Tests of pulmonary function before thoracic surgery

Pulmonary function tests form part of the comprehensive preoperative assessment of patients undergoing thoracic surgery. They aim not only to assess the severity and nature of the underlying lung pathology, but also to determine whether a patient will be able to tolerate a pulmonary resection. Tests which assess respiratory mechanics evaluate the mechanical delivery of oxygen to the alveoli and these include spirometry, measurement of lung volumes and flow–volume analysis. The forced expiratory volume in 1 second (FEV1) and the predicted postoperative FEV1 (ppoFEV1) in particular are useful predictors of postoperative respiratory complications. Parenchymal function refers to the ability of the lung to exchange oxygen and carbon dioxide between the pulmonary blood and the alveoli, and this is assessed by determining the diffusing capacity of carbon monoxide and arterial blood gas analysis. Cardiopulmonary interaction, which is important in ensuring adequate cellular respiration in skeletal muscle, is assessed using exercise tests that include the formal cardiopulmonary exercise test and other surrogates such as the 6-minute walk test, shuttle walk test and stair-climbing. Other tests including ventilation perfusion scintigraphy and split-lung function tests are also briefly mentioned.