L3. Diving and hyperbaria Flashcards
What are the primary environmental challenges of scuba diving?
Cold, pressure changes, gas toxicity, and nitrogen narcosis
Who invented the first scuba diving system?
Jacques Cousteau
What is the physiological significance of Boyle’s law in diving?
It explains the relationship between pressure and volume, crucial for understanding gas behavior under pressure
What is immersion pulmonary oedema (IPO) and its primary cause?
A form of hydrostatic pulmonary oedema caused by immersion-induced pressure changes
How does nitrogen narcosis affect divers at depth?
It impairs judgment and motor skills due to the anesthetic properties of nitrogen at high partial pressures
What are the two types of oxygen toxicity in diving?
Pulmonary and central nervous system toxicity
What is decompression sickness (DCS), commonly known as ‘the bends’?
A condition caused by nitrogen bubbles forming in tissues during rapid decompression
What is the primary mechanism of bubble formation during decompression?
Bubbles form due to decreased pressure allowing dissolved gases to come out of solution
How does increased gas density at depth affect divers?
It increases work of breathing and exacerbates narcosis and oxygen toxicity
What is the role of hyperbaric oxygen therapy in treating decompression illness?
It recompresses and crushes bubbles while providing 100% oxygen to aid nitrogen elimination
What are the physiological effects of a rapid ascent on lung tissue?
Rapid expansion of air can rupture alveoli, leading to arterial gas embolism
What are the main gas mixtures used in technical diving?
Air, nitrox, normoxic trimix, hypoxic trimix, and heliox
What is the function of closed-circuit rebreathers in diving?
To recycle exhaled gas by scrubbing CO2 and adding O2, reducing gas consumption
What factors increase the risk of IPO in divers?
Hyperhydration, exertion, negative-pressure breathing, and cold-induced vasoconstriction
What is the significance of the oxygen window in decompression?
It refers to the partial pressure difference between arterial and venous blood aiding nitrogen elimination
How do exercise and diving interact to influence decompression risk?
Post-dive exercise reduces bubble formation; intense exercise can increase decompression risk
What is the role of endothelial microparticles (EMPs) in diving physiology?
They are released by endothelial cells after pressure changes, playing a role in inflammation and coagulation
What are the symptoms of nitrogen narcosis at depths of 50-60 meters?
Sleepiness, illusions, and impaired judgment
How does hypoxic trimix help in deep technical dives?
By replacing nitrogen with helium to reduce narcosis and oxygen with helium to mitigate toxicity
What are the long-term effects of repeated exposure to hyperbaric conditions?
Potential lung damage, neurological changes, and vascular issues
What experiment demonstrated the relationship between nitrogen bubbles and decompression sickness?
Haldane’s goat experiments showed nitrogen bubbles in decompressed tissues
What did Haldane’s studies reveal about decompression rates?
Slow decompression rates reduce bubble formation and decompression sickness risk
What are the findings about pulmonary oedema in closed-circuit rebreather divers?
Negative-pressure breathing increases susceptibility to IPO in back-mounted counter-lung systems
How does exercise before a dive affect venous gas emboli (VGE) formation?
Pre-dive exercise reduces VGE formation by improving endothelial function
What mechanisms are proposed for bubble nucleation during decompression?
Micronuclei, crevice model, and tribonucleation are leading theories
What factors were identified as major contributors to immersion pulmonary oedema (IPO)?
Hyperhydration, exertion, and cold-induced vasoconstriction were key factors
What evidence links endothelial microparticles (EMPs) to decompression sickness?
EMPs activate inflammatory pathways and impair endothelial function
What did MRI studies reveal about brain changes in divers after nitrogen narcosis?
Brain swelling and microbleeds were observed after narcosis episodes
What role do calcium channel blockers play in mitigating IPO?
They reduce pulmonary vascular resistance and mitigate IPO
What physiological evidence supports the oxygen window theory?
Lower venous partial pressures due to metabolic oxygen consumption support it
How do variations in heart rate and bradycardia correlate with diving response?
Increased bradycardia and heart rate variability occur during cold immersion
What long-term cardiovascular changes are seen in professional divers?
Increased arterial stiffness and ventricular hypertrophy were observed
What findings were associated with nitric oxide and its role in oxygen toxicity?
Nitric oxide combines with ROS to form peroxynitrite, causing oxidative damage
What did the Doppler studies reveal about VGE and ascent rate?
Higher ascent rates correlated with increased VGE formation
What adaptations reduce nitrogen narcosis susceptibility in frequent divers?
Repeated exposure improves tolerance, possibly through synaptic plasticity
How does gas density influence the work of breathing at depth?
Higher density increases resistance, making breathing harder
What experimental findings link cold-induced vasoconstriction to IPO?
Peripheral vasoconstriction increased central blood volume and pulmonary pressures
What role do RL shunts play in arterialising venous gas bubbles?
Shunts allow bubbles to bypass pulmonary filtration, leading to arterialisation
What findings suggest genetic predispositions to diving illnesses?
Variants in EPAS1 and PFO presence increase risk of diving illnesses
What experimental models have been used to study oxygen toxicity in the CNS?
Rodent models demonstrated seizures at high oxygen pressures
