SCUBA-RELATED QUESTIONS WITH ANSWERS

Lawrence Martin, M.D.

This Quiz ran from February through December, 1998. It is based on the Dr. Martin's book Scuba Diving Explained: Questions and Answers on Physiology and Medical Aspects, published 1997 by Best Publishing Co., Flagstaff, AZ. The book is now out of print, but most of it is on the web at web at www.lakesidepress.com/pulmonary/books/scuba/contents.htm"

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FEBRUARY 12, 1998

True or False:

While diving on compressed air, the partial pressure of inhaled oxygen increases with increasing depth, while the percentage of inhaled oxygen remains unchanged.


ANSWER TO FEBRUARY 12 QUESTION

True. The total pressure of inhaled gases increases with depth, so the partial pressure of each component gas also increases with depth. However, the percentage of each gas in the mixture (i.e., in air) remains the same. Thus scuba divers inhale 21% oxygen (when diving with compressed air) at any depth, but the pressure of inhaled oxygen (and, of course, inhaled nitrogen) increases with increasing depth.

Reference: Scuba Diving Explained--Section D


QUESTION FOR FEBRUARY 18, 1998

A scuba diver takes a closed tank of compressed air to a depth of 99 feet sea water, which he does not breathe from. Compared to the same tank at sea level, what are the density and volume of air in the tank? (Assume temperature is constant).

a. same
b. higher
c. lower


ANSWER TO FEBRUARY 18 QUESTION

Same. The tank is closed, so no air is escaping. Due to its solid construction, the air it contains will be unaffected by water pressure (in contrast, say, to a compressible balloon or your lungs). Changes in temperature, however, could affect the tank's air pressure.

Reference: Scuba Diving Explained--Section D


QUESTION FOR FEBRUARY 25, 1998

At a depth of 66 feet sea water, air breathed from a scuba tank as it enters the diver's lungs is how much denser than air breathed at sea level?

a) same density
b) twice as dense
c) three times as dense
d) four times as dense
e) depends on amount of air left in scuba tank at that point.


Answer for FEBRUARY 25, 1998:

c) three times as dense.

Each 33 feet of sea water = 1 atmosphere. 66 feet equals two atmospheres plus the one at sea level, for a total of 3 atmospheres. Air leaving the scuba tank at this depth thus is three times as dense.

Reference: Scuba Diving Explained--Section E


QUESTION FOR MARCH 5, 1998

All of the following are forms of barotrauma except one:

a) pnemothorax
b) mask squeeze
c) air embolism
d) the bends
e) ear squeeze


Answer for MARCH 5, 1998:

d) The bends is not a considered form of barotrauma, but instead due to nitrogen bubbles forming from too rapid an ascent and blocking the circulation or impinging on the nerves. Barotrauma refers to damage from unequal pressures in two contiguous body compartments, resulting in some form of tissue damage occurs. All the other situations are examples of barotrauma.

Reference: Scuba Diving Explained--Section F


QUESTION FOR MARCH 12, 1998

In which of the following conditions has it been proved that there is increased risk of death or severe injury from scuba diving?

a) asthma
b) diabetes
c) epilepsy
d) pregnancy
e) none of the above


ANSWER TO QUESTION FOR MARCH 12, 1998

e) None of the above. Each condition presents theoretical risks, but for a variety of reasons no data are available to "prove" an increased risk. For asthma, diabetes, and epilepsy, the risks are no doubt correlated with severity of the condition, but NOT with the simple fact of diagnosis. For pregnancy, there are not proven risks, but precisely because the risks are unknown, and the fact that diving presents a highly altered environment for the fetus, common sense suggests the pregnant woman should refrain from scuba diving.

Scuba Diving Explained--Section M - Women and Diving
Section N - Fitness for Diving
Section O - Asthma and Diving


QUESTION FOR MARCH 19, 1998

The "bends" can result from too rapid ascent after diving with compressed air. Name two other situations in which people can (and have) developed the bends.

ANSWER FOR MARCH 19, 1998

One can develop the bends from too rapid ascent to altitude, a condition long recognized in jet pilots. The principle is the same as when diving; nitrogen leaves the blood & tissues too quickly due to a decrease in ambient pressure, forming bubbles.

The other way one can develop the bends, albeit relatively uncommon, is by free diving. Free divers who go deep and long with only the air in their lungs can dissovle enough extra nitrogen in their tissues, so that on ascent it bubbles out too quickly -- causing the bends. This should not happen with free diving to shallow depths for brief periods.


QUESTION FOR MARCH 28, 1998

OK, "Titanic" won many Acacdemy Awards and the underwater scenes were awsome. But you will never scuba dive that ship, because it's at 12,500 feet. However, some almost-as-famous wrecks are divable with self-contained breathing apparatus. Select the wrecks below that an intrepid scuba diver could reach (and safely return from) using AIR ONLY. Dry suit, extra scuba tanks and recognized decompression tables are allowed, if needed.

a) Andrea Dorea, near Nantucket
b) Edmund Fitzgerald, Lake Superior
c) Pandora, off coast of Australia
d) Atocha, off Southern tip of Florida
e) Central America, near Charleston, SC
f) San Diego, off Long Island, N.Y.
g) Bismarck, between France and Iceland

ANSWER FOR MARCH 28, 1998

a) Andrea Dorea - YES - depth 240 fsw (feet sea water)
b) Edmund Fitzgerald - NO - 530 fsw
c) Pandora - YES - 110 fsw
d) Atocha - YES - 132 fsw
e) Central America - NO - 8045 fsw
f) San Diego - YES - 75 fsw
g) Bismarck - NO - 15700 fsw


QUESTION FOR APRIL 10, 1998

Which of the following conditions would be the most prohibitive of participating in scuba diving?

a) a history of asthma, diver on medication
b) a history of epilepsy, diver on medication
c) insulin-dependent diabetes
d) blebs or "bullae" seen on chest x-ray, diver has no symptoms
e) an episode of the bends two months earlier, treated in a hyperbaric chamber with no residual defects

ANSWER FOR APRIL 10, 1998

d) blebs or "bullae" seen on chest x-ray, diver has no symptoms

This is the only condition among those listed that presents an "absolute contraindication" to diving with compressed air. Each of the other conditions is problematic, and any recommendation or prohibition should be based on a thorough review of the individual's medical history and current condition.

Section N - Fitness for Diving


QUESTION FOR APRIL 20, 1998

Assume a scuba diver goes to 130 feet using Nitrox, but follows the dive tables for compressed air. Of the following potential problems, the risk of which one is increased by the use of Nitrox?

1) Nitrogen narcosis
2) Arterial gas embolism
3) Decompression sickness (the bends)
4) Oxygen toxicity
5) Hypothermia

ANSWER FOR APRIL 20, 1998

4) Oxygen toxicity. The other problems are not lessened by using Nitrox. Nitrox is less nitrogen and more oxygen than air (21% O2, 79% N2); eg, 32% oxygen, 68% nitrogen. Thus with nitrox there is a greater risk of oxygen toxicity at depth than with air. There is a lower risk of the bends (decompression sickness) if one uses air tables, but "the bends" was not one of the answers.

Reference: Scuba Diving Explained--Section L


QUESTION FOR MAY 25, 1998

A patent foramen ovale (PFO) is an opening between the two chambers of the heart known as left and right atria. About a quarter of the population has a patent foramen ovale, either all the time or just during some activities, such as the Valsalva maneuver. With rare exception, a PFO is inconsequential during everyday activity. The main importance of a PFO for scuba divers is that it may increase the risk of:

1) developing venous nitrogen bubbles
2) developing arterial air bubbles
3) letting nitrogen bubbles get to the brain
4) letting arterial air bubbles get to the brain
5) none of the above


ANSWER FOR MAY 25, 1998

3) letting nitrogen bubbles get to the brain

Reference: Scuba Diving Explained--Section G


QUESTION FOR JUNE 2, 1998

Shallow water blackout in free or breath-hold divers is due to:

a) Build-up of CO2 from staying under water too long.
b) Lack of oxygen near the end of the dive.
c) Running out of compressed air near the surface.
d) A combination of a), b), and c).
e) None of the above.

ANSWER FOR JUNE 2, 1998

b) Lack of oxygen near the end of the dive.

Reference: Scuba Diving Explained--Section I


QUESTION FOR JUNE 10, 1998

This question is in two parts.

Part 1. Which holds more air?
a) A steel tank with 80-cubic-feet of air compressed to 3500 psi.
b) A steel tank with 80-cubic-feet of air compressed to 3000 psi.

Part 2.
What size box would the air in tank a) fill at sea level pressure?
What size box would the air in tank b) fill at sea level pressure?

ANSWER FOR JUNE 10, 1998

PART 1. They hold the same amount: 80 cubic feet of air.
PART 2. A box containing 80 cubic feet of space, for example 3.3 feet x 3.3 feet by 7 feet (or any other combination of measurements whose product is 80 cubic feet).


QUESTION FOR JUNE 26, 1998

A scuba diver is inhaling compressed air that is 5 times the density of air at sea level. She is at what depth?

a) 99 feet.
b) 132 feet.
c) 165 feet.
d) Can't determine without knowing the air tank's residual air pressure.
e) Depends on her frequency of breathing (whether she is taking partial or full inhalations).

ANSWER FOR JUNE 26, 1998

b) 132 feet. Each 33 feet of depth is one atmosphere, so at 33 feet the inhaled air is twice as dense as at sea level, at 66 feet 3x as dense, at 99 feet 4x as dense, and at 132 feet 5x as dense.


QUESTION FOR JULY 6, 1998

A scuba diver ascends rapidly from 20 foot depth, where she has been for 15 minutes on her only dive of the day. Potential hazard(s) from a rapid ascent in this case include:

a) Air embolism
b) Decompression sickness (bends)
c) Both
d) Neither

ANSWER FOR JULY 6, 1998

a) Air Embolism. As a practical matter, at this depth and length of dive, decompression sickness is not a potential hazard. On the other hand, rapid ascent (especially with breathhold) can occur in as little as four feet of water!


QUESTION FOR AUGUST 3, 1998

The most frequently reported seafood-related poisoning in the U.S. is:
a) Salmonella
b) Shigella
c) Ciguatera
d) Scombroid
e) Giardia

ANSWER FOR AUGUST 3, 1998

c) Ciguatera poisoning. This is the most frequently reported sea food poisoning in the U.S. It occurs from the toxins (ciguatoxin and others) supplied by dino-flagellates that are ingested by plant eating fish. As these smaller fish are ingested by larger carnivorous fish, the toxin increases in quantity, until the larger fish is caught and eaten by humans. Most commonly implicated fish: barracuda, grouper, jack and snapper.


QUESTION FOR AUGUST 17, 1998

Which of the following is not a UHMS-approved indication for hyperbaric oxygen therapy?

a) Arterial gas embolism in a patient without neurologic impairment
b) Severe blood loss anemia
c) Clostridial myonecrosis (muscle death due to infection with Clostridia)
d) Multiple sclerosis
e) Chronic refractory osteomyelitis (bone infection)
f) Non-healing diabetic ulcers

ANSWER FOR AUGUST 17, 1998

d) multiple sclerosis. Check out UHMS.


QUESTION FOR AUGUST 27, 1998

You are scuba diving in the Virgin Islands. At a depth of 66 feet you come upon the Atlantis Submarine, full of passengers, who stare at you with a mixture of awe and bewilderment. Which statement most accurately represents the AMBIENT (surrounding) pressures at that point?

a) Your pressure 3 atmospheres, Atlantis hull pressure 2 atmospheres, passenger pressure 1 atmosphere.
b) Your pressure 3 atmospheres, Atlantis hull pressure 3 atmospheres, passenger pressure 2 atmosphere.
c) Your pressure 2 atmospheres, Atlantis hull pressure 2 atmospheres, passenger pressure 1 atmosphere.
d) Your pressure 3 atmospheres, Atlantis hull pressure 3 atmospheres, passenger pressure 1 atmosphere.
e) Your pressure 3 atmospheres, Atlantis hull pressure 1 atmosphere, passenger pressure 1 atmosphere.

ANSWER FOR AUGUST 27, 1998

d) Your pressure 3 atmospheres, Atlantis hull pressure 3 atmospheres, passenger pressure 1 atmosphere.


QUESTION FOR SEPTEMBER 7, 1998

The largest ship to sink in the Great Lakes went under on November 10, 1975. At over 700 feet, with a width of 75 feet, she sank while carrying 26,216 tons of ore. What was her name and in which lake did she sink?

NAME
a) The Carl D. Bradley
b) The Edmund Fitzgerald
c) The William Clay Ford
d) The Arthur M. Anderson
e) The Ernest M. McSorley

LAKE
a) Superior
b) Ontario
c) Erie
d) Huron
e) Michigan

ANSWER FOR SEPTEMBER 7, 1998

b) The Edmund Fitzgerald
a) Lake Superior


QUESTION FOR SEPTEMBER 18, 1998

The main reason "asthma" is a controversial condition for scuba diving is (choose best answer):

a) Some published studies show an increase in diving accidents in asthmatics, whereas other studies do not.
b) The possibility of an asthma attack on or under water, or a blow out of the lung under water from air trapping, concerns some professionals more than others.
c) Asthmatics often don't know how bad they are, and may well dive when they shouldn't.
d) Some inhaled asthma drugs can increase the risk of air way obstruction in asthmatics exposed to ocean environments (salt water cooler than body temperature).

ANSWER FOR SEPTEMBER 18, 1998

The main reason "asthma" is a controversial condition for scuba diving is because
b) The possibility of an asthma attack on or under water, or a blow out of the lung under water from air trapping, concerns some professionals more than others. This variable concern makes the condition controversial for diving. Of the other statements, only c) is true. There are no published studies showing increase in diving accidents among asthmatics, and there is no interaction of drugs and salt water that makes asthma worse.


QUESTION FOR OCTOBER 12, 1998

1. When diving with compressed air, what is the
a) the percentage of inhaled oxygen AND
b) the atmospheres of inhaled oxygen,
at each of the following depths? (fsw = feet sea water)

a. 33 fsw
b. 66 fsw
c. 99 fsw

ANSWER FOR OCTOBER 12, 1998 .

a. 33 fsw -- FIO2 21%; .42 atm. inhaled oxygen
b. 66 fsw -- FIO2 21%; .63 atm. inhaled oxygen
c. 99 fsw -- FIO2 21%; .84 atm. inhaled oxygen


QUESTION FOR OCTOBER 31, 1998.

The presence of patent foramen ovale is known to occur in about 30% of the population, and therefore in about the same percentage of divers. The test to find a PFO is called echocardiography, which is a sound wave test with no needles or injections. Given the known incidence of decompression sickness, does the prevalence of PFO warrant routine screening for PFO in divers? Yes or no.

ANSWER FOR OCTOBER 31, 1998.

According to a review in Undersea & Hyperbaric Medicine, the answer is no. The incidence of DCS is so small (2.28/10,000 dives) that the risk of developing DCS because of PFO doesn't warrant routine screening for the defect.

Risk of decompression sickness with patent forament ovale, in UHM Volume 25, Number 3, Fall 1998, by Dr. A. A. Bove.


QUESTION FOR November 16, 1998 .

Cousteau's Aqua Lung was used only in Europe for the first few years. It drew attention in the U.S. because of publication of an article about Cousteau in an American magazine. The article was by a famous contemporary of Cousteau's, and appeared December, 1948. The title of the article was "The First of the Menfish." Which magazine and who was the author?

a) Saturday Evening Post
b) Life
c) Science Illustrated
d) Skin Diver
e) Popular Mechanics

a) Emile Gagnan
b) James Dugan
c) Frederic Dumas
d) Phillippe Talliez
e) Mrs. Cousteau

ANSWER FOR November 16, 1998 . a) Science Illustrated, by James Dugan.


QUESTION FOR December 31, 1998.

The blockbuster movie of the year was TITANIC. The plot used in the movie could not have been written before the ship was found. The final question of the year concerns the ship's discovery. Which scientist (he led to expedition) discovered the ship? What year? What is the ship's depth? (Hint -- too deep for scuba diving). And, finally, what controversial aspect of the sinking was confirmed when the ship was found? (This is not a multiple choice question.)

ANSWER FOR December 31, 1998.

The ship was found by scientist Dr. Robert Ballard, in 1985, about 400 miles off the coast of Newfoundland. The depth is usually reported as "2 1/2 miles" down, which is about 13,200 feet. The ship was found broken into two gigantic sections, about a quarter of a mile apart. Survivors reported that they thought the ship broke in two at the time of sinking, but absent any photographic record, that was always a source of speculation until Ballard discovered the wreck.


END OF QUIZ. This Quiz ran from February through December, 1998. It is based on the Dr. Martin's book Scuba Diving Explained: Questions and Answers on Physiology and Medical Aspects, published 1997 by Best Publishing Co., Flagstaff, AZ.


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