The Effect of Photobiomodulation on Microvascular Blood Flow: The Role of Wavelength and Skin Temperature

Evaluation of Hemodynamic Changes in Peripheral Microcirculation in Response to Photobiomodulation Using Non-Invasive Optical and Thermal Technologies

The objective of this study is to assess peripheral microcirculatory hemodynamic responses to photobiomodulation in participants with normal circulation and with functional peripheral vasoconstriction, using noninvasive thermography, photoplethysmography, and laser Doppler flowmetry.

This is a within-subject experimental study in which each participant completes two study sessions. Microvascular and systemic variables are continuously monitored in response to photobiomodulation delivered at either a blue or near-infrared wavelength, with each wavelength applied in a separate session.

Each session includes a baseline period with controlled breathing, followed by photobiomodulation and a 20-minute post-intervention follow-up period. Peripheral microcirculatory responses are assessed using noninvasive thermography, photoplethysmography, and laser Doppler flowmetry.

Inclusion Criteria:

1. Healthy males and females, between 20 and 75 years of age.
2. Willing to sign informed consent.
3. Willing to participate in two separate sessions, one for each wavelength.
4. Able to avoid caffeine and alcohol for at least 3 hours before each session.
5. Able to sit comfortably with both hands at heart level for the full measurement duration.

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. History of photosensitive conditions or use of photosensitizing medications
5. Suffering from significant concurrent illness, such as cardiac disorders or pertinent neurological disorders.
6. As per the Investigator's discretion, any physical or mental condition that might make it unsafe for the subject to participate in this study.