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E J Ostfeld

Publications and source records attributed to E J Ostfeld.

5 recordsLinked to original sources
PubMed1992

Theoretic analysis of middle ear gas composition under conditions of nonphysiologic ventilation.

As gas flows in and out of the nasopharynx, the pressure in that region fluctuates. It drops below or rises above atmospheric pressure, which is itself not constant but is subject to changes in altitude and weather. Such pressure changes in the nasopharynx produce a pumping of gas into and out of the middle ear. The net amount of middle ear gas transferred from or to the nasopharynx will, component for component, in steady state exactly equal the amount of middle ear gas transferred to or from the microcirculation by means of diffusional absorption by (or release from) the mucosa. In the case of a permanently patulous eustachian tube, a single parameter, characteristic of the rate of ventilation through the open eustachian tube, is found to determine the gas composition in the middle ear, whereas in the case of a middle ear ventilated by tympanostomy, two rate-of-ventilation parameters, one for gas flow through the ventilation tube and one for flow through a periodically open eustachian tube, determine the steady state gas composition. A high rate of ventilation favors absorption of oxygen and venting of carbon dioxide from the middle ear in both cases.

Carbon Dioxide↗
PubMed1991

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.

Ear, Middle↗
PubMed1991

Biocompatible implantable antimicrobial release for necrotizing external otitis.

The efficacy of a biocompatible, surgically implantable, antimicrobial release system (IARS) as the exclusive antimicrobial therapy of necrotizing external otitis (NEO) was evaluated in six NEO patients. Gentamicin incorporated polymethyl-methacrylate beads were implanted, following surgical debridement and were removed two months later. Post-implantation alleviation of clinical symptoms: pain, periauricular tissue swelling, otorrhoea, eradication of pseudomonal infection (100 per cent) and substantially shortened hospitalization (4-15 days) were the salient results of this therapeutic modality. Three patients recovered. Two patients who died, one of sudden cardiac arrest and the other of paralytic ileus, 15 and 60 days post-operatively while the beads were still implanted, were symptomless. Recurrence was seen in one patient with early bead extrusion. Ipsilateral sensorineural hearing loss (one patient) and external meatal stenosis were the main complications. IARS appears to offer an effective alternative to long-term systemic antibiotic administration for the eradication of NEO-pseudomonal infection in patients who are sensitive, develop resistance, or when quinolone medical treatment has failed or is contra-indicated.

Aged↗
PubMed1991

Gas composition and pressure in the middle ear: a model for the physiological steady state.

The gas contents of the physiological middle ear periodically cycle through two phases in steady state. During phase I, the eustachian tube is shut and the middle ear gas space is effectively closed. Gas is absorbed or produced at the mucosal surface, and the total pressure changes correspondingly. During phase II, which is of very short duration, the eustachian tube opens, a bolus of gas passes between the middle ear and the nasopharynx, and the total pressure in the middle ear rapidly adjusts to that in the nasopharynx. Since nasopharyngeal pressure fluctuates in time, so does the pressure in the middle ear. The effect of these pressure changes is to produce a level of ventilation in the middle ear, which depends on a combination of three parameters: the volume of the middle ear, multiplied by the mean amplitude of pressure variations in the nasopharynx, divided by the mean elapsed time between successive eustachian tube openings. Assuming steady-state conditions, the composition of middle ear gas can be computed and is predicted to range from PN2 = 621, PO2 = 46, PCO2 = 46, PH2O = 47 mm Hg in the case when nasopharynx fluctuations are small, to a match with nasopharyngeal gas composition, when the fluctuations are large.

Biological Transport↗