Q. An 80-year-old male presents with shortness of breath, agonal breathing, and slight wheezing. A spirometry test shows FEV1 at 52.5% of predicted and FVC at 65% or predicting, giving an FEV1:FVC ratio of 81%. His flow volume loop is shown below. He admits to being diagnosed with atrial fibrillation about 11 years ago but states it has been well managed with medication. What is most likely causing his clinical findings?