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Difficulty: MediumDrawing Logical Conclusions

Commercial deep-sea divers replace atmospheric nitrogen with helium in their breathing mixtures to eliminate the risk of nitrogen narcosis at extreme depths. However, helium conducts thermal energy away from the human body approximately six times faster than nitrogen. In cold underwater environments, a diver inhaling cold helium-oxygen gas loses core body heat rapidly through respiration alone, even when wearing an insulated drysuit that prevents external water contact.

Based on the passage, which of the following is the most logical conclusion?

  1. A
    Eliminating nitrogen from breathing mixtures increases a diver's susceptibility to cognitive impairment at high ambient pressures.
  2. B
    Deep-sea divers can prevent hypothermia solely by increasing the thickness and insulation of their external drysuits.
  3. Protecting deep-sea divers from hypothermia requires managing the temperature of their breathing gas in addition to insulating the body.Answer
  4. D
    Helium gas mixtures significantly elevate the risk of decompression sickness during rapid ascents to the surface.

Answer

Protecting deep-sea divers from hypothermia requires managing the temperature of their breathing gas in addition to insulating the body.
The passage establishes that helium is necessary to prevent cognitive impairment at depth, but its high thermal conductivity causes severe core heat loss through inhalation that external drysuits cannot stop. Logically, keeping divers safe from cold exposure requires thermal management of the inhaled breathing gas itself alongside standard body insulation.

Step-by-Step Solution

1
Analyze the stated problem and physical constraints in the passage.
Helium is necessary to avoid nitrogen narcosis, but its high thermal conductivity causes rapid internal heat loss through breathing, which external drysuits fail to stop.
Identifying the operational conflict between gas requirements and internal thermal loss establishes the premise for a deduction.
2
Synthesize the facts to deduce the necessary condition for diver safety.
Since external drysuits only protect against external water contact and cannot stop internal respiratory cooling from cold helium, safety requires addressing the thermal state of the inhaled gas.
A logical conclusion connects the limitation of existing protection (drysuits) with the specific pathway of vulnerability (inhalation).

Key Concept

Synthesizing constraints to deduce a necessary procedural or physical condition
Estimated Time:1m 15s
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Drawing Logical Conclusions

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