Diving

interactive physiology
Prof. dr. Milan Taradi, M.D. PhD.
Department of Physiology and
Immunology
Faculty of Medicine, Zagreb
Flying High,
Diving Deep

interactive physiology
PHYSIOLOGY OF
DEEP-SEA DIVING
Prof. dr. Milan Taradi, M.D. PhD.
Department of Physiology and
Immunology
Faculty of Medicine, Zagreb

interactive physiology diving Taradi 3
Types of Underwater Diving
o Ambient diving in which the diver's
body is exposed to the pressure of the
ambient water.
o Diving in a heavy-walled vehicle that
protects divers from the water
pressure.

1. Ambient Diving
o Breath-hold diving (free diving, skin
diving) is the oldest and simplest
form of diving.
o Diving with compressed air supplied
from the surface involves wearing a
water-proof suit and a helmet.
o Diving with compressed air or other
gas mixture in metal tanks that are
carried by the diver (SCUBA diving)

2. Diving in a Heavy-walled Vehicle
o Articulated armor is a metal suit
which covers the entire body.
o Submarines are the largest diving
vehicles mostly warships that carry
powerful weapons.
o Bathyscaph consists of a steel sphere
attached to the bottom of a tank filled
with gasoline.

Basic Problem is Hyperbaric Condition
o Water pressure on the body
increases with water depth.
o Pressure increases for 1 atm
(101 kPa) for every 10 m of
depth
o Effect of depth on the volume of
gases
o To keep the lungs from collapsing,
the air must be supplied (to inflate
them) also under high pressure.
o An ambient diver may be squeezed
(barotrauma).

Effect of Depth on the Volume of
Gases
o Boyle’s Law
o Pressure and Volume
o P1 V1 = P2 V2
o Charle’s Law
o Gas dissolving in
liquid due to
pressure
o PX = Gas% * Pt

The Challenges of Diving
o 1. Biological effect of high partial
pressures of gases
o 2. Physical problems of diving
o 3. Drowning

Biological Effect of High Partial
Pressures of Gases
o NITROGEN narcosis at high nitrogen
pressure (“raptures of the depths”).
o OXYGEN toxicity at high pressure (acute
or chronic poisoning)
o CARBON DIOXIDE toxicity caused by
rebreathing
o HELIUM has also a narcotic effect, but at
very high pressure
1

Nitrogen Narcosis and “Raptures
of the Depths”
o Nitrogen is an inert gas existing in largest
quantity in the atmosphere, 79% in air. It
is inert, meaning it does not take part in
energy transformations.
o It is the gas that causes nitrogen narcosis
through the effect of Dalton's law.
o It is the gas that causes decompression
sickness on ascent from depth with
reduction of pressure (Boyle's Law).
o Nitrogen is the gas that determines
decompression schedules.
1

Raptures of the (maybe not so) Deep
Signs and Symptoms
o 30 m (100 ft) - Mild impairment of performance. Mildly
impaired reasoning. Mild euphoria.
o 30-50 m (100-165 ft) - Delayed response to visual /
auditory stimuli. Reasoning and immediate memory
affected. Calculation errors. Wrong choices. Over
confidence and sense of well-being. Anxiety.
o 50-70 m (165-230 ft) - Impaired judgment. Confusion.
Sleepiness. Severe delay in response to signals or
instruction. Terror. Hallucinations in some.
o 70-90 m (230-300 ft) - Poor concentration. Mental
confusion. Loss of memory. Further decrease in judgment.
o 90 m - (300 ft-) - Hallucination. Increased intensity of
vision and hearing. Sense of impending blackout. Manic or
depressive state. Unconsciousness. Death.
1

Treatment of Nitrogen Narcosis
o The treatment of nitrogen narcosis is
immediate controlled ascent to the
surface.
o Administration of O2
o Temporary cessation of diving
o Prevention should be the best treatment,
with no further diving below 30 m (120
feet).
o To avoid narcosis, the diver should breath
a gas mixture that contains helium instead
of nitrogen.
1

Oxygen Toxicity at High Pressure
(Acute or Chronic Poisoning)
o When the PO2 is bellow 200 kPa the
hemoglobin-oxygen buffer keeps the
tissue PO2 in normal range, but not in the
lungs.
oChronic oxygen poisoning causes pulmonary
disability.
oAfter only 12 hours of 1 atm oxygen exposure
the damage of bronchi and alveoli begins to
develop.
o Extremly high pressure of PO2 (above 200
kPa) causes acute poisoning.
oSymptoms are: nausea, muscle twitchings,
dizzines, disorientation, disturbance of vision,
seizures, coma and death.
1

Carbon Dioxide Toxicity at Great
Depths (Hypercapnia)
oThe deapth does not increase the
carbon dioxide partial pressure in
the alveoli; as long as the diver
continues to breathe a normal tidal
volume.
oThe early signs of carbon dioxide
poisoning are:
oincreasing of minute respiratory
volume, shortness of breath, headache,
severe respirotory acidosis, lethargy,
narcosis, anesthesia and death
1

Helium Also Has a Narcotic Effect
at Very High Pressure
o In very deep dives helium is usually used for
four reasons:
o It has only about one-fifth of the narcotic effect of
nitrogen.
o Helium dissolves only about one half as much volume
as nitrogen.
o Helium diffuses out of the tissue several times as
rapidly as nitrogen does.
o The airway resistance is smaller.
o "Helium narcosis" starts at higher pressures
(160 m).
o In very deep dives 1% of oxygen in inspiration
gas is usually used to avoid acute poisoning.
1

pressures of gases
o 3. Drowning

Physics and Problems
o Decompression sickness (dysbarism)
o Tremendous airflow is required to wash carbon
dioxid out of the lungs.
o The gas mixture becomes very dense and the
airflow resistence high.
o Increased pressure, as the diver descends, can
collapse air chambers of the body.
o As the diver ascends, the gases in the air
chambers can cause rupture of hollow organs.
o Hypothermia (heat loss)
2

Decompression Sickness
(Dysbarism)
o At sea level,
almost 1 liter of
nitrogen is
dissolved in the
entire body. For
each 10 m (100
kPa) of depth
additional 1 liter
is dissolved.
o When the diver
suddenly comes
back to the
surface,
significant
quantities of
nitrogen bubbles
can be developed
in his body fluids.
2

Decompression Sickness
(Dysbarism)
o Most of the symptoms are caused by gas
bubbles
o In the central nervous system (pain, dizziness,
confusion, paralysis, collapse and
unconsciousness)
o In the circulation (ischemia, shortness of breath,
pulmonar edema, death).
o Treatment of decompression sickness is to
send the diver back in the depth or put him
in a decompression tank.
2

Tremendous Airflow is Required to Wash
Carbon Dioxide out of the Lungs
o A tidal volume of 0.5 liter at 100 meter
depth would be a sea level volume of 5.5
liters.
o A compressor operating at sea level must
pump 500 liters of air to the diver at 100
meter depth in every minute.
2

Change in Density of the Air
o The density of the air increases in
proportion to the pressure.
o The resistance of the air flow throught
the respiratory passageways increases
directly in proportion to the density.
o The maximum breathing capacity
decreases.
2

Barotrauma – Effect of Rapid Descent
o An ambient diver may be
injured if the pressure in the
lungs and other air spaces in
the body does not equal the
water pressure.
o Such an injury is called
barotrauma or squeeze.
2
S = compressible air
chamber
NS = uncompressible
tissue

Air Embolism – Overexpanding of
the Lungs on Rapid Ascent
o During ascent, the pressure in the
lungs must be kept equal to the
decreasing water pressure.
o Otherwise, a serious condition
called air embolism may result.
o The gases in the lungs expand
and sometimes rupture a
pulmonary vessel, allowing the
gases to enter the pulmonary
vascular system.
2

Human Dive Reflex
2
o Stimulated by emersion in
water
o Serve to concentrate blood
flow to brain and heart
o Apneic Bradycardia -
slowing of heart rate
o Peripheral Vasoconstriction
- blood flow prevented
from supplying non vital
organs
o Increased Blood Pressure -
fills chest with blood to
prevent collapse

Limits of Free Diving
2
o Pressure
o Preventing Lung Collapse
o TLC ≥ RLV
o O2 Consumption
o Metabolic Rate
o Hypoxia Tolerance
o CO2 Storage
o Hyperventilation
o Reducing Build Up
o Shallow Water Blackout
o Dive too long
o Upon ascent lungs expands = pO2 ↓
o Diver enters anoxic state just before surfacing
o Anoxic State = Unconsciousness

pressures of gases
o 3. Drowning

Drowning
o ASPHYXIA IN DROWNING - Approximately 30 %
of all persons who drown do not inhale water.
The person dies of asphyxia in five to eight
minutes.
o INHALATION OF FRESH WATER – CARDIAC
FIBRILLATION - When a drowning person inhales
fresh water, water is absorbed trough the
alveolar membrane into the blood, causing death
within one to three minutes.
o THE EFFECT OF INHALING SALT WATER - If a
drowning person inhales salt water, osmosis of
water occures in the opposit direction. The
person dies of asphyxia in five to eight minutes.
3
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