Aeromedical: Hyperventilation & Pressure Changes

Question 1

Hyperventillation

Answer 1

An excessive rate & depth of respiration leading to abnormal loss of CO2 from the blood.

• Condition occurs more often among aviators than generally recognized.
• The human body reacts under conditions of stress & anxiety.
• Often, a marked increase in breathing occurs. This leads to a significant decrease in the CO2 content of the body & a change in the acid-base balance.

Question 2

Signs & Symptoms of Hyperventillation

Answer 2

• dizziness
• muscle spasms
• unconsciousness
• visual impairment
• tingling sensations
• hot/cold sensations.

Question 3

Treatment of Hyperventillation

Answer 3

Most effective treatment: Reduction of respiration rate.

• The normal rate is 12 to 16 breaths per minute.
• Treat by controlling breathing & go to 100% O2.
• If symptoms continue & conscious control of respiration is not possible, the individual should talk or sing. It is physiologically impossible to talk & hyperventilate at the same time.

Question 4

Pressure change effects: DYSBARISM

Answer 4

refers to the various manifestations of gas expansions induced by decreased barometric pressures.

Question 5

Boyle’s Law:

Answer 5

States that the volume of a gas is inversely proportional to its pressure, with temperature remaining constant.

Like a ballon in a bell jar. As you lower atmmospheric pressure around ballon, air trapped inside of the ballon causes the volume to increase.

https://youtu.be/N5xft2fIqQU

Question 6

Trapped Gas Disorders.

Answer 6

Free gas normally present in various body cavities expands.

Examples: GI, Middle Ear, Sinus

If the escape of the expanded volume is impeded, pressure builds up and pain is experienced.

Greater pressure changes occur from 15,000’ down to 0’ PA, especially 5000’ to 0’ PA.

Question 7

Gastrointestinal pressure

Answer 7

Gas expansion in digestive tract. Not serious most of the time, unless above altitudes of 25,000’.

• Preventive measures:
  
  • avoid eating high gas foods, such as: onions, cabbages, raw apples, radishes, dried beans, cucumbers, & melons.
  • Chewing the food well is important.
  • Avoid carbonated drinks & chewing gum during ascent.
• Relief:
  
  • belching or passing flatus
  • if pain persists descend to lower altitude

Question 8

Middle Ear Discomforts

Answer 8

The Eustachian tube normally allows air to pass outward from the middle ear.

However, with an increase in pressure during descent, the pressure of the external ear is higher than the pressure in the middle ear & the ear drum is forced inward. If the pressure differential increases appreciably, it may be impossible to open the eustachian tube.

Very painful & eardrum can rupture if the pressure is not equalized

• Relief:
  
  • Normally you can equalize pressure by swallowing, yawning, or tensing the throat muscles.
  • Valsalva maneuver.
  • If the pain increases with further descent, relief can only be obtained by ascending to an altitude where the pressure can be equalized. Then a slow descent is recommended.

Question 9

Sinus Pain

Answer 9

Sinus openings may become obstructed when the mucous membrane lining swells as a result of an infection or allegoric reaction. These conditions may make it impossible to equalize pressure.

Unlike, the ears, the sinuses are equally affected by ascent & descent.

Could involve any three of areas of the sinuses: ethmoid, frontal, & maxillary.

Question 10

Evolved Gas Disorders

Answer 10

Occurs inflight as a direct result of a reduction of atmospheric pressure.

Also known as decompression sickness.

Typically, pressure altitudes over 18,000’.

Examples: Bends, Chokes, Parasthesia, CNS

Question 11

Henry’s Law:

Answer 11

states that the amount of gas dissolved in a solution is directly proportional to the pressure of the gas over the solution.

Henry’s Heineken - Gas in an unoopened can of beer or soda is trapped in the solution, once open it equalizes with the environment eventually going flat.

https://youtu.be/18Y_2IAM5qY

Question 12

The Bends

Answer 12

Result of Henry’s Law

Typically seen in Scuba divers who surface too quickly. Gasses like Nitrogen, are dissolved in the blood due to pressure, on surfacing they escape blood and become trapped in joints and tissues.

Signs & Symptoms: At the onset, pain in the joints & related tissues may be mild, but it can become deep, gnawing, penetrating, & eventually intolerable. The pain is progressive & gets worse if ascent is continued.

Question 13

Chokes

Answer 13

Symptoms occurring in the thorax are caused by innumerable small bubbles that block the smaller pulmonary vessels.

Result of Henry’s law

• At first, a burning sensation is citied under the sternum.
• As the condition progresses, the pain becomes stabbing& inhalation is markedly deeper.
• There is almost uncontrollable desire to cough.
• Finally, there is a sensation of suffocation; breathing becomes more shallow & the skin bluish.
• An immediate descent is imperative.

Question 14

Paresthesia

Answer 14

Tingling, itching, cold, & warm sensations that are believed to be caused by bubbles formed locally or in the CNS where they involve nerve tracts leading to the affected areas in the skin.

Result of Henry’s Law

Question 15

CNS Dysfunction

Answer 15

In rare cases when aircrews are exposed to high altitude, symptoms may indicate that the brain or the spinal cord is affected by nitrogen bubble formation.

The most common symptoms are visual disturbances such as the perception of lights flashing or flickering when they’re actually steady.

Result of Henry’s Law