Dr. Heather Williamson is a 2000 graduate of KCOM and is board certified in family medicine and disaster medicine. She also has a CAQ in occupational medicine. She currently practices in the urgent care and occupational health settings with Mercy Hospital in St. Louis, Missouri. And as Jeffrey said, Heather is virtual, but she will answer questions. Heather, it's all you. I should have just let her take it. Okay, welcome back, everybody. It's me again, Heather Williamson. We're going to talk about physical hazards. So just kind of give you some idea. The fatal workplace injuries in 2020, it was nearing 5,000. It doesn't include the COVID-related deaths, but this is more just accidents. A worker died every 111 minutes from a work-related injury. So it's a pretty significant number going on. The deaths are most commonly in the transportation incidents, like car accidents, hit by trains, stuff like that. Fall slips and trips, violence and other injuries by persons or animals. Contact with objects and equipment is next. Exposure to harmful substances or environments and fires and explosions. So physical hazards in the workplace include things like thermal injuries, radiation, noise, vibration, barometric traumas, and physical traumas. Starting with thermal hazards, heat is an integral part of many industrial processes and operations. It's a waste byproduct in other operations. It can be both like an environmental hazard where there's high ambient temperature, humidity, heat sources, or hot air moving around, and exertional hazards. So somebody that may be in a reasonable temperature environment, but is doing a lot of very strenuous physical activity and is overheating. It's also a contact hazard as far as burns go. And you can get burns both from heat sources and from extreme cold. Things like touching a very, very cold piece of metal or liquid nitrogen, that sort of thing. So risk factors for heat-related illness include age, obesity, alcoholism, as well as acute alcohol intoxication, but even the chronic diagnosis of alcoholism plays into this. Poor physical fitness, certain drugs and medications like anticholinergics, antihistamines, phenothiazines, and numerous psychoactive meds, alcohol, cocaine, doing a lot of heavy physical activity and exertion, especially if wearing clothing or PPE that does not allow for heat loss. And also, if you've had a prior history of heat-related illness, it makes you more susceptible to having a subsequent heat-related illness. Evaporation is the most important source of heat loss for us. The higher the ambient humidity, the less sufficient the heat loss because the water doesn't want to evaporate. High ambient humidity, which decreases the cooling effect of sweating, and prolonged strenuous exertion, which increases heat production by the muscles, overall is a perfect storm for increasing the risk of developing a heat-related illness. So this is the heat index. You can see that even on a reasonable day, let's say, you know, if it's 75% humidity and the temperature, you know, is 84, you're still at a caution. There's still an increased risk of heat-related illness from that. And then when you start getting out into the 90s or even the 100s, especially, you know, if you're in the Midwest or the Southwest or the South, you know, temperatures in the summertime regularly get up into the 100s. It does not take much humidity to get you all the way into the extreme danger zone. Where I'm from, which is Missouri, we have frequent days in the summer that are in the 90s with 90-95% humidity. So we think about the confounding factors. Obviously, this person here who's all decked out in their fireman PPE and is about to go run into a burning building, they've got two sources of potential risks for a heat-related illness. So there's this one on the right here with pouring liquid metal out in their heat-protective suit. Keeps heat out, but also keeps their heat in for the most part. But we sometimes forget about us. So healthcare providers, especially in the height of COVID, when people were working outdoors, swabbing people in cars, and they're fully decked out in their Tyvek suit and their mask and goggles and gloves, it does not take a lot of heat or humidity for them to overheat. So the first of the heat-related skin disorders we'll talk about is miliaria. It's aka heat rash. It's caused by sweat retention or blocked up sweat glands. And there's four different forms of this. It starts with the mildest, which is the miliaria crystallina. And then the moderate versions are the miliaria rubra and the pustulosa. And then the more severe one is the miliaria profunda, if you couldn't guess from the name. Okay, so this is miliaria crystallina. It's also known sometimes as miliaria pseudomena. These are superficial, non-inflammed vesicles. They look like water drops almost on the skin. They rupture easily when you run your finger or hand across them. This is pretty much mild and self-limited. This is the more moderate form here, miliaria rubra, also known as prickly heat. This is when sweat gets blocked up and moves into the epidermis and upper dermis. There is inflammation present, so you have this redness there. It's pruritic, and you can have firm papules or vesicles associated with this. So this is much more uncomfortable for them than the miliaria crystallina. Okay, so moving on to miliaria pustulosa. This starts out as miliaria rubra, which we saw in the previous slide. The vesicles can get secondarily infected with bacteria, so this becomes pruritic and painful. It sort of looks like what we would expect for folliculitis, but it's usually pretty dense areas of folliculitis. Okay, this is miliaria profunda. This is where retained sweat gets out of the sweat glands and leaks into the dermis. This is usually due to exposure to intense heat. You get discrete flesh-colored papules to sometimes somewhat larger nodules. This increases the risk of systemic heat-related illness because now, instead of being able to sweat and have the sweat evaporate from the surface of the skin, it's now backing up into the dermis and into these nodules and papules, so you lose your evaporative capacity to dissipate heat. So what do we do about this miliaria? General treatment for all the types, you've got to prevent exposure to heat and humidity so that sweating is not stimulated. Continuing to sweat in these areas will just continue to prolong or worsen the rash. You should also try to avoid skin occluding items like bandages, medication patches. If it's in an area where somebody's been wearing nitrile or latex gloves, you've got to get those off and keep them off. You don't really have to do too much else for the crystallina version of this, but by the time we get to miliaria rubra, if needed, if it's significant enough, you can add a mild to mid-potency corticosteroid like triamcinolone, 0.1%, something like that topically for a week or two. For the miliaria pustulosa, you can add a topical antibiotic for the bacterial infection. And for miliaria profunda, there's not a lot of data out there about what to do about this. One study reported good results with oral tretinoin and topical anhydrous lanolin, but I don't think there's a lot of official recommendations out there for what to do about the miliaria profunda. So moving on to heat cramps. These are exercise-induced cramps of striated muscle that results from excessive fluid intake without sodium replacement. So these are the people that are out working hard in the heat, sweating a whole lot, losing plenty of sodium in their sweat, and they're drinking a lot of water. They think they're doing everything right, but in fact, they're not getting any salt replacement with it. The skin tends to be moist and cool. They get slow, painful contractions lasting one to three minutes, and they can continue to occur periodically. The treatment is move them to a cool environment and to get a balanced salt solution or oral saline solution into them, which is four teaspoons of salt per gallon of water. Don't just hand them a tablespoon of salt or a salt tablet. If you happen to get lab tests in these people, it usually shows hyponatremia, but often shows that they are not dehydrated because they've been drinking plenty of water. Then they should rest for one to three days before exposing themselves to high heat and humidity where they would have excessive sweating. And then there's heat exhaustion. Exhaustion is excessive fluid. This can get altered mental status, and that can precede seizures or coma. Okay, sorry. I understand we lost sound with our remote people, so I'm gonna try to figure out how to get that back. I was trying to fix it so our room would get better audio. I saw a dolphin outside our room. Oh, cool. Yeah. And I saw a ray yesterday. It's a wonderful story. Yeah, I just looked out, and I was like, look, there's a ray. And we just saw the dolphin. That's why there's car accidents on the causeway. They're watching the dolphins. I believe it. Seriously. I used to look at them. OK, I'm going to try to start again. Can y'all tell me if you hear the sound? Can you still see the video? Great. If you lose your homeostatic mechanism, your body temperature goes rapidly, and this heat stroke can occur. Yes. And I hear it. If it's not, you'll need me to rewind it a bit. Interventions are not taken. If it goes hours of this extreme hyperpyrexia, they're likely to have permanent brain damage. Basically, the brain cooks at that temperature. Men over age 40 were 10 times more likely to have heat stroke than younger men. So age is definitely a risk factor for this. Acclimatization. This refers to easing into exposure to high ambient temperatures. So 50% to 70% of outdoor work-related fatalities occur within the first few days of working in a warm or hot environment. So you take somebody that may have worked in the air conditioning, and then you put them in an outdoor job, and then down they go with heat exhaustion or heat stroke. The body needs time to develop a tolerance to the heat gradually. So people that live and work outside every day in Arizona will handle the heat a lot better than somebody who lives and works outside in the summer in Canada. NIOSH recommends a 7 to 14 day acclimatization time for those new to working in hot environments. Also, workers who are away from working in a hot environment for more than a week, so they go on vacation, they will need to re-acclimatize. But they can usually do so gradually over four days instead of the 7 to 14 day. So NIOSH basically recommends limiting the number of hours per day of exposure to the high heat so that they can get used to it. Acclimatization is better maintained by those who are physically fit. So being obese and out of shape is not going to help you maintain your acclimatization. So if you go on vacation, you definitely are going to need to ease back into it when you get returned to work. So treatment for heat exhaustion, heat stroke, stop the activity and move to a cool environment immediately. If they just have heat exhaustion, they're still talking to you. They don't have neurologic signs, severe neurologic signs. You give them cold fluids to drink, remove their outer clothing. You can apply cold compresses or cold water to their skin or put ice packs on their groin and their arms and around their neck or chest. But if they have heat stroke, by that point, they're probably not super cooperative with you. And they may not be able to protect their own airway. So you really don't want to give them PO fluids if they can't protect their airway. So you want to remove their outer clothing, rapid cooling with cold water or an ice bath if you can get it available, and then circulate the air, like put fans on them or fan them with something if you need to, at least until help can arrive and they can get off to the hospital for that. For prevention, the ACGIH has a set of threshold limit values and action limit values based on meteorological data like temperature and humidity, what type of clothing or PPE the worker's wearing, their age and weight, their acclimatization status, how much exertion goes into their work. I included the link there. It's a little cumbersome to calculate all of this. It doesn't really lend itself well to a singular chart. But if you have somebody that works in frequent hot environments or you practice in an area where it's hot, this may be helpful to master and help figure out along with your clients how to go about bringing on new workers and preventing heat-related illness in existing workers. Employers whose workers are exposed to high temperatures should have a heat illness prevention program, and it should include how they're going to get increased fluids and probably electrolytes intake. If they're in full PPE and they can't take off the PPE for hours, they're not getting any fluids in while they're still protected in their suits. So there has to be a plan in place for how to get them out of their PPE and allow them to drink fluids. They should have frequent cooling breaks, enough to bring down their core body temperature. You should train the workers to recognize and respond to heat-related illness because early intervention is key. You wanna get this when it starts to be more mild heat exhaustion and not all the way to heat stroke, which is life-threatening. Last year, OSHA announced expanded measures to try and protect workers, prioritizing interventions and inspections on days when heat index exceeds 80. So really, you need to start being aware of the potential for heat-related illness, even when it does not seem excessively hot outside. They'll probably come out with an OSHA standard at some point for this, but it hasn't happened yet. Other prevention strategies include things like cooling vests or neck wraps. Really, the neck wraps or scarves for cooling are the least effective of these, but the cooling vests come in a variety of different types. You have the evaporative ones, which they can just wet that, preferably in cool water, but it can be wet in water thrown on over the other clothing and as that water evaporates, they will lose heat that way, but they don't last terribly long depending on the ambient humidity and their effectiveness also depends on the ambient humidity. You can get vests that have ice pack inserts, like little pockets where you slip in all these different ice packs and that can help keep the core body temperature cool, but once they melt, then they have to be replaced with others, so extras have to be purchased. And again, those may not last more than a few hours. Some have phase-changing materials like paraffin, which tend to melt on closer to body temperature. You don't have to wet them or freeze them or anything, but again, once it's sort of melted, you've got to take it off and switch it out for a new one or go to a different type of vest. Certain places that have a lot of exposure, usually in more of a controlled geographic area, so like if you're in a plant that has a lot of heat from a particular process and you have workers that are standing or not moving a lot nearby, they can get these ice water circulating vests, but they have to be hooked up to an external reservoir. So like if you're in landscaping or something where you're moving all over the place, it's not really feasible to carry along this ice reservoir with you at all times. Limitations still with that once the ice water melts, or once the ice melts and the water warms up, you've got to replace that. Cooling time on all of these varies, but it's generally like one to four hours. They require replacement of the ice or cold water frequently to maintain the cooling effect. And the vests themselves can weigh one to 3.5 kilos or sometimes even more. And so that can also increase the exertional level of the person wearing them. Okay, talking about burns. These can be due to any external heat source capable of raising the temperature of the skin and the deeper tissues to a level that causes cell death and protein coagulation or charring. These can also be caused by severe cold like liquid nitrogen, liquid helium, people that work around anything that has to be cooled. With those gases can be exposed to significant cold burns as well. But the most common causes are flames, scalding liquids and hot objects or gases contacting the skin. The extent and depth of the damage depends on the amount of energy transferred. Burns usually come in three degrees here. The first degree is just where it gets red. Think of this as like a sunburn. The tissue blanches with pressure, the damage is minimal. There's no blistering or scarring and it tends to just get better over time and without really any intervention. Second degree burns are partial thickness. They do go down into the dermis. They have associated pain blistering, but sensation is intact. These hurt to touch. These go completely through the skin all the way through the dermis to the subcutaneous tissue and sometimes even below. The skin can look charred or it can be translucent white. It can also have like a tan colored appearance as well. And then you can have surrounding erythema and blistering from second degree burns, but that central area really is painless to touch. The second degree burns are just like a sunburn and they're not as painful as the first degree burns. The central area really is painless to touch. The second degree burns around the rim of it are painful, but the center of the burn where it's black, brown, or white is generally painless to touch and that's when you know you've got big problems and these need to be managed at a burn center preferably. So talking about cold hazards, these are generated in some chemical processes, commonly used as storage and product life extension. Even things in your hospital, things like MRI machines have to be cooled with liquid nitrogen. These are fairly common, you know, environmental hazard. You can have localized effects or systemic effects. So you can get hypothermia or cold burns or other effects of the localized area. Frostnip is the sort of mildest injury that you see with exposure to cold temperatures. It's reversible and it's due to injury due to sub-freezing conditions. So it's kind of the first stage of frostbite. The skin turns red and feels very cold. They can have pain or tingling, especially as it warms up. Can be treated by warming the affected area with like the other hand or a warm object like a heating pad or something like that. And over here in this picture, you can see, you know, on the left, that's normal. Frostnip just affects the very superficial layers of the skin and turns them red. And then as we get farther over here, we'll talk more about frostbite, which causes blistering and gets down into pretty much the deepest levels of the dermis. And then deep frostbite, which gets even further past the dermis and into the subcutaneous tissues. So frostbite, that's an injury due to the freezing of tissue cells. So in the extremities, it occurs in extreme cold and even more prone to those who have extreme cold at high altitude. Ice crystals form within or between the tissue cells and basal constriction occurs to reduce the heat loss from the skin and peripheral tissues. Much of the damage occurs during rewarming like a reperfusion injury. All degrees of frostbite can produce long-term symptoms like sensitivity to cold, excessive sweating, scarring, faulty nail growth if it happens on the fingertips, and numbness. So if you've got somebody with frostbite, the area is cold, hard, white, and numb. When warmed, it can become blotchy red, swollen, and painful. Blisters will develop usually within four to six hours. So blistering is not an immediate sign of frostbite. It takes a while for that to develop. Those blisters are usually filled with clear serum and located distally on the digits. When it's distal on those digits, like it indicates superficial damage. If it gets more proximal, like into the palm of the hand or above the toes and the foot, then you're looking at potential for a lot deeper damage. If those blisters are blood filled, then they indicate also deep damage and full thickness dermis loss. So almost like third degree burn. The regular frostbite's the second degree burn, but when you get to the deep frostbite, that's the third degrees. It can cause wet or dry gangrene as a result of that tissue death. So on the left here is frostnip. Again, almost looks like a little patchy sunburn. The skin is red, but there's no blistering, and this is more of a superficial injury. Then you get to the superficial frostbite here. You see the blisters on the digits, and that is a sign of equivalent to like a second degree burn and managed in much the same way by the time it reaches this stage. And then you can actually get the gangrene or the full thickness tissue loss. These should absolutely be managed by some burn specialists in the hospital setting. Another type of cold-related injury is called immersion foot or trench foot. This is due to exposure to wet and cold, but the temperatures are above freezing. So this isn't enough to actually freeze the full thickness of the skin, but it's more chronic, or at least longer duration exposure to cold and wet. So this was named trench foot because a lot of people, especially in World War II, a lot of soldiers got this from hanging out in the wet trenches, and their feet were wet all the time and it was cold. But honestly, I've seen this from, I had one patient who had a lot of, his feet just sweat a lot. That was just him. They'd always done that, but he worked outside and it was a day that was probably in the 40s or 50s, but he'd been working hard and his feet had sweated a ton. His soaps were just totally soaked. You could like wring out the sweat from them. And he had pretty much chronic trench foot from that. The stages of it. The first is the injury phase where the tissue's cold, numb, red or white, but not particularly painful. So they go on working during this span of time. It doesn't cause them to immediate warning that something's going on there. And then immediately post-injury, once it gets warmed up, then it can get kind of blue from vasospasm, cold, numb. You can also get some edema. And then hyperemic phase, which can last up to two weeks to three months. It gets hot, red, dry skin, tingling, sometimes blistering. And then the chronic recovery phase, the post-hyperemic phase, that can be lifelong and they can have long-term cold sensitivity, tingling and pain, sometimes chronic ulcers there as well. Hyperhidrosis as a result of this can persist for years, but sometimes hyperhidrosis is also the cause of this. They can also have pain due to autonomic dysfunction. Here's a couple of pictures of this. This is the milder version. You can see it kind of looks like all pruny, like they've been in water for too long, but they also get these fissures there that show up. So not only are the skin folds accentuated, but sometimes they'll actually get like open areas of skin extending into the dermis that are kind of red at the base from this fissuring and cracking of the skin. And then in severe cases, you can get actual like blistering and ulceration there from it. Another cold-related injury is chilblains, also called perneo. This is a result usually of repeated exposure to cold, but not freezing air. So again, this is not cold enough to cause frostbite necessarily, but they're exposed to a lot of cold air. Painful erythematous, peridic, and sometimes blistering skin lesions, most often on like the hands and feet, fingers, toes, usually resolves on its own within one to three weeks, but prolonged exposure or repeated exposure can lead to chronic perneo, which can cause erythema, vesicles, ulceration, and or blue toes, chronically blue toes. Scarring, fibrosis, and atrophy can follow. COVID toes actually have quite a similar appearance to chilblains, so kind of keep that in mind when looking at people with these skin changes. You can see on the pictures here on the top, this sort of erythematous, sometime like a few vesicles there on the dorsum of the fingers and then the tips of the toes there as well. We move on to the systemic symptoms of cold exposure, which is hypothermia. The body core temperature falls below 35 degrees C or 95 degrees Fahrenheit. Hypothermia is most common during the cold weather or immersion in water, but it can occur on a summer's day or even in warmer climates if the metabolic and exertional heat dissipating mechanisms like shivering cannot sustain core temperatures. So if you get somebody that's cold and wet and is in a brisk wind at 50 degrees, they can absolutely get hypothermia, even if they appear to be dressed appropriately. Age increases the risk, as does certain medications like oral antihyperglycemics, beta blockers, and clonidine. Hypothermia can also be caused by infection, low blood sugar, adrenal insufficiency, hypothyroidism, or an overdose. So keep those in mind if you're seeing people that have measured hypothermia. So this gives you an idea of the wind chill here. So if you have someone that's exposed to maybe cold temperatures, but not excessively cold, just looking at the thermometer, but when you combine that with wind, you can start to get into some significant increasing levels of danger. So let's say you have somebody that's working at, it's 20 degrees outside, they may be dressed warmly in what you think is appropriate for the weather, but if there's like, let's say a 30 mile an hour wind, then they're getting into way below zero temperature exposure. So you gotta keep that in mind. And this can therefore cause varying degrees of risk, even from morning to afternoon. So the various classifications or severities of hypothermia. The first one is cold stress, which is not really a hypothermia because the core temperature stays 95 to 98.6 Fahrenheit or 35 to 37 Celsius. They have normal mental status, but they're cold and shivering. They're able to care for themselves. You just get them inside and they'll warm up. Then you have mild hypothermia, where the core temperature gets down to 32 to 35. So 32 to 35 degrees Celsius, which is 90 to 95 degrees Fahrenheit for those of us who are stuck on Fahrenheit. They have shivering, tachycardia, tachypnea, peripheral vasoconstriction. They may or may not have altered mental status, but frequently they're not able to care for themselves. They need to be led inside. They need to be, you know, instructed or helped to do the measures that will help them warm up. Moderate, the core temperature gets down to 28 to 32 degrees Celsius or 82 to 90 degrees Fahrenheit. Mental status changes here, you know, predominate. They have slurred speech, loss of fine motor skills. And then you have the severe, which is less than 82 Fahrenheit or 28 degrees Celsius. They're usually unconscious. They have low heart rate, respiratory rate, low blood pressure. They may be hallucinating. They can have pulmonary edema, cardiac arrhythmias, dilated pupils. That's very, very bad. That's right before they die. You can get what's called paradoxical undressing with both moderate or severe hypothermia. That's where all of a sudden, you know, they'd been very, very cold and shivering. And now they think they feel very, very hot. And so they want to take off their clothes and their boots and just stand out there in the freezing cold weather with nothing on. So that actually makes the whole situation worse. So if you ever see that, you know, you're at least moderate, you know, you better get them warmed up and to medical assistance immediately. So what do we do about it when we see it? If it's mild, we move them to a warm environment, get their wet clothing off, cover them in blankets. They can have heating pads or hot water bottles, that kind of thing, and a forced air warming system like those blankets. They have them on most of the ambulances. If it's moderate, you do the same as the mild, but you also give warmed IV fluids and warmed humidified oxygen. For severe, sometimes they have to put them on cardiopulmonary bypass or ECMO to help warm up the core temp. If that's not available, then you can also use hemodialysis or continual arteriovenous rewarming or even peritoneal irrigation with warm saline. A lot of these people with severe, they'll have cardiac arrhythmias. You can try to defibrillate them, but it's rarely successful until the core temperature is above 86 Fahrenheit or 30 degrees Celsius. Thing to keep in mind between hypothermia, they're not dead until they're warm and dead. So you keep your resuscitation efforts going full force while you rewarm them and you continue CPR or defibrillation until the core temperature is at least 32 degrees or 90 degrees Fahrenheit, because some of these people that did not respond when their body temperature was colder will respond as they warm up. Ordinary clinical thermometers, can't measure below about 93 degrees Fahrenheit. You have to have a special low temperature thermometer for that. So if you take their temp and it's 93 Fahrenheit, well, it may be far, far lower, but that's as low as your scope. So either way, you got to get prompt emergency medical attention for them. They'll use a distal esophageal probe to measure core temperature in unresponsive people and sometimes bladder or rectal temperatures if they're not comatose. But under the arm or under the tongue does not work. So moving on to noise exposure, I will just kind of touch on this briefly since that will be covered in a separate lecture, but it can obviously cause hearing loss. It's also a general biologic stressor. So it can contribute to the development or aggravation of certain stress related conditions like high blood pressure, coronary disease, ulcers, colitis and migraines. There's some evidence to suggest it can be related to birth defects and low birth weight babies and may increase susceptibility to viral infections or the adverse effects of toxic substances. It has been used as a tactic in war to stress the enemy. So to give you a basic idea about how loud is too loud, average human conversations, probably 65 decibels. You start having a risk of permanent damage at 85 decibels. That's over an eight hour period. You start getting much above that and you start getting discomfort, pain at 160 decibels. You can actually have eardrum rupture solely from the sound there. To give you an idea of where various noises fall into that, you know, like a dishwasher is about 75 decibels. Heavy duty city traffic or school cafeteria is 85. Sometimes like people who wear earbuds or headphones, they crank those up a little too high that can go up to like 105 decibels, which is damaging their hearing long term. Jackhammers can be up to 110 decibels, and then a jet taking off is 140. And firecrackers and shotguns can be up in the 140 to 165. You can also have impulse noise. That's explosive sound that builds rapidly to a high intensity and then falls off rapidly. So things like weapon fire or artillery fire. That's detrimental to hearing when the intensity exceeds 140 decibels. So even just a 22 rifle, I can produce 140 decibels and medium to larger caliber handguns go over 175. So even if someone is just practicing, you know, at the range, they absolutely need to have hearing protection on. Sort of auditory or ambient noise induced hearing loss. It's the leading diagnosis for disability and occupationally related diseases. It's ubiquitous in the workplace and outside environment. Common exposures above acceptable levels, acceptable levels, 85 decibels on an eight hour time weighted average, a scale. I think that will be covered more in a different lecture. Smartphone apps, there are those out there for decibels, decibel meters, but they can be plus or minus 10 decibels. So it might be an okay to give you a ballpark idea that something is going on. But if you're seeing 75 decibels or above, it's probably time to get an official industrial hygienist to come in and measure the ambient noise exposure in that area. Hearing protection is needed above 85 decibels, but it's the least used form of personal protective devices in the workplace. So this can cause a lot of damage to the hearing, but people don't seem to be willing to use the personal protective equipment to prevent it. Hearing loss is caused by erosion of the nerve hair sensors in the inner ear. It's permanent, often preventable if they'd wear the hearing protection. OSHA does require that employers have a hearing conservation program and hearing protectors available in workplaces with noise levels above the 85 decibel threshold. And then all permanent standard threshold shifts are OSHA recordable. A standard threshold shift is a change from baseline of an average of 10 decibels or more averaged at the 2,000, 3,000, or 4,000 hertz in the same year. So if they're getting, because they have a hearing conservation program, they're getting regular hearing tests, and if there's a significant deviation that's not otherwise explainable by something like cerumen impaction or otitis media, something like that, then that's definitely an OSHA recordable event. Moving on to vibration. The connective tissue that binds the major organs together reacts to vibration in the same way as springs. When the body is subject to certain frequencies, the tissue and organs will begin to resonate, and that increases the amplitude. When objects reach the resonant frequencies, like when you run your finger around a wine glass and it makes a resonant noise, that increases the intensity with each oscillation. Without any kind of shock absorption, that vibration will damage the structure or organ. Specifically when you're looking at the hands and arms with chronic vibration exposure, there's a thing called hand-arm vibration syndrome. It comes from the repeated or prolonged use of vibratory tools, including things like sanders, grinders, polishers, hammer tools or drills, chainsaws, hedge trimmers, powered mowers. The most damaging frequencies are usually in the 125 to 300 hertz range, and an industrial hygienist can put an accelerometer on a piece of equipment and figure out the hertz frequency on that. The symptoms can manifest days to years after starting the job duties, so it's not something that would happen right away, all the time. There's increased risk when they use hammer tools, like hammer drills, for more than 15 minutes a day, or other vibratory tool types for more than an hour a day, and also smoking contributes to this as well. So what to look for? It starts out usually as tingling and numbness, decreased sensation, decreased strength or dexterity, pain or discomfort anywhere from fingers all the way up to the elbows. And they can also, in the later stages, get Raynaud's phenomenon, which is also called vibration-induced white fingering. You can see the picture of that there. They'll have digital vasospasm that's usually temporary, but we'll turn the fingers, blanch them white. Hand-arm vibration injury and carpal tunnel syndrome are not the same thing, even though they have a lot of overlapping symptoms with pain, discomfort, numbness, tingling. But carpal tunnel syndrome is a potentially reversible compression of the median nerve, usually due to swollen tendons, whereas the hand-arm vibration syndrome is an irreversible peripheral neuropathy caused by the vibration. So it does not get better with treatment, and really the only treatment they have is halting the progression by eliminating or drastically reducing the exposure to vibration. Prevention is also emphasized using things like engineering controls, like vibration dampening gloves and tools, trying to limit the exposure to vibration whenever possible, and also trying to take a 10-minute break per hour from vibratory tools. There's also whole-body vibration injury. This is repeated or prolonged exposure from things like driving or riding in vehicles on uneven terrain or with very poor suspension, you know, the seat that bounces up and down a whole lot. Earth-moving machines, jackhammers, those are also implicated in the hand-arm vibration as well. Or standing or sitting on a structure that's attached to vibrating machinery. Acute symptoms include things like fatigue, headache, loss of balance, back pain, or just feeling shaky. Unfortunately, these are all kind of nondescript, but chronically, it contributes to lower back pain. There's some evidence it also contributes to peripheral neuropathy and may be a link to certain GI, female reproductive, vestibular, and peripheral vascular problems as well, though that's not as well-established as the back pain. All right, moving on to altitude. Humans can adapt to changing pressures and high altitudes, but we can't adapt quickly. The biggest effect is on hollow organs and gas transport capability. This comes into play in aviation space industries, scuba diving, mining, and tunneling. This is, if everybody thinks back to medical school, the oxygen-hemoglobin dissociation curve. So, basically, if you're at sea level, which is all the way here on the right, and you've got, you know, your hemoglobin is getting pretty well saturated with oxygen, and you're in that 96 to 100 range and all as well. As you start to go up to things like 8,000 feet, now you're starting to get, you know, down to 92% O2 sat, and then you get up even higher to 15,000 feet, and it's going down to 80. So, when you start really getting above 8,000 feet, that's when you start seeing a lot of these altitude-related illnesses. So, when we talk about high altitude, very high altitude, and extreme altitude, what we are talking about high altitude starts about 5,000 feet and goes up to about 11,500 feet. Very high is from there up to 18,000 feet, and extreme altitude is 18,000 feet and over. So, I'm talking about altitude sickness, also known as, like, mountain sickness, and then certain parts of the world it's called Seroche or Puna. About 20% of people that go above 8,000 feet in less than one day develop some form of altitude sickness, if they're not acclimatized to it. Most people acclimatize to altitudes of up to 10,000 feet within a few days, but the higher the altitude, the longer that it takes. Above 17,000 feet, deterioration starts to get rapid. No one really can live at that altitude permanently. I think the highest village or city in the world is 16,000 feet, and most of the people that live there have genetic capacity to respond to the altitude a lot better and have definitely acclimatized. Features of the acclimatization include you get sustained hyperventilation, so you're breathing fast, with partially compensated alkalosis. You get an initial increase in cardiac output, increased RBC in the peripheral circulation, and increased tolerance for anaerobic work. All right, talking about acute mountain sickness, or AMS. This happens one to 24 hours after arrival to a high altitude. Can manifest as headache, lightheadedness, malaise, anorexia, maybe nausea, less commonly vomiting, but those get frequently disturbed sleep, like waking up a lot. This usually resolves within one to three days, as long as they don't go to a higher altitude. Some people will prophylax with acetazolamide. That can be started before ascent if the person is moderate to high risk, but isn't really needed if they're lower risk. Treatment with acetazolamide is also done, but there's not much data on the efficacy with that. Okay, talking about high altitude cerebral edema. This is a much more significant and life-threatening than the acute mountain sickness. This usually doesn't happen until you get to about 9,800 feet or so. People can get ataxia, lassitude, declining mental function and consciousness, and abnormal coordination. When you see encephalopathic type of symptoms, descent is the definitive treatment. Even going down 1,000 meters, they don't have to go all the way down to sea level, but even going down 1,000 meters can save their life. Dexamethasone, oxygen, and hyperbaric therapy can be used until evacuation can take place, especially if you're in a remote area, but it's really not at all a substitute for descent. Descent really is what's needed to treat this. The most life-threatening of all the high altitude syndromes is called HAPE, or high altitude pulmonary edema. This can happen two to four days after a rapid ascent over 8,000 feet. It usually starts out with a mild, non-productive cough, sort of looks like a benign upper respiratory infection. They'll have some dyspnea on exertion that can often be attributed to normal breathlessness at altitude, but the hallmark of this becoming more than just a nuisance is an early progression from dyspnea on exertion to dyspnea at rest. The cough can then become productive of a pink, frothy sputum or sometimes even frank blood. They can have low-grade fever, tachycardia, tachypnea, hypoxia, inspiratory rails, which for some reason start in the right middle lobe and then become more diffuse. Descent again is the definitive treatment, but you also need to give supplemental O2, hyperbaric therapy if it's available. Some medications have been used like nifedipine, tadalafil, sedenafil, and dexamethasone and even salmeterol. They can be useful, but there's not a whole lot of data on their efficacy in general. All right, barotrauma. When you take off in a regular commercial airliner, the cabin pressure is equivalent to about being up in the mountains about 5,000 to 8,000 feet. At such pressures, the free air in body cavities expands by about 25%, so that includes things like little air pockets around the teeth and in the middle ear and in the sinuses and even the gut. Upper respiratory inflammation or allergy can result in obstructed eustachian tubes and may result in the barotitis mediae or barosinusitis, but this is basically why babies cry during takeoff and descent because they can't open their own eustachian tubes and they have a lot of pressure in their middle ear. At the other extreme, when going underwater, a diver 33 feet down, only 10 meters down, is exposed to a pressure of about one atmosphere higher than the barometric pressure at the surface. So the total pressure when they're down 33 feet is two atmospheres, which is the weight of the water plus the weight of the air on top of that water. Every additional 33 feet they descend adds another atmosphere of pressure onto them. When you get people that are working in tunnels or caissons underground or in deep water, and compressed air is used to keep water from the work site, that reflects the pressure of the water outside. So even if they're down in a tunnel, if they're 100 feet underground in a tunnel, they're still under significant pressure and they should not rapidly ascent. Slow decompression back to one atmosphere is essential for preventing illness. Some of the complications that you can get with rapid ascent are an arterial gas embolism. It can be life threatening when it gets in the cerebral coronary or pulmonary arteries. It can also affect the function of other organs, such as liver, kidneys. You basically figure you're denying certain sections of these organs oxygen containing blood because the vessels are all blocked up with air. Presentations variable. It can be subtle neurologic changes all the way to full-on cardiac arrest, but it usually begins within several minutes of reaching the surface. So it's pretty rapid. Other barotraumas that can happen, one's alveolar rupture, which is actually not from an arterial gas embolism. This can be from holding breath on ascent or less commonly descent. That can cause pneumomediastinum, subcutaneous emphysema, and pneumothorax. You figure if you're holding your breath on ascent, if you've got a big lung full of air at 30 feet down or 60 feet down and you don't let that out, it's going to expand as the pressure around you decreases and so can actually pop some of the alveoli. The ear barotrauma can happen with everything from pressure or pain in the ears to hearing loss or ruptured eardrums. Acute unilateral TM rupture while diving. So if somebody goes down and their TM ruptures while diving, they can get vertigo, nausea, and disorientation, almost like you gave them a cold caloric because cold water will run into their ear. And so that can actually be life-threatening because they can no longer manage their dive and they will need assistance. You can also get inner ear barotrauma, like rupture of the round or oval window, giving you a fistula there that can give you tinnitus, vertigo, or hearing loss. You can also get sinus barotrauma, like headache, epistaxis, localized sinus pain, rarely pneumocephalus where it actually, you'll end up with air around the brain. And you can also get dental barotrauma, there are sometimes little air patches around the roots of the teeth and that can cause toothache or sometimes breakdown of the tooth itself. Decompression sickness. That usually begins within three hours of surfacing, so it doesn't always have to be right away, but it can present up to 24 hours after coming back up from a significant depth. They always say to wait 48 hours to fly after scuba diving because otherwise it's like going from a deep depth all the way to the top of a mountain, which is not good. You can get gas bubbles that form from the dissolved nitrogen and other gases in the blood that were fine at a deeper depth and higher pressures but are not good as the pressure gets lower. You can get everything from localized joint pain, paresthesias, weakness, urinary retention, memory loss, ataxia, visual changes, changes in speech or personality or affect, pruritus, a scarlet tinniform rash, mottled skin, lymphatic obstruction, cardiopulmonary symptoms, so pretty much anything that happens that looks really abnormal after somebody comes up from diving even up to 24 hours afterwards, you've got to assume that it's related to decompression sickness and they need to be in the hospital ASAP. If you see any patients, if you have any clients that have divers or people that work underground or in caissons or tunnels, that kind of thing, and you're seeing anybody that you're concerned about a decompression illness or a barotrauma, you can call 24 hours a day the Duke University Divers Alert Network and there's their phone number and they have experts that can help you manage that patient. Moving on to physical traumas, the workplace has got a lot of directly hazardous processes and operations. You can have falls, crush injuries, lacerations, lifting, contact with moving objects are the most common. Eye foreign bodies are the most common occupational eye injuries and you can also have workplace violence either from one employee to another or domestic violence that spills over into the workplace. I'm talking about personal protective equipment. This could be a whole lecture in and of itself, but one thing I commonly see from physical hazards that is involved in this is pieces of metal getting into eyes or eye foreign bodies. I get a lot of people that grind or weld on metal and when you talk to them about what they're actually doing for their PPE, it's often insufficient. So if they're wearing a face shield and safety glasses, that's good. This guy's doing it the right way here on the left. I get an awful lot of people that will just wear the safety glasses and no face shield and they'll get a piece of metal that'll come off of that grinder and it'll go up underneath the bottom rim of the safety glasses or around the side because there's a gap there and it'll end up in their eye. And a lot of these people will chronically not use eye protection correctly, even though this is their third or fourth episode of having a metallic foreign body in their eye. I don't know what the guy on the right was thinking, but I guess, you know, plastic buckets the same as safety glasses and a face shield, right? Here's your nail gun injury, so that's more of a penetrating ocular injury that absolutely has to be, do not pull that out, that has to be managed by ophthalmology. Then you can also get pieces of metal that end up in the surface of the eye, the cornea, the conjunctiva, under the lids, that sort of thing, but you can also get a piece that goes and penetrates into the eye. If you've got any concern for like a penetrating eye injury of anything, it's usually metal, so get an x-ray. If it's non-metal, you'll need MRI or ultrasound to see that. Non-select electrical burns and electrical injuries, these burns are the most common at the site of electrical contact, so the sort of body area that comes in contact with the wire or current and in areas that have been in contact with the ground at the time because it goes through the body and into the ground. The degree of the external injury of these electrical burns is not indicative of the degree of the extent of the internal damage, so you can have a pretty mild-looking skin burn, but really significant internal injuries along the path of that electricity as it went from the source down into the ground. So that's especially true with low-voltage injuries. You can also get things called a kissing burn. This occurs at flexor creases like the elbow or underneath the arm where the skin surfaces adjacent to a joint touch and the current will sort of skip over there instead of going all the way through the joints, it'll sort of skip over to the skin there and you'll get external evidence of the path of that electrical current. The type of current affects the severity of the injury. DC current tends to cause convulsive contraction of muscles, often forcing the victim away from the current source. Their muscles contract and it can break the circuit at that point, so it can be a lower duration exposure. AC, alternating current, which is usually household current, produces muscle tetany, which often freezes the hand or the body to the current source. So you can get somebody that's almost stuck there with the current going through their body and down to the ground. Anybody that touches them while they're doing that without something that's insulated to protect them can be also affected by that same electrical current. Electrical injury, particularly from alternating current, can cause immediate respiratory paralysis, V-fib or both, so it can be pretty serious. The higher the volts in the amps, the greater the damage from either type of current. If you get electrocutions, arrhythmia is present in approximately 15% of these. It usually manifests either immediately or within the first few hours, but actual, like myocardial infarction caused by an embolism, that's pretty rare. It can also affect the kidneys because you can get rhabdomyolysis due to massive tissue necrosis and acute kidney injury. You can get a variety of neurologic problems like loss of consciousness, weakness, paralysis, respiratory depression, autonomic dysfunction, memory problems. You can also get peripheral nerve involvement with sensory and motor deficits, and those sensory and motor deficits don't have to correspond to each other, so it doesn't have to affect the same nerve. You might have sensory damage in one nerve and motor damage in another. The clinical symptoms, sometimes from the high voltage exposures, can be delayed for days to months after the injury. You can also get a variety of issues with eyes, ears, circulatory and musculoskeletal system. Don't forget to look for other injuries in cases of full-on electrocution, such as fractures and head injuries sometimes caused by associated falls or striking nearby objects on their way down. If you have somebody coming in to see you that's asymptomatic after a low voltage exposure with a normal physical exam, you know, you see them in your clinic, they can be reassured they've been discharged. Mild symptoms or minor skin burns, as long as they've got a normal EKG and a normal UA, which doesn't show any hemoglobinuria to suggest they're getting rhabdo, they can be observed for a few hours and discharged. If you get high voltage, like over 1,000 volts, or those patients that come in with, you know, they have chest pain, a documented loss of consciousness, they have an arrhythmia, history of cardiac disease, those should really be admitted to the hospital for cardiac monitoring for 12 to 24 hours. And then obviously anybody that has significant other injuries, those should be managed inpatient or outpatient, depending on the severity. Thank you everybody for listening. It's good to know we've got job security due to people like this.

workplace hazards

fatal injuries

thermal hazards

heat-related illnesses

cold-related injuries

noise exposure

vibration impacts

altitude risks

personal protective equipment