A COPD patient was having pedal oedema for which thiazides were prescribed. Since he was complaining of excessive sleepiness an ABG sample was taken. Repo is pH= 7.42, pCO2= 67 mmHg and HCO3 = 42mEq with Na =140 mEq, K = 3.0, CL- =88 mEq. What is the diagnosis?