Using Pre-Operative Incentive Spirometer Reduces Chances of Basal Atelectasis in Patients Undergoing Upper Abdominal Surgeries - A Randomized Controlled Trial. - Naeem, Muhammad; Aziz, Majid; Saeed, Bilal; Hashmi, Syed Daood; Ali, Muhammad; Jalil, Meezan (Pakistan Armed Forces Medical Journal, 2025)