The T1 does not know it left sea level. You do.
Dalton
PIO2 = FiO2 × (Pbar − 47). At 8,000 ft Pbar is ~565 mmHg. 50% oxygen is not the 50% you had on the ramp. SpO2 will lag the climb by under a minute.
Boyle
Trapped gas expands. ET cuff, pneumothorax, bowel, ETT pilot balloon. Recheck cuff. Recheck the chest. Ask for sea-level cabin when the airframe can give it.
What to do before lift
Ask for sea-level or 2,000 ft on the train screen (Sea-level / 2,000). Climb events cannot exceed that request. Raise FiO2 10–20 points before the climb, not after the sat falls. If a pneumo is even a rumor, decompress on the ground — the clock will not do it for you.
Turbulence
False triggers. Raise the flow trigger to 4–5 L/min. Do not hide in SIMV 'so it doesn't fight.'