I'm with you on tiramisu. If I could only have one dessert for the rest of my life, that would be it!
How much strawberry and banana did you add and when? I know you need a lot of strawberry to get any flavor, but I would've guessed banana would come through stronger.
I would guess the effect would be more pronounced, the more hops you use. So, I wonder why he decided to use a recipe with so little hops.
The human body can only detect a buildup of carbon dioxide in the lungs, not a lack of oxygen. This is why it's uncomfortable to hold your breath for a long time. If you inhale pure nitrogen while being able to exhale, there is no build up of CO2 and therefore little to no discomfort.
Wikipedia cites a USAF text, saying: "Some individuals experience headache, dizziness, fatigue, nausea and euphoria, and some become unconscious without warning."