Fig. 9: Long-wave infrared thermography (LWIT) images taken from an healthy, 28-year-old, female subject.

All assessments were taken while in head-down tilt (HDT) position, except for the post-225 min timepoint, when the subject was seated for 30 min. The color reference scale measures thermal energy gradient in degrees Celsius, with increasing oxygenation approaching red and decreasing oxygenation; values >0 indicate hyperperfusion, while values <0 indicate hypoperfusion. In the above images, an initial increase in thermal energy emitted from the head and neck was greater on the right side, compared to the left, indicating increased perfusion or suspected venous engorgement over time in the HDT position. After manual lymphatic drainage (MLD) at post-195 min in the HDT position and post-225 min in the sitting position, there was a visual reduction of perfusion (or venous engorgement) in the head and neck towards normalcy.