A 65-year-old male is admitted to the progressive care unit with a diagnosis of pneumonia. He has a past history of pulmonary disease and diabetes. A set of arterial blood gases is obtained on admission on room air including the following: pH 7.35; PaCO2 55 mm Hg; bicarbonate 30 mEq/L; PaO2 65 mm Hg. These levels reflect: