Pressure breathing equipment requires a different training regime. You do not, and will not, have pressure breathing equipment on an aeroplane for which you are not trained in its use. You have a mask that has an overpressure for the smoke scenarios and it provides 100% oxygen above approx 30000 feet. It mixes this with ambient below this level.
These masks increase the amount of O2 available to you and do NOT work by increasing the pressure of the O2 to get it into your haemoglobin. It is the partial pressure of the O2 within the gas (atmosphere) that does this. The O2 partial pressure decreases as we climb, which is why more O2 is required. We are NOT pressure breathing in a decompression.