Certified Flight Registered Nurse (CFRN) Practice Exam

At what altitude does night vision begin to be adversely affected?

1. 3,000 ft MSL

2. 4,000 ft MSL

3. 5,000 ft MSL

4. 6,000 ft MSL

The correct answer is: 5,000 ft MSL

Night vision typically begins to be adversely affected at altitudes around 5,000 feet MSL. The reason for this relates to physiological changes that occur when a person ascends to higher elevations. At altitudes above approximately 5,000 feet, factors such as reduced atmospheric pressure and lower oxygen levels can affect the body's ability to adapt to darkness. As altitude increases, the partial pressure of oxygen decreases, which can lead to hypoxia if the body does not receive enough oxygen. This can impair the function of the eyes and reduce their ability to adapt to low-light conditions, making it more challenging to see at night. Additionally, the transition from light to dark conditions can take longer as altitude increases due to these impairments. Understanding this aspect of human physiology is crucial for flight nurses and those involved in medical transport, as it affects both the crew's and the patients' ability to see and respond to their environment effectively during night operations. Therefore, recognizing the significance of altitude on night vision is essential for maintaining safety and effective decision-making in aerial medical care.