Post-COVID Persistent Restriction

A 61-year-old male with obesity and hypertension presents 8 months after severe COVID-19 pneumonia requiring 21 days of mechanical ventilation and 6 days of ECMO. He reports persistent exertional dyspnea (mMRC 3), dry cough, and inability to work. Examination reveals bilateral fine crackles at lung bases. HRCT shows bilateral peripheral reticulation, traction bronchiectasis, and early honeycombing consistent with post-COVID fibrosis. The flow-volume loop shown displays the pattern marked **A** — a distinctly small loop with smooth convex expiratory curve and preserved FEV1/FVC ratio of 0.86. Which of the following best characterizes the pathophysiology underlying the restrictive small-loop pattern marked **A** in this patient?