Diving Physiology PDF

 diving physiology Photo @ ucla med  Diving Physiology – Learning Objectives The basics of circulatory and respiratory system function, especially as it relates to diving physiology. Types of respiratory injuries that can occur in diving, how to prevent them, a...

 diving physiology Photo @ ucla med  Diving Physiology – Learning Objectives The basics of circulatory and respiratory system function, especially as it relates to diving physiology. Types of respiratory injuries that can occur in diving, how to prevent them, and an overview of the treatment of them. Temperature-related injuries in diving. Pressure effects on the body, direct and indirect and the injuries that can occur from them. Criteria for fitness to dive, common areas of injury, and steps you can take to prevent injury.  The Musculoskeletal System The Skeletal System The skeletal system provides structure and support for muscles to attach to help move the body, as well as protecting the organs. Muscles Muscles help move the body and move food through the digestive system. There are 3 types of muscles: smooth, cardiac, and skeletal. Some are controlled consciously and others autonomically. Musculoskeletal System and Dive Injuries Common scuba injuries can involve tearing muscles or injuring joints by attempting to move heavy gear, strenuous in-water activities, and slips and falls.  The Nervous System Consists of: Brain Neurons (nerve cells) Spinal Cord Glial cells (nerve support) The Brain - Central hub and command center of the nervous system Uses 20% of oxygen in the blood to generate adenosine triphosphate (ATP) which controls the electrical pulses of the neurons Without oxygen to supply energy, the nerve cells can’t maintain their electrically charged state and will swell and die. If there is a lack of oxygen, the cells (brain nerves) begin to die within 4 – 6 minutes.  The Nervous System and dive injuries In instances of decompression sickness: if bubbles of inert gas press on neurons, nervous system functions may be impeded in various parts of the body can also be affected by high partial pressures of oxygen, as we'll describe in a later section. Image from Deep Sea Tech Diving  The Digestive System Consists of: Mouth Large Intestine Stomach Pancreas Small Intestine Liver Gall Bladder The function of this system is to mechanically and chemically break down food into a form that is usable by our cells. The smaller forms of the food, if soluble, can easily pass into the blood and be carried to other cells throughout the body. If not soluble, specialized proteins are utilized to transport the nutrients across cell membrane barriers.  The Digestive System and dive injuries What does the digestive system have to do with diving? The digestive system contains air spaces that can be compressed during diving. Certain diseases that may cause gastric and intestinal gas-trapping at depth could be contraindications to diving due to the danger of expansion and possible rupture on ascent.  The Respiratory System Consists of: Nose Respiration is the process of taking in and exhaling gas. Mouth Pharynx (throat) In more detail, respiration is the movement of oxygen into the cells and the transport of carbon dioxide out. It is a Larynx (voice box) crucial process for survival at the cellular level. Trachea (wind pipe) Airway Lungs  Lungs Lungs breathing  Lung Anatomy Upon inhalation, air comes into the system down the trachea, then branches into two bronchi at the top of each lung. The passageways keep dividing into smaller bronchopulmonary branches that make up the five lobes of the lungs; 3 lobes on the right lung and 2 on the left, with the heart occupying space on the left where the 3rd lobe might be. Branches divide further into bronchioles. This structural organization is an adaptation to allow for greater surface area. Small, air-filled pouches within the bronchioles are called alveoli. The alveoli are surrounded by capillaries. Alveoli and capillaries are only 1 cell thick, allowing for easy gas exchange in and out of the bloodstream.  Lung Anatomy Lungs Bronchi/ Alveoli Bronchioles Greater surface area = greater efficiency of gas exchange Gas diffusion A large difference in partial pressure from one side of the cell wall to the other, combined with THIN cell walls and HIGH surface area allow gasses to freely diffuse.  Gas exchange in the lungs The body needs oxygen for cellular respiration. Oxygen is primarily carried in the blood by the protein hemoglobin, and is transported to the rest of the body's cells by the circulatory system where gas exchange occurs at the cellular level by diffusion. This oxygen is then used, along with carbohydrates, to undergo cellular respiration and produce ATP (Chemical energy). Carbon dioxide, a by-product of this process, is carried back to the lungs via the bloodstream and exhaled.  Controls of Respiration The brain sends the signal to initiate breathing when increased levels of CO2 are detected. This can be a result of: Concentrations of CO2 in the blood over 40 mmHg. At this level the brain tells the diaphragm muscle and some of the rib cage muscles to contract. Moments of increased CO2 levels, for example during exercise. The brain receptors detect the elevated levels and signal increased ventilation rates.  The mechanical process of respiration During inhalation, the intercostal and diaphragm muscles contract, pulling on pleura surrounding the lungs. This increases lung volume and pulls air in (at a concentration of 21% Oxygen using atmospheric air, as opposed to Nitrox/Mixed gas). When those muscles relax, air is pushed out. This results in the exhalation of air that contains 15-16% Oxygen.  Circulatory Structure Consists of: Arteries are the largest blood transport channels; they branch into arterioles, and finally into capillaries. Heart This configuration allows for increased surface area, which Arteries provides more efficient oxygen transport to cells and Arterioles tissues of the body. Capillaries Veins  Circulatory Route De-oxygenated blood enters the right side of the heart via a large vein called the vena cava. It travels through the right atrium (upper chamber), then the right ventricle (lower chamber) and is sent to the lungs via the pulmonary artery. After gas exchange occurs in the lungs, the oxygenated blood moves from the lungs back into the left atrium of the heart via the pulmonary vein. This oxygenated blood then leaves the heart via the aorta through the left ventricle and travels to the rest of the tissues of the body.  Transport and Exchange of gasses Oxygen is transported in the blood via the protein hemoglobin. There is a cooperative binding process, which means that each oxygen molecule that binds, makes another bind more tightly, increasing hemoglobin’s affinity for oxygen. During activity, the gas exchange systems of the body adjust to meet the higher demands of exercise. Ultimately, heart rate increases and the depth and rate of breathing changes in order to supply more oxygen to muscles and remove more carbon dioxide. Typically in a healthy human, more alveoli are recruited for gas exchange during exercise, through larger lung volume breathing. Ultimately, longer/deeper breathes will result in better gas exchange. Being healthy and fit for diving allows the body to do this more easily.  Respiratory Fatigue The ability of our lungs, heart, and blood vessels to deliver oxygen, and the cells' abilities to extract/use it is related to our aerobic fitness level. The better the aerobic fitness, the more work the body can do without reaching its maximum oxygen processing ability; in other words, without experiencing respiratory fatigue. This means that a higher level of aerobic fitness makes you a safer scientific diver! This is particularly true under challenging environmental conditions or when performing work underwater.  Insufficient Oxygen Brain cells need a constant supply of oxygen. If oxygen levels get too low, brain nerve cell death will occur. Irreversible brain/nerve cell damage can happen in as little as 4 – 6 minutes without oxygen. If circulation (and thus oxygen circulation) slows too far or stops, consciousness can be lost in seconds. If an incident occurs underwater, you see how this could be very dangerous?! A low level of oxygen in the body is known as hypoxia The absence of oxygen reaching tissues is known as anoxia  Hypoxia and Anoxia Hypoxia and anoxia can be caused by a number of issues in diving, including being out of breathing gas underwater. Additionally, while it might seem counterintuitive at first, hyperventilation may also cause hypoxia. We'll cover this more deeply in breath-hold diving, but hyperventilation drastically increases our oxygen level and decreases carbon dioxide levels. As we just learned a few slides earlier, this decreases the brain signals to breathe, which could result in hypoxia.  Pressure Direct Effects - Descents Any gas that exists in your body will be compressed on descent. This compression effects the air spaces and the surrounding soft and hard tissues. In the next few pages, we'll examine different areas of the body commonly affected by air compression. It is worth mentioning here, and frequently throughout, that your best defense against negative effects of compression is to equalize air spaces early and often. Injuries in diving caused by pressure are termed barotraumas, or more commonly referred to as squeezes. These injuries involve physical damage to tissues in the body due to a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or fluid. Equalize early and often!  Air spaces and pressure changes Ears Lungs Teeth Sinuses Mask/eyes Exposure suit Mask/Eyes Your mask is an airspace and as you descend the volume in the mask decreases (remember Boyle's law?). To compensate for this, make sure to exhale into your mask (through your nose) occasionally on descent. If you don't, the volume decrease can cause a squeeze on your face; this in turn can injure/rupture small capillaries in your face and eyes. If these ruptures do occur, a diver may end the dive with red eyes and/or what looks like bruising around the eyes. This is often a temporary injury that will generally heal over time without medical intervention. Wear a mask that fits properly!!! Equalize early and often!  Air spaces and pressure changes Sinuses The sinuses are air passageways in our heads. They generally equalize without any action in a healthy person. In cases where there is congestion in the sinus pathways, they may not equalize as you try to descend. It is very important to not force a sinus squeeze! There are lots of delicate bones, some that you could literally bend with your fingers, in those passageways. Equalize early and often!  Sinus squeeze Symptoms of a sinus squeeze: Tightness in the cheeks, forehead, upper nose or behind the eyes Ways to mitigate a sinus squeeze: (which one(s)) a) Sudafed b) Aspirin c) Tylenol NONE OF THE ABOVE! d) Afrin Don’t dive when congested!!! Equalize early and often!  Air spaces and pressure changes Teeth/Gums If there is an airspace within or under a tooth, the pressure of descent can cause discomfort. With modern dentistry this is rarely an issue, but if you have current dental issues or recent tooth extractions, you'll want to wait to dive until those issues are resolved. Equalize early and often! @ Divers Alert Network (DAN) The ear canal A diver might first experience a little bit of pressure or discomfort, but this can quickly move to pain and injury. Equalize early and often!  Equalization Techniques Equalize early and often! Valsalva Maneuver Close off your nose (often by pinching it off with two fingers) and blow against the closed nostrils. Don't force this technique! If done too hard or for too long (aim for no more than ~ 5 seconds) it is possible to rupture the round or oval windows of the ear. Frenzel Maneuver Close of your nostrils, but then close the back of your throat and make the sound of the letter "K". Unlike the Valsalva, this will encourage the Eustachian tubes to open. Toynbee Maneuver Pinch of your nose closed in this one also, and then swallow. The muscle movement of swallowing tends to open the Eustachian tubes, while the tongue moving pushes air into them. Voluntary Tubal Opening Tense the throat and soft palate while making the first movement of a yawn, that of pushing the jaw forward and down. Middle Ear Barotrauma or Ear Squeeze If the ears do not properly equalize during descent, a pressure imbalance can occur in the middle ear spaces. This will cause tissues to swell, and fluid and blood from ruptured vessels may leak into these spaces, along with the eardrum bulging inward. This is known as middle ear barotrauma or Barotitis Media. Symptoms after the dive could include hearing loss or a feeling of "fullness" in the ear, as if you have water in them. Cease all diving until symptoms have been resolved! Typically, the injury will heal in a few days. Seek medical attention if symptoms don’t resolve. Inner Ear Barotrauma The inner ear is separated from the external world by the middle ear. It is the organ for hearing and balance. When the pressure in the middle-ear space is properly equalized, the risk of inner-ear barotrauma is extremely low. If you fail to properly equalize the middle ear, the water pressure on the eardrum transfers inward through the middle-ear ossicles to the oval windows, and the round window bulges outward. If the pressure is excessive, either the oval window or, more commonly, the round window may tear, and the inner-ear fluid may leak into the middle ear. Symptoms include vertigo, vomiting, hearing loss, and ringing in ears (tinnitus).  Ear Drum Rupture It is possible for the tympanic membrane (also known as the eardrum) to be ruptured, either with a small hole, or a larger rupture. This can be caused by large impact from the water (common in surfing and high diving), or from prolonged lack of equalization. If this rupture occurs underwater it is often preceded by strong pain from middle ear barotrauma, but followed by relief from the pain as the pressure releases. At this time the diver may suffer intense vertigo from cold water rushing into the middle and inner ear. Symptoms can include pain, bleeding, and also sometimes hearing loss. If you suspect an eardrum rupture seek medical attention, do not re-enter the water as the infection risk is high without the eardrum to protect the inside of the ear. Do not use eardrops or put anything in your ear until you see a medical professional.  Important take home messages If you are having trouble equalizing, do not continue your descent. Stop and ascend a little to relieve pressure and allow the Eustachian tubes to reopen. Do not perform forceful or prolonged equalization! The inability to equalize can be caused by poor technique, an overly fast descent, or by congestion caused by a cold, allergies, or other inflammation. During the dive, symptoms may be a feeling of pressure in the ear, followed by pain, then more intense pain if the descent continues. Diving should not hurt! If you experience pain, stop your descent immediately! If equalizing is also uncomfortable, refrain from continuing to equalize on the surface and seek medical attention. Equalize early and often!  Outer Ear Issues Infection While technically not a descent related injury, Otitis externa, or “swimmers ear” inflammation, can occur with persistent moisture in the ear canal. Symptoms include itching, pain in the outer ear and jaw, and redness of the ear. Preventative measures include using solutions to clean and treat the ear canal and taking breaks from diving allowing the ear to dry out; especially if multiple dives are planned over consecutive days. Ear Canal Vessel Rupture This is a less common injury and generally involves a hood or some kind of seal that restricts water flow in and out of the ear canal. This can cause a pressure differential and an outer ear squeeze, similar to a mask squeeze. The major symptom is minor bleeding, which is similar to a potentially more serious injury, so you should seek medical assessment before continuing to dive.  Ascent Issues - Ears/Sinuses Reverse Block When the increasing gas volume cannot escape. This can put pressure on the mechanisms of the ear and is an ascent barotrauma. This issue can be caused by taking decongestant medicines, which clear the passageways during the dive. As the medicine wears off, those same passageways become blocked/clogged again, making it difficult to properly equalize on the ascent. Alternobaric Vertigo Caused by unequal pressure between left and right ears, created by differences in equalization state. This usually occurs on ascent as opposed to descent. The brain can potentially perceive the difference in equalization as movement, causing strong dizziness.  Indirect Pressure related effects Nitrogen Narcosis Oxygen Toxicity Carbon Monoxide Poisoning Impairing effects of drugs  Inert Gas/Nitrogen Narcosis The cause of narcosis is not fully understood, but one explanation may be that cell membranes expand with inert gas buildup. This can cause an anesthetic effect by effectively “numbing” nerve cells in the brain. The narcotic effect is generally temporary and subsides quickly upon ascending, even a few feet. There is data to support that repeated exposure to inert gases under pressure creates an adaptive effect, allowing the diver to experience less nitrogen narcosis with the more “deep” dives they conduct. More research is needed on this and other aspects of this physical phenomenon. It is important for you to be aware of your mental state as well as your buddy's during deeper dives. The more in tune you are, the better you'll be able to detect slight variations in behavior that could indicate impaired judgment.  Inert Gas/Nitrogen Narcosis Symptoms: Paranoia Euphoria Dizziness Poor judgement Elation Confusion Anxiety The exact effects are different for each diver and may even vary from dive to dive. The major risk with these symptoms is that our cognitive awareness is reduced, potentially making managing breathing gas, navigation, depth, and other mental tasks difficult or impossible.  Inert Gas/Nitrogen Narcosis It is important for you to be aware of your mental state as well as your buddy's during deeper dives. The more in tune you are, the better you'll be able to detect slight variations in behavior that could indicate impaired judgment. Stick together! Watch out for each other!  Oxygen Toxicity Two Types: Pulmonary and Central Nervous System (CNS) Pulmonary toxicity involves irritation of the lungs and symptoms including coughing, burning, and other respiratory discomfort. Not common in diving utilizing standard air. Long, very deep dives on mixed gasses may be the exception, and therefore require additional training. The other instance divers may encounter pulmonary toxicity is during hyperbaric treatment.  Oxygen Toxicity CNS is a far more significant concern for divers. It has been observed at oxygen partial pressures of 1.4atm and above in active divers. CNS is a greater risk when diving Enriched Air/Nitrox, or for divers using rebreathers with breathing gas mixes higher than 21% Oxygen. CNS can cause confusion, lethargy, vertigo/nausea, tingling, irritability, dizziness, twitching of the lips or other areas, tunnel vision or flashing lights, auditory phenomenon such as ringing in the ears, and of greatest concern, convulsions. A convulsion at depth can easily be fatal for a diver. Be aware of your depth limits and any potential toxicity concerns for the breathing gas you are using.  Carbon Monoxide (CO) poisoning It is rare but possible to have carbon monoxide contamination in a SCUBA cylinder. The most common cause of this rare circumstance is combustion fumes at the intake of a dive compressor system. In the cylinder safety module, we'll detail the air standards and systems in place to reduce the likelihood of this occurrence. Carbon monoxide is dangerous to inhale because it binds 200-300 times more tightly to the hemoglobin than oxygen. Thus, it fills all the “spots” where oxygen normally binds, and the body is unable to get oxygen to the organs, eventually becoming hypoxic. Symptoms of carbon monoxide poisoning include: dull headache, weakness, dizziness, nausea or vomiting, shortness of breath, confusion, blurred vision, and loss of consciousness Smoking can also cause carbon monoxide poisoning. The exhaled breath of a smoker can have more carbon monoxide than AAUS allows in its compressed air for diving standards (!!!). Smoking is a habit that is incompatible with diving  Drugs and diving Due to the increased pressure, the effects (or side effects) of drugs, both medical and recreational, can be magnified at depth. It is wise to consult with a physician knowledgeable about diving or the Divers Alert Network if you take any new medications. Decongestants and Diving As previously noted, having decongestants wear off during a dive can put a diver at severe risk for reverse block. Never take decongestants before diving. If you are ill with congestion or experiencing allergies, you should not be diving.  Ascent injuries – Lung overexpansion Pulmonary barotrauma, or lung overexpansion or over-inflation injury, occurs when the volume of gas in the lungs exceeds the elastic capacity of the lungs, causing a rupture. This is generally caused by a diver holding their breath and experiencing a reduction in pressure (such as during an ascent), or gas pockets trapped in the lungs due to some kind of respiratory disease.  Ascent injuries – Lung overexpansion The gas from the rupture leaks into one or more of the following areas and causes the associated injury: 1. The bloodstream, specifically ending up in the arteries, causing the most life-threatening dive injury - the Arterial Gas Embolism. Similar symptoms can be caused by nitrogen bubbles from decompression sickness collecting in similar places in the circulatory system, but the mechanism of gas getting into the bloodstream is different. 2. The space between the chest wall and lungs, known as the pleural space. This can cause pressure on the lungs; resulting in partial or full lung collapse, known as pneumothorax. 3. The area surrounding the heart. This is known as mediastinal emphysema. 4. Subsurface to the skin of the upper back/chest/neck. This is known as subcutaneous emphysema. To avoid pulmonary barotrauma: never hold your breath while diving, ascend slowly, do not dive if you have a compromised respiratory system. Following the ascent rate on a dive computer while breathing normally will help prevent lung overexpansion injuries.  Air Embolism As a diver ascends, air in the lungs expands. If the diver fails to exhale sufficiently, the expanding air may rupture lung tissue (pulmonary barotrauma) and release gas bubbles into the arteries (arterial gas embolism) or elsewhere in the body. These bubbles can restrict blood flow and cause damage in the brain and other body tissues.  AGE Recognition and Treatment Arterial Gas Embolism (AGE) is one of the most serious medical emergencies a diver may experience. The signs and symptoms of AGE typically occur within 15 minutes of surfacing and may include: Loss of consciousness Confusion Convulsions Bloody froth from the mouth or nose Weakness or paralysis in the extremities other stroke-like symptoms requires immediate medical treatment contact emergency medical services and provide the diver with emergency oxygen  Pneumothorax a partially or fully collapsed lung. When too much pressure builds up inside the lung (when a diver holds his breath while ascending, for example), tissue can tear, allowing air to leak into the intra-pleural space, interrupting the negative pressure that holds the two pleural layers together. Eventually, the entire lung can collapse, resulting in rapid, shallow breathing, a bluish cast to lips, skin and fingernails (due to a lack of oxygen) and chest pain. An especially dangerous type is a tension pneumothorax. In this case, air is pressing on the heart and other structures, impeding their function.  Pneumothorax Any form of pneumothorax requires medical treatment. In some cases, a physician may insert a chest tube, withdraw air from the chest cavity and allow the lung to reinflate. If the pneumothorax is small, breathing 100 percent oxygen may hasten the resorption of gas without the need for a chest tube or invasive procedure. Unless it occurs with decompression illness in divers (where bubbles enter into the arterial system and affect the brain), pneumothorax does not require recompression. In the event of a chamber treatment, a chest tube may be required to help equalize the pressure and prevent further injury or enlargement  Emphysemas Emphysema is simply a condition where the air sacs of the lungs are damaged or there is air abnormally present in body tissues. Pulmonary barotrauma can manifest as two types of emphysemas: mediastinal subcutaneous  Mediastinal Emphysemas Mediastinal emphysema is “around the heart”. The principal symptom of mediastinal emphysema is a substernal ache or chest tightness. On occasion a diver may experience sharp pain in the shoulders, back or neck that may be aggravated by deep breathing, swallowing, movement of the neck or trunk, coughing or lying flat. Voice changes are also common.  Subcutaneous Emphysemas Subcutaneous emphysema is “under the skin”. Most often occurs in the skin covering the chest wall or neck, but can also occur in other parts of the body. Subcutaneous emphysema can often be seen as a smooth bulging of the skin and it produces an unusual crackling sensation as the gas is pushed through the tissue. Other symptoms may include sore throat, neck pain and even difficulty breathing. Subcutaneous emphysema will usually resolve in about ten days without serious complications.  More on pulmonary barotraumas Generally speaking, people with lung conditions that may increase the risk of pulmonary barotrauma are advised to avoid scuba diving. For those with underlying lung diseases, the risk of pulmonary barotrauma increases with rapid ascents, especially when conducted close to the surface, where the relative pressure changes are greatest. The administration of highly concentrated oxygen is often used as a treatment for emphysemas since it helps the body to absorb the subcutaneous air more quickly. Physicians trained in dive medicine recommend that anyone who has experienced pulmonary barotrauma be properly evaluated before returning to diving.  Decompression Sickness (DCS) Caused by the formation of nitrogen bubbles in the body after ascending from a dive. In the module about decompression theory, you'll learn about tissue compartments, M-values, and the development of modern methods for controlling our decompression risks. These topics will give you a greater understanding of the mechanisms of bubble formation. The symptoms and severity of DCS are controlled by where and how many bubbles form. In the section on Dive Injuries we'll discuss the many symptoms of DCS and the first aid treatments.  Temperature Effects on Divers The body maintains an ideal core temperature to ensure biological equilibrium (and so that cellular proteins and processes do not break down). Control for this temperature maintenance involves feedback loops between the central nervous system and the endocrine system. The body has a number of adaptive processes in place to deal with temperature changes. However, exposure to an environment that is too cold or too warm can overwhelm the body's defenses. Hypothermia Hyperthermia  Hypothermia Hypothermia is the reduction of core temperature below 95º F. Before this occurs the body will begin shivering, lose dexterity in the fingers, and potentially be incapacitated in other ways. There can also be a reduction in short-term memory and the ability to think clearly. These can all cause negative impacts on a diver's ability to manipulate gear and coordinate movements while wearing heavy equipment.  Hyperthermia Hyperthermia, or over-heating, is obviously more common in warmer climates, but can certainly occur on a warm day in temperate dive locations, especially during strenuous activities such as moving gear around or a long time spent at the surface in a drysuit or heavy wetsuit. Signs include exhaustion, flushed or red skin, muscle cramps, headache or mild light-headedness and nausea. The body attempts to normalize it's temperature by sweating, but at a certain point, it may not be able to overcome high heat exposure. Temperatures above 100º F start to become dangerous at a cellular level.  Fitness to Dive Your required dive physical examination for scientific diving screens for many of these underlying health conditions, but it is important that you consult with a physician if your medical status changes, and equally important that you make appropriate choices for your general dive fitness. Fitness - Maintaining good physical fitness levels and sufficient aerobic capacity will increase your ability to respond to the rigorous physical demands of general scientific diving and the even higher demands of a rescue situation. Rest - Get enough sleep before dive days. A well rested body and mind perform more efficiently. Hydration & Nutrition -Keep yourself well hydrated, and eat enough to keep yourself fueled for the hard work of diving. Smoking, Drugs & Alcohol -Avoid smoking and the use of substances that can negatively affect decision making while diving. Lift Carefully -Move mindfully to avoid mechanical injury from lifting heavy equipment