You are one of the medical officers in a renowned medical center and have recently presented with a clinical case investigation below:A 40-year-old female, Mrs. Smith, works as a sales manager in the marketing department of her pharmaceutical company. Her job sometimes requires sitting in a meeting for hours together or traveling around the city on her two- wheeler for a full day. She complains of persistent cough with expectoration for the last two to three years, which increases every three to four months & then goes away for some time. Recently, she had to be admitted for exacerbation of her symptoms & was on medication with oxygen therapy for a week. Upon further investigation, she revealed that she was a smoker for eight years & has quit on regular counseling for the last two years. She also has difficulty breathing on stair climbing to her office on the first floor for almost one and a half years. Mrs. Smith also complains of getting very tired till the end of the day & does not want to go to any social event in the evening with family or friends.

Based on the clinical case presentation by Mrs. Smiths, what is likely the initial speculated disease diagnosed and why do you make such a speculation?