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BCEN CTRNFree Certified Transport Registered Nurse practice test
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Which gas law states that the quantity of gas that dissolves into a liquid is directly proportional to the partial pressure of that gas above the liquid's surface?
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Q1. Which gas law states that the quantity of gas that dissolves into a liquid is directly proportional to the partial pressure of that gas above the liquid's surface?
Correct answer: C. Henry's Law
Henry's Law governs gas solubility in liquids: as the partial pressure of a gas over a liquid rises, more of that gas dissolves into the liquid. When the pressure is removed, the dissolved gas escapes. Boyle's Law describes the inverse relationship between gas pressure and volume. Dalton's Law states that total gas pressure equals the sum of each constituent gas's partial pressure. Charles' Law relates gas volume to absolute temperature.
Q2. Which gas law describes the direct relationship between the absolute temperature of a gas and its volume?
Correct answer: A. Charles' Law
Charles' Law (V1/T1 = V2/T2) states that as temperature falls, gas volume decreases proportionally, and vice versa. Colder, denser air explains why rotor-wing aircraft generate more lift in cold weather. Boyle's Law links gas volume to pressure. Henry's Law addresses how much gas dissolves in a liquid. Fick's Law describes gas diffusion across membranes under varying pressure gradients.
Q3. What is the recommended minimum size for a helicopter landing zone?
Correct answer: D. 100 ft x 100 ft
A 100 ft x 100 ft area is the standard minimum dimension for a safe helicopter landing zone. Smaller dimensions such as 25×25, 60×60, or 70×70 feet do not provide adequate clearance for safe rotorcraft operations.
Q4. At a mass-casualty incident involving a chemical plant explosion, medical air rescue personnel are transporting burn victims to a specialized burn unit. Under the Incident Command System (ICS), which of the five functional areas do these field personnel fall under?
Correct answer: A. Operations
The ICS organizes major incident response into five functional areas: command, operations, planning, logistics, and finance/administration. In most incidents that are not extremely large-scale, only command and operations personnel are activated. Medical air crews, along with EMS, fire, and law enforcement, are categorized under the Operations branch, which handles direct tactical execution at the incident.
Q5. A patient has sustained a massive pulmonary embolism that is obstructing pulmonary circulation. Which category of hypoxia best describes this patient's condition?
Correct answer: C. Stagnant hypoxia
Stagnant hypoxia results from impaired blood circulation that prevents adequate oxygen delivery to tissues. A large pulmonary embolism obstructs pulmonary blood flow, fitting this category. Hypoxic hypoxia occurs when inspired oxygen is insufficient. Histotoxic hypoxia results from a toxin that blocks cellular oxygen utilization. Hypemic hypoxia involves reduced oxygen-carrying capacity of the blood due to blood loss or anemia.
Q6. During a transport, a patient is identified as having cyanide toxicity. Knowing that cyanide blocks mitochondrial oxygen utilization at the cellular level, which type of hypoxia is this patient experiencing?
Correct answer: C. Histotoxic hypoxia
Histotoxic hypoxia occurs when cells are unable to use available oxygen despite adequate delivery, as seen in cyanide poisoning. Hypemic hypoxia results from decreased oxygen-carrying capacity due to anemia or hemorrhage. Stagnant hypoxia is caused by circulatory failure such as from a massive pulmonary embolism. Hypoxic hypoxia results from inadequate inspired oxygen.
Q7. A rotor-wing transport crew is flying a patient with suspected pneumothorax at 10,000 feet. The patient's pulse oximetry readings begin declining, requiring increased supplemental oxygen delivery. Which gas law accounts for the decreased partial pressure of oxygen at altitude and the resulting need for supplemental oxygen?
Correct answer: A. Dalton's law
Dalton's Law states that total atmospheric pressure is the sum of the partial pressures of all constituent gases. At higher altitudes, total atmospheric pressure falls, so the partial pressure of oxygen decreases proportionally, leading to lower SpO2 and greater supplemental oxygen requirements. Boyle's Law explains expansion of gas-filled spaces (e.g., pneumothorax enlargement) as altitude rises. Charles' Law relates temperature to gas volume. Gay-Lussac's Law links pressure to temperature, explaining why ambient temperature drops at altitude.
Q8. During rotor-wing transport at 10,000 feet, a patient with a suspected pneumothorax reports feeling cold and requests additional blankets. Which gas law explains why ambient temperature decreases as altitude increases in an unpressurized aircraft?
Correct answer: D. Gay-Lussac's law
Gay-Lussac's Law describes the relationship between pressure and temperature: as altitude increases, atmospheric pressure drops, resulting in lower ambient temperatures. Occupants of unpressurized aircraft at altitude therefore experience colder conditions and may require extra insulation. Dalton's Law governs partial pressures of gas mixtures. Charles' Law relates temperature to volume. Boyle's Law describes the inverse relationship between pressure and gas volume.
Q9. A patient develops a tension pneumothorax in-flight. This compresses the mediastinum and obstructs venous return. Which type of hypoxia does this clinical scenario represent?
Correct answer: B. Stagnant hypoxia
Stagnant hypoxia is defined by inadequate blood flow preventing oxygen delivery to tissues. A tension pneumothorax compresses the mediastinum and vena cava, obstructing venous return and reducing cardiac output, which fits this classification. Histotoxic hypoxia is caused by cellular-level toxin interference. Hypoxic hypoxia results from insufficient inspired oxygen. Hypemic hypoxia stems from reduced blood oxygen-carrying capacity due to blood loss or anemia.
Q10. A COPD patient is being transported by ground ambulance to the hospital during an acute exacerbation. Which of the following is considered an unreliable clinical sign when assessing for hypoxia?
Correct answer: B. Cyanosis
Common reliable indicators of hypoxia include dyspnea, elevated blood pressure, increased heart rate, respiratory rate, pallor, and confusion, and the treatment is 100% supplemental oxygen. Cyanosis, however, is an unreliable sign because it only becomes visible when oxygen saturation falls below approximately 75% in patients with normal hemoglobin, meaning severe hypoxia may already be present before cyanosis appears.
Exam facts and objectives sourced from the official BCEN (Board of Certification for Emergency Nursing) certification page. Last reviewed June 2026.
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