What is the primary preventive measure for DCS in unpressurized flights above 18,000 ft?

What is the primary preventive measure for DCS in unpressurized flights above 18,000 ft?

• A. Pre-breath 100% O2 for 30 minutes prior to flight
• B. De-nitrogenation (for all unpressurized flights above 18,000 ft)
• C. Pressurized cabin
• D. Limit time at altitude

Answer: (B)

When flying unpressurized above 18,000 ft, the main threat for decompression sickness is nitrogen dissolved in body tissues coming out of solution as ambient pressure drops. The most effective way to prevent this is de-nitrogenation: wash out the tissues of nitrogen by breathing 100% oxygen before the flight so that dissolved nitrogen is reduced. This lowers the tissue nitrogen tension, making bubble formation far less likely when you ascend or experience lower pressure. A practical way to achieve this is a pre-breathe routine with 100% oxygen, but the underlying concept is removing nitrogen from the tissues. Pressurizing the cabin isn’t available in this scenario, and while limiting time at altitude helps, it doesn’t address the root cause as directly as nitrogen washing does.

When flying unpressurized above 18,000 ft, the main threat for decompression sickness is nitrogen dissolved in body tissues coming out of solution as ambient pressure drops. The most effective way to prevent this is de-nitrogenation: wash out the tissues of nitrogen by breathing 100% oxygen before the flight so that dissolved nitrogen is reduced. This lowers the tissue nitrogen tension, making bubble formation far less likely when you ascend or experience lower pressure. A practical way to achieve this is a pre-breathe routine with 100% oxygen, but the underlying concept is removing nitrogen from the tissues. Pressurizing the cabin isn’t available in this scenario, and while limiting time at altitude helps, it doesn’t address the root cause as directly as nitrogen washing does.