Incentive spirometry
Agostini P, Singh S (2009) Incentive spirometry following thoracic surgery: what should we be doing? Physiotherapy, 95, 2, 76-82
postoperative physiotherapy regimes, with or without incentive spirometry, are effective following thoracic surgery compared with no physiotherapy.

Alaparthi GK, Augustine AJ, Mahale ARA (2014) Comparison of flow and volume oriented incentive spirometry on lung function and diaphragm movement after laparoscopic abdominal surgery: a randomized clinical pilot trial. Internat J Physiother Res; 1(5):274-278

Bellet PS et al (1995) Incentive spirometry to prevent acute pulmonary complications in sickle cell disease. New Eng J Med, 333, 699-703

Choi JY, Rha D, Park ES (2016) Change in pulmonary function after incentive spirometer exercise in children with spastic cerebral palsy: a randomized controlled study. Yonsei Medical Journal; 57(3):769-775. doi: 10.3349/ymj.2016.57.3.769
incentive spirometry can help children with cerebral palsy by assisting breath control for speech production

Garg R, Dutta K (2016) Incentive spirometry through tracheostomy stoma. Anaesth Intensive Care; 44(1):125-7 (letter)

Gosselink R et al (2000) Incentive spirometry does not enhance recovery after thoracic surgery. Crit Care Med, 28, 679-83;jsessionid=DOLjRI8Y5ndT9lhuVm2OYxWuZZa1YITpfzx2j5g2WI7WKvDCA7si!-365670234!-949856145!9001!-1
routine use of IS after thoracic surgery seems to be ineffective, but could be beneficial in high-risk patients.

Hall JC, Tarala RA, Tapper J (1996) Prevention of respiratory complications after abdominal surgery. Br Med J; 312:148-53
deep breathing for low-risk and incentive spirometry for high-risk patients

Kumar AS, Alaparthi GK, Augustine AJ et al (2016) Comparison of flow and volume incentive spirometry on pulmonary function and exercise tolerance in open abdominal surgery: a randomized clinical trial. J Clin Diagnostic Res; 10(1):KC01-KC06. doi: 10.7860/JCDR/2016/16164.7064.

Milgrom LB, Brooks JA, Qi R (2004) Pain levels experienced with activities after cardiac surgery. Am J Crit Care; 13(2):116-25.
postoperative pain is less when using incentive spirometry than when deep breathing, possibly due to the distraction of using a device

Narayanan ALT, Hamid SRGS, Supriyanto E (2016) Evidence regarding patient compliance with incentive spirometry interventions after cardiac, thoracic and abdominal surgeries: A systematic literature review. Canadian J Respir Ther; 52(1):17-26

Paisan D de M (2013) Volume rather than flow incentive spirometry is effective in improving chest wall expansion and abdominal displacement using optoelectronic plethysmography. Respir Care, 58(8):1360-6

Rupp M et al (2013) Incentive spirometry in postoperative abdominal/thoracic surgery patients. AACN Adv Crit Care, 24(3):255-263

Sokol G, Vilozni D, Hakimi R et al (2015) The short-term effect of breathing tasks via an incentive spirometer on lung function compared with autogenic drainage in subjects with cystic fibrosis. Respir Care; 60(12):1819-1825

Weindler J, Kiefer RT (2001). The efficacy of postoperative incentive is influenced by the device-specific imposed work of breathing. Chest, 119, 1858-64
some devices (e.g. Mediflo) impose a greater inspiratory work of breathing than others (e.g. Coach).
the former did not affect the maximal inspired volume of patients with severely impaired respiratory function, but did reduce the maximal inspired volume in patients who had moderately impaired respiratory function.

Wren SM, Martin M, Yoon JK et al (2010) Postoperative pneumonia-prevention program for the inpatient surgical ward. J Am Coll Surg, 210, 4, 491-5. doi: 10.1016/j.jamcollsurg.2010.01.009.
Incentive spirometry beneficial as part of a package

AARC = American Association for Respiratory Care
CABG = coronary artery bypass graft
IS = incentive spirometry