D.Z., a 68-year-old man, is admitted at 1600 to a medical floor with a diagnosis of acute exacerbation of chronic obstructive pulmonary disease (COPD). His other past medical history includes hypertension and type 2 diabetes. He has had pneumonia yearly for the past 3 years and has been a two-pack-a-day smoker for 38 years. His current medications include enalapril (Vasotec), hydrochlorothiazide (HCTZ), metformin (Glucophage), and fluticasone/salmeterol (Advair). He appears a cachectic man who is experiencing difficulty breathing at rest. D.Z. seems irritable and anxious; he complains of sleeping poorly and states that lately he feels tired most of the time. He reports cough productive of thick yellow-green sputum. You auscultate decreased breath sounds, expiratory wheezes, and coarse crackles in both lower lobes anteriorly and posteriorly. His vital signs (VS) are 162/84, 124, 36, 102° F (38.9° C), and Spo2 88%.