In vivo measurement of O2 and CO2 gas exchange across the human tympanic membrane

Conclusion. The hypothesis that the human tympanic membrane (TM) is permeable to CO2 and O2 at physiologic pressure gradients is supported but additional experiments need to be done to validate this methodology. Objective. Gas exchange between the middle ear and adjacent compartments determines the trajectory of middle ear pressure change. Little information is available regarding the permeability of the TM to physiological gases. This study aimed to determine in vivo if the human TM is permeable to O2 and CO2 at physiologic transTM pressure gradients. Subjects and methods. An ear canal (EC) probe (ECP) constructed from a custom-fitted acrylic body, a glass capillary tube enclosing an oil meniscus to maintain ambient ECP + EC pressure and a silica glass microtube linked to a mass spectrometer (MS) for measuring gas composition was hermetically sealed within one EC in each of 15 adults. ECP + EC volume was measured and gas samples were taken at 10 min intervals for 1 h. Epinephrine (1:100 000) was applied ...