Abstract
The author investigated the effect of changing posture and blood flow on the middle ear pressure of humans. First, a sudden change of posture, from sitting to the head down position was induced in 38 normal persons (65 ears) in normal and hyper and hypobaric environments. Then blood flow was changed by SGB or excercise. The SGB procedure was applied to 3 normal persons and 3 patients with sudden deafness, and 9 normal persons were tested during exercise. PO2 in the middle ear was measured simultaneously with the measurement of the middle ear pressure. The change of pressure was estimated by tympanometry, and the PO2 value was measured by a sensor introduced into the middle ear via the Eustachian tube.
At both normal and abnormal atmospheric pressures, the middle ear pressure increased when the posture was changed from the sitting to the head down position. Pressure change caused by posture change was 2.4 times greater in a relatively hypobaric than in a relatively hyperbaric environment. When blood flow was raised by SGB or excercise, PO2 in the middle ear increased, but the pressure decreased.
It was concluded that middle ear pressure is increased by a rise of venous pressure and also by adiminution of middle ear volume caused by temporary swelling of mucous membranes. Middle ear pressure changes due to variations of blood flow may also be related to changes in gas metabolism, especially the production and influence of CO2.
