A 60-year-old woman comes to the emergency department with shortness of breath.An arterial blood sample is obtained,and the following data are noted: Partial pressure of oxygen (Po₂): 75 mm Hg (normal: 75 to 100 mm Hg)
Pco₂: 58 mm Hg (normal: 33 to 44 mm Hg)
[HCO₃⁻]: 24 mEq/L (normal: 22 to 28 mEq/L)
PH: 7.24 (normal: 7.35 to 7.45)
What is the acid-base disorder?