Transient pressure changes in the middle ear.

Transient increases in total pressure in the ear (1) during sleep, after hypoventilating in a supine position with a closed eustachian tube, and (2) after the partial pressures in middle-ear gas are lowered by a total pressure decrease and the eustachian tube is voluntarily maintained closed can be accounted for quantitatively on the basis of the standard mucosal gas exchange model and the following data: (1) partial pressures in tissue: pN2* = 573 mm Hg (7621 decaPascals [daPa]), pO2* = 40 mm Hg (532 daPa), pCO2* = 46 mm Hg (612 daPa), and pH2O* R = 47 mm Hg (625 daPa); (2) partial pressures in the nasopharynx: pN2' = 566 mm Hg (7528 daPa), pO2' = 120 mm Hg (1596 daPa), pCO2' = 27 mm Hg (359 daPa), and pH20' = 47 mm Hg (625 daPa); (3) a middle-ear gas space of 2 x 10(-5) m3; (4) an absorption rate for nitrogen, when the partial pressure difference is 1 atm, of 3 x 10(15) molecules per second; and (5) mucosal absorption rates for oxygen and carbon dioxide 1.8 and 34 times larger, respectively, than for nitrogen.