The Mechanic with Hypertension and Hearing Losss: Clinical Problem Solving Case
University of Massachusetts Medical School
Instructor(s): Rest, Kathleen; Pransky, Glenn; Sweet, Charles
Subject area: Health / Medicine
Department: Family and Community Medicine
Duration of exercise: 1 hour
Learning objective: Develop Individual Skills, Provide Information
Teaching style: Group Activity, In-class Activity
Please note that the copyright for this course project is retained by the instructor.
The following faculty guide is for a problem solving case used during a two day interclerkship course on the Environment and Health for medical students at the University of Massachusetts Medical School. The case focuses on noise induced hearing loss and hypertension. For more information on the interclerkship course, follow the related Second Nature database entry link found at the bottom of the page.
Note to instructors: Distribute Part 1 of the case (2 pp) to the students. The student materials will not include the information shown in bold on these pages. Have them read these first 2 pp, and then work with them to answer the questions. Keep the focus on the questions and limit the discussion to 10 minutes so you can go on to the rest of the case. Once this section is completed, you will distribute Part 2 of the case.
A 41-year-old white male comes to your office with a chief complaint of newly diagnosed high blood pressure. He states that he has generally been in good health, and did not know that he had high blood pressure until last week, when he visited a free community walk-in blood pressure screening program after work. They told him that his blood pressure was 150/100 and suggested that he make an appointment with his doctor.
He denies any headaches, nocturia, excessive thirst, palpitations, chest pain, history of kidney, heart, blood sugar, or other blood problems. His last medical checkup was 2 1/2 years ago. At that time, he had some blood tests done; he says that all the blood tests were perfectly normal. He also recalls that his blood pressure was normal at that time.
A more detailed past medical history reveals nothing unremarkable, except for some time out of work several years ago due to a back injury at work. He also broke a shoulder bone while playing football in high school.
He says that he drinks only occasionally, does not smoke, and that his weight has been stable, at 185, for the last 5 years or so. He thinks this is a fairly normal weight for him, as he has a muscular build. Although he does not follow a low-salt diet, he says that he rarely eats pickles, potato chips, pretzels, or other salty foods. He drinks 2-3 cups of coffee a day, while at work, but he does not drink coffee on weekends. He doesn't notice any jitters or palpations when drinking coffee.
He lives in East Boston, is married, and has 2 children who are alive and well. He works as a truck mechanic for Marriott Food Services at Logan Airport. He has 1 younger brother, with no medical problems. Both of his parents are alive; his father has mild angina. Neither parent has high blood pressure.
Your physical examination reveals a healthy-appearing white male, with normal facies. Blood pressure is 150/100 sitting and 150/105 standing, with a pulse rate of 65 sitting and 78 standing. Head, eyes, ears, and throat are unremarkable; fundi are normal : without any AV nicking. There are no carotid bruits. Chest is clear to auscultation. Heart has regular sinus rhythm, somewhat forceful PMI, no murmurs or bruits. There are no abdominal or renal bruits, and abdominal palpation is negative, without striae. Pulses are normal and symmetrical in extremities, and a brief neurologic examination is normal. Because you have been speaking somewhat loudly during the examination, you check and find that there appears to be some loss in both ears of the ability to hear a fully exhaled whisper.
You obtain blood tests, which show BUN 18, creatinine 1.1, and normal electrolytes. Blood sugar is 98, and urine dipstick is negative.
Instuctor: Work with the students to answer the following questions. Encourage their discussion of the answers, but limit this to 10 minutes in order to have time for the rest of the case.
1. His first question to you: I'm completely healthy - why do I have this problem?" What are some of the possible medical causes of HTN In this patient? How can they be Identified?
There does not appear to be a secondary cause here, although it is unusual to have essential hypertension without a positive family history. Thus, you might want to inquire more about the parents' medical history. Medical conditions that most commonly lead to hypertension are renovascular and renal parenchymal causes, hyperaldosteronism, and oral contraceptive -induced hypertension. The history, physical exam, and laboratory tests virtually exclude these conditions. A rise in diastolic pressure (as in this case) when going from supine to standing is consistent with essential hypertension; a fall is more consistent with secondary medical causes.
However, approximately 94% of all hypertensive patients do not have a definable secondary cause (defined as another medical condition responsible for the hypertension), and thus have essential hypertension. Would you pursue additional studies here, or just begin treatment?
2. What other factors might be contributing to hypertension here?
In contrast to the paucity of medical causes for hypertension, environmental factors commonly contribute to hypertension (through causation or exacerbation). For example, at least 60% of hypertensives are sensitive to salt intake, and the majority of obese patients will have substantial BP reductions with > 10% weight loss. Other environmental factors linked to hypertension (as either causes or exacerbators) include diet (caffeine, epinephrine-like OTC medications), race, family history, stress and noise. We'll get to the noise exposure later in this case.
3. What do you advise this patient?
Before prescribing medications, it would be important to review the possible etiologic factors in this case which, if corrected, might reverse this patient's hypertension. You explain that many cases are idiopathic, but that exacerbatory factors include salt, stress, caffeinated beverages, weight, and other factors. You review the essential aspects of a low-salt diet, and advise him to discontinue caffeine. You ask him to follow-up with you in 2 weeks to see how his blood pressure has changed.
4. What else did you find on the evaluation?
Hearing loss was detected on the examination. Demonstrate to the students how to do a whisper test to detect subtle hearing loss -- and/or review the attached Hearing Handicap Inventory Questions. Distribute a copy of the Inventory to the class.
5. What are some of the possible causes of this problem?
Many possible causes. Middle ear problems include eardrum rupture, infections, and otosclerosis. Cochlear problems include infection (usually viral, or from bacterial meningitis), genetic (congenital deformity, or one of many genetic hearing-loss syndromes- about half of all cases of adult-onset hearing loss), drug-induced (aminoglycosides), traumatic (skull fracture or noise-induced), neoplastic (acoustic neuromas), and idiopathic age-related loss (perhaps a third of cases).
6. How would you further evaluate this problem?
First, a careful history will be very helpful. Distribute Part 2 of the case and have students read it (or have someone read it aloud).
You are interested in the patient's other problem that you detected, namely mild hearing loss, and you ask whether he has noticed this problem. He says that it's not something he thinks about. He doesn't feel that his hearing is different in one ear compared to the other. However, he says his wife is always complaining that he turns the TV up too loud, especially over the past 2 years. He reports that communicates pretty well with his co-workers at work.
He denies ear infections or episodes of hearing loss as a child, ear or head trauma, or taking any medications, such as antibiotics. No one else in his family has hearing loss to his knowledge. He denies tinnitus or vertigo.
You examine his ears further and find that his tympanic membranes are clear and intact. With a tuning fork, air conduction is better than bone conduction bilaterally, although air conduction seems to be decreased symmetrically (Rinné's test), and applying the tuning fork to the midline of the skull does not lateralize (Weber's test). His Rhomberg test is negative.
Instructor: Facilitate discussion of these questions.
7. Based on this Information, what is the most likely differential diagnosis?
The history and physical examination should establish that the problem is cochlear, bilateral, of gradual onset, and not obviously associated with other medical problems or medications. Rinne and Weber tests help to differentiate unilateral vs. bilateral problems, but most patients with unilateral problems will readily describe that one ear is significantly worse than the other. Therefore, the two most likely remaining diagnoses are presbycusis (idiopathic or genetic) and noise-induced hearing loss.
8. What further information do you want to know about the most likely etiology of this condition?
Instructor: Prompt the students to ask for more information and provide the information that follows. They should ask you for an occupational and environmental history, with a description of occupational and environmental noise exposures. In addition to workplace noise, they should ask about various hobbies that can lead to noise-induced hearing loss. e.g., shooting, recreational vehicles, wood-working or other hobbies that involve power tools, loud music, power farming equipment, and lawn mowers.
Instructor: Provide the following information to the student's' questions.
The patient works as a mechanic in a garage. He has been doing this job for over 10 years. Trucks come in and out all the time. He does all sorts of work on them, and is often working on one truck while another one is running and being loaded next to him. The garage is very noisy, but the loudest noise at work comes from jets taking off and landing on nearby runways. The garage is well-ventilated, and there is no problem
Hobbies - He has a small cottage in New Hampshire. During the winter, he occasionally goes snowmobiling on weekends. He doesn't think this is so bad. Although several of his buddies have started wearing earplugs, he doesn't feel that he needs them. He denies woodworking, shooting, motorcycle use, loud music, or using a lawn mower.
9. In this case, what are the most Important exposures?
See attached figures to illustrate the noise levels associated with common exposures. -- Figure 13-1, "Examples of Outdoor Day-Night Average Sound Levels in dB Measured in Various Locations" [note airport data] and Figure 13-2 "Sound Levels and Human Response." Students have these figures attached to Part 2 of the case. Compare his exposures to the OSHA recommendation of 85 dB maximum levels.
10. How will you counsel this patient about his hearing problem before he leaves the office? What more would you do?
You suspect that his hearing loss may be related to his noise exposure at work, but you would like to schedule him an audiometric evaluation before his next visit. In the meantime, you should advise him to wear hearing protection at work and when
engaged in other noisy activities, such as snowmobiling.
You arrange for the patient to have an audiometric evaluation, the results of which are attached. A normal audiogram and an audiogram of a patient with presbycusis are also attached for comparison.
11. What can you tell by looking at the patients audiogram? When the patient returns for follow-up, what will you tell him about his hearing loss and what will you recommend?
The patient's audiogram is provided, along with a normal one as well as one from a patient with presbycusis for comparison. Students have these, too. Ask the students to describe the differences. They should notice the sharp drop-off in higher frequencies in noise-induced hearing loss, compared with normal thresholds and the pattern in presbycusis. An audiogram is useful to differentiate the type of hearing loss. Noise-induced Hearing Loss (NIHL) has a characteristic appearance, with bilateral, symmetrical high-frequency loss, compared to presbycusis or viral causes (loss more evenly distributed across all frequencies).
At first, patients have a high frequency "notch" -- with some difficulty distinguishing between "s" and "f" and hearing high-pitched sounds. Later, the notch increases and there is loss in the frequencies required for speech discrimination (1000 - 3000), sometimes with tinnitus. His audiogram shows fairly mild NIHL, and may not fully explain his symptoms which seem to be worse after work. Perhaps his hearing difficulty is related to a noise-induced temporary threshold shift, which resolves with time away from exposure. His audiogram may also have been done after time away from exposure. .
Most who present in middle age, with bilateral disease, such as this patient, have NIHL. Noise exposure damages the inner ear, primarily affecting the sensory hair cells within the Organ of Corti .
When the patient returns for follow-up, you will explain that the loss which has already occurred is irreversible, and that it is important to avoid any further exposure so it won't get worse. NIHL can result in poor communication with co-workers and family, leading to social isolation and increased danger from not being able to hear warnings. Secondary effects may include stress and exacerbation of hypertension. You can mention that several studies have demonstrated that noise exposure can temporarily exacerbate high blood pressure during the period of exposure. The association is controversial for etioloqy, but it is well-demonstrated for exacerbation/elevation/contribution.
Additional teaching points to make here:
NIHL loss affects over 10 million Americans, and the likelihood of occurrence is directly related to cumulative exposure over 80 decibels. There is a range of susceptibility, but the majority of workers will have NIHL if exposed to over 85 dB at work for over 15 years. Some will have noise-induced hearing loss if levels are consistently over 70 dB. Nevertheless, OSHA mandates hearing protection only if average exposures are over 90 dB for an eight-hour period, and requires audiometnc screening if average levels are over 85 dB. Of course, the rate and extent of hearing loss is greater with louder noises, and depends on the total exposure from all sources - work, hobbies, and ambient sources. Sudden impact noises are more injurious. : Shooting and recreational vehicles are the most important non-occupational causes of hearing loss, followed by personal music equipment - a growing concern.
Instructor: Distribute Part 3 of the case and have students read it (or have someone read it aloud).
In 2 weeks, the patient returns to your office, accompanied by his wife and children. He says that he has complied with your recommendations about discontinuing coffee, decreasing noise exposure by wearing ear plugs at work, watching his salt intake, and getting a little more exercise.
He is happy to hear that his blood pressure today is 120/88. You then talk to him about his hearing loss and ways to prevent further damage.
After listening to this, the patient's wife mentions a concern about their 14 year old son. It seems that a teacher has complained that he may have some problems following directions, and that this has been a little worse over the last year. The teacher noted that, when in the midst of a group of children or near other children who are talking, the boy occasionally seems to miss out on what is going on. However, when the teacher interviewed him, the boy didn't seem to have any difficulty understanding what others were saying or doing. Otherwise, the boy is perfectly healthy, with no difficulty sleeping, no difficulty understanding or following directions, and no behavioral or hyperactivity problems or evidence of difficulty concentrating at home.
The mother mentions that she occasionally has trouble calling him down from upstairs and that when she asks him something from another room, he sometimes doesn't respond. She attributes this primarily to his recent love of rock-and-roll music and purchase of a Walkman, which he wears constantly.
The boy has no recent history of ear infections and has no medical problems. A brief examination reveals a healthy-appearing boy, with no ear problems on physical exam. On more detailed examination, he has a slightly decreased ability to hear whispered words, in both ears. An office audiometric screening test shows a 20-30 dB loss in the higher frequencies and normal hearing in the lower frequencies. [The boy told the technician that he had not used his Walkman for a couple of days because "the batteries conked out."]
You sit the family down and explain that this is most likely early noise-induced hearing loss, and that you have heard reports of this being induced by excessive use of personal radios at high volume. However, the boy says that he only listens to music occasionally on the Walkman. You ask about other sources of noise exposure, such as snowmobiling with his father, dirt bikes, motor cycles, etc. He denies all of them.
He reports that his favorite activity for many years has been playing baseball. During the spring and summer months, he usually plays at a field near his house, which is in East Boston and very close to the airport. In fact, the kids often have difficulty understanding each other during games and use signs to communicate while playing ball. The father occasionally goes to the baseball field with his son, and agrees that, yes, the noise levels are quite high. He is fascinated by how well they are able to : play ball, despite the roar of overhead jets.
Instructor. Facilitate discussion of the following questions.
12. What are the sources of noise-induced hearing loss in this child? How could you find out about noise levels In the neighborhood?
Airplane noise and music from personal stereo. Airplane noise can easily reach 110 dB on the ground near runways, and Walkmans can generate sound levels that are over 90 dB. If bystanders can easily hear the music from the headphones, sound levels are probably near or over 90 dB. If the boy is outside 4 hours per day for 3 days per week with average ambient noise levels of 100 dB, this exposure is roughly equivalent to working in a factory with high noise levels (90 d8 average) for eight hours, three days per week! (You can refer back to the noise level figures if you want.)
Because of the significant impact of noise from Logan Airport on the surrounding community, Massport has spent millions of dollars studying and reducing noise exposures from airplanes. The Office of Noise Abatement has documented that several areas of East Boston and Winthrop are exposed to average sound levels over 85 dB, and have targeted these areas for home renovations designed to decrease noise exposure inside houses. Despite limitations on runway use between 10 pm and 8 am, redesign of jet engines for quieter operation, and structural changes to runways and access areas, outdoor community exposures are still substantial. You can call the Noise Abatement Office to obtain information on exposures at the ballpark.
13. What do you recommend to this boy?
Decrease the volume on the Walkman and wear earplugs when playing baseball at this park. The boy's clinical signs (comments about his difficulty hearing from his teacher and mother) suggest a higher degree of hearing loss than seen on his screening audiogram. His problems may involve a temporary threshold shift, which occurs after noise exposure. Moreover, the audiogram may have been done at a time when he had not used his Walkman or had not been playing outdoors for 8+ hours.
END CASE AND DISTRIBUTE ARTICLE
This document was last modified on 06/14/2000 03:08:03 PM
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