Certified Flight Registered Nurse (CFRN) Practice Exam

At which altitude does the risk for decompression sickness increase during flight?

1. 10,000 ft MSL

2. 18,000 ft MSL

3. 5,000 ft MSL

4. 8,000 ft MSL

The correct answer is: 18,000 ft MSL

The risk for decompression sickness significantly increases at altitudes around 18,000 feet MSL (Mean Sea Level) due to the decrease in atmospheric pressure. At lower altitudes, the partial pressure of nitrogen in the air is higher, allowing for a greater amount of nitrogen to be dissolved in body fluids and tissues. As altitude increases and atmospheric pressure decreases, nitrogen comes out of solution and can form bubbles in the tissues and bloodstream, leading to decompression sickness. At 18,000 feet, the environment becomes particularly susceptible to this phenomenon because the lower pressure means that diversifying nitrogen levels in the body can be problematic. This is why regulatory agencies and medical professionals often highlight the altitude of 18,000 feet as a critical threshold where the risks associated with decreased atmospheric pressure warrant heightened awareness and preparedness among medical personnel, such as flight nurses and air medical providers. Understanding these physiological changes and their associated risks is essential for Certified Flight Registered Nurses who frequently operate at elevated altitudes where such conditions can arise.