Sublobar resection: functional evaluation and pathophysiological considerations
To date, pulmonary function tests (PFTs) are part of consolidated standard operating procedures in thoracic surgery. PFTs are usually used to assess the pre-operative risk, post-operative outcomes and complications after pulmonary resections. The only functional parameter used in common practice is the forced expiratory volume in one second (FEV1). However, the FEV1 alone poorly reflects lung pathophysiology, especially in patients with pre-operative emphysema and airflow obstruction; moreover, the predictive power of spirometric parameters in guiding the surgical approach in terms of the extension of the excision is currently unknown. In the present critical overview, we report and discuss the results of four studies that compared pre and post-surgery FEV1 and forced vital capacity (FVC) in patients undergoing lobectomy or segmentectomy, highlighting the critical aspects of spirometry in lung surgery and suggesting new approaches for the interpretation of pulmonary mechanics in patients undergoing major or minor parenchymal resections. Overall, the literature on the topic is limited to spirometric parameters, and post- surgical function loss and the consequent recovery are often analysed in inhomogeneous study samples, with varying respiratory comorbidities and functional phenotypes. We underline the role of static lung volumes in the patients’ initial assessment. In fact, they tend to decrease in patients with emphysema that undergo a lobectomy, followed by a decrease in lung compliance; some of these patients experience also an increase in closing volume, a condition that worsens the stresses implicated in lung ventilation and promotes the damage to the remaining airways. Spirometric data should be therefore always associated to body-plethysmography and indexes of ventilation distribution, to improve the evaluation of the functional characteristics in patients undergoing lung surgery. Prospective studies are needed to establish the relationship and long-term consequences of different surgical approaches in terms of lung mechanics and functional loss.