Atelectasis is a preventable complication that often occurs after upper abdominal surgery. In our 1-year randomized, researcher-blinded trial, low-risk cholecystectomy patients were subjected to either the thoracic lymphatic pump (n = 21) or incentive spirometry (n = 21) to prevent atelectasis. The treatment groups were equal with respect to risk factors for atelectasis and deviation of preoperative respiratory parameters (forced vital capacity [FVC] and forced expiratory volume in one second [FEV1]) from the predicted values. Atelectasis occurred in 2 (5%) of 21 patients regardless of whether incentive spirometry or thoracic lymphatic pump treatment was used. Study patients treated with the thoracic lymphatic pump technique had an earlier recovery and quicker return toward preoperative values for FVC and FEV1 than patients treated with incentive spirometry.