Altitude & Decompression Sickness

Altitude and Decompression Sickness

Decompression sickness (DCS) and altitude sickness are two significant medical concerns that can affect pilots and passengers when exposed to high altitudes. Understanding their causes, symptoms, and preventive measures is essential for ensuring flight safety.

Decompression Sickness (DCS)

Causes of DCS

DCS occurs when a person is exposed to a rapid decrease in barometric pressure, causing nitrogen dissolved in body tissues and fluids to come out of physical solution and form bubbles. This condition typically arises when flying in unpressurized aircraft at high altitudes or following a rapid decompression event.

Symptoms of DCS

The symptoms of DCS can vary depending on where the nitrogen bubbles form in the body. Common categories of DCS symptoms include:

• The Bends: Joint and muscle pain, typically in the large joints such as the knees, shoulders, or elbows.

• Neurological Symptoms: Dizziness, headaches, confusion, memory loss, vision problems, and even unconsciousness.

• Chokes: Severe chest pain, coughing, and difficulty breathing.

• Skin Bends: Itching, skin mottling, or a sensation of insects crawling on the skin.

Figure 1 Signs and symptoms of altitude decompression sickness (Pilots Handbook of Aeronautical Knowledge)

Responding to DCS

If DCS symptoms occur in flight:

• Put on oxygen immediately using a 100% oxygen supply.

• Initiate an emergency descent to a lower altitude.

• Land as soon as possible for medical evaluation.

• Keep the affected area still if experiencing joint pain to prevent further injury.

• Seek specialized medical care from an FAA medical officer, AME, or hyperbaric medicine specialist.

DCS After Scuba Diving

Flying after scuba diving poses an increased risk of DCS due to the excess nitrogen absorbed into body tissues during a dive. Recommended waiting times before flying are as follows:

• At least 12 hours after non-decompression stop diving (dives that don’t require controlled ascent).

• At least 24 hours after dives requiring controlled ascent (decompression stop dives).

• At least 24 hours before flying above 8,000 feet MSL.

Failure to adhere to these guidelines can lead to a serious inflight medical emergency.

Altitude Sickness

Causes of Altitude Sickness

Altitude sickness, also known as hypobaric hypoxia, occurs when the body is unable to adjust to reduced oxygen levels at higher altitudes. It is most common above 8,000 feet and can develop even in pressurized cabins if the pressurization system fails.

Symptoms of Altitude Sickness

Common symptoms of altitude sickness include:

• Headache

• Dizziness or lightheadedness

• Nausea or vomiting

• Fatigue or weakness

• Shortness of breath

• Impaired cognitive function

In severe cases, altitude sickness can lead to high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE), both of which are life-threatening conditions.

Preventing and Managing Altitude Sickness

To reduce the risk of altitude sickness:

• Ascend gradually and allow time for acclimatization when flying to high altitudes.

• Use supplemental oxygen when necessary.

• Stay hydrated and maintain a healthy diet.

• Avoid alcohol and sedatives that can depress the respiratory system.

• Monitor for symptoms and descend to a lower altitude if symptoms worsen.

If symptoms occur during flight, the immediate response should include using supplemental oxygen and initiating a descent to a safer altitude.

Decompression sickness and altitude sickness are preventable conditions when proper precautions are taken. Pilots should remain vigilant, follow recommended guidelines, and act promptly if symptoms arise. By understanding these physiological risks, flight crews can ensure the safety and well-being of themselves and their passengers at all altitudes.