Diving Physiology

Objectives Identify the primary components of air. Discuss the processes of respiration and circulation. Identify the breathing stimulus. Describe the proper breathing pattern for a scuba diver and explain why. Describe three improper breathing patterns for a scuba diver. Identify the breathing gas you will be trained to use for scuba and explain why. State the cause, prevention, signs/symptoms, and first aid for: Decompression sickness (Bends), Nitrogen Narcosis, Air Embolism, and Over-Exertion.

Components of Air Nitrogen Oxygen Miscellaneous gases Metabolically inert Makes up approximately 79% of the air we breathe Oxygen Metabolically active Makes up approximately 20% of the air we breathe Miscellaneous gases less than 1%

Partial Pressures Each component gas of air exerts its own pressure. The pressure of each individual gas is referred to as the partial pressure of the gas. The sum of the individual gas pressures represents the total pressure of the gas. The effect of the gas on the diver is determined by the partial pressure of the gas. Your regulator delivers the gas you breathe at ambient pressure and volume. At depth the mixture of the gas you breathe remains unchanged, the partial pressure of each of the component gases in the mix increases.

Effects of Partial Pressure The increased partial pressure of the component gases in the air you breathe at depth explains why divers must be concerned with: Decompression Sickness (DCS) Nitrogen Narcosis (Narc’d) Oxygen Toxicity (OxTox) Carbon Monoxide

Respiration/Circulation Air taken into lungs 02 absorbed into blood by Hemoglobin 02 carried to body Used and converted to CO2 CO2 carried to lungs where it is eliminated by respiration.

Breathing Stimulus Excess CO2

Breathing Patterns Proper Breathing Pattern Deeper and slower than normal. Overcome resistance of dense air and regulator or snorkel Provides a calming effect

Breathing Patterns Hyperventilation Panting Skip Breathing

Breathing Gas Air 02, CO2, CO and other contaminants can be toxic. 21% 02 02, CO2, CO and other contaminants can be toxic. Fill your cylinder only with air from a reputable air fill station. Breathe only gases you have been trained to use.

Contaminated air Indications Any smell Any taste Any texture Do not dive until the problem has been identified and corrected.

Decompression Sickness Other Names DCS Bends Taking a hit Niggles Throwing a bubble

Henry’s Law Gas solubility: The amount of gas that dissolves in a fluid increases as the pressure of the gas in contact with the fluid increases. This process continues until equilibrium is reached. The reverse is also true; as the pressure of a gas in contact with a fluid decreases, the amount of gas dissolved in the fluid decreases to the point of equilibrium.

DCS cont Bubble Formation: Decompression: If the pressure of a gas dissolved in a fluid is released too quickly, bubbles form within the fluid. Decompression: If the pressure on a gas dissolved in a fluid is released gradually, excess gas can exit the liquid without bubbles forming.

DCS cont Application to scuba: Cause of Decompression Sickness Scuba divers absorb N2 at increased pressure N2 pressure within the diver increases. If the scuba diver ascends too quickly, N2 bubbles can form within the blood. This can lead to Decompression Sickness (DCS or Bends). Cause of Decompression Sickness Ascending too quickly Too deep for too Long

DCS cont Prevention: Observe time and depth limits Adhere to proper ascent rates 30 feet per minute Include safety stops at the end of your dives

Residual Nitrogen Time Residual Nitrogen Time (RNT) N2 remains in the body for up to 24 hours after a dive RNT must be accounted for on all repetitive dives Rep dive = any dive made within 24 hours of a previous dive

DCS cont Skin rash Weakness Paralysis Staggering Slurred speech Coughing Shortness of breath Unconscious Skin itch Joint or limb pain Unusual fatigue Numbness/tingling Chest/abdominal pain Incontinence Headache/dizziness Nausea

DCS cont Onset Typically within 20 minutes-2 hours post dive May not show up for several hours

DCS cont First Aid Treat for Shock First aid as necessary Provide 100% 02 Contact Emergency Medical System Arrange transport to a recompression chamber as appropriate/necessary

Entry bay to Catalina Hyperbaric Chamber

Inside of hyperbaric chamber

DCS cont Contributing Factors Poor physical condition Reverse Profiles Strenuous exercise during or post dive Dehydration/Alcohol Fatigue Repetitive/multi day diving Cold Hot tubs post dive Altitude

There is never a guarantee you will not get DCS!

Nitrogen Narcosis Other Names Narced Rapture of the deep

Narcosis cont. Cause Depth at which Narcosis occurs Narcotic effect of N2 at depth Depth at which Narcosis occurs Varies with the individual For the same individual can vary from dive to dive.

What’s Your Limit?

Narcosis cont. Symptoms/Signs Feeling of well being or euphoria (may be similar to alcoholic intoxication) Idea fixation Anxiety

Narcosis cont. Consequences Impaired performance Lack of awareness Depth Time Air Buddy Direction

Narcosis cont. Onset Prevention First Aid Sudden or rapid may worsen with time. Prevention Dive within your limits. Expand your limits in controlled settings Minimize task loading. First Aid Ascend to a shallower depth End dive if necessary

Air Embolism Other Names Embolism Arterial Gas Embolism (AGE) Pulmonary overpressure Lung Overpressure

Embolism cont. Cause Holding breath on ascent Air in lungs expands and escapes from the lungs into the bloodstream Air bubble in the bloodstream blocks blood flow to the heart or brain.

Embolism cont Unconsciousness (immediately or soon after surfacing) Paralysis or weakness Convulsions Respiratory Arrest Bloody Froth (rare) Personality change Dizziness Visual Disturbance Chest Pain Disorientation Paralysis or Weakness Death

Embolism cont Onset Prevention Typically immediately after the dive Breath normally at all times Never hold your breath especially during ascent This is most critical between 10 feet and the surface

Embolism cont Contributing Factors First Aid Rapid ascent Breath-holding Lung congestion Asthma Lung damage or history of lung collapse Other air trapping conditions First Aid Treat for Shock First aid as necessary Provide 100% 02 Contact Emergency Medical System Arrange transport to a recompression chamber as appropriate/necessary

DAN is the clearinghouse for diving medicine. Diving medicine FAQ Membership Insurance supplement Student insurance http://www.diversalertnetwork.org/membership/student/faq

Overexertion Causes Poor buoyancy control Diving overweighted Exceeding you limits Environmental conditions (surf, surge, current, surf)

Overexertion cont Indications Unable to keep up with buddy Fatigue Cold Gasping for breathe Muscle cramps

Overexertion cont Prevention First Aid Know your limits and dive within your limits Practice good buoyancy control Wear the proper amount of weight Stop and rest before you are exhausted First Aid Stop and rest until recovered. End the dive.

Dehydration Cause Symptoms Breathing dehumidified air from cylinder Dry mouth Thirst

Dehydration cont. Prevention First Aid Drink plenty of water 2 liters a day plus 1 glass for each 20 minutes of exercise or each dive First Aid

Divers Dieresis Cause Symptoms Increased pressure on body while diving Body withdrawing blood to core to preserve core temperature Symptoms You will feel the need to urinate more frequently than normal while diving

Ear Injuries While decompression sickness and lung overpressure are the most serious scuba maladies, ear injuries are the most common. Descents should be performed feet first through the first 10-15 feet and slowly to allow time to equalize.

Summary Air is a mixed gas Each component of air exerts it’s own partial pressure Because your regulator delivers air at ambient pressure and volume the, at depth the pressure of the gas is increased. DCS, Narcosis, and 02 toxicity can result from increased partial pressures.

Summary cont. Breathe only gases you are trained to breath. Air embolism can result from air expansion while holding your breath on ascent. Breathe normally at all times. Ear injuries are the most common injuries in scuba. Descents should be feet first and slow.