Diving Fundamentals and Risks: Exploring Underwater Realities

1. DON Discussion Ryan Kenney

2. Water is over 800 times denser than air. • For every 33 feet underwater the ambient pressure increases by one atmosphere • Standard atmospheric pressure is roughly 14.7 psi at sea level

3. Effect on the Human Body • The human body is mostly water, and therefore pressure equalizes naturally • Except in air cavities, such as the lungs an sinuses. • All but the ear drums will automatically equalize, so long as the diver is not congested. • Because there is no normal force acting on divers they feel weightless.

4. Basic setup

5. Mask • As light passes from one medium to another it becomes refracted • The refraction of light by a divers mask redirects the path of the light rays so that we are able to see clearly • As a side effect images become magnified, appearing significantly closer than they appear.

6. Buoyancy • “Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by an object” – Archimedes • Divers naturally displace more water than they weigh and as a result, float. • They use weights to increase their mass (and therefore weight) with a minimal increase in surface area to overcome their buoyancy.

7. BCD • Weights are imprecise and only render the diver negatively buoyant • To achieve neutral buoyancy, floating motionlessly in the water, divers fill the bladder of the BC with air.

8. Regulators • The first stage regulator, located directly on the tank, reduces the pressure of the air from 3000 psi to 1500 psi. • The primary second stage regulator and octopus reduce the pressure to match the ambient pressure • This guarantees that the lungs fully expand, without bursting.

9. Inherent problems • The deeper you go the more air you intake per breath, which shortens the dive. • A decrease in ambient pressure (i.e. swimming up) will cause the gas to expand proportionately. • This can cause an AGE or the lungs to burst. • This is why divers are taught to never hold their breath.

10. Inert Gases • With the increase in pressure comes an increase in the concentration of inert gases inhaled and then diffused into the blood stream. • If a diver ascends faster than 60ft/minnitrogenwill come out of solution, essentially boiling out of the blood. • This is known as Decompression sickness

11. Decompression Sickness • Divers refer to decompression sickness as the bends. • The bubbles resulting from the gases coming out of solution can form and migrate to anywhere in the body. • As a result symptoms vary from joint pain, to rashes, and more severe such as paralysis or even death.

12. Treatment • If the diver is still able it is recommended they descend to avoid decompression sickness. • If this is not possible 100% oxygen should be administered and the victim should be taken to a hyperbaric chamber as soon as possible. • With proper treatment very few suffer long term effects.

15. Narcosis • Nitrogen can cause problems even when in solution. • For unknown reasons high concentrations of nitrogen significantly impact cognitive function. • Divers feel a sense of euphoria and are cognitively impaired. • This is known as nitrogen narcosis.

16. Symptoms become progressively worse as depth increases. • Being “narked” is harmless, but can cause divers to make dangerous decisions as they are essentially drunk. • To relieve symptoms one need only to ascend.

17. Oxygen Toxicity • Breathing in high concentrations of oxygen at high pressure results in hyperoxia, excess oxygen in the body tissues. • Symptoms include breathing problems, changes to vision and disorientation. • Prolonged exposure can cause oxidative damage to cell membranes, collapse the alveoli, retinal detachment, and seizures. • Treatment is the same as for the bends.

18. To descend any farther than 130 ft requires specialized training. • This falls within the realm of expert and tec divers • They use special gas mixes such as such as trimix of heliox.