Your Body and the Underwater World

1
Chapter 3

• Your Body and the Underwater World

2
Objectives

• Describe the effects of increasing pressure on
  your body
• What does breathing compressed gas do to your
  body.
• Understand how partial pressures effect you as a
  diver.
• Describe proper ascent procedures and rate.
• List the causes, treatment and prevention of
  nitrogen narcosis, decompression sickness and
  over expansion injuries.

3
Effects of Increasing Pressure

• Pressure
• A force per unit area, common expressed in psi.
• Sea Level
• 14.7 psi or 1 bar 1 atmosphere
• the amount of downward force exerted by a 1 inch
  (25mm) column of air from the top of the
  atmosphere to sea level (approx 60 mi / 100 km).

4
(No Transcript)
5

• Ambient Pressure.
• The total pressure surrounding the diver at any
  given depth.
• Greater depth more pressure
• Sea level 1 atm 14.7 psi 1 bar
• 33 sw 2 atm 29.4 psi 2 bar
• 66 sw 3 atm 44.1 psi 3 bar
• Odd infinitum or on and on and on

6
The Big Squeeze

• How does it affect you?
• Air cavities in your body
• Sinuses
• Middle ear
• Lungs

7
Sinus Squeeze

• Sinus passages are normally open and self
  equalize.
• Congested or swollen passages need to be
  equalized.
• Blocked passages no diving.

8
Sinuses
9
Ear Squeeze

• Occurs when ambient pressure in the ear canal is
  greater than pressure in the Eustachian Tube.
• To equalize, pinch nose shut, blow gently with
  mouth closed.

10
Pressure and your ear
11
Mask squeeze

• Occurs when the air cavity in your mask has
  lower pressure than ambient pressure.
• Resolved by gently breathing out through the
  nose.

12
The Hood

• Sometimes air is trapped under your hood.
• Prevent ear squeeze by letting water into the
  hood just after you drop down under the water.

13
Breathing under water

• The Lungs Breath Control.
• Take slow steady breaths.
• Normal rhythm should be a slow steady, deep and
  regular.
• Anxiety can cause irregular breathing.
• Anxiety control
• Stop, Breathe, Think then Act.

14
Why Breathe

• Function of the lungs.
• To deliver fuel (oxygen) to the cells of your
  body and eliminate the waste (carbon dioxide).
• Gas exchange occurs in the avoli.
• Sustained shallow breathing can lead to a
  buildup of carbon dioxide in the bloodstream.

15
The Human Lung
16
(No Transcript)
17
Boyles Law

• In the mid 1600s Robert Boyle studied the
  relationship between pressure P and the volume
  V of a confined gas held at a constant temp.
  Boyle observed that the product of the pressure
  and volume are observed to be nearly constant.
  The product of pressure and volume is exactly
  constant for an ideal gas.
• P V Constant

18
www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html
19
(No Transcript)
20
Partial Pressures

• Daltons Law
• John Dalton studied the effect of gases in a
  mixture. He observed that the Total Pressure of a
  gas mixture was the sum of the Partial Pressure
  of each gas.
• P total P1 P2 P3 .......Pn

21
What in the world does that mean?

• Air is a mixture of gasses
• 20 oxygen
• 80 Nitrogen
• Partial pressures increase as depth increases.
• At 1 atm. Partial pres. of 02 is 20
• At 2 atm. Partial pres. Of 02 is 40
• At 3 atm. Partial pres. Of 02 is 60

22

• Nitrogen
• at 1 atm. partial pres. of N2 is .8
• at 2 atm. partial pres. of N2 is 1.6
• at 3 atm. partial pres. of N2 is 2.4
• Henrys Law
• The amount of a gas that will dissolve in a
  liquid at a given temp. is almost directly
  proportional to the partial pressure of that gas
• As the partial pres. of solution increases, a
  larger amount of gas is held in the solution.

23
Nitrogen Narcosis

• What is it?
• High partial pres. Of N2 in bloodstream.
• Effects or Wow man that fish can swim.
• How to deal with it.
• The recreational limit.

24
Decreasing Pressure

• Surfacing
• Reversing Boyles law.
• Assent rate.
• 1st rule of SCUBA.
• Prevention.

25
Reversing Daltons Law
26
Over Expansion Injuries

• Air Embolism.
• Air Bubbles in the blood.
• Emphysema
• Subcutaneous.
• Mediastinal.

27
(No Transcript)
28
Decompression Sickness

• Getting Bent.
• At depth gas remains in solution but as you
  rise.
• Ascent rate controls gas release
• Decompression stops.
• DCS symptoms.
• Irritable rash.
• Dizziness, numbness in the extremities.
• arthritic ache in joints.

29
DCS Continued

• Most important symptoms
• Dizziness, paralysis, temporary blindness,
  convulsions and unconsciousness.
• Symptoms usually occur within 15 min. to 12 hrs.
  of diving.

30
First Aid

• Overexpansion injuries and DCI symptoms are very
  similar.
• Get trained help!
• 100 02
• Get comfortable.
• Drink water if conscious.
• Long term for the bends is Hyperbaric Chamber

31
(No Transcript)
32
Staying in control

• Buoyancy
• Positive
• Negative
• Neutral
• Weighting
• Neutral buoyancy check.
• Descending, compression and becoming negative.

33
Exposure to the Environment

• Why am I so cold?
• Water conducts heat away from the body.
• Shivering.
• Hypothermia-
• Normal body temp. 98.6 F
• Hypothermic at 95