Respiratory Muscle Strength in Patients Submitted to Lung Resection: Implications in Postoperative Pulmonary Complications, Functional Recovery and Quality of Life

Abstract

Lung cancer is the leading cause of death from cancer. Pulmonary resection is the treatment of choice for the early stages of lung cancer, however this surgery carries risks mostly dependent on patients' lung and heart function. Thus, it is necessary to evaluate the patient's ability to withstand the loss of lung tissue in order to prevent postoperative pulmonary complications (PPC). However, the risk assessment model does not contemplate the evaluation of respiratory muscle function. In addition, the efficacy of respiratory muscles training in the reduction of PPC and length of hospital stay (LOS) in patients submitted to pulmonary surgery is not clarified. Considering the favourable results observed in patients with chronic obstructive pulmonary disease, it is plausible that respiratory muscle training after hospital discharge may contribute to the recovery of pulmonary function, improve physical fitness, daily levels physical activity and quality of life (QoL). The present thesis encompasses four studies: i) a narrative review of the literature in order to appreciate the state of the art of physiotherapy for patients submitted to lung resection; II) an observational study seeking to determine the association of respiratory muscles function, physical fitness and daily physical activity in the prediction of PPC; III) a meta-analysis, aiming to verify the effect of IMT on the reduction of PPC and LOS, as well as other correlating or determinant factors, including training doses; IV) and a randomized controlled trial to verify the effect of inspiratory and / or expiratory muscle training, alone or in combination, on the function of these muscles, on pulmonary function, on daily levels of physical activity (AF) and on quality of life of patients after hospital discharge. The results showed that maximal expiratory pressure (expiratory muscle strength) was the strongest independent predictor of PPC, while maximal inspiratory pressure (MIP), physical fitness and daily AF were not significant PPC predictors. However, MIP may be considered a predictor of PPP, as demonstrated in the meta-analysis, since IMT has the power to reduce the risk of PPP and LOS. It has also been shown that IMT is even more important in pulmonary surgery than in cardiac and abdominal surgery, especially in high-risk patients under specific conditions: i) if supervised, ii) with an imposed load increase, iii) with training duration greater than two weeks, iv) and training sessions of 15 or more minutes, and v) in combination with general exercise. After hospital discharge, the implementation of home-based respiratory training programs proved to be effective in increasing MIP in all training groups, particularly in the combined training group, IMT and EMT, respectively. Additionally, in the IMT and EMT groups, significant reductions in sedentary time and increase in total and light PA were observed. Training of respiratory muscles did not influence patients QoL. In conclusion, the function of respiratory muscles should be included in the risk model evaluation of patients selected for pulmonary resection. In addition, both inspiratory muscle training with expiratory muscles should be part of the recovery not only in the preoperative period but also in the postoperative period of these patients.