L3. Diving and hyperbaria

Question 1

What are the primary environmental challenges of scuba diving?

Answer 1

Cold, pressure changes, gas toxicity, and nitrogen narcosis

Question 2

Who invented the first scuba diving system?

Answer 2

Jacques Cousteau

Question 3

What is the physiological significance of Boyle’s law in diving?

Answer 3

It explains the relationship between pressure and volume, crucial for understanding gas behavior under pressure

Question 4

What is immersion pulmonary oedema (IPO) and its primary cause?

Answer 4

A form of hydrostatic pulmonary oedema caused by immersion-induced pressure changes

Question 5

How does nitrogen narcosis affect divers at depth?

Answer 5

It impairs judgment and motor skills due to the anesthetic properties of nitrogen at high partial pressures

Question 6

What are the two types of oxygen toxicity in diving?

Answer 6

Pulmonary and central nervous system toxicity

Question 7

What is decompression sickness (DCS), commonly known as ‘the bends’?

Answer 7

A condition caused by nitrogen bubbles forming in tissues during rapid decompression

Question 8

What is the primary mechanism of bubble formation during decompression?

Answer 8

Bubbles form due to decreased pressure allowing dissolved gases to come out of solution

Question 9

How does increased gas density at depth affect divers?

Answer 9

It increases work of breathing and exacerbates narcosis and oxygen toxicity

Question 10

What is the role of hyperbaric oxygen therapy in treating decompression illness?

Answer 10

It recompresses and crushes bubbles while providing 100% oxygen to aid nitrogen elimination

Question 11

What are the physiological effects of a rapid ascent on lung tissue?

Answer 11

Rapid expansion of air can rupture alveoli, leading to arterial gas embolism

Question 12

What are the main gas mixtures used in technical diving?

Answer 12

Air, nitrox, normoxic trimix, hypoxic trimix, and heliox

Question 13

What is the function of closed-circuit rebreathers in diving?

Answer 13

To recycle exhaled gas by scrubbing CO2 and adding O2, reducing gas consumption

Question 14

What factors increase the risk of IPO in divers?

Answer 14

Hyperhydration, exertion, negative-pressure breathing, and cold-induced vasoconstriction

Question 15

What is the significance of the oxygen window in decompression?

Answer 15

It refers to the partial pressure difference between arterial and venous blood aiding nitrogen elimination

Question 16

How do exercise and diving interact to influence decompression risk?

Answer 16

Post-dive exercise reduces bubble formation; intense exercise can increase decompression risk

Question 17

What is the role of endothelial microparticles (EMPs) in diving physiology?

Answer 17

They are released by endothelial cells after pressure changes, playing a role in inflammation and coagulation

Question 18

What are the symptoms of nitrogen narcosis at depths of 50-60 meters?

Answer 18

Sleepiness, illusions, and impaired judgment

Question 19

How does hypoxic trimix help in deep technical dives?

Answer 19

By replacing nitrogen with helium to reduce narcosis and oxygen with helium to mitigate toxicity

Question 20

What are the long-term effects of repeated exposure to hyperbaric conditions?

Answer 20

Potential lung damage, neurological changes, and vascular issues

Question 21

What experiment demonstrated the relationship between nitrogen bubbles and decompression sickness?

Answer 21

Haldane’s goat experiments showed nitrogen bubbles in decompressed tissues

Question 22

What did Haldane’s studies reveal about decompression rates?

Answer 22

Slow decompression rates reduce bubble formation and decompression sickness risk

Question 23

What are the findings about pulmonary oedema in closed-circuit rebreather divers?

Answer 23

Negative-pressure breathing increases susceptibility to IPO in back-mounted counter-lung systems

Question 24

How does exercise before a dive affect venous gas emboli (VGE) formation?

Answer 24

Pre-dive exercise reduces VGE formation by improving endothelial function

Question 25

What mechanisms are proposed for bubble nucleation during decompression?

Answer 25

Micronuclei, crevice model, and tribonucleation are leading theories

Question 26

What factors were identified as major contributors to immersion pulmonary oedema (IPO)?

Answer 26

Hyperhydration, exertion, and cold-induced vasoconstriction were key factors

Question 27

What evidence links endothelial microparticles (EMPs) to decompression sickness?

Answer 27

EMPs activate inflammatory pathways and impair endothelial function

Question 28

What did MRI studies reveal about brain changes in divers after nitrogen narcosis?

Answer 28

Brain swelling and microbleeds were observed after narcosis episodes

Question 29

What role do calcium channel blockers play in mitigating IPO?

Answer 29

They reduce pulmonary vascular resistance and mitigate IPO

Question 30

What physiological evidence supports the oxygen window theory?

Answer 30

Lower venous partial pressures due to metabolic oxygen consumption support it

Question 31

How do variations in heart rate and bradycardia correlate with diving response?

Answer 31

Increased bradycardia and heart rate variability occur during cold immersion

Question 32

What long-term cardiovascular changes are seen in professional divers?

Answer 32

Increased arterial stiffness and ventricular hypertrophy were observed

Question 33

What findings were associated with nitric oxide and its role in oxygen toxicity?

Answer 33

Nitric oxide combines with ROS to form peroxynitrite, causing oxidative damage

Question 34

What did the Doppler studies reveal about VGE and ascent rate?

Answer 34

Higher ascent rates correlated with increased VGE formation

Question 35

What adaptations reduce nitrogen narcosis susceptibility in frequent divers?

Answer 35

Repeated exposure improves tolerance, possibly through synaptic plasticity

Question 36

How does gas density influence the work of breathing at depth?

Answer 36

Higher density increases resistance, making breathing harder

Question 37

What experimental findings link cold-induced vasoconstriction to IPO?

Answer 37

Peripheral vasoconstriction increased central blood volume and pulmonary pressures

Question 38

What role do RL shunts play in arterialising venous gas bubbles?

Answer 38

Shunts allow bubbles to bypass pulmonary filtration, leading to arterialisation

Question 39

What findings suggest genetic predispositions to diving illnesses?

Answer 39

Variants in EPAS1 and PFO presence increase risk of diving illnesses

Question 40

What experimental models have been used to study oxygen toxicity in the CNS?

Answer 40

Rodent models demonstrated seizures at high oxygen pressures