Module 3 - Physiology and Medicine of Diving and Immersion Flashcards
What are the types of Hyperbaric Exposures?
- SCUBA diving
- Rebreathers
- Umbilical (surface supply) device
- Hyperbaric Chamber Exposure
- Breathhold/Free Diving: Pearl Divers; Syncro Swimmers
Describe SCUBA Diving
Breath air or gas from a tank and it goes to the environment
- Open Circuit
- Expired Gases Released
- Bubbles
Describe Rebreathers
Uses Same gas, more than once, good for stealth
- Apparatus
- Closed Circuit
- No Bubbles Exhausted
- Rarely used by Civilians
Describe Umbilical/Surface Supply diving
old-timey diving
- connection from diver and ship
- air pumped from above water
- exclusively used by commercial divers
- long duration
Describe a JIM suit
Mix between exoskeleton and personal submarine
- surface rigid
- pressure inside different from pressure outside
- Dexterity and mobility reduced
Describe Free Diving
- Single Breath
When is Free Diving used?
- Competition: athletes
- Commercial: spear fishers, pearl divers
- Recreational
Describe Boyle’s Law
- Pressure of given mass of ideal gas is inversely proportional to its volume at constant temperature
How does Boyle’s Law relate to diving?
- Deeper dive = increased pressure = decreased volume
- every 10m of depth increased in pressure by 1atm, volume decrease by 1/2
- on the way up, it is reverse
- Density of gas remains the same
What is Shallow Water Blackout?
- Passing out in water and drowning
- Results due to low O2
How does Shallow Water Blackout Occur?
O2 decreases below the threshold for consciousness before CO2 increases above the threshold for the urge to breathe
- Hyperventilation before diving: Reduces CO2 in blood
- Diving deep: increases pressure, increases O2 in blood
- On the way up Pressure decreases, O2 decreases and you pass out
How do you avoid blackout?
- Never Swim Alone
- Never ignore urge to breathe
- Certified lifeguard on duty
- Do not attempt long or competitive kicks for any reason
- Only perform underwater training activities with proper supervision
- Never compete with other swimmers to see who can swim the farthest underwater
- Never play breath holding games
- Never hyperventilate before performing underwater swim or kick
- Proper buffer time between training
What is the common term ‘squeezes’ referring to?
- Hyperbaric Trauma
- Pressure Injury
Describe a Mask Squeeze
- pressure difference between Scooba Mask and ambient pressure
- Blood squeezes outside of blood vessels in the eye, white part
- Does not affect vision or long-term vison
Describe Ear Squeeze
- Pressure difference between the middle and outer ear
- Outside tympanic membrane: ambient pressure
- Inside tympanic membrane: different pressure
- Eustachian tube: allows for pressure equalization
What are the risk factors of Ear Squeeze?
- Upper respiratory infection
- Difficulty clearing ears
What is the main symptom of Ear Squeeze?
- Pain
Describe a Sinus Squeeze
- Poor communication to nose
- Congestion, edema, bleeding
When does a Sinus Squeeze occur?
- Infection; edema; or swelling
- Interference in communication with sinus and nasal pharynx
Describe Skin Squeeze
- Dry suit seals to wrist, neck and ankles
- Volume decreases with depth
- Suit presses against the skin
When is a dry suit used while diving?
- in Cold Water
- To keep you dry
How can Skin Squeeze be reduced?
- Better technique
What is pulmonary Barotrauma?
- Pressure injury in the lung
What are the two types of Pulmonary Barotrauma?
- Pneumothorax
- Arterial Gas Embolism
What happens when you go up to fast in the water when diving?
- Air expands and can burst lung
Where can air expand and damage the lung when rising to fast when diving?
Alveolus
- Into Capillary: Arterial Gas Embolism
- Into Mediastinum or Pleural Cavity: Pneumothorax
What is a Pneumothorax?
- Collapsed Lung
What is an Arterial Gas Embolism?
- Air Bubbles in the blood
What is a Pulmonary Embolism?
- Clot that gets lodged
What can happen with Gas trapping? What can it lead to?
Pulmonary Barotrauma
- No gas exchange: hypoxic
Describe the facts of Arterial Gas Embolism
- Sometimes called Air Embolism
- Kills 5% of divers immediately
- 50% will completely recover
- Symptoms depend on tissue affected
- Extremely Variable
How does Arterial Gas Embolism occur?
- Bubbles of air leave alveoli
- Enters Arterial Side
- Travels throughout body causing blockages to blood flow
How do 5% of divers die immediately when they get an Arterial Gas Embolism?
- Cardiac Arrest
What are the different types of symptoms for Arterial Gas Embolism?
- Cerebral: Numbness; weakness; altered consciousness; poor cognition
- Cardiac: Cardiac Arrest; Myocardial Infraction
- Other Organs: Aspiration; Altered Laboratory Enzymes
What are the prehospital treatments of an arterial gas embolism?
- emergency evacuation
- Oxygen: increase temporary oxygen can lessen hypoxia
- Positioning Trendelenburg: Position head down, bubbles against gravity
- Treat near-drowning if necessary
- Fluids (IV if possible): improve blood flow
What is the treatment for an Arterial Gas Embolism at the hospital?
- Use Recompression Chamber
- Increase pressure to allow bubbles to decrease in volume
What are the parameters for the recompression chamber?
- Typically 2.8-6atm of pressure
- 100% O2
- Resolubilizes the bubbles
- Variety of different protocols
What are the causes of decompression sickness?
- Formation of bubbles of inert gases in the bloodstream
- Occurs upon ascent/depressurization
How does Decompression Sickness happen?
When diving
- Nitrogen dissolves in blood at high pressure (deep depths)
When Returning to the Surface
- Very small bubbles that come out of solution
- Get lodged in small vessels in the bloodstream
What is similar between Pulmonary Barotrauma and Decompression Sickness? What is different?
Both
- Bubbles end up in the bloodstream
- Dangerous
Pulmonary Barotrauma
- Bubbles come from lungs
Decompression Sickness
- Bubbles dissolve out of solution (bloodstream)
What is Henry’s Law?
- The amount of gas that will dissolve in the liquid relates directly to the pressure of the gas
What are the symptoms and signs of Musculoskeletal Decompression Sickness?
Symptoms
- Joint Pain
- Tingling
- Numbness
- Swelling
Signs
- Tenderness
- Pain with joint motion
What are the symptoms and signs of Neurological Decompression Sickness?
Symptoms
- Back Pain
- Abdominal Pain
- Weakness or Paralysis
- Urine Retention
- Incontinence
Signs
- Decreased Sensation
- Weakness
What are the symptoms and signs of Brain Decompression Sickness?
Symptoms
- Visual Loss
- Headache
- Confusion
Signs
- Disorientation
- Abnormal Visual Field Testing
What are the symptoms and signs of Cutaneous Decompression Sickness?
Symptoms
- Pruritis (itchiness)
Signs
- Mottled Skin
What are the symptoms and signs of the Chokes?
Symptoms
- Dyspnoea
- Cough
- Chest Pain
Signs
- Cyanosis
- Tachycardia
- Tachypnoea
What are the symptoms and signs of Decompression Shock?
Symptoms
- Weakness
- Sweating
- Unconsciousness
Signs
- Hypotension
- Tachycardia
- Pallor
- Decreased Urination
What is the prehospital treatment for Decompression Sickness?
- Emergent Evacuation
- Give Oxygen
- Treat near-drowning if necessary
- Fluids (IV if possible)
What is the Hospital Treatment for Decompression Sickness?
- Use Recompression Chamber
What are the outcomes of Decompression Sickness Treatment?
Most patients do well
- 75% of patients become completely asymptomatic
- 16% will have residual symptoms at 3 months
What’s the best way to avoid Decompression Sickness?
- Dive Tables: estimate nitrogen build-up
- Dive Computers: Track Diving Data (shows nitrogen build-up)
What are the greatest risk factors of decompression sickness?
- Exceeding depth-time exposure limits
- Rapid Ascent
- Dehydration
- Residual Deficits from previous decompression Sickness
- Obesity
- Lung Disease
- Intracardiac Septal Defects
Is it safe to fly after diving?
- Not for 12 hours
Why might Asthma be a problem for scuba divers?
- Asthma causes airway obstruction
- Gas Trapping, can lead to pulmonary barotrauma
What are the current Guidelines for Asthmatics and Diving from the British Thoracic Society?
Do not dive if:
- Wheeze precipitated by cold, exercise, or emotion
Dive if (without medication):
- Free of Asthma Symptoms
- Normal lung Function Tests
- Normal Exercise Tests
What should asthmatics who wish to dive do?
Monitor Asthma with:
- Twice Daily peak flow tests
- Refrain from diving if symptomatic
- Refrain from diving if Peak Flow rates < 90% normal
What is common about all the epidemiological evidence for the risk of asthma during diving?
- low quality
- potential for bias
What is Immersion Platypnea?
- Combination of upright status, immersion and exertion
- Platypnea = shortness of breath, relieved when lying down
What is Immersion Pulmonary Edema thought to be caused by?
- Exercise and immersion-induced increase in pulmonary artery pressure
- overpressure and leakage
What is thought to exacerbate Immersion Pulmonary Edema? why?
- Cold water
- Immersion
- Exercise
Why? - Raise in Pulmonary Artery Pressure
What are the Symptoms of Immersion Pulmonary Edema?
- Cough
- Dyspnea
- Haemoptysis
- Hypoxemia
- Loss of Consciousness
- Death
Why does immersion impact pulmonary edema?
- Blood pools in core
- Increases pulmonary artery pressure
What are the Risk factors of Immersion Pulmonary Edema?
- Heavy Exertion
- Cold Water
- Immersion
Who gets Immersion Pulmonary Edema?
- Healthy Divers
- Swimmers
- Some Special Forces
What conditions can lead to immersion pulmonary edema?
- Short to prolonged exposure
- Cold to thermoneutral temperature
What are some Facts about Immersion Pulmonary Edema?
- 197 cases now reported in literature
- SCUBA divers, breathhold divers, military swimmers and triathletes
- Surface to 72m depth, all temperature ranges (2-25Degrees)
What is the treatment for immersion pulmonary edema?
- Nifedipine reduces La threshold and peak power in athletes
- Dexamethasone - prohibited substance
- Salmeterol (LABA): potential for alveolar fluid clearance
- Sildenafil (Viagra): shown reduce in PAP in IPE susceptibles
- All proposed treatments
What’s the difference between Decompression Illness and Decompression Sickness?
Decompression Illness
- Overarching term that covers both decompression sickness and arterial gas embolism
How can you prevent Decompression Illness and other conditions?
- Follow dive tables
- Avoid Rapid Ascents
- Decompression stops on all dives: go up slowly, take stops
- Never hold breath will diving: like an expanding balloon
- No Flying after Diving
