CFRN General 2 — Questions and Answers
Question 1: According to Boyle's Law, what happens to a gas-filled space (e.g., pneumothorax) as aircraft altitude increases?
- Volume decreases proportionally
- Volume remains unchanged
- Volume expands as pressure decreases (Correct answer)
- Volume doubles every 1,000 feet
Correct answer: Volume expands as pressure decreases
Boyle's Law states that at constant temperature, gas volume is inversely proportional to pressure, so trapped gas expands as altitude increases and atmospheric pressure falls.
Question 2: A flight nurse is transporting a patient with a closed head injury. Which altitude-related concern is MOST critical?
- Hypothermia risk from cabin cooling
- Expansion of intracranial air and worsening ICP (Correct answer)
- Dehydration from low cabin humidity
- Hypercapnia from reduced ventilation
Correct answer: Expansion of intracranial air and worsening ICP
Trapped intracranial air expands at altitude per Boyle's Law, increasing intracranial pressure and potentially worsening herniation in head-injured patients.
Question 3: What is the primary cause of hypoxia experienced by flight crew and patients at altitude without supplemental oxygen?
- Increased carbon dioxide production
- Decreased partial pressure of oxygen (Correct answer)
- Hyperventilation-induced alkalosis
- Reduced nitrogen in inspired air
Correct answer: Decreased partial pressure of oxygen
As altitude increases, barometric pressure drops, reducing the partial pressure of oxygen (PaO2) in inspired air even though the percentage of oxygen remains 21%.
Question 4: During air transport, a patient's endotracheal tube cuff is inflated with air. What is the recommended management?
- Leave cuff pressure unchanged; air fluctuation is negligible
- Deflate the cuff completely during flight
- Inflate with normal saline or use a pressure-regulated cuff (Correct answer)
- Add extra air to compensate for altitude changes
Correct answer: Inflate with normal saline or use a pressure-regulated cuff
ETT cuffs inflated with air expand at altitude, potentially causing tracheal ischemia; filling with saline or using a pressure regulator maintains consistent cuff pressure.
Question 5: A CFRN is assessing a patient for potential time of useful consciousness (TUC) after cabin decompression. At 25,000 feet, TUC is approximately:
- 3–5 minutes
- 30–60 seconds (Correct answer)
- 10–15 minutes
- 2–3 hours
Correct answer: 30–60 seconds
At 25,000 feet the TUC is approximately 3–5 minutes; at 35,000+ feet it drops to 30–60 seconds, requiring immediate oxygen supplementation.
Question 6: Which flight physiology principle explains why sinusitis or ear pain may worsen during aircraft descent?
- Henry's Law — gas dissolving into blood
- Dalton's Law — partial pressure changes
- Gay-Lussac's Law — pressure-temperature relationship
- Boyle's Law — gas compression in blocked cavities (Correct answer)
Correct answer: Boyle's Law — gas compression in blocked cavities
During descent, atmospheric pressure rises and gas in blocked sinuses or middle ear cannot equalize, compressing trapped air and causing pain or barotrauma.
Question 7: Which of the following patients poses the GREATEST risk for decompression sickness during air transport?
- A patient who underwent laparoscopic surgery 48 hours ago
- A patient who completed SCUBA diving 4 hours ago (Correct answer)
- A patient with a simple closed femur fracture
- A patient recovering from uncomplicated appendectomy
Correct answer: A patient who completed SCUBA diving 4 hours ago
Nitrogen bubbles from recent SCUBA diving can expand and cause decompression sickness when cabin altitude increases; standard guidance is to wait 12–24 hours before flying after diving.
CFRN General 2
According to Boyle's Law, what happens to a gas-filled space (e.g., pneumothorax) as aircraft altitude increases?