do you understand compensated vs uncompensated? after learning resp vs metabolic and acidosis/alkalosis, that's the next important thing.
also, Bipap is a great device to assist people in avoiding an ET tube but they have to have an adequate respiratory effort for it to work effectively. e.g. a gentleman in the ER a few weeks ago, pH 7.13, pCO2 > 80, pO2 < 60 with altered mental status and very labored respirations. Placed him on bipap, 2 hours later his gases were essentially unchanged so he got admitted to us and was subsequently intubated. his respiratory effort was so ineffective that the bipap didn't do any good (which we could have told the ER doc if he'd asked us).
for interpreting ABGs, #1 look at the pH. #2 remember that high CO2 is respiratory acidosis regardless of the pH (the actual pH only tells you if it is compensated or not), low pCO2 is respiratory alkalosis. Same is true with metabolic derangements based on HCO3/BE.
Also, look at the patient and find an explanation for the problem. sometimes it's very obvious but other times it's not. I remember a LONG time ago, in the ER a lady came in with RR 4, awake and alert, 5 day hx-n/v/d. She was in metabolic alkalosis from losing too much H+. Someone thought she needed to be intubated, but it was obvious that her body was trying to hold onto CO2 in order to lower her pH...respiratory compensation for a metabolic problem. over-zealous ventilations would have compounded her problem even more....it's those uncommon presentations that we need to be prepared for.
sorry, it's 5am. I hope this made some sense and helped a little bit.