# First Aid/Pressure-Related Illness & Injury
## Pressure-Related Illness & Injury

Divers and swimmers alike must avoid injuries caused by changes in air pressure. The weight of the water column above the diver causes an increase in air pressure in any compressible material (wetsuit, lungs, sinus) in proportion to depth, in the same way that atmospheric air causes a pressure of 14.7 lbs per square inch at sea level. These pressure injuries & illnesses are most common in divers, but some can affect skin divers (snorkelers) or swimmers.

### Treatment

* Call EMS.
* Monitor ABCs and vitals.
* Raise the victim's legs and feet if possible.
       If there are bubbles present in the bloodstream, this will help keep them from the internal organs. Bubbles tend to travel up - away from the brain (preventing stroke) and heart (preventing heart attack).
* Recompression may be required; tell EMS that the situation involves a pressure-related injury or illness.
* If you are trained in oxygen administration and have the appropriate equipment, administer high-flow O$_2$.

## Decompression Sickness (the Bends)

As divers ascend, the pressure the water column exerts on them decreases, which decreases the solubility of gasses. Those gases will no longer stay dissolved in the bloodstream, and escape at a maximum rate. If the ascent is faster than the rate that the gases can escape from the bloodstream is, then the gases form bubbles. The location of these bubbles determines what type of decompression sickness develops; if the bubbles form in the lungs, then air embolism develops.

### Recognition

Bubbles can form anywhere in the body, but symptomatic sensation is most frequently observed in the shoulders, elbows, knees, and ankles.
This table gives symptoms for the different DCS types.
* The "bends" (joint pain) accounts for about 60 to 70 percent of all altitude DCS cases, with the shoulder being the most common site. These types are classified medically as DCS I.
* Neurological symptoms are present in 10 to 15 percent of all DCS cases with headache and visual disturbances the most common. DCS cases with neurological symptoms are generally classified as DCS II.
* The "chokes" are rare and occur in less than two-percent of all DCS cases.
* Skin manifestations are present in about 10 to 15 percent of all DCS cases.
Signs and symptoms of decompression sickness. :
| DCS Type | Bubble Location | Signs & Symptoms |
| BENDS | Mostly large joints of the body (elbows, shoulders, hip, wrists, knees, ankles) | Localized deep pain, ranging from mild (a "niggle") to excruciating. Sometimes a dull ache, but rarely a sharp pain. Active and passive motion of the joint aggravates the pain. The pain may be reduced by bending the joint to find a more comfortable position. If caused by altitude, pain can occur immediately or up to many hours later. |
| NEUROLOGIC | Brain | Confusion or memory loss Headache Spots in visual field, tunnel vision, double vision, or blurry vision Unexplained extreme fatigue or behaviour changes Seizures, dizziness, vertigo, nausea, vomiting and unconsciousness may occur |
| NEUROLOGIC | Spinal Cord | Abnormal sensations such as burning, stinging, and tingling around the lower chest and back Symptoms may spread from the feet up and may be accompanied by ascending weakness or paralysis Girdling abdominal or chest pain |
| NEUROLOGIC | Peripheral Nerves | Urinary and rectal incontinence Abnormal sensations, such as numbness, burning, stinging and tingling Muscle weakness or twitching |
| CHOKES | Lungs | Burning deep chest pain (under the sternum) Pain is aggravated by breathing Shortness of breath Dry constant cough |
| SKIN BENDS | Skin | Itching usually around the ears, face, neck arms, and upper torso Sensation of tiny insects crawling over the skin Mottled or marbled skin usually around the shoulders, upper chest and abdomen, with itching Swelling of the skin, accompanied by tiny scar-like skin depressions |

## Oxygen Toxicity

Oxygen toxicity occurs when oxygen in the body exceeds a safe level.

### Recognition

* Dizziness
* Nausea and twitching, especially on the face
* Seizures
* Unconscioussness

## Air Embolism

As divers ascend, the pressure the water column exerts on them decreases, which decreases the solubility of gasses. Those gases will no longer stay dissolved in the bloodstream, and escape at a maximum rate. If the ascent is faster than the rate that the gases can escape from the bloodstream is, then the gases form bubbles. The location of these bubbles determines what type of decompression sickness develops; if the bubbles form in the lungs, then air embolism develops.
Air embolism can also develop when a diver receives pressure damage to their lungs following a rapid ascent where the breath is inappropriately held against a closed glottis, allowing pressure to build up inside the lungs, relative to the blood. The gas bubbles can impede the flow of oxygen-rich blood to the brain and vital organs. They can also cause clots to form in blood vessels.
Gas embolism and decompression sickness (DCS) may be difficult to distinguish, as they may have similar symptoms, especially in the central nervous system. The treatment for both is the same, because they are both the result of gas bubbles in the body.

## Shallow-Water Blackout

Shallow water blackout is loss of consciousness caused by lack of oxygen in the blood towards the end of a breath-hold dive in shallow water, when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it.
The urge to breathe (more precisely: to exhale) is triggered by rising carbon dioxide (CO$_2$) levels in the bloodstream. Hyperventilation artificially depletes these, causing a low blood carbon dioxide condition called hypocapnia. Hypocapnia reduces the reflexive respiratory drive, allows the delay of breathing and leaves the diver susceptible to loss of consciousness from hypoxia.