James Crawford. MD, LTC, MC, CPS/A
According to the Occupational Safety and Health Administration (OSHA) Hearing Conservation Amendment, the Certified Professional Supervisor of the Audiometric Monitoring Component (CPS/A) of a hearing conservation program (HCP) must be a licensed or certified audiologist, otolaryngologist, or other qualified physician. As an otolaryngologist, I can attest that there are few otolaryngologists serving the role of professional supervisor in a HCP. In reality, the vast majority of professional supervisors are audiologists, specifically, occupational or industrial audiologists. In addition, preventive and occupational medicine physicians frequently fill the role of professional supervisor. In this article, we hope to show what a professional supervisor can contribute to a hearing conservation program.
Whenever a threshold shift is identified, the certified professional supervisor is responsible for determination of whether that shift was caused or aggravated by occupational noise exposure. Furthermore, the professional supervisor should ensure that the hearing loss is not due to a medical pathology. This often requires a referral for a formal audiologic evaluation and otologic examination. After it has been determined that a hearing loss was caused or aggravated by occupational noise exposure, for the individual who presents to my clinic, there are two primary objectives: (1) ensure that there is not a progressive medical condition that may cause increased hearing loss, and (2) determine whether the hearing loss is able to be rehabilitated.
The air conduction audiometric screening used in hearing conservation programs was designed to be repeatable and easy to administer; however, it is not complete. By itself, it does not distinguish between sensorineural or conductive hearing loss. Fortunately, a formal audiologic evaluation, typically administered by an audiologist, does provide a more definitive picture of a person’s hearing sensitivity. A diagnostic hearing assessment may also evaluate if there is a significant concern regarding a listener’s speech discrimination ability. With that additional clinical information, an otologic examination can be much more meaningful.
The otologic examination includes an inspection of the auricle, external auditory canal, and the tympanic membrane. Such an examination is conducted to ensure that no active infection, chronic ear disease, or fluid behind the tympanic membrane exists. Fluid behind the eardrum, especially if only in one ear, may indicate that there is an obstructing mass in the back of the nose (nasopharynx), occluding the eustachian tube. A nasopharyngeal examination in that case may be the manner in which a cancer is identified. In addition, individuals that present with asymmetric auditory findings (hearing loss or speech discrimination worse in one ear than in the other or unilateral tinnitus) require an evaluation (otologic and audiologic) to ensure that they do not have a brainstem tumor. This diagnosis is classically made with use of magnetic resonance imaging (MRI). The most common of the brainstem tumors is benign, and grows on the vestibular nerve. It is a tumor referred to as a vestibular schwanoma. Early identification of these tumors allows for more favorable management and outcomes for patients.
The other issue that the audiologist and otolaryngologist will address is how best to rehabilitate the hearing loss. In some cases, that means the prescription of amplification devices, such as hearing aids. In other cases, especially those with conductive hearing loss, the hearing loss may be improved with surgery. Conductive hearing loss occurs when there is a problem with the mechanical conduction portion of the auditory pathway – the tympanic membrane and/or the ossicular chain. There are several disease states that alter the way sound waves are transmitted to the inner ear – a number of these conditions can be corrected surgically. The tympanic membrane, or eardrum, must be intact for sounds waves to be conducted properly. The eardrum gets its name because it is just that – like a drum. It operates like a snare drum in that sound waves hit the drum, and those sound waves then cause movement of the malleus, or hammer, which is the only of the three ossicles attached to the ear drum. After a sound wave is conducted through the ossicular chain, it is then transmitted into the inner ear. If the eardrum has a hole in it (or if it is retracted or flaccid), it will lack the ability to transmit sound waves efficiently, which will likely result in a conductive hearing loss. Besides the eardrum, damage to any of the ossicles can cause a conductive hearing loss.
The three ossicles (ossicular chain) are the smallest bones in the human body, and whenever there is injury to the ear and areas around it, there may be damage of one or more of the ossicles. Even pressure from a retracted eardrum can cause damage to the ossicles. It is possible for the eardrum to become so retracted that it begins to trap the skin debris that normally clears out of the ear as part of the cerumen. When this occurs, a cholesteatoma may form. Simply stated, cholesteatomas are trapped skin, but they can become destructive and often lead to chronic ear infection and ear drainage. Cholesteatomas need to be removed surgically. Oftentimes, otolaryngologists are able to surgically correct both the eardrum and ossicles. We rebuild the eardrum in a procedure called a tympanoplasty. Ossicles may be replaced with a prosthetic that connects directly to the eardrum and whichever of the ossicles remains functioning. If there are no ossicles, the prosthesis can directly interface with the inner ear. An otolaryngologist, who is functioning as a professional supervisor in a hearing conservation program, can use a clinical exam and a formal audiologic evaluation to directly determine if a conductive hearing loss is surgically correctable.
Sensorineural hearing loss, on the other hand, is generally not amenable to surgical correction. Patients with very severe hearing loss may benefit from a cochlear implant, but for the vast majority of people with hearing loss, hearing aids are the best choice for rehabilitation. Hearing aids work by amplifying sound. As hearing aid technology continues to advance, audiologists are better able to match a hearing loss with a hearing aid that will provide optimum rehabilitation. Hearing aids also help people with conductive hearing losses that cannot be surgically corrected. With electronic hearing protection devices, it is sometimes possible to have the device behave as a hearing rehabilitation instrument as well.
Overall, the hearing conservation program must be a team effort. It is critical that a hearing loss identified as a result of the audiometric monitoring program is followed through to identify if there are serious health concerns related to the presenting condition of the worker. A professional supervisor can help ensure that individuals are properly evaluated, and that adverse condition are correctly treated and rehabilitated.