Certified Transport Registered Nurse Certification Practice Exam

At what altitude is the physiologic zone or indifferent stage recognized?

1. 5,000 ft

2. 10,000 ft

3. 15,000 ft

4. 20,000 ft

The correct answer is: 10,000 ft

The physiologic zone, also known as the indifferent stage, is typically recognized at an altitude of approximately 10,000 feet. At this altitude, the human body still functions normally, although there are minor physiological changes that begin to occur as a response to reduced atmospheric pressure and oxygen availability. In this zone, individuals may experience some initial effects of altitude like slight breathlessness during exertion but are usually able to acclimatize without significant complications. This stage serves as an important reference point for understanding how altitude affects human physiology and informs protocols for both medical care and transport nursing, where awareness of altitudinal impacts is crucial for patient safety and care during air transport. Higher altitudes, such as those listed beyond 10,000 feet, introduce more pronounced physiological stress, leading to increased risks of altitude sickness and other complications, primarily related to oxygen deprivation. Understanding the indifferent stage is vital for those in transport roles, as it guides planning and risk management strategies when transporting patients at altitude.