There is an air cylinder and a locking mechanism under the thoracic area.
The locking mechanism is locked and unlocked by the trigger on the corner of the thoracic cushion.
The thoracic area can be locked at any angle or in the "up" position, level with the other cushions.
The arrow is pointing to the unlocking trigger for the thoracic release.
When it is unlocked then sufficient air pressure can be adjusted into the breakaway cylinder to buoy that area of the patient anatomy.
