Morphology of the Middle Ear in the Rhesus Monkey (&lt;i&gt;Macaca Mulatta&lt;/i&gt;)

International Journal of Pediatric Otorhinolaryngology

2007

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Section: Introductionmentioning

confidence: 99%

The mastoid as a functional rate-limiter of middle ear pressure change

International Journal of Pediatric Otorhinolaryngology

2007

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“…For example, a more rapid N 2 O blood saturation was reported for infants and children compared with adults. 18 This will establish a higher N 2 O blood-ME gradient earlier in children and during the time period over which the rate of ME pressure change is usually measured (typically the first 10 minutes after onset of breathing the anesthetic gas mixture). From Eq 8 [␦P e N2O /␦t ϭ (P a N2O Ϫ P e N2O )K e N2O ], a larger blood-ME N 2 O gradient will cause a faster increase in ME pressure for equal N 2 O time constants.…”

Section: Discussionmentioning

confidence: 99%

“…The monkey was chosen for this experiment because of the documented similarity in ME anatomy and function between old-world monkeys and humans. 18 Specifically, and in contrast to canid and rodent species, monkeys have a mastoid antrum and a welldeveloped, mastoid air-cell system. Also, monkeys were used previously to model gas exchange between ME and blood.…”

mentioning

confidence: 99%

Rate of Nitrous Oxide Exchange Across the Middle Ear Mucosa in Monkeys Before and After Blockage of the Mastoid Antrum

Otolaryngol.--head neck surg.

Alper

Banks

et al. 2003

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OBJECTIVES: We tested the hypothesis that mastoid volume buffers the rate of change in middle ear pressure caused by transmucosal, inert gas exchange. STUDYDESIGN: Twelve monkeys were randomly assigned to group 1 or group 2. Right ears of group 1 had sham surgery and of group 2 had obstruction of the mastoid antrum. Before and after surgery, the time constant for transmucosal N2O exchange was estimated from N2O breathing experiments. The hypothesis predicts that the postoperative time constant measured for right ears of group 2 but not group 1 is greater than that measured before surgery. RESULTS: Mastoid antrum block significantly decreased right middle ear volume but did not affect the time constant for transmucosal N2O exchange. CONCLUSION: A mastoid gas-reserve function is not supported by the experimental data. SIGNIFICANCE: These results for monkeys and the theory developed to explain the effect of mastoid volume on transmucosal inert gas exchange suggest that the results for previous experiments in humans interpreted as evidencing a mastoid gas-reserve function are consistent with alternative explanations.

“…The rhesus monkey was chosen for these experiments because past reports showed that species to be similar in ME anatomy and physiology to humans and because data relevant to estimating the exchange rates over different pathways were published for monkeys (5,7,8,(17)(18)(19)(20). The principle underlying these experiments was to determine the rate of accumulation of a gas species in one compartment (the probe/external canal) after creating stable partial pressures of that species in a second compartment (the ME).…”

Section: Discussionmentioning

confidence: 99%

Exchange Rates of Gases Across the Tympanic Membrane in Rhesus Monkeys

Alper²,

Seroky³

et al. 1998

Acta Oto-Laryngologica

The exchange rates of CO2 and He across the tympanic membrane were estimated in 5 monkeys. For these experiments, the monkey was anesthetized and one arm of a polyethylene "T" tube was introduced into the external canal of the test ear and sealed to the ambient environment with wax. One arm of the T tube was attached to a pressure transducer and the other to an argon gas source via a valve. Silica tubing sealed within the probe provided periodic gas samples for composition analysis by an online mass spectrometer. Prior to each experiment, the probe was washed with Argon. In 5 experiments the probe was sealed within the external canal of animals with physiological middle ear gas compositions, and in 5 experiments the probe was sealed within the external canal of animals whose middle ears were partially washed with He. The gas in the probe was sampled and analyzed at 10-min intervals for up to 4 h. The results documented a significant increase in the percentage composition of CO2 but not He in the experiments conducted with physiological middle ear gas compositions, and increases in both He and CO2 in the experiments conducted after the middle ear was washed with He. Estimated, average exchange constants for He and CO2 were 0.0005 microl/min/mmHg and 0.0103 microl/min/mmHg, respectively. Using data from previous experiments, the relative trans-mucosal to trans-tympanic membrane gas exchange rates in monkeys are estimated to be in the order of 10:1 for inert gases and 180:1 for chemically active gases.