Amanda Ortmann

Temporal and genetic influences on protection against noise-induced hearing loss by hypoxic preconditioning in mice

The protective benefits of hypoxic preconditioning (HPC) against permanent noise-induced hearing loss (NIHL) were investigated in mice. Hypoxia induced by exposure to 8% O2 for 4 h conferred significant protection against damaging broadband noise delivered 24-48 h later in male and female CBA/J (CBA) and CBA/CaJ mice. No protection was found in C57BL/6 (B6) mice, their B6.CAST-Cdh23(CAST) (B6.CAST) congenics, or in CBAxB6 F1 hybrid mice over the same interval, suggesting that the potential for HPC depends on one or a few autosomal recessive alleles carried by CBA-related strains, and is not influenced by the Cdh23 locus. Protection against NIHL in CBA mice was associated with significant up-regulation of hypoxia-inducible factor-1alpha (HIF-1alpha) within the organ of Corti, not found in B6.CAST. In both CBA and B6.CAST mice, some hypoxia-noise intervals shorter than 24 h were associated with exacerbation of NIHL. Cellular cascades underlying the early exacerbation of NIHL by hypoxia are therefore common to both strains, and not mechanistically linked to later protection. Elucidation of the events that underlie HPC, and how these are impacted by genetics, may lead to pharmacologic approaches to mimic HPC, and may help identify individuals with elevated risk of NIHL.

Quality-of-life technology for vision and hearing loss [Highlights of Recent Developments and Current Challenges in Technology]

Quality-of-life technology (QoLT) provides an ideal of human-centered intelligent systems. These technologies are tested and evaluated in both clinical and natural end-user testbeds. QoLT ranges from individual devices to comprehensive environments that can compensate for or replace diminished function. Hearing and vision technology provides a reality replete with challenges for QoLT research. Having been somewhat isolated from the mainstream of assistive technology (AT) development and engineering, hearing and vision technology offers clinically prescribed individual devices, such as hearing aids, or task-related devices, such as reading machines. This article describes the state of the art and some of the challenges in the development of hearing and vision technology.

Changes in the Compressive Nonlinearity of the Cochlea During Early Aging: Estimates From Distortion OAE Input/Output Functions.

Objectives: The level-dependent growth of distortion product otoacoustic emissions (DPOAEs) provides an indirect metric of cochlear compressive nonlinearity. Recent evidence suggests that aging reduces nonlinear distortion emissions more than those associated with linear reflection. Therefore, in this study, we generate input/output (I/O) functions from the isolated distortion component of the DPOAE to probe the effects of early aging on the compressive nonlinearity of the cochlea. Design: Thirty adults whose ages ranged from 18 to 64 years participated in this study, forming a continuum of young to middle-age subjects. When necessary for analyses, subjects were divided into a young-adult group with a mean age of 21 years, and a middle-aged group with a mean age of 52 years. All young-adult subjects and 11 of the middle-aged subjects had normal hearing; 4 middle-aged ears had slight audiometric threshold elevation at mid-to-high frequencies. DPOAEs (2f1 − f2) were recorded using primary tones swept upward in frequency from 0.5 to 8 kHz, and varied from 25 to 80 dB sound pressure level. The nonlinear distortion component of the total DPOAE was separated and used to create I/O functions at one-half octave intervals from 1.3 to 7.4 kHz. Four features of OAE compression were extracted from a fit to these functions: compression threshold, range of compression, compression slope, and low-level growth. These values were compared between age groups and correlational analyses were conducted between OAE compression threshold and age with audiometric threshold controlled. Results: Older ears had reduced DPOAE amplitude compared with young-adult ears. The OAE compression threshold was elevated at test frequencies above 2 kHz in the middle-aged subjects by 19 dB (35 versus 54 dB SPL), thereby reducing the compression range. In addition, middle-aged ears showed steeper amplitude growth beyond the compression threshold. Audiometric threshold was initially found to be a confound in establishing the relationship between compression and age; however, statistical analyses allowed us to control its variance. Correlations performed while controlling for age differences in high-frequency audiometric thresholds showed significant relationships between the DPOAE I/O compression threshold and age: Older subjects tended to have elevated compression thresholds compared with younger subjects and an extended range of monotonic growth. Conclusions: Cochlear manifestations of nonlinearity, such as the DPOAE, weaken during early aging, and DPOAE I/O functions become linearized. Commensurate changes in high-frequency audiometric thresholds are not sufficient to fully explain these changes. The results suggest that age-related changes in compressive nonlinearity could produce a reduced dynamic range of hearing, and contribute to perceptual difficulties in older listeners.

Sudden sensorineural hearing loss and delayed complete sudden spontaneous recovery.

This is a case report of a 53-yr-old female who experienced sudden sensorineural hearing loss (SSNHL) accompanied by roaring tinnitus in her right ear. The patients hearing partially improved in the low frequencies in response to intratympanic injections. Given that her hearing loss did not improve further, the patient was fitted with a hearing aid to mask the tinnitus and restore a sense of balance between the two ears. Approximately 9 mo postonset of the SSNHL, a complete spontaneous recovery of hearing occurred. Such a delayed and complete recovery is highly unusual. This case highlights that the spontaneous recovery in hearing indicates that the pathological cause for the SSNHL involved a process that was capable of repair or regeneration, thus ruling out pathologies related to cochlear hair cell destruction or nerve fiber loss. This leaves a possibility that the event causing the onset of the SSNHL resulted in a disruption of the ion homeostatic properties of the cochlea via the production of the endocochlear potential.

Noise in the neonatal intensive care unit: a new approach to examining acoustic events

Introduction: Environmental noise is associated with negative developmental outcomes for infants treated in the neonatal intensive care unit (NICU). The existing noise level recommendations are outdated, with current studies showing that these standards are universally unattainable in the modern NICU environment. Study Aim: This study sought to identify the types, rate, and levels of acoustic events that occur in the NICU and their potential effects on infant physiologic state. Materials and Methods: Dosimeters were used to record the acoustic environment in open and private room settings of a large hospital NICU. Heart and respiratory rate data of three infants located near the dosimeters were obtained. Infant physiologic data measured at time points when there was a marked increase in sound levels were compared to data measured at time points when the acoustic levels were steady. Results: All recorded sound levels exceeded the recommended noise level of 45 decibels, A-weighted (dBA). The 4-h Leq of the open-pod environment was 58.1 dBA, while the private room was 54.7 dBA. The average level of acoustic events was 11–14 dB higher than the background noise. The occurrence of transient events was 600% greater in the open room when compared to the private room. While correlations between acoustic events and infant physiologic state could not be established due to the extreme variability of infant state, a few trends were visible. Increasing the number of data points to overcome the extreme physiologic variability of medically fragile neonates would not be feasible or cost-effective in this environment. Conclusion: NICU noise level recommendations need to be modified with an emphasis placed on reducing acoustic events that disrupt infant state. The goal of all future standards should be to optimize infant neurodevelopmental outcomes.

Amplification and the Geriatric Patient

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