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Questions and Answers on
Physiology and Medical Aspects of Scuba Diving


Lawrence Martin, M.D. Copyright 1997


Buy the book
Scuba quiz
Myths & Misconceptions
Disclaimer & Invitation

Brief History of Diving
Recreational  Diving
The Respiratory System
Explanation of Pressure

Water & Physical Laws
Unequal Air Pressures
Decompression Sickness
Oxygen Therapy
Gas Pressure at Depth

Dive Tables & Computers
Stress & Diving
Non-air Gas Mixtures
Women & Diving
Medical Fitness for Diving
Asthma & Diving
The Great Debate

All About DAN
Scuba Training Agencies
Magazines & Newsletters
Books & Videos

Diving Odds N' Ends

Internet Links

Frequently Asked Questions & Answers

A. A Brief History of Diving, from Antiquity to the Present
What is the early history of diving?
What are some important events in the history of diving?

B. Recreational Scuba Diving: An Overview
What does "Scuba" stand for?
How popular is Scuba diving?
Who teaches Scuba?
How does recreational Scuba diving differ from other forms of Scuba diving?
What is the buddy system?
Why is 130 feet the maximum depth in recreational diving?
What is mandatory decompression and why is it not part of recreational Scuba diving?
Are there different levels of recreational diving?
What is sport surface-supplied compressed air diving and how does it differ from scuba?
What is the future of RSD?

C. The Respiratory System: A Brief Review
Why this Chapter?
What is the function of the respiratory system?
How does gas exchange occur?
Does the respiratory system have functions besides gas exchange?
Do fish sleep?
How long do fish live?

D. An Explanation of Pressure and the Laws of Dalton, Boyle, Charles and Henry
What is pressure?
What is air pressure?
What is the difference between ambient, barometric and atmospheric pressure?
What are the measurement units for the ambient pressure?
What is an "atmosphere" of pressure?
What is the difference between absolute pressure and gauge pressure?
What causes changes in atmospheric pressure?
What is the composition of air?
What are the gas laws and why are they important to diving?
What is Boyle's Law?
What is Charles' Law?
What is Dalton's Law?
What is partial pressure?
What does Dalton's Law predict about changes in partial pressure with changes in ambient pressure?
What is Henry's Law?

E. Water and the Physical Laws That Affect All Divers
What are the important differences between air and water?
What does Boyle's Law predict about changes in pressure with depth?
What does Boyle's Law predict about breath-hold diving?
What does Boyle's Law predict for the diver breathing compressed air?
How much air is in a scuba tank?
How does air pressure change from the scuba tank to the diver's lungs?
What is buoyancy?
What is buoyancy control?
What causes weightlessness under water?
How does one learn to acquire proper buoyancy?

F. Effects of Unequal Air Pressures While Scuba Diving: Ear Squeeze, Sinus Squeeze, Air Embolism and Other Forms of Barotrauma
What does Boyle's Law predict about unequal pressures?
What is the difference between scuba diving with the Glottis closed and open?
What is barotrauma?
What barotrauma problems can occur on descent?
What is the cause of middle-ear squeeze and how can it be prevented?
What is the treatment of middle-ear squeeze?
What other forms of barotrauma occur on descent?
What barotrauma problems can occur on ascent?
What is pulmonary barotrauma?
How does pulmonary barotrauma occur?
Why does pulmonary barotrauma occur?
What is arterial gas embolism?
What is treatment of AGE?

G. Effects of Increased Dissolved Nitrogen From Scuba Diving: Decompression Sickness
What happens to inhaled air at depth?
How does the increased pressure at depth affect gas in the body?
Is there risk of oxygen toxicity in diving?
How does nitrogen differ from oxygen and CO2?
What is the history of decompression sickness?
What causes decompression sickness?
Is "the bends" the same thing as DCS?
What are the differences between DCS and AGE?
What is the treatment for DCS?
What is decompression illness?
What is a patent foramen ovale?
Should divers be checked for a patent foramen ovale?
Why is it unsafe to fly soon after diving?
How long should a diver wait before flying?
Why don't whales get the bends?

H. Oxygen Therapy for Diving Accidents: At Atmospheric and Hyperbaric Pressure
What is oxygen therapy?
What is oxygen toxicity?
What is the difference between oxygen therapy for bubble disease and other medical conditions?
Why is 100% oxygen recommended for all victims of a scuba diving accident?
How is oxygen used at atmospheric pressure?
What are atmospheres of oxygen?
How is oxygen used at the dive site?
What are the types of oxygen masks available for dive accident victims?
What are the advantages of supplemental oxygen therapy for dive accident victims?
What is the physiologic basis for oxygen therapy?
Why does a PaO2 six times normal provide only 7% more oxygen in the blood?
Why does replacing nitrogen with oxygen shrink bubbles?
How is oxygen therapy used at hyperbaric pressures?
What else is hyperbaric therapy used for?
What is a hyperbaric treatment table?
Are divers hurting reefs?

I. Effects of Gas Pressures at Depth: Nitrogen Narcosis CO2 Narcosis, CO and Oxygen Toxicity
What happens to gas pressures at depth?
What is nitrogen narcosis?
What is oxygen toxicity, and can it develop while diving?
What exactly determines risk of oxygen toxicity?
How do atmospheres of O2 relate to oxygen toxicity?
How can oxygen toxicity be minimized?
How does carbon monoxide toxicity occur in scuba diving?
What is carbon dioxide toxicity?
What causes headache under water?
What is shallow-water blackout?

J. Dive Tables and Dive Computers: Their History and Utility
Why do divers not routinely use dive tables?
How is a dive table used?
What is the origin of dive tables?
What is the theory behind dive tables?
What is "saturation"?
How do half times affect nitrogen loading and unloading?
So what do half-times and saturation have to do with dive tables?
What is supersaturation?
Have the tables been modified for recreational diving?
What is doppler ultrasound?
Does diving "by the tables" guarantee a diver won't develop DCS?
What is the difference between square wave and multi- level diving?
What is the origin of dive computers?
What do dive computers do?
Are dive computers preferred over dive tables?
How accurate are dive computers?
What are odd dive patterns?
How are computers abused?

K. Stress, Hyperventilation, and Hypothermia
What is stress?
Why is an understanding of stress important for divers?
What is a panic reaction?
How do I know when I'm in a stressful situation?
What is hyperventilation?
What is hypothermia?
What is the treatment of hypothermia?
What is hyperthermia?

L. Diving with Non-air Gas Mixtures: Nitrox, Heliox, Trimix, et. al.
What is nitrox?
Why nitrox?
What are the hazards of nitrox?
Why isn't nitrox routinely used by recreational divers?
But is nitrox dangerous?
Who certifies for nitrox diving?
What is heliox?
What is trimix?
Are there other gas mixtures used for scuba diving?

M. Women and Diving
Does one's sex affect scuba diving?
Are women at greater risk than men for developing decompression illness?
What about psychological differences between men and women regarding scuba diving?
Do changes during menstruation pose any risk?
Do oral contraceptives pose a risk to women divers?
What about diving during pregnancy?
How soon can one dive after pregnancy?
What should be done if a woman inadvertently dives while pregnant?
Should women expect special treatment when scuba diving?

N. Medical Fitness for Diving: Guidelines Real and Imagined
Are there regulations regarding who may scuba dive?
Who is fit for diving?
Can one dive while taking a decongestant?
What conditions should prohibit diving?
Why are some conditions controversial for diving?
Why are some conditions considered prohibitive for scuba diving?

O. Should Asthmatics Not Scuba Dive?
Should asthmatics not scuba dive?
Why is there a wide range of opinion on asthma and diving?
What is the informed consent approach?
What about medicolegal concerns?

P. But Is Recreational Scuba Diving Safe? The Great Debate
Is scuba diving safe?
Is recreational scuba diving safe?

Q. Glossary
R. All About DAN, or: Where are the Hyperbaric Chambers?
S. U.S. Scuba Training Agencies
T. U.S. Scuba Magazines and Newsletters
U. Distributors of Scuba Books and Videos and Internet Addresses for Additional Information

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Last updated: 28/10/97