Respiratory devices lung volumes

A third method for measuring lung volumes uses a device known as a body plethysmograph, also referred to as a body box. The body box is a large rigid-walled structure in which the patient is seated, after which the door is closed and sealed completely. In one variety, a small hole in the wall of the cabinet leads to a spirometer or flow sensor. Respiratory efforts within the box cause changes in volume to be recorded on this spirometer as chest wall movement displaces air within the box. In a second variety of body box, there is no hole in the wall of the box and respiratory efforts instead... 

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