Methods and apparatus for assessing vascular health
A method for digital thermal monitoring assessment of vascular function comprising a temporary arterial occlusion using a pneumatic cuff positioned on a subject's upper limb, monitoring skin temperature at the fingertip of the occluded limb for a period of time before, during, and after the occlusion, calculating a Zero Reactivity Curve based on variables including start temperature, room temperature, and the slope of temperature decline during the occlusion, and assessing vascular function based on comparing the Zero Reactivity Curve and the observed temperature rebound after the occlusion is removed. A vascular reactivity monitoring apparatus for measuring skin surface temperature comprising an inflatable cuff for placement around a subject's limb, a digital thermal measuring device and photoplethysmography measuring device for placement on a finger of the subject's limb wearing the cuff and a second digital monitoring device and photoplethysmography measuring device for placement on a finger of the subject's contralateral limb.
1. A method for assessment of microvascular function, comprising:
(a) creating a temporary arterial occlusion;
(b) monitoring skin temperature before, during, and after the arterial occlusion;
(c) calculating Zero Reactivity Curve (ZRC) based on variables including baseline skin temperature, room temperature, and the observed slope of temperature decline during the arterial occlusion using the following formula
ZRC[ t ]=(StartTemp)+(Mintemp−RightStartTemp)*(exp(−1 *c *((37−RoomTemp)/(37−RightStartTemp))* t ))
wherein c=−dfdt/(StartTemp−RoomTemp), wherein StartTemp is baseline temperature of a right finger where the occlusion happens, Mintemp is minimum temperature of the right finger after occlusion, RoomTemp is room temperature, and t is time in seconds after minimum temperature of the right finger after occlusion; and
(d) assessing microvascular function based on comparing the observed temperature rebound after the occlusion and the Zero Reactivity Curve.
2. A method for simultaneous assessment of microvascular function and macrovascular function using a skin temperature sensor and a photoplethysmography (PPG) sensor, comprising:
(a) creating a temporary arterial occlusion;
(b) measuring skin temperature and PPG signals before, during, and after the arterial occlusion;
(c) calculating Zero Reactivity Curve (ZRC) based on variables including baseline skin temperature decline during the arterial occlusion according to below formula:
ZRC[ t ]=(StartTemp)+(Mintemp−RightStartTemp)*(exp(−1 *c *((37−RoomTemp)/(37−RightStartTemp))* t ))
wherein c=−dfdt/(StartTemp−RoomTemp), wherein StartTemp is baseline temperature of a right finger where the occlusion happens, Mintemp is minimum temperature of the right finger after occlusion, RoomTemp is room temperature, and t is time in seconds after minimum temperature of the right finger after occlusion;
(d) calculating peak-to-base amplitude, peak-to-trough amplitude, pulse waveform analysis, area under the curve analysis, reflectance waveform analysis, or a combination thereof from the PPG signals;
(e) assessing microvascular function based on comparing observed temperature rebound after the occlusion and the ZRC; and
(f) accessing macrovascular function based on comparing peak-to-base amplitude, peak-to-trough amplitude, pulse waveform analysis, area under the curve analysis, reflectance waveform analysis, or a combination thereof from the PPG signals, before and after the arterial occlusion.
3. The method of claim 2 further comprising: obtaining an electrocardiography (ECG) signal using an electrocardiography sensor for enabling cardiac function assessment in addition to vascular in addition to micro and macro vascular function assessments.
4. A method of claim 3 further comprising: of calculating pulse wave velocity by comparing pulse events in PPG and ECG signals, and calculating heart rate variability by using PPG signals.