I'll second that. If you put air in the bottle it will begin to degrade the N and it will continue to degrade over time. The reason the lady in the video pushes air into the bottle is for the reason of exchanging the volume of air to the ratio of medicine she extracts and it is for pressurisation reasons like you suggested but with the 200ml bottles of N they are much thicker stronger glass and the small amount of liquid we take for testing is a very small percentage of the overall volume. Those small vials would be more prone to pressure issues. Chances are it won't brrak but eventually it would become harder to pull liquid from it with a syringe. If you were to intend to use the N frequently and take multiple doses that way from the bottle then yes, then you would probably need to start doing that exchange of air/volume ratio thing but in our cases, just for testing it's not necessary. Many have reported doing so without issue.