title: Mechanism and rate of middle ear fluid absorption.
abstract: Several mechanisms have been suggested to explain the clearance of fluids from the middle ear. These include a pumping action through the eustachian tube, mucociliary beating through the tube, outflow of water to the blood due to osmotic gradients and an active Na(+) transport driving water absorption. In order to assess these mechanisms, the middle ear cavity of paralyzed, ventilated (eustachian tube occluded) guinea pigs was filled with fluids varying in osmotic pressure (hypotonic, isotonic, hypertonic) to which a vertical tube was attached. The change in height of fluid in the tube was taken as a measure of changes in middle ear fluid volume. A greater fluid volume reduction was seen with the hypotonic (1/5 saline) solution. A small volume increase was observed with the hypertonic solution. These results provide evidence that in these experimental conditions, water absorption due to osmotic gradients can contribute to middle ear fluid clearance.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Hadassah University Hospital, Jerusalem, Israel.
authors.forename: Petia
authors.initials: P
authors.lastname: Petrova
authors.forename: Sharon
authors.initials: S
authors.lastname: Freeman
authors.forename: Haim
authors.initials: H
authors.lastname: Sohmer
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002923:Cilia / Q000502:physiology; D004432:Ear, Middle / Q000378:metabolism*; D005064:Eustachian Tube / Q000378:metabolism; D006168:Guinea Pigs; D007038:Hypotonic Solutions / Q000493:pharmacokinetics; D007552:Isotonic Solutions / Q000493:pharmacokinetics; D009997:Osmotic Pressure; D010034:Otitis Media with Effusion / Q000378:metabolism*; D012462:Saline Solution, Hypertonic / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D007038:Hypotonic Solutions; D007552:Isotonic Solutions; D012462:Saline Solution, Hypertonic; D012964:Sodium