Turning on Oxygen switch part way through flight doesn't prevent or cure hypoxia

[bitwrestler]

When you turn on oxygen part way into a flight (because I forgot to turn it on on cold startup), you still get hypoxia at high altitudes until you lower your altitude even if its been on for 30+ minutes.

Steps to reproduce the behavior:

1. Don't turn on Oxygen at startup
2. Turn it on part way through flight while still below 20K
3. Fly high for a while above 20K (not sure how long)
4. Vision blurs until you lower to below about 12-25K even with Oxygen on shortly after take off

I would think turning oxygen on anytime would pretty quickly cure hypoxia or prevent it from happening

Software Information (please complete the following information):

• DCS 2.9.1.48336 open beta
• A-4E Version 2.2

[Drofseh]

This definitely used to work, as I have made the mistake of forgetting it before and turned it on midflight.