Mr. R. is a 66-year-old man who has smoked 1.5 packs of cigarettes a day for 40 years (60 pack-years). He is admitted with an acute exacerbation of COPD. His baseline ABGs drawn in the clinic 2 weeks...

Mr. R. is a 66-year-old man who has smoked 1.5 packs of cigarettes a day for 40 years (60 pack-years). He is admitted with an acute exacerbation of COPD. His baseline ABGs drawn in the clinic 2 weeks ago showed: pH, 7.36; PaCO₂, 55 mm Hg; PaO₂, 69 mm Hg; bicarbonate, 30 mEq/L; SaO₂, 92%. In the critical care unit, Mr. R. has coarse crackles in his left lower lung base and a mild expiratory wheeze bilaterally. His cough is productive of thick yellow sputum. His skin turgor is poor; he is febrile, tachycardic, and tachypneic. Currently, Mr. R.’s ABGs while receiving O₂
at 2 L/min via a nasal cannula are: pH, 7.32; PaCO₂, 64 mm Hg; PaO₂, 50 mm Hg; bicarbonate, 30 mEq/L; SaO₂, 86%.

a. What is your interpretation of Mr. R.’s baseline ABGs from the clinic?

b. What is the probable cause of Mr. R.’s COPD exacerbation, and what treatment is indicated at this time?

c. What ABG changes would indicate that Mr. R.’s respiratory status is deteriorating?