Think you are ready for the CFRN (Certified Flight Registered Nurse) exam? Our deck rates 495 of its 1000 flashcards as hard. Try the free samples below; if they feel comfortable, you are in good shape.
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A patient is being transported at sea level with a 500 mL pneumothorax. If the aircraft ascends to 18,000 feet (where atmospheric pressure is 0.5 atm or 380 mmHg), what will be the theoretical new volume of the pneumothorax, assuming temperature remains constant?
Show answer →Using Boyle's Law (P1V1 = P2V2): P1 = 1.0 atm (Sea Level) V1 = 500 mL P2 = 0.5 atm (18,000 ft) V2 = (P1 x V1) / P2 V2 = (1.0 x 500) / 0.5 = 1,000 mL. Rationale: The volume doubles because the pressure is halved. CFRN Hard Concept: While most flights don't reach 18,000 ft cabin altitude, the BCEN uses these doubling points (Sea Level to 18k, or 18k to 33k) to test your mathematical understanding of the inverse relationship. Expansion is most dramatic at lower altitudes (the greatest pressure change per foot occurs closest to sea level).
A patient presents with a suspected ruptured globe after a penetrating eye injury. Why is air transport in a non-pressurized aircraft particularly hazardous for this patient, and what is the required transport modification?
Show answer →If air is trapped within the globe (vitreous chamber), Boyle's Law dictates it will expand during ascent. This can cause a massive increase in intraocular pressure (IOP), leading to permanent blindness or extrusion of intraocular contents. Management: 1. Ideally, transport via ground. 2. If air transport is mandatory, the pilot must maintain a Sea Level Cabin (cabin altitude <1,000 ft) or fly at the lowest possible safe altitude. Exam Note: This is an absolute consideration for flight nurses. Any trapped gas in a non-distensible space (eye, skull) requires sea-level cabin pressure.
A flight nurse experiences sharp, localized tooth pain during a rapid ascent but notices the pain resolves immediately upon descent. What is the specific term for this condition, and which gas law is the primary culprit?
Show answer →This is Barodontalgia (Flyer's Toothache). Pathophysiology: Air trapped in a diseased tooth or under a failing dental restoration (filling/crown) expands during ascent due to Boyle's Law. The pressure against the nerve causes acute pain. Distinction for Exam: 1. Barodontalgia occurs on ASCENT. 2. Barosinusitis (sinus squeeze) and Barotitis Media (ear squeeze) typically cause the most severe pain on DESCENT (as volume decreases and creates a vacuum effect). BCEN Strategy: Differentiate between ascent-related and descent-related barotrauma.
Why is the use of glass IV bottles contraindicated in the aeromedical environment, and how does Boyle's Law apply to the administration of IV fluids from plastic bags?
Show answer →1. Glass bottles cannot collapse. As altitude increases, the air above the fluid expands (Boyle's Law), which can increase the flow rate uncontrollably or lead to an air embolism. 2. Plastic bags are preferred because they collapse. However, any air trapped inside the bag will still expand, potentially stopping the pump or causing an air bolus. Clinical Pearl: Always burp IV bags to remove all air before spiking. Exam Tip: BCEN emphasizes air elimination in all fluid systems (IV bags, pressure bags, and arterial lines) to prevent Boyle's Law-related complications.
You are performing a rapid ascent in a helicopter to clear a mountain ridge. The patient, who has a clamped chest tube, suddenly develops tracheal deviation and hypotension. Explain why this occurred faster during the first 5,000 feet than it would at higher altitudes.
Show answer →This is due to the non-linear pressure changes in the atmosphere. The pressure gradient is steepest near the Earth's surface. Physics: The change in pressure per 1,000 feet is much greater between Sea Level and 5,000 feet than it is between 25,000 and 30,000 feet. Consequently, the proportional expansion of trapped gas (Boyle's Law) is most significant and rapid during the initial phases of ascent from sea level. Clinical Action: Never clamp a chest tube during flight. The sudden tension pneumothorax was caused by the rapid expansion of trapped pleural air that had no way to escape.
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Assessment
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Diagnostics
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Infection Control
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Management
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Pathology
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Pharmacology
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Physiology
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Procedures
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