A 65-year-old man complains of two years of persistent cough. He says that he coughs up whitish sputum almost every morning on waking, and then continues coughing throughout the day. He also complains of exertional shortness of breath that becomes disabling if he gets an upper respiratory infection. He has smoked one pack of cigarettes daily for the past 40 years. Pulmonary function testing reveals a vital capacity that is 65% of his predicted. Which of the following best explains this finding?

Question

A 65-year-old man complains of two years of persistent cough.  He says that he coughs up whitish sputum almost every morning on waking, and then continues coughing throughout the day.  He also complains of exertional shortness of breath that becomes disabling if he gets an upper respiratory infection.  He has smoked one pack of cigarettes daily for the past 40 years.  Pulmonary function testing reveals a vital capacity that is 65% of his predicted.  Which of the following best explains this finding?

Quizplus · Accepted Answer

This patient's history and presentation are classic for chronic obstructive pulmonary disease (COPD), with components of both chronic bronchitis (chronic cough with sputum production) and emphysema (dyspnea). Typically caused by cigarette smoking, COPD is marked by progressive decreases in the expiratory airflow rate, which manifests as a forced expiratory volume in 1 second (FEV₁) to forced vital capacity (FVC) ratio of less than 0.7. As airflow limitation increases, more air is trapped during expiration and the residual and total lung volumes increase. Air trapping and airflow obstruction in severe disease also decrease the vital capacity (VC) as described in this patient. An accompanying process is destruction of the alveolar-capillary membrane, possibly due to excessive lysis of lung structural proteins. (Choice A) The alveolar-capillary membrane is the site of respiratory gas exchange. This membrane is destroyed in COPD. (Choice B) Due to air trapping, COPD patients have increased functional residual and total lung capacities. (Choice D) The alveolar-capillary membrane is destroyed in COPD, resulting in increased lung distensibility and compliance. Lung distensibility is decreased in pulmonary fibrosis. (Choice E) Respiratory muscle fatigue occurs in a number of diseases like botulism, Guillain-Barré syndrome, amyotrophic lateral sclerosis, and myasthenia gravis. Respiratory muscle failure is not a hallmark of early COPD. Educational objective: COPD is characterized by progressive expiratory airflow limitation which causes air trapping, decreased VC and increased total lung capacity. FEV1 is disproportionately decreased as compared to VC.

A 65-Year-Old Man Complains of Two Years of Persistent Cough