Free diving Flashcards
What is the historial significance of free diving?
Used for hunting and gathering
Military
Sport
Physiological challenges of apnea diving
Hypoxia and hypercapnia
Extreme hydrostatic pressure
Increased gas uptake and nitrogen saturation
Body response to diving
Bradycardia
Spleen contraction
Elevated blood pressure
Vasoconstriction of peripheral vascular beds
What is bradycardia?
Reduction in heart rate
What happens to cerebral blood flow during static apnea?
Hypercapnia and hypoxia causes cerebral vasodilation (but important to manage intracranial pressure)
The spleen is innervated by
The sympathetic and parasympathetic nervous system
White pulp function in the spleen
Immunological
Red pulp function in the spleen
Erythrocyte filter and reservoir
Describe reduction in spleen volume
~20-40% reduction in spleen volume causes 3-9% increase in O2 carrying capacity of blood
Length of time Mirounga Angustirostris spend at sea
9-10 months
80-90% of that is underwater
Average dive >400m deep
Describe SaO2 levels in Mirounga
<80% for ~80% of their dive
~6.5 month/year <80%
Describe SaO2 levels in Mirounga
<80% for ~80% of their dive
~6.5 month/year <80%
Describe SaO2 levels in Mirounga
<80% for ~80% of their dive
~6.5 month/year <80%
Physiological adaptations of Mirounga
High amounts of carbon monoxide protects against intermittent hypoxia
Injury associated with deep dives
Lung squeeze
Symptoms of lung squeeze
Tightness/irritation in chest, trachea or larynx
Hemopytsis (coughing up blood, or blood stained mucus)
Cough
Dyspnea
Symptoms of lung squeeze
Tightness/irritation in chest, trachea or larynx
Hemopytsis (coughing up blood, or blood stained mucus)
Cough
Dyspnea
Describe airway when diving
5 seconds to lower into water - normal airway
10 seconds while diving - narrowed airway
5 seconds to get back to top - closed airway
Compare Bajau and Ama diver depth average
Ama - 7.5m (minimum 5, maximum 12m)
Bajau - 5m (minimum 5m, maximum 7m)
Physiological features of Ama, Bajau and elite divers
Increased lung volumes
Aortic stiffness
Spleen volume
Spleen contraction
Underwater eyesight
What we dont know about free-diving populations
Structural or functional changes to the heart
Vascular adaptation
Blood volume
Antioxidant activity
Challenges to studying indigenous divers
Time (loss of trained adaptations)
Population decline (urbanization, commercialization, migration)
Hard accessibility
Describe scuba diving
Self-contained underwater breathing apparatus that prolongs time underwater by using compressed gas
What gases are used in scuba diving
Nitrox/air; O2 and N2
Heliox; O2 and He
Trimix; O2, He, N2
Describe the deepest scuba dive
332m
9 gas tanks
12-minute descent
15-hour ascent
What is nitrogen narcosis caused by
Breathing a high concentration of nitrogen that the gas functions as a mild anaesthetic
Why does nitrogen cause a mild anaesthetic
Disruption of the ion transport channels or direct impact on receptors in the CNS
Risk factors to nitrogen narcosis
Fatigue and exertion
Hypothermia
Age
Hypercapnia
Anxiety
What is decompression sickness?
Happens during ascent, and its the release of gas in tissue. Severe outcomes related to CNS impacts.
How is DCS prevented?
Dive time
Depth
Ascent rate
Surface intervals
What does DCS effect?
Cerebral system (nausea, dizziness, convulsions)
Spinal cord (back pain, paraplegia)
Cerebellar (ataxia, vertigo)
Lungs
Inner ear
Joint
Lymphatics
Skin
Risk factors for DCS
% body fat
Older age
Poor fitness
Dehydration
Pathologies
Exertion
Diving experience (rapid ascent, repetitive dives, short surface interval)
Cold
Airline travel
Treatment for DCS
Get to a recompression chamber ASAP
What is barotrauma?
Rise or fall in pressure of trapped gas causing damage to surrounding tissue
Different types of barotrauma
Tympanic/inner ear
Pulmonary
Ocular
Sinus
Describe the 28 days spent in commercial saturation diving
Days 1-4 - compression (gradually avoid HPNS)
Days 4-21 - work phase (bell winched down to dive site daily)
Days 21-28 - decompression (very gradual to avoid DCS)
High pressure neurological syndrome occurs at what depth
> 200m, but can occur earlier
High pressure neurological syndrome is characterized by
Helium gas
Tremor
Memory/cognitive impairments
Epilepsy-like episodes
CNS hypersensitivity
High pressure neurological syndrome increases with
Increasing depth (rate of compression and individual susceptibility)
