KIN 3304: Diving Physiology

-Air only exerts 14.7 PSI -At sea-level, we are exposed to about 14.7 psi of pressure. This means that each square inch of our bodies has the equivalent force of about 14.7 pounds pressing on it.

◦ Water is about 800x more dense than air. ◦ The pressure we feel exerted on our body in 10 miles of air is equaled by a mere 33 feet of sea water. ◦ For every 33 feet, we get 1 atm. ◦ Pressure is main factor when discussing diving.

◦ Results from a reduction in the ambient pressure surrounding a body. ◦ 3 types: ▪ DCS- Decompression Sickness ▪ AGE- Arterial Gas Embolism ▪ Lung Over-expansion Injuries

◦ AKA Caisson disease, “the bends” ◦ 2.8 cases of Caisson disease per 10,000 dives. ▪ Males have a 2.6 times greater risk to get than females( usually because males are more stupid and try dumb things)

Most divers breathe air when they go underwater. This results in increased concentrations of nitrogen dissolved in the blood and tissues of the diver. If a diver spends sufficient time at depth, the blood and tissues will have elevated concentrations of dissolved nitrogen in them. These nitrogen molecules are "held" in the blood by the ambient pressure acting on the diver's body at depth. If the diver were to suddenly ascend to the surface, the pressure which "held" the nitrogen in solution would be greatly reduced. In this situation, the nitrogen molecules would either form bubbles, or (more likely) cause pre-existing and harmlessly small "microbubbles" in the blood to grow large enough to cause problems. Whether these bubbles cause harm directly by blocking blood flow in capillaries, or by causing clotting via the complement system, it seems almost certain that the bubbles are ultimately what leads to decompression sickness.

Builders who made Brooklyn Bridge would have to go down the caisson cylinder-like structures that were in the water. Although they weren't diving underwater, they still felt the pressure the water put on the caisson structures. Once they would come back up to the surface the pressure change and nitrogen bubbles would cause the symptoms of DCS or the bends.

That's because nitrogen bubbles blocking circulation in the small veins of joints (elbows, knees, shoulders) cause pain that a diver may seek to relieve by bending those joints

All cases of decompression sickness should be treated initially with 100% oxygen until hyperbaric oxygen therapy (100% oxygen delivered in a high-pressure chamber) can be provided -This device works by gradually increasing and then decreasing air pressure around the body, which forces gas bubbles to dissolve.

▪ An embolism is anything in blood stream that can block blood flow. ▪ AGE then is → a bubble on the arterial side., that can therefore, block blood flow to parts of the body such as the brain, and will eventually cause a stroke. Causes: most often by the expansion of respiratory gases during ascent, it also occurs when the breath is held during ascent from a dive

▪ Pneumothorax – rupture of a lung into the pleural cavity collapsing the lung either partially or completely. ▪ Mediastinal Emphysema – air is trapped in center of the chest pressing on the heart and major blood vessels. • Subcutaneous Emphysema – when air migrates under the skin to the base of the neck. Occurs in conjunction with Mediastinal emphysema.

◦ relatively little effect on non-divers. ◦ Bubbles can be found in lungs after dives → normally trapped by lungs and filtered out. ◦ Bubbles in people with PFO bypass the lungs and can lead to complications such as DCS.

◦ pressures incurred while diving cause gases to dissolve into the blood allowing a high percentage to reach the nervous system. ◦ The higher amount causes a narcotic effect such as euphoria or anesthesia. ▪ ^^ kind of like laughing gas (N2O) that dentists use. -Signs of nitrogen narcosis are euphoric feelings, fixations, lapses in concentration, a loss of good judgement -- all a bit similar to the effects of alcohol. The onset of nitrogen narcosis varies from person to person

◦ the air we breath is 78% Nitrogen, 20.93% Oxygen, 0.03% CO2, and 1% trace gases. ◦ Pure O2 can be lethal beyond 30 feet below sea level. ◦ Deeper depths and higher concentrations of O2 raise risk of oxygen toxicity. ◦ 2 types: ▪ Pulmonary ▪ Central Nervous System

▪ form of oxygen poisoning that directly affects the lungs ▪ rare in recreational diving, more of a concern with TECH diving ▪ Symptoms are that it begins with throat irritation, then goes to lungs, and in severe cases, causes a burning sensation in the chest → can lead to a decrease in vital capacity.

▪ more serious → CNS toxicity doesn't have a useful PO2 and time relationship. ▪ Symptoms are visual disturbances, ear disturbances, nausea, twitching, irritability, and dizziness. ▪ Most serious problems are hyperoxic seizures. This means that the victim has serious convulsions causing unconsciousness followed by repeated powerful contractions of nearly every muscle in the body, diver will eventually let go of their mouthpiece and drown.

When diving, the rising water pressure increases, according to Dalton's Law, the partial pressure of oxygen. Oxygen represents about 20% of air at sea level. However, while that percentage stays the same at depth, we inhale many more oxygen molecules. At the 130 feet dive limit for recreational divers, the number of oxygen molecules we inhale would represent 100% oxygen at the surface! Under pressure, oxygen atoms don't always combine with something else, and roam as free radicals.. Free radicals destroy enzymes, damages nervous tissue, and lead to seizures, coma, death

◦ AKA shallow water blackout ◦ lack of CO2 ◦ From either hyperventilation or unintentional (due to stress or fright). ▪ Example/ Swimming in a shallow part of a lake casually, all of a sudden, you brush against something, believing you accidentally brushed against a shark (in reality, some plant or fish) and you begin to freak out... Most common reason why people die underwater.

Hyperventilation artificially depletes CO2 causing hypocapnia. Hypocapnia reduces the reflexive respiratory drive, allows the delay of breathing and leaves the diver susceptible to loss of consciousness from hypoxia. Thus it is not the lack of oxygen that creates in us the urge to breathe, but the build-up of carbon dioxide. Normally, as the oxygen level in the blood falls, the carbon dioxide level rises and we feel a need to breathe. When diving, things can be a different. For example, a breath-hold diver may rapidly take a number of deep breaths before diving. That hyperventilation removes carbon dioxide and thus increases the period of time before s/he'll be overcome with the urge to breathe again. Once underwater, the diver may use up oxygen without feeling a need to breathe, and eventually s/he may black out from insufficient oxygen in the blood

-abnormally elevated CO2 levels in the blood ◦ usually result of over exertion, but can be from dead air spaces (in a mask or snorkel). ◦ Related to “skip” breathing → ▪ causes headaches, confusion, and a feeling of air starvation. ◦ Loss of consciousness is your body's way of resetting proper breathing, but can be problematic for divers.

◦ contaminated air can contain carbon monoxide ◦ hemoglobin binds with CO more readily than O2 (can take 8-12 hours to eliminate once in the respiratory system). Increased pressure allows oxygen to continue bonding at depth, but as the diver ascends, and the pressure is reduced, O2 binding fails and the diver unexpectedly passes out

◦ related to deep diving ◦ can happen as shallow as 300 feet but ore common beyond 400 feet. ◦ Symptoms are hand tremors, cramps, nausea, vertigo, and loss of coordination. ◦ No clear cause to why!!! BUT it does result from helium interfering with the peripheral nervous system. ◦ Can be offset by narcotic effect of using nitrogen or hydrogen.

◦ Can be a positive or negative thing ◦ Exercise more than 12 hours before diving can have a protective effect ◦ Avoid rigorous exercise immediately (within a couple hours) before or after diving. ◦ Dehydration and Fatigue can be a precursor to dive related injuries. ▪ Example// When on vacation at a beach, you drink alcohol, become dehydrated, so it's a bad idea to go diving that day. ◦ Rigorous exercise may raise the # of gas micronuclei on which bubbles form.