A 67-year-old man with a 45-pack-year smoking history presented with worsening dyspnea. His resting oxygen saturation was 94%, declining to 86% after walking for 60 meters. A pulmonary examination revealed inspiratory crackles at the bases and diminished breath sounds at the apices. A cardiovascular examination showed normal results, without peripheral edema. A chest x-ray showed hyperinflation and increased interstitial markings. Pulmonary function tests were obtained (Table; Figure).
Heckman EJ, O’Connor GT. Pulmonary Function Tests for Diagnosing Lung Disease. JAMA. 2015;313(22):2278-2279. doi:10.1001/jama.2015.4466