Rupture pressures of membranes in the ear

Acute Intraoperative Tympanic Membrane Rupture in Patient Anesthetized With Desflurane Without Nitrous Oxide: A Case Report

We report a case of acute intraoperative tympanic membrane (TM) rupture in a patient anesthetized with desflurane without N2O. The patient was undergoing endoscopic retrograde cholangiopancreatography (ERCP) to treat ascending cholangitis. TM rupture is known to occur with N2O but has not been reported in the literature with the use of inhaled volatile anesthetics without N2O. We suspect that several factors contributed to this complication, including prone positioning, a remote history of ear trauma, and the selection of desflurane as the maintenance anesthetic as opposed to a vapor with a higher blood-gas partition coefficient.

Paper Patching Versus Watchful Waiting of Traumatic Tympanic Membrane Perforations: A Meta-Analysis

OBJECTIVES/HYPOTHESIS

The aim of the study was to investigate the healing rates, the restoration of hearing, and the time for complete healing of paper patching versus watchful waiting for traumatic tympanic membrane perforations (TTMPs).

STUDY DESIGN

Systematic review with meta analysis.

METHODS

Publications were selected by a search on "PubMed," "Embase," and "Web of Science." A meta-analysis of risk ratios for paper patching (intervention arm) and watchful waiting (control arm) was performed.

RESULTS

Five studies describing 393 TTMPs were included in the quantitative meta-analysis. TTMP healing rates ranged between 84.2% and 95.2% in the intervention arm and between 76.7% and 84.8% in the control arm. The pooled risk ratio of healed TTMPs was significantly higher in the intervention arm than in the control arm (risk ratio: 1.12, 95% confidence interval: 1.04-1.21).

CONCLUSIONS

TTMPs have high healing potential with and without intervention. The healing rate of paper patching was superior to that of watchful waiting alone.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:2091-2097, 2021.

An insight to tympanic membrane perforation pressure through morphometry: A cadaver study

INTRODUCTION

A cadaveric experimental investigation aimed to show the rupture pressure of the tympanic membrane (TM) for otologists to evaluate its tensile strength.

METHODS

Twenty adult ears in 10 fresh frozen whole cadaveric heads (four males, six females) mean age 72.8 (SD 13.8) years (range 40-86) were studied. The tensile strength of the TM was evaluated with bursting pressure of the membrane. The dimensions of the membranes and perforations were measured with digital imaging software.

RESULTS

The mean bursting pressure of the TM was 97.71 (SD 36.20) kPa. The mean area, vertical and horizontal diameters of the TM were 57.46 (16.23) mm², 9.54 (1.27) mm, 7.99 (1.08) mm respectively. The mean area, length and width of the perforations were 0.55 (0.25) mm², 1.37 (0.50) mm, and 0.52 (0.22) mm, respectively. Comparisons of TM dimension, bursting pressure, and perforation size by laterality and gender showed no significant differences. The bursting pressure did not correlate (positively or negatively) with the TM or perforation sizes.

CONCLUSIONS

The TM can rupture during activities such as freediving or scuba diving, potentially leading to serious problems including brain injuries. Studying such events via cadaveric studies and data from case studies is of fundamental importance. The minimum experimental bursting pressures might better be taken into consideration rather than average values as the danger threshold for prevention of TM damage (and complications thereof) by barotrauma.

In Vivo Measurement of Middle Ear Pressure Changes during Balloon Eustachian Tuboplasty

Background

Balloon Eustachian tuboplasty (BET) is known as a treatment for chronic obstructive Eustachian tube dysfunction (OETD). The precise mechanism of action is not fully understood. Observations in sheep cadavers and human cadavers have shown specific middle ear pressure changes related to BET.

Methods

In this prospective study using a microfibre optical pressure sensor, pressure changes during BET were for the first time monitored transtympanically in five normal human middle ears in vivo.

Results

Middle ear pressure changes during 21 BETs consisted of five stages (insertion, inflation, deflation, withdrawal, and recovery). The highest pressure change occurred in most of the cases during the withdrawal of the balloon catheter. Withdrawal pressure yielded a mean middle ear pressure of 4.76 mmHg (61.89 daPa) with a maximum of 13.88 mmHg (179.55 daPa). Pressure amplitudes capable of causing barotrauma to ear structures were not detected. Internal carotid artery dehiscences were detected as causative of sinusidual pressure changes.

Conclusion

The middle ear pressure changes detected in vivo during BET can be attributed to the balloon inflation. Further human studies with patients affected by OETD are necessary to gain more insight into the mechanism of action of BET to clarify a possible pressure related second mechanism of action of BET.

Measurement of middle ear pressure changes during balloon eustachian tuboplasty: a pilot study

CONCLUSION

The middle ear pressure changes detected during BET can be directly attributed to the balloon inflation and may represent a second, immediate, mechanism of action of BET. BET seems to be safe with respect to the risk of a barotrauma. Further human studies are now necessary to confirm the results and gain more insight into the mechanism of action of BET.

OBJECTIVE

Since the introduction of Balloon Eustachian Tuboplasty (BET) as a treatment of chronic Eustachian tube dysfunction, the precise mechanism of action is unknown. Long-term effects of BET may be related to observed microfractures of the Eustachian tube cartilage. However, clinical observations indicate a second, immediate mode of action. Therefore, this study investigated and characterized middle ear pressure changes occurring directly during BET procedure.

METHODS

Using a micro-optical pressure sensor, pressure changes during BET were monitored transtympanically in a cadaveric animal study using heathland sheep.

RESULTS

Middle ear pressure amplitudes during BET are dependent on the speed of balloon inflation as well as the maximum inflation pressure. A 10-bar inflation pressure yielded a mean middle ear pressure of 5.34 mmHg (71.0 daPA). Negative pressure amplitudes occurring on withdrawal of the balloon catheter are influenced by the speed of withdrawal. No pressure amplitudes capable of causing barotrauma to membranous ear structures could be detected.

Middle Ear Pressure Changes during Balloon Eustachian Tuboplasty

Objective Balloon eustachian tuboplasty (BET) has entered clinical use as a treatment for eustachian tube dysfunction. Some surgeons perform myringotomy prior to BET due to concerns that the increase in middle ear (ME) pressure caused by BET may cause otic barotrauma. We investigated the ME pressure changes occurring during BET in cadavers. Study design Human cadaver investigation of a surgical technique Setting Laboratory study at a tertiary referral center. Subjects and Methods ME pressures were recorded from fresh-frozen cadavers, and BET was performed with the Bielefeld balloon catheter inflated to 10 bar. Peak ME pressures were recorded during catheter insertion, inflation, deflation, and removal. A second pressure measurement was taken 15 seconds after each stage to assess the residual pressures. All BET procedures were repeated at least once. Where transmastoid recordings were made, BET was repeated, measuring pressure via a myringotomy to ensure equivalence. Results Data from 25 procedures in 13 ears (9 heads) were analyzed. A consistent pattern of ME pressure change was observed in all cases. Positive pressures occurred on insertion (maximum, 26 daPa) and inflation (maximum, 99 daPa) and negative pressures on deflation (maximum, -46 daPa) and removal (maximum, -42 daPa). There were no significant pressure differences between first and second procedures, except at 15 seconds after insertion ( P = .04). Conclusion In adult cadaveric specimens, BET induces ME pressures within the normal physiologic range. On this basis, routine myringotomy prior to BET in adults is not necessary.

Tolerability of N-chlorotaurine in the guinea pig middle ear: a pilot study using an improved application system

The tissue tolerance of N-chlorotaurine (NCT), a mild endogenous antimicrobial oxidant, has been investigated by application to the guinea pig middle ear. The animals were implanted with a novel cannula system that allows chronic external drug delivery to the round window niche. In the first part of the study, 3 animals each received 100 microL of 0.1% NCT (5.5 mmol/L) and 1% NCT, respectively, in aqueous solution twice daily for 8 days. In the second part, NCT was dissolved in phosphate-buffered saline solution to 300 milliosmolar (isotonic), and 27 microL was injected in 3 additional animals twice daily for 7 days. The guinea pigs injected with 100 microL of NCT developed immediate dizziness and nystagmus and did not thrive. Other reactions included mucosal thickening in the middle ear, rupture of the tympanic membrane, and blood and gelatinous material in the cochlea accompanied by hair cell loss and a 10- to 90-dB elevation of the hearing threshold as determined by auditory brain stem responses. The effects seemed to be dose-dependent, but the rate of variability was high across animals. In contrast, the guinea pigs treated with 27 microL of isotonic NCT showed no signs of discomfort, no or only moderate thickening of the middle ear mucosa, no shift of the hearing threshold, and no hair cell loss. Positive control animals injected with 10% neomycin sulfate developed extensive hair cell loss. Provided that the membranes of the inner ear are intact and that low single-dose volumes are used to avoid increased middle ear pressure, isotonic NCT seems to be well tolerated in the tympanic cavity. The new drug delivery system proved to be advantageous for ototoxicity studies.

Bacterial otitis media: a new non-invasive rat model

This study describes the development of a physiological rat model for otitis media. The model is based on the assumption that bacteria, intranasally introduced into the nasopharynx, will be transferred into the middle ear cavity during swallowing provided that the ambient air pressure is higher than the middle ear pressure. This model demonstrates that small pressure changes, generated in a pressure cabin under controlled conditions, can be used as driving force for the transfer of bacteria into the middle ear cavity resulting in bilateral otitis media. Because invasive techniques or biochemical agents are not applied, this model is suited to investigate immunological aspects of otitis media, including the effects of vaccination.

Pressures of the porcine tympanic membrane

The mean rupture pressure of the porcine tympanic membrane (TM) was measured in 9 specimens. Pressure was delivered gradually into the external ear canal of an excised piece of temporal bone, via a syringe and polyurethane tubing attached to the canal. Tympanometry was used to ascertain the structural integrity of the TM before pressure delivery. Rupture pressure was defined to be that point at which a sudden drop occurred in the overpressure in the ear canal, as measured by a pressure gauge. From the results, we concluded that the mean rupture pressure for the porcine TM is 1.2 +/- 0.3 atm. This is of the same order of magnitude as and slightly less than pressures obtained for the human TM.

How can the hooded seal dive to a depth of 1000 m without rupturing its tympanic membrane? A morphological and functional study

Recent studies using a satellite-linked dive recorder have shown that the hooded seal (Cystophora cristata), a common Arctic pinniped, can dive to a depth of > 1000 m and stay submerged for close to 1 h. At these depths the water pressure reaches 100 atm, entailing obvious risk of serious damage to the hearing apparatus, mainly the tympanic membrane (TM) and middle ear (ME). We dissected and photodocumented the temporal bones of five newborn and three adult hooded seals in order to study the temporal bone structure and reveal its protective mechanisms for extreme pressure changes. Specimens were sectioned and stained for light microscopy. The thicknesses of the pars tensa and pars flaccida were found to average 60 and 180 microm, respectively. The ME cavity hosts a cavernous tissue of thin-walled vessels beneath the modified respiratory epithelium. The ME and external ear canal (EAC) volumes can be altered appreciably by filling/emptying the cavernous tissue with blood. The ossicles were fixed by contracting the tensor tympani and stapedius muscles simultaneously with complete occlusion of the EAC. According to Boyle's law, the volume of the gas-filled ME cavity at a depth of 1000 m is only 1% of its volume at the surface of the sea. Ascent from such a depth allows the gas in the ME cavity to expand, causing the TM to bulge laterally. This movement is counteracted by a reduction in the blood volume inside the cavernous sinuses, action in the tensor tympani and stapedius muscles and discharge of gas through the Eustachian tube. The presence of a firm, broad-based exostosis in the floor of the EAC lateral to the TM helps to obstruct the EAC.

Acoustic impedances at the oval window, and sound pressure transformation of the middle ear in Norwegian cattle

In 15 cadaver ears from Norwegian cattle, sound pressure transfer functions have been measured (1) for sound input to the tympanic membrane, (2) for sound input to the oval window with the footplate in place, but with the ossicular chain removed, and (3) for sound input to the oval window with also the footplate removed. The output pressure was measured in an enclosure cemented to the round window. The data allow calculation of equivalent sound pressures at the input positions, as well as the acoustic input impedances at the oval window with intact footplate, Z(sc), and with the footplate removed, Z(c). The difference Z(s)=Z(sc)-Z(c) is the acoustic impedance contribution of the footplate and annular ligament. Z(sc) is mainly determined by the stiffness of the annular ligament at low frequencies, and by the cochlear input impedance Z(c) at higher frequencies. Z(c) is predominately resistive, a minor reactive part at low frequencies is attributed to the stiffness of the round window membrane. Z(s) and Z(c) are equal in magnitude at about 0.4 kHz. Rather close RLC fits have been obtained for all the three impedances, Z(sc), Z(s), and Z(c). The fitted values for the resistive parts of Z(sc) and Z(c) are 62.9 and 58.2 acoustic Gomega, respectively. The relatively small difference, 4.7 Gomega, is attributed to the resistance of the annular ligament. The fitted resistance of Z(s) is somewhat larger, 8.6 Gomega, but is anyway of minor importance relative to the dynamic stiffness of the annular ligament. This stiffness depends on the static pressure difference across the footplate. Each of the averaged Z(sc) corresponds to minimum stiffness. The fitted acoustic compliance is 6.89 x 10(-15) m3/Pa. The acoustic inertance plays a minor role. It is attributed to the mass of the footplate and the co-vibrating liquid in the inner ear, and has a fitted value of 4.7 x 10(5) Pa s2/m3. A sound pressure at the eardrum is equivalent to a larger pressure at the footplate, about 16 dB larger at frequencies below 100 Hz, increasing to about 30 dB at 10 kHz. In the vestibulum at the inner side of the footplate, the sound pressure at 20 Hz is about 20 dB below the equivalent pressure at the outer side. The two pressures approach toward higher frequencies, and above 1 kHz they are nearly equal.