Lecture 4: Diving 4 Flashcards
Explain what happens to the gas in humans when they dive.
When human divers descend, they breathe compressed air under high pressure for a long time, and body tissues become saturated with nitrogen
(the longer the person stays down in the water, the
more nitrogen is absorbed)
- Ocean pressure at depth keeps dissolved gas in
solution
- When diver ascends, time is needed for nitrogen to
be expelled slowly from the body
What causes the bends?
- Effects of gas bubbles forming in the body due to changing RAPIDLY from high-pressure
environment to lower pressure during ascent - Nitrogen bubbles build up in the bloodstream and tissues of the body
What happens when a human diver comes up slowly from a dive?
the nitrogen can return to
the lungs and be exhaled
What happens if a diver ascends too fast from a dive?
the nitrogen may come out of the solution and form bubbles without time to diffuse back into the lungs
What happens to the nitrogen bubbles at shallower depth and less pressure?
the nitrogen
bubbles expand in the bloodstream and tissue,
causing pain and damage
What is another word for “the bends”?
decompression sickness
True/False: At atmospheric pressure, body tissues contain
small amounts of gases present in air
True
What are the clinical signs of decompression sickness?
Clinical signs are caused by gas bubbles blocking
blood vessels in different tissues
What are some symptoms of decompression sickness?
- Usually, people experience pain in joints and muscles of their legs and arms and affected people cannot straighten their joints (e.g. “The Bends”)
- Other signs: CNS – dizziness, loss of consciousness; breathing problems
Where did the name “the bends” come from?
people cannot straighten their joints
What happens during thoracic squeeze?
Hydrostatic pressure -> crushes rib cage -> death
Explain how marine mammals avoid decompression sickness using lung air.
= Isolation of lung air from alveoli during a dive; air
is compressed away from alveoli into dead space, preventing gas exchange and nitrogen from
entering blood
1. Dolphins: lung, trachea and bronchi collapse during a
dive, ribs compress lungs, forcing air out of alveoli
Explain what happens to the alveoli of marine mammals to avoid decompression sickness.
When a diving dolphin reaches
100 meters, alveoli (and
probably bronchioles) collapse
via collapse of thorax (chest)
2. Seals exhale before dive
3. Sea lions exhale on the way
down
this all prevents nitrogen form entering the blood
Explain how marine mammals avoid decompression sickness using their flexible thorax.
Flexible thorax with distensible veins, rete mirabile
All probably allow alveoli to collapse and prevent
nitrogen from entering blood during a dive
(without thoracic squeeze seen in human divers)
True/False: Human breath-hold divers don’t absorb nitrogen
True
