A 52-year-old patient suffers from marked dyspnea during physical exertion, non-productive cough. The patient's condition has been persisting for 8 months. The patient has been a smoker for 30 years. In the lungs there are cellophane-type crackles auscultated on both sides. Respiration rate is 26/min., oxygen saturation of blood is 92%. On spirometry: moderate restrictive-type disturbance of external respiration. What is the most likely diagnosis?