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Flashcards in Operational Aerospace Medicine Deck (49):

The aeromedical evacuation of an anemic patient can present serious hazards in regard to O2 delivery to tissues at altitude. When transporting a patient with an anemia of unknown etiology whose hemoglobin is approximately 7.5 grams, the flight surgeon should:
a) transfuse the patient with whole blood, then evacuate by aircraft.
b) not transport the patient by aircraft but should utilize surface transportation as expeditiously as possible.
c) transport by air if most feasible and administer O2 in flight.
d) None of the above.

c) transport by air and administer O2 in flight. While anemia results in the reduction of the O2 capacity of blood, it does not necessarily change the O2 saturation of hemoglobin. Those with a hemoglobin of 7 grams at sea level and at rest can compensate quite readily. At altitude, however, the O2 saturation may be reduced; therefore, the administration of O2 can ensure 100% O2 saturation of the available hemoglobin. It is generally accepted that an anemic patient can be evacuated and that oxygen should be given if the hemoglobin is below 8.5 grams. Administration of whole blood may shift the hemoglobin dissociation curve due to increased 2,3 DPG in stored blood.


Loudness is a subjective awareness of sound as contrasted to sound intensity. Even if a sound is made 20 dB more intense, it may be no louder if the patient still cannot hear it. An abnormally rapid increase in loudness is termed:
a) amplification
b) recruitment
c) shadow curve
d) diplacusis

b. Recruitment is an abnormally rapid increase in loudness. A person with normal hearing interprets any two sounds having the same intensity as being equally loud when listening through earphones. When cochlier disease is unlateral as in Meniere's disease, one ear may exhibit recruitment and the other may not. Sounds of equal intensity, presented as threshold levels, will be heard by the good ear but not by the recruiting ear because it is partially deafened and cannot hear faint sounds at all. The phenomenon of recruitment is apparent when the sound intensity is raised sufficiently for the recruiting ear to hear. Amplification is the increase in sound intensity. Diplacusis is the term used to denote double hearing. A shadow curve is produced normally when a patient is presented with an intense sound to a unilateral dead ear through headphones. The sound travels across his head to his normal ear and is reported as being heard.


Most weather occurs at this area of the atmosphere:
a) Stratosphere
b) Troposphere
c) Mesosphere
d) Thermosphere

b) Troposphere- Most weather occurs here. Varying water vapor and moisture content, turbulent air, constant rate of temperature decrease with altitude.


This area of the atmosphere has an almost complete absence of moisture and a nearly uniform temperature of -55 degrees C, varying with latitude more than altitude. Most ozone exists at this level.



This is the layer of the atmosphere where most meteors disappear.



This area of the atmosphere has a gradual increase in temperature, no upper limit, and is the domain of auroras.



An exception to the rule on classification on the basis of temperature, the __________ starts at roughly 50 miles and ends at 600 miles. It acts as a reflector for long-wavelength electromagnetic radiation.



The atmosphere may also be classified based on pressure zones. Physiologic pressure zone ranges from the surface to _________ feet.

10,000 feet.


The physiologic deficient pressure zone ranges from _________ to _______ feet and oxygen is required.

10,000 to 50,000 feet


The Space Equivalent pressure zone ranges from _________ to 120 miles and the pressure decreases to 1mm Hg. full pressure suit or pressurized cabin is required.

50,000 feet


From the pressure zone perspective, space begins at what altitude?

120 miles


The volume varies inversely with pressure; V1/V2 = P2/P1 is an example of what gas law?

Boyle's Law. Wet gas occupies more volume than dry gas. At 18,000 feet a gas bubble is twice its sea-level size.


This law covers mixed gases and states that the total pressure of a mixed gas is equal to the sum of each of the individual gas pressures. It helps explain partial pressures and why less oxygen is available per volume at altitude.

Dalton's Law.


This law states that the quantity of a gas dissolved in a liquid is proportional to the partial pressure of the gas in contact with the liquid; the law responsible for decompression sickness.

Henry's Law


When we ascend to altitude the environment is one of changing ________ due to the Law of Dalton, changing __________ due to the Law of Boyle, and finally also changing dissolved inert gas loads in the body due to the Law of ___________.

Pressure, Volume, Henry


40 mm Hg on the Oxygen Dissociation Curve corresponds to what saturation of oxygen assuming a normal venous partial pressure of oxygen?



At 60 mmHg on the Oxygen Hemoglobin Dissociation curve corresponds to what saturation of oxygen assuming a normal venous partial pressure of oxygen?



Hyperventilation will ensure below an alveolar PO2 of ____________.

55 to 60 mmHg. This results in a decrease in the partial pressure of CO2 and respiratory alkalosis. This in turn decreases P50 resulting in decreased tissue oxygenation and increased nerve irritability.


This type of hypoxia is secondary to a lack of oxygen in the atmosphere at altitude and is caused by decreased partial pressure of oxygen in the ambient atmosphere.

Hypoxic hypoxia


This type of hypoxia is caused by decreased tissue profusion or circulation of blood flow to the tissues. It can occur with sustained acceleration and in heart failure or shock.

Stagnant hypoxia


This type of hypoxia occurs due to the inability of the body to use oxygen at the cell and tissue level because of toxins that impart those functions. A classic mechanism for this to occur is cyanide poisoning.

Histotoxic hypoxia


This type of hypoxia is due to a decreased ability of the blood to carry oxygen to the body tissues. This can be due to a lack of blood as the carriers of oxygen or the contamination of blood with substances like carbon monoxide or methemoglobin, which impairs its ability to carry oxygen to the tissues.

Anemia or hypemic hypoxia


The "amount of time in which a person is able to effectively or adequately perform flight duties with an insufficient supply of oxygen" is the definition of what?

Effective Performance Time aka Time of Useful Consciousness


What is the effective performance time at 18,000 feet?

20 to 30 minutes


What is the effective performance time at 35,000 feet?

30 to 60 seconds


What is the effective performance time at 43,000 feet?

less than 10 seconds.


At altitudes greater than _________ a full pressure suit or a closed cabin with pressurized oxygen is required and pressure breathing alone is not sufficient.

50,000 feet


At sea level, the volume of a given unit of gas will double at what altitude?

18,000 feet


At sea level, the volume of a given amount of gas will triple at what altitude?

28,000 feet


At sea level, the volume of a given amount of gas will QUINTUPLE at what altitude?

39,000 feet


Any decompression that occurs is less than _______ seconds is considered to be explosive in nature.

0.5 seconds.


Time of Useful Consciousness is cut by ________ by a rapid decompression.

50%, literally in half.


Haldane noted that DCS could be prevented by avoiding pressure ratios exceeding a _______ ratio in pressure changes.



Regarding flying after diving, the recommended waiting period before going to altitudes of 8,000 feet or above is _____________ after a non-decompression stop dive, and ___________ after decompression stop diving.

12 hours, 24 hours.


Notes- Fetal hemoglobin and Bohr effect compensates for reduced PaO2 at 8,000 feet.
First trimester- bleeding or cramping, do not fly.

Over 36 weeks, greater chance of delivery in flight.


NOTES- NASA- Two crewmembers trained as CMO's. Limited 7 day quarantine.

No absolute contraindications for MEDEVAC. Untreated pneumothorax is contraindication for critical care air transport. If you place the chest tube on heimlich valve you should be ok. Wait 5-7 days post op for abdominal surgery where gas was used (laparoscopy).


NOTES- COPD HAST test. 85% nitrogen 15% oxygen (equal to 8,000 feet) if less than 55 mmHg PaO2, they will have difficulty and need supplemental O2. Best predictor is a PaO2 of less than 60 at sea level.

How soon can you fly a patient with active TB before they are no longer a risk to other aircraft passengers? 2 weeks after medication started.


NOTES- FAA rules governing transportation of patients by air. There are no rules by the FAA. They are concerned with pilots, not patients. They do not address patient care recommendations.

If transporting an anemic patient with 7.5 grams of hemoglobin, what should you do? Transport by air if most feasible and administer O2 in flight. Why not transfuse then fly? Increased 2,3 DPG.
Regarding flying a DCS patient. Fly in pressurized cabin. If not available, helicopter is acceptable is you can stay at 200 AGL.


NOTES- Airport must have an emergency plan, and provide medical assistance and transport for largest aircraft. Must be reviewed annually and exercised every three years.

FAR 25.803- REquires that a full passenger load be evacuated from the aircraft within 90 secs, with half the emergency exits blocked.
Panic is not common in disasters, getting people to evacuate is.


NOTES- DMORTS- Mortuary teams, 10 regional.
Three Disaster Portable Morgue Units.
Triage is the MOST important factor in disaster survival.

JCAHO requires hospitals to test the hospital disaster plan twice a year.
Disasters use the Incident Command System.
EMS is under the control of the Chief of Operations in the ICS system.
Airports review the emergency plan with all involved parties annually and test it with a drill every three years.


NOTES- Air Transport pilots (1st class) must have physical every 6 months if over 40, and annually is less than 40 years of age.
Class 2 pilots must have a physical annually.
Class 3 pilots 40 and over every 2 years, less than 40 every 5 years.

If a pilots class one expires, they may perform the next lowest class for 6 more months. After that, may perform 3rd class for 12 more months.


Notes- All flight service stations (FSS) are contractor supported now (Lockhead) EXCEPT for Alaska. Sen Stevens still has Alaska serviced by the FAA.
ATC's have FAA requirements. FAA Order 3930.3 B states that ATC standard now equivalent to FAA class 2 pilot medical standard

SODA is a statement of demonstrated ability. Must demonstrate proficiency to an FAA inspector (loss of eye or limb etc).

Appeals must be filed within 60 days of FAA decision. Pilot may petition to NTSB for review. Administrative law judge at NTSB hears the case. Has the agency applied its standards appropriately to pilot. Can appeal all the way to Supreme Court.


NOTES- There is no "ground chit" in the FAA.
At NASA MMPB coordinates medical system support for ISS.
MSMB medical certifies all crewmembers for spaceflight on ISS.

Fatality rates are calculated per 100,000 hours. General aviation has 2 per 100,000 per year.


NOTES- What's an accident?
ICAO definition:
Any occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight until such time as all such persons have disembarked.

FAA and NTSB subscribe to that definition. Fatal accident is any of above that involves a fatality within 30 days of the accident. Military has no time limit on fatality. It also includes any incident that has greater than $50K in damages.
85% of General Aviation accidents are due to human error. Air Transport accidents 38% are human error.
The largest single cause of general aviation accidents is SPATIAL DISORIENTATION


NOTES- NASA administers the ASRS (Aviation Safety Reporting System). Anonymous.

Impact to fire ratio of death 2:1. Deformation of seats and restraints kill passengers.


NOTES- Standards of evidence when identifying a body:
Visual, personal effects, physical features (hair, eye color, tattoo, blood type), Flight manifest. The greater number that match, the greater certainty of ID.

Positive evidence: 5 things
Fingerprints, footprints, dental comparison, xray comparison, DNA analysis (gold standard)
Best specimen for alcohol or tox is the vitreous of the eye.
Aviator's Astragalus- Fracture of the talus resulting from impact, most commonly in helicopter operators. Forces applied by the rudder bar.


Mnemonic for organizing crash survival factors: CREEP
Container: Occupiable space in the aircraft
Restraint: occupant restraints
Environment: Conditions in cabin during crash (breaking of seats, etc)
Energy absorption: attenuate crash forces
Post crash environment: Fire, smoke, etc.

Low molecular weight heparin may be indicated for DVT prophylaxis in passengers with prior DVT or risk factors.


When determining to what extent individuals are suited to air traffic control work, which of the following factors is not considered protective?

College Grade Point Average


What percent of fatally injured aircraft occupants of structurally survivable general aviation accidents have demonstrated head trauma?