Thoracic independent volume
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
A term coined by Dr. Gerald Gause of the University of Florida College of Pharmacy, Thoracic Independent Volume is the volume of the thoracic cavity without the lungs. Another way of looking at it is TIV is the volume at which the thoracic cavity's elastic forces are at equilibrium independent of the lung's inward elastic forces.
This volume is approximately 70% of Total Lung Capacity, or 4060 mL in a typical healthy male of 70 kg. At any volume lower than TIV, the thoracic cavity wants to expand. At any volume higher, it wants to contract.
When taking into account the inward elastic forces of the lungs; above TIV, the forces work congruously (inward recoil of the lung, inward recoil of the thoracic cavity), below TIV, the forces work opposite (inward recoil of the lung, outward recoil of the thoracic cavity).