An 80-year-old woman presents to ER with a two day history of persistent vomiting. She is lethargic and weak and has myalgia. Her mucous membranes are dry and her capillary refill is prolonged. She is diagnosed as having gastroenteritis and dehydration. Her ABG shows: PH 7.5, PaO2 85 mm Hg, PaCO2 43 mm Hg, and HCO3 37 mmol/L The acid-base disorder shown is uncompensated