A 58-year-old female smoker with end-stage chronic obstructive pulmonary disease and osteoarthritis is on ipratropium bromide and albuterol inhalers, and hydrocodone-acetaminophen. She presents with respiratory distress for 2 days accompanied by increased thick, yellow sputum production, low grade fever, and increasing confusion. On examination she is mildly obtunded but arousable, BP 160/100, pulse 115/min, RR 30/min, O2 saturation 84% on her usual 3 L/min nasal cannula oxygen. She is using accessory muscles to breath, has diffuse wheezing and rhonchi bilaterally, a prolonged expiratory phase, distant but regular heart sounds, and no peripheral edema.Arterial blood gases (ABGs) on arrival are as follows:pH: 7.20,PO2: 70 mm HgPCO2: 65 mm Hgcalculated HCO3 29 mEq/L.Electrolytes return shortly thereafter as follows:Na: 140 mEq/LK: 5.1 mEq/LHCO3: 29 mEq/LCl: 100 mEq/LBUN 20 mg/dL creatinine 1.5 mg/dLglucose 89 mg/dL.After prompt initiation of noninvasive positive pressure ventilation (Bi-pap), blood cultures, toxicology screen, intravenous fluids, and IV antibiotics, you have time to consider the patient's metabolic situation. Choose the answer which best describes the acid-base condition and its etiology.