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Will prior hyperventilation reduce cerebral blood flow during escape from a submarine?
C M House1, D F Grist, D D Denison
1Institute of Naval Medicine, Gosport, United Kingdom.
Summary
Hyperventilation significantly lowers cerebral blood velocity (CBV), but this effect is not sustained during submarine escape simulations. Therefore, hyperventilation is not recommended to prevent decompression illness (DCI).
Area of Science:
- Physiology
- Aerospace Medicine
- Diving Medicine
Background:
- Decompression illness (DCI) is a risk during submarine escape.
- Cerebral blood velocity (CBV) is a potential indicator for DCI risk.
- Hyperventilation is explored as a method to reduce CBV.
Purpose of the Study:
- To investigate if hyperventilation reduces CBV during simulated submarine escape.
- To assess if reduced CBV can mitigate DCI risk and allow deeper escapes.
Main Methods:
- Eight subjects underwent mock submarine escape exercises.
- Cerebral blood velocity (CBV) measured via Doppler ultrasound.
- Conditions included rest, hyperventilation, and post-hyperventilation rest before escape.
Main Results:
- Hyperventilation reduced mean CBV by 45%.
- CBV was 10% lower during initial immersion after hyperventilation (P < 0.05).
- CBV reduction was not consistently sustained during the escape procedure.
Conclusions:
- Hyperventilation effectively reduces CBV.
- The CBV reduction is not sustained or consistent enough for submarine escape.
- Hyperventilation is not recommended for preventing DCI during submarine escape.