A 62-year-old man is a smoker with a 10-year history of cough productive of copious mucopurulent sputum. Over the past 6 months, he has developed progressive dyspnea. Physical examination shows bilateral pedal edema and a soft but enlarged liver. A chest radiograph shows bilateral pleural effusions and a prominent right heart border. Arterial blood gas values are PO2, 60 mm Hg; PCO2, 52 mm Hg; pH, 7.30; and HCO3-, 29 mEq/L. He is intubated and placed on a ventilator, and he requires increasing amounts of oxygen. Which of the following microscopic findings is most likely to be present in the affected lungs?