Evaluating the State of Microvessels by Minimum Rise Time (MRT01)

Evaluating an Optical Index (Minimum Rise Time) as a Measure for the State of Microvessels

Photoplethysmography (PPG) is a simple uncalibrated optical method of monitoring variations in skin blood volume. The objective of the current study is to investigate a potential relationship between MRT (minimum rise time, in time units) a measure derived from PPG and the state of microvessels.

This study includes a 1-2 hour single session per subject during which PPG and other microvascular and systemic variables will be monitored in response to non-invasive interventions that are known to elicit microvascular responses.

Photoplethysmography (PPG) is a simple uncalibrated optical method of monitoring variations in skin blood volume. A major limitation of PPG is the lack of a quantitative method for calibrating this signal. A method that provides an absolute measure (in time units) called 'minimum rise time' (MRT) was published in 1985 by Dr. Benjamin Gavish, one of the study investigators. However, a possible relationship between MRT and the state of arterioles that determines the microvascular flow has never been investigated. Such relationship, if validated, could have clinical impact in noninvasive diagnosis of vascular diseases and monitoring microvascular response to treatments that affect at both clinic and home setting.

The objective of the current study is to investigate a potential relationship between variations of MRT (minimum rise time, in time units) and microcirculatory variables induced by interventions that are expected to have acute effect on the state of arterioles and the tissue oxygenation.

This study includes a single 1-2 hour session per subject, during which PPG and other microvascular and systemic variables will be monitored in healthy volunteers in response to a number of non-invasive interventions/device that are approved for clinical use and known to elicit microvascular responses. These interventions are applied consecutively, include breathing at different rates, low power visible light in the red-to-near-infrared range, and local temperature changes. The experimental sessions will be conducted at the Afeka College by the study investigators.

Inclusion Criteria:

1. Healthy males and females, between 18 and 65 years of age.
2. Willing to sign informed consent.

Exclusion Criteria:

1. Currently smoking
2. Any abnormal skin condition in the area of light irradiation.
3. Pregnant having given birth less than 3 months ago, and/or breastfeeding.
4. Having a history of diseases stimulated by heat, such as recurrent Herpes Simplex in the treated area, unless treatment is conducted following a prophylactic regimen.
5. Having any illness that might affect the vasculature, such as diabetes (type I or II)
6. Suffering from significant concurrent illness, such as cardiac disorders, , or pertinent neurological disorders.
7. As per the Investigator's discretion, any physical or mental condition which might make it unsafe for the subject to participate in this study.