Gravity effects on foot perfusion (GELL-P)

Researchers sought to investigate how gravitational changes affect the blood flow into the lower limbs of individuals. As space tourism and long distance space travel become increasingly likely, there is a need for more research in the area into blood flow affects and healing potential.

A direct consequence of exposure to weightlessness is that astronauts experience several physiological changes that can lead to serious medical implications. Most immediate and significant are a headward shift of body fluids and the removal of gravitational loading from bone and muscle. During this time the cardiovascular system is subject to rapid changes which have been demonstrated to include increased facial puffiness, decreased leg volume, increased stroke volume of the heart and decreased plasma volume. As a lack of gravity increases the blood volume in the core of the individual, this redistribution of blood volume may influence lower limb tissue perfusion and potentially affect tissue healing due to the combined effect of these elements.

So, as space travel and long-range missions are being developed, more knowledge on body system behaviour under micro- and hyper-gravity conditions needs to be gained to maintain the health and healing ability of those in that environment, particularly given the risk of tissue injury, especially to the feet.

This parabolic flight study was designed to provide some information on how the body’s blood flow to the foot responds in response to the exposure of changing gravitational forces. 

The study primarily utilised peripheral capillary oxygen saturation measurement (SpO₂) with secondary monitoring of toe systolic pressures (TSP), foot temperatures and TcPO₂ levels, to evaluate any circulation or skin perfusion changes.
 
It involved monitoring 14 participants, each observed during 5 parabolas. Using four pieces of equipment positioned onto or around each participant's foot, SpO₂, TSP, TcPO₂ and foot temperatures were measured.
> A thermal imaging camera was placed above the leg to record temperature
> The Dopplex DMX toe pressure cuff was placed around their big toe,
> The Moor VMS Oxy capillary bed probe was rested gently on the metatarsal head
> The Pulse Oximeter was on participants' 3rd or 4th toe.

During the flight, data analysis was performed on each piece of equipment individually at the 3 gravity levels (0g, 1g and 1.8g) during 5 parabolas of the flight.

The use of these pieces of equipment are enabling the team to evaluate if there are observable changes to the perfusion of tissues during the parabolic flight and thus to increase the knowledge on how different gravitational conditions affect blood perfusion to the foot.

This project aimed to assist in the application of thermal camera imagery into clinical practice within Podiatry and to provide a platform to routinely utilise the four pieces of equipment during vascular assessments of individuals on a routine basis.

The data from the research will also expand the current understanding of how foot perfusion is altered during parabolic flights and enable a platform for further research into this area and feed into foot perfusion studies in 0g arenas.