Operational Aerospace Medicine Flashcards
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.
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.
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.
Stratosphere.
This is the layer of the atmosphere where most meteors disappear.
Mesosphere
This area of the atmosphere has a gradual increase in temperature, no upper limit, and is the domain of auroras.
Thermosphere
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.
Ionosphere
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?
75%
At 60 mmHg on the Oxygen Hemoglobin Dissociation curve corresponds to what saturation of oxygen assuming a normal venous partial pressure of oxygen?
90%
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
