Efeito agudo da pressão expiratória positiva sobre a capacidade de exercício em pacientes com doença pulmonar obstrutiva crônica

Abstract

Chronic obstructive pulmonary disease (COPD) is a multisystem, preventable, and treatable disease characterized by persistent airflow limitation. Patients afflicted with this disease have reduced exercise capacity and an investigation of strategies to improve this capacity becomes important. Among the instrumental devices for chest physiotherapy used to promote alveolar ventilation increase, the EPAP (Expiratory Positive Airway Pressure) is highlighted. In this study, it was hypothesized that the use of EPAP during or before exercise of constant load on the cycle ergometer may contribute to the increase of exercise capacity in patients with COPD. Thus, the primary aim of this study was to evaluate the acute effects of EPAP on exercise capacity in patients with COPD, through exercise time of a constant-load test on the cycle ergometer. The secondary aim was to assess responses of some respiratory pattern variables and thoracic chest wall operating volumes. With these aims, a quasiexperimental study, whose sample size was 34 subjects, being the present study performed with the participation of nine patients with moderate to very severe COPD, of both sexes, and age of 66 ± 8 years. Patients underwent three constant-load tests on the cycle ergometer with 80% of maximal exercise load, which was estimated byequation obtained for performance an incremental shuttle walk test. The constant-load tests were performed in three different conditions: EPAP 7.5 cmH2O during the test (Protocol 1 - P1), EPAP 7.5 cmH2O before the test (Protocol 2 - P2) and EPAP sham before the test (Protocol 3 - P3). During the tests, the respiratory pattern and the thoracoabdominal movement were recorded by use of optoelectronic plethysmography, and three moments were analyzed later: rest (M1), half of the time of the constant-load exercise (M2) and end time of the constant-load exercise (M3). The comparisons between the different protocols (P1, P2 and P3), between the different moments (M1, M2 and M3) and interaction effect (P x M) were performed by use of generalized estimating equations. A 5% alpha was considered significant. The post hoc comparisons were performed using the Bonferroni test. Statistical Package for Social Sciences (SPSS 15.0, Chicago, IL, USA) was used to analyze data, and they were presented as average and standard deviation. The P1 exercise time (124.44 ± 48.65 seconds) was significantly lower comparing to P2 (211.44 ± 105.76 seconds, p = 0.040) and P3 (228.22 ± 104.57 seconds; P = 0.017), with no significant difference between P2 and P3 (p = 0.186). The degree of dyspnea observed during P1 (7.78 ± 1.99) was significantly higher in relation to P2 (2.61 ± 1.74, p <0.001) and P3 (2.72 ± 1.62; p < 0.001) without significant difference between P2 and P3. The perception of effort in lower limbs was higher during P1 (6.33 ± 2.40) in relation to P2 (3.78 ± 2.53, p = 0.009) and P3 (3.55 ± 2.30; P = 0.046), with no significant difference between P2 and P3. Chest wall tidal volume (Vcw), respiratory rate (RR) and minute ventilation (VE) increased significantly with exercise progression in all protocols. The Vcw during P2 and P3 was statistically different from P1, independent of the moment analyzed. There was an increase of RR throughout the exercise in all protocols, however, without significant increase in the half of the exercise comparing to the rest and in the half of the exercise comparing to the end of the exercise in the P1. The VE increased significantly in all protocols. Regarding the chest wall volumes (inspiratory and end expiratory), no significant differences were found between rest and end of exercise in any of the protocols. In conclusion, the results of the present study demonstrated that the use of EPAP, with load of 7.5 cmH2O, during or before constant-load test was not able to increase the exercise capacity of the patients evaluated.