Surgeons sometimes ask patients to whistle after surgery to check if their lungs and diaphragm are working properly.

Post-operative pulmonary complications (PPCs) occur in approximately 5% to 10% of patients undergoing major surgery. General anesthesia and neuromuscular blocking agents like succinylcholine can temporarily weaken the diaphragm and intercostal muscles. This weakness often leads to atelectasis, a condition where the small air sacs called alveoli collapse due to shallow breathing.Whistling serves as a form of incentive spirometry, a technique used since the 1970s to improve lung function. Unlike normal speech, whistling requires a sustained, pressurized exhalation that forces the diaphragm to contract more forcefully. This increased intra-abdominal pressure helps clinicians verify that the phrenic nerve, which controls the diaphragm, was not damaged during the procedure.Medical studies, such as those published in the Journal of Clinical Anesthesia, highlight the importance of early mobilization and deep breathing exercises. Whistling acts as a natural 'positive expiratory pressure' (PEP) therapy. This resistance helps keep the airways open longer and facilitates the clearance of mucus from the lungs.By successfully whistling a clear note, a patient demonstrates that they have sufficient 'vital capacity,' which is the maximum amount of air a person can expel from the lungs after a maximum inhalation. This simple bedside test is particularly useful in recovery rooms to ensure a patient can cough effectively. A strong cough is the body's primary defense against post-surgical pneumonia.