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Flashcards in Decompression and Hyperbarics Deck (48):
1

Key tenets that encompass treatment of serious decompression sickness (severe and progressive neurologic signs) include which of the following?
a) Immediate high dose corticosteroid therapy administerted intravenously
b) Hyperbaric oxygen therapy
c) Calcium Channel Blockade
d) High flow oxygen 100% at sea level pressure
e) Intravenous perfluorocarbons emulsions combined with high flow oxygen by closed face mask

b) Hyperbaric oxygen therapy

2

The beneficial in vivo effect of Hyperbaric Oxygen Therapy in the treatment of gas gangrene is that:
a) O2 is bacteriocidal for Clostridial organisms at tensions of 250mmHg.
b) O2 is bacteriostatic for Clostridial organisms, at tensions above 1400mmHg.
c) O2 stops alpha toxin production by Clostridial organisms at tension of 250mmHg.
d) O2 stops alpha toxin production by Clostridial organisms at tensions above 1400mmHg.

c) O2 tensions of 250mmHg stop alph toxin production. Although 1400mmHg will kill Clostridial organisms, measured tissue oxygen levels in the phlegmon regions of the organism reach only about 400-600mmHg at 3 times sea level pressure.

3

When a person hyperventilates at Altitude:
a) the blood pH increases
b) the respiratory quotient is driven below 1.
c) the kidney will retain bicarbonate
d) carbonic acid levels fall faster than carbon dioxide levels.
e) all the above

a) the blood pH increases (alkalosis due to blowing off CO2) This leads to a respiratory alkalosis. The RQ will be driven above 1 rather than below. CO2 tension changes at a faster rate than carbonic acid levels.

4

Exercise prior to decompression:
a) increases incidence and severity of decompression sickness during subsequent high altitude exposure.
b) can reduce incidence of DCS during subsequent high altitude exposure if performed during prebreathe.
c) increases the likelihood of hypoxia during subsequent high altitude exposure due to residual effects of increased metabolic rate.
d) has the same effect on incidence and severity of DCS as exercise performed during subsequent high altitude exposure.
e) has no effect on incidence and severity of DCS during subsequent high altitude exposure.

b) The exercise enhances perfusion and diffusion during prebreathing which facilitates removal of nitrogen.

5

Breathing gas supplied via diluter demand regulators set to NORMAL (no 100% oxygen) at a cabin altitude of 22,500 feet provides:
a) sufficient oxygen to preclude symptoms of hypoxia at that altitude
b) insufficient oxygen to preclude hypoxia immediately following rapid decompression to 40,000 feet.
c) as much as 40% nitrogen, negating efficient denitrogenation
d) all of the above
e) none of the above

d) all of the above.

6

Altitude decompression sickness symptoms typically:
a) consist of joint pain
b) resolve on descent from altitude
c) are not observed during research chamber exposures to 22,500 to 24,000 feet.
d) all of the above
e) a and b above

e) a and b

7

Positive pressure breathing for altitude is directed at:
a) get me down scenarios
b) maintaining normal sea level arterial oxygen levels
c) maintaining an alveolar oxygen concentration above 60 mmHg.
d) use only above 50,000 ft.
e) a and c above.

e) a and c above

8

Ebullism:
a) is a misspelling of embolism
b) occurs above 63,000 ft the Armstrongs line
c) results from tissue water vaporization
d) refers to altitude decompression sickness within tissues.
e) b and c above.

e) b and c above

9

On theoretical grounds, from the standpoint of no available oxygen in the lungs without hyperventilation when breathing oxygen, the lowest physiologic equivalent altitude to that of being in outer space is:
a) 45,000
b) 50,000
c) 61,000
d) 100,000

b) 50,000 feet

10

At altitudes above 63,000 feet, the barometric pressure is less than the vapor pressure of body fluids, with all of the implications of anoxia and the boiling phenomenon. Consequently, a decompression to a near vacuum invariably results in:
a) immediate cardiac arrest
b) virtual equalization of arterial and venous pressures
c) death within less than one minute
d) irreversible brain damage

b) The combination of anoxia, vaporization and degassing of body fluids has a profound effect on the cardiovascular system with an immediate abnormal increase in the venous pressure together with a rapid decrease in the arterial pressure such that, with a few seconds, the venous pressure equals or exceeds the arterial pressure. Cardiac output virtually ceases and severe bradycardia ensues. If not recompressed within 90 seconds, death will ensue.

11

After a rapid decompression to an altitude of about 53,00 feet while breathing oxygen, the loss of consciousness can only be avoided by recompression to a safe pressure altitude within:
a) 3 seconds
b) 6 seconds
c) 12 seconds
d) 15 seconds

b) despite being on oxygen, it is unpressurized, such that TUC is less than 15 seconds, but since it was a rapid decompression, you must half that amount, so 6-7 seconds would be the number.

12

When considering the possible physiologic effects of a rapid decompression at high altitudes, it is necessary to distinguish between those effects that might occur during the decompression process itself and the physiologic consequences that can occur at some time after the decompression. Which one of the following effects might most likely only occur during a rapid decompression:
a) cerebral hypoxia
b) decompression sickness
c) pneumothorax
d) barotitis media

c. pneumothorax, resulting from the tearing of lung tissue, would most likely only occur during the rapid decompression itself, particularly if the pulmonary airways are obstructed or completely blocked.

13

The onset of critical hypoxia and incapacitation following sudden loss of cabin pressure during high altitude flight is inevitable without adequate oxygen equipment for the aircrew and passengers. Experimental rapid decompressions from 8000 feet to 40,000 feet within 3 seconds, while breathing the cabin air, have shown that performance can be significantly impaired if the use of 100% oxygen is delayed by:
a) 0 seconds
b) 5 seconds
c) 10 seconds
d) 15 seconds

a) 0 seconds. Studies by the RAF have shown that even when oxygen breathing is started immediately after such a decompression to 38,000 to 40,000 feet, a transient episode of hypoxia severe enough to impair the crew may often occur.

14

The most catastrophic consequences that can result from a rapid decompression, even though recompression to a safe pressure altitude is initiated immediately, is on that occurs:
a) within less than one second
b) to the vacuum of space
c) with breath-holding
d) while wearing the pressure demand oxygen mask

c. With breath holding. It can cause rapid expansion of the lungs, pneumothorax and airway trauma.

15

A 50 year old male was ascending from 20 feet of water, breathing normally and ascending at the rate of 60 feet per minute. At the surface he developed puffiness in his neck, a high pitched voice, and nausea. Physical exam revealed subcutaneous emphysema on the neck and a mediastinal crunch over the precordium, and the neurologic exam was normal. The most likely diagnosis is:
a) cerebral gas embolism
b) pneumothorax
c) subcutaneous emphysema, mediastinal emphysema, and pneumopericardium.
d) none of the above

c. Subcutaneous emphysema, mediastinal emphysema, and pneumopericardium.

16

The average time of useful consciousness is based on inactive subjects (meaning someone who is active about the cabin is burning up more oxygen in the muscle and cardiac tissue and their TUC would be less). The average time of useful consciousness breathing ambient air at 35,000 feet is approximately ____________.

45 seconds. Assumes a non-rapid decompression and resting person.

17

In pressurized aircraft, the rate and time of an aircraft decompression is determined by:
a) flight altitude, pressure ratio, and cabin temperature
b) size of the opening in the cabin, volume of the cabin, and the pressure differential
c) pressure differential, direction of the airflow, and volume of the cabin
d) size of the opening, direction of the airflow, and cabin temperature

b) Size of the opening, volume of the cabin, and the pressure differential

18

During high altitude flight in a pressurized aircraft, failure of the cabin may result in a rapid, violent loss of the environmental pressure. The severity during such a sudden decompression is most dependent on which one of the following factors?
a) a large cabin volume
b) a large pressure differential
c) a large pressure ratio
d) a low ambient atmospheric pressure

b) A large pressure differential

19

Without pressure suit protection, the most imminent danger following a rapid decompression to altitudes above 50,000 feet is:
a) decompression sickness
b) lung rupture
c) oxygen lack
d) boiling of body fluids

c) lack of oxygen

20

The most common mechanism operative in barotrauma is:
a) production of a relatively positive pressure in a body cavity
b) production of a relatively negative pressure in a body cavity
c) formation of bubbles of gas in an organ or along a tissue plane
d) absorption of oxygen from a body cavity
e) expansion of gas in a body cavity

b) production of a relatively negative pressure in a body cavity is by far the most common type of mechanical effect.

21

Following a rapid decompression, effective performance time is reduced by up to:
a) 75%
b) 50%
c) 25%
d) 15%
e) 5%

b) 50%

22

Pain from expanded and entrapped gastrointestinal gas at altitude is usually not incapacitating. However, it may cause:
a) syncope
b) paresthesias
c) decompression sickness
d) arterial hypoxemia

a) syncope. Vagal tone causing bradycardia.

23

At high altitude, the mechanical problem of compression of air because of its low density limits the utilization of the pressurized cabin to:
a) 16 km (10 miles)
b) 26 km (16 miles)
c) 39 km (24 miles)
d) 45 km (28 miles)

b. 26 km (16 miles). The air density above 26 km is so low that the technical problem of compression is almost impossible.

24

According to Haldane's Law, what is the lowest pressure altitude at which decompression sickness can occur?
a) 25,000
b) 22,000
c) 18,000
d) 14,000

c) 18,000 ft.

25

Which of the following factors underlies the risk of flying after diving?
a) Fatigue
b) N2 supersaturation
c) Decreased CO2 elimination
d) pulmonary barotrauma

b) N2 supersaturation

26

Neurologic decompression sickness has nearly the same incidence rate in flying and diving. Pathologic fatigue is a common complaint in flying and diving decompression sickness and there is no predilection to peripheral nerve involvement in either environment. Classical teaching states that altitude induced neurologic decompression sickness usually involves the ________ as opposed to the ________.

Brain over spinal cord.

27

Which of the following statements is TRUE with reference to cerebral gas embolism secondary to pulmonary baratrauma?
a) In diving it is seen most frequently in depths greater than 60 feet.
b) Signs and symptoms appear slowly over time.
c) It can rarely be distinguished from neurologic decompression sickness
d) It rarely occurs with rapid ascent to altitude

d) it rarely occurs in ascent in an aircraft to altitude. It can be seen in as little as 4 FSW if the diver is holding his breath. Air embolism symptoms occur within 10 minutes after the injury in almost all cases and are usually dramatic in onset, unlike neurologic decompression sickness which usually takes several hours.

28

Which of the following represents limitations on the use of US Navy diving tables for recreational divers?
a) multiple dive depths
b) flying following diving
c) diving altitudes above sea level
d) all of the above

d) All of the above. None of these issues are addressed by the US Navy dive table.

29

Which of the following is not a manifestation of decompression illness?
a) monoparesis
b) urinary retention
c) lymphedema
d) urticaria
e) joint effusion

e) Joint effusion. Joint pain is common but almost never associated with effusion.

30

A pilot flying an aircraft at a cabin altitude of 24,000 ft develops numbness and weakness of his left arm two hours after takeoff. Within 30 mins after landing the symptoms improve, with resolution of the weakness and only mild residual paresthesia. Neurologic exam is normal. Which of the following tests will probably demonstrate an abnormality?
a) Brain MRI
b) SSEP
c) EMG
d) xray of left arm
e) none of the above

e) None of the above.

31

At 35,000 feet, 10 mins after a rapid decompression, a pilot experiences cough and shortness of breath. After landing 20 minutes later he is unable to climb out of the cockpit. The first recorded blood pressure is 84/56, pulse rate of 120. Which of the following observations is likely?
a) pulmonary artery wedge pressure of 28
b) hematocrit of 55%
c) pneumomediastinum
d) None of the above

b) Hematocrit of 55. Extravasation of plasma can occur in severe decompression sickness due to endothelial damage caused by circulating bubbles, resulting in a high hematocrit.

32

Decompression Illness includes both ________ and ________.

DCS and AGE

33

Altitude decompression sickness is unusual below altitudes of __________

15,000 to 18,000 feet.

34

Decompression sickness is a result of:
a) hypoxia
b) an increase in barometric pressure
c) a decrease in barometric pressure
d) hypercapnia
e) a and c

c) a decrease in barometric pressure allowing expansion of gas bubbles.

35

Which of the following is UNCOMMON as a sign or symptom of decompression sickness?
a) Coughing
b) joint pain
c) cyanosis
d) blurred vision
e) personality change

c) cyanosis

36

How long must a person remain at sea level after diving before flying is allowed according to US Air Force regulations?
a) 2 hours
b) 6 hours
c) 12 hours
d) 18 hours
e) 24 hours

e) 24 hours

37

What is the best initial first aid for decompression sickness?

100% oxygen

38

The chokes as a manifestation of decompression sickness would best be characterized by which of the following symptoms?
a) thermal sensations of hot and cold
b) joint pain
c) substernal distress
d) blurred vision and numbness of extremities.

c) substernal distress

39

The most common form of barotrauma with both flying and diving is which of the following?
a) sinus squeeze
b) gastrointestinal squeeze
c) ear squeeze
d) pulmonary barotrauma

c) ear squeeze

40

With 100% oxygen breathing at 2.4 ATA, additional oxygen (compared to 100% oxygen breathing at sea level) is provided to tissues mostly by which of the following mechanisms?
a) skin absorption
b) enhanced hemoglobin carriage of oxygen
c) wound absorption
d) physical solution in plasma

d) physical solution in plasma

41

When a diver presents with both arterial air embolism and pain only decompression sickness following a panic ascent, the course to be followed is which of the following?
a) sea level oxygen, fluids, and observation
b) treat for air embolism
c) sea level oxygen and observation
d) treat for decompression sickness

b) treat for air embolism

42

It is of no value to refer a patient with an air embolism to a hyperbaric chamber if the time elapsed after the embolism is more than which of the following?
a) 1 hour
b) 8 hours
c) 24 hours
d) None of the above

d) None of the above. Even after a long delay between the onset of injury and treatment, hyperbaric oxygen may still be of benefit.

43

"Limb bend" pain:

May result from tissues distortion by bubbles or regional tissue hypoxia.

44

When breathing 100% oxygen under hyperbaric conditions at 2 ATA, there is a rise in cerebral venous PCO2 of about 5-6 Hg. This rise is due to:
a) the acid shift in pH
b) 100% saturation of Hgb with O2 resulting in a loss of reduced Hgb able to carry the CO2.
c) the decrease in CO2 solubility
d) toxic effect of O2 on carbonic anhydrase

b) 100% saturation of Hgb with O2 resulting in a loss of reduced Hgb to transport CO2. About 20% of CO2 is carried by reduced hemoglobin.

45

What is the primary factor limiting routine Hyperbaric Oxygen treatment of decompression sickness at 60 feet?

Oxygen toxicity. Pulmonary toxicity will occur if 100% oxygen therapy is prolonged.

46

The single most common early clinical feature of clostridial myonecrosis or gas gangrene is what?

Pain

47

The beneficial in vivo effect of HBO therapy in the treatment of gas gangrene is what?

O2 stops alpha toxin production by Clostridial organisms at tensions of 250 mmHg.

48

HBO therapy is beneficial in the treatment of carbon monoxide poisoning because:
a) increased partial pressure of O2 decrease the half life of carboxyhemoglobin
b) increased plasma dissolved oxygen results in rapid tissue oxygenation even before carboxyhemoglobin elimination is accomplished
c) increased partial pressures of O2 reverse the toxic effects of CO on the cytochrome system.
d) all the above

d) all the above