The relationship between temperature, moisture, airflow, and the skin

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 Wheelchair users can have difficulty in managing temperature, often as a result of their physical condition but also compounded by seating systems that are inherently insulating and lack ventilation. Whilst seated there is a buildup of heat and moisture on the seat/back contact areas. This creates a microclimate that compromises skin integrity due to the heat and moisture build up and the process of maceration occurring and its effect upon tissue structures and their ability to withstand forces such as friction and shear against the seat/back surface. This can lead to pressure injuries and moisture related skin damage, as well as the other systemic effects that overheating and sweating causes such as discomfort, ill health and care needs. 




Heat and Moisture build-up: the impact on skin tissue

Microclimate: “the temperature, moisture (relative humidity) level and airflow at the skin/support surface interface”.

 Skin microclimate changes throughout the day according to the environmental conditions and movements surrounding it. The body and our behaviour helps manage microclimate by sensing and making adjustments to aid the processes of heat and moisture exchange to make us feel more comfortable and maintain healthy skin. 

• This is more difficult to achieve when you have a physical/neurological condition and/or reduced mobility. 

Microclimate is significantly affected when objects or support surfaces (such as seating systems) are against the skin. 

The support surface impedes airflow and processes of heat and moisture exchange, such as conduction, convection, and evaporation. 

As a result, there is rapid build-up of heat and moisture at the skin and seat surfaces. 

Increased temperature raises metabolic demand, and increased moisture leads to maceration of the skin. These factors combined affect the skin’s physiological resilience, exposing it to the risk of damaging forces such as pressure, shear and friction. 

Due to the moisture, the macerated skin in contact with a solid surface equals a higher coefficient of friction. Friction can lead to skin shear, which can lead to tissue ischemia and localised tissue necrosis. 

The combination of high pressure over bony prominences and a decrease in skin tolerance due to the microclimate makes the ischial tuberosity (IT) and sacral regions most prone to pressure ulcer development. 

When choosing a seating solution, it is important to consider the system is air and moisture permeable to enable movement of air to improve microclimate and so reduce the risk of skin damage. 

User Case Study: Mr. R

 12 month study- performed by NHS Guy & St Thomas Wheelchair Services (King’s College) 

Mr. R is a man with CP, LD, asthma and h/o respiratory failure. He has complex seating needs: pelvic obliquity ↑L, scoliosis concave L, reduced L hip flexion (75º), R posterior rib hump and a large abdominal mass. Mr. R has extreme temperature regulation issues and tends to scratch his knees and forehead as well as develop redness on his back. Seating and positioning Mr. R has always been challenging as he requires a close-fitting seating system due to his complex seating needs and impingement issues. His longstanding issues with overheating and perspiration all year round also prove to be a challenging factor when manufacturing an intimate seating system. 

 Without WheelAir 

  • Excess sweating 
  • Extreme discomfort 
  • Redness and skin scratching 
  • 4x t-shirt changes per day 
  • 2x sling changes per day 
  • Use of pedestal fans and wiping sweat from face 
  • Skin breakdown and irritation 

 With WheelAir Integration 

  • 1-2 t-shirt changes per day 
  • Major skin improvement 
  • No need for sling changes 
  • No scratching 
  • No need for pedestal fans 
  • No need to wipe sweat from face 
  • Improved comfort 
  • Improved quality of life for him, his family and care givers 

WheelAir: the airflow technology solution for controlling temperature and reducing moisture

Through active and controlled airflow WheelAir positively influences microclimate; reducing skin temperature and moisture by providing the tools for heat and moisture exchange at the support surface that are otherwise occluded from such processes. 

This innovation is the first temperature control system designed specifically for wheelchair seating systems to help address these problems. The system allows user controlled air ventilation to the wheelchair back and seat. By processes of conduction, evaporation and convection WheelAir helps regulate not only body temperature and thermal comfort but assists in maintaining skin integrity by reducing the risk of heat and moisture associated skin damage too by keeping skin cool and dry. 

The WheelAir system integrates seamlessly into all wheelchair seating systems including sling backs, rigid backs, powerchairs, and custom moulded seating. 

A little air goes a long way

 If using a normal wheelchair backrest cushion, after 30 minutes of use the user’s back temperature will on average have risen by 2.2˚C or a 6.9% increase. 

When turning the WheelAir on after that 30 minute period, within 3 minutes the user’s back temperature on average has decreased 2.4˚C. 

Using the WheelAir a further 27 minutes (so 30 minutes in total) lowers the back temperature on average 8˚C. 

 WheelAir is most effective when used preventively, ensuring the user’s back and body stays at a constant temperature, reducing fatigue and heat stress, and improving comfort. By selecting the right airflow setting in the right environment, WheelAir can avoid that 2.2˚C temperature rise all together. 

The graphs suggest the back’s response to the 4* airflow levels in different ambient environments. 

Backrest temperature after 10 minutes seated (29.8ºC)
Backrest temperature after 10 minutes seated with WheelAir on (25.7ºC)

WheelAir V2

  • Bluetooth connection 
  • 27 hour battery life 
  • Wireless remote 
  • Always on connection 
  • USB-C input, USB-A output 
  • 80% charge in 2 hours 
  • 9m/s-28m/s airflow output 
  • Magnetic connection with channels 
  • Charging state LED 
  • On/off switch on fanbox 
  • IEC60601 and CE certified