermograms that implements the suppression of low-frequency and high-frequency spatial components of temperature fluctuations, and the subsequent detection of local minima, makes it possible using the infrared thermography method to study not only the temperature dynamics, but also the sweat glands activity. Conclusion: Thus, the thermographic recording of the limb's reaction to a respiratory test using the algorithm for detecting the sweat pore count can be positioned as a tool for studying the body's sympathetic response to a functional load. The method is interest for the prophylactic detection of small vessel's neuropathy's various forms in diabetes mellitus, thyroid disorders and Raynaud's syndrome.