Evaluation of Changes in Pleural Pressure, Spirometry and Their Effects on Dyspnoea and the Six-Minute Walk Test (6-MWT) Following Thoracentesis for Symptomatic Pleural Effusion.

Introduction The presence of pleural effusion impairs daily activity, including a decrease in exercise capacity. Aspiration of pleural fluid results in improvement of symptoms, but the impact, especially on exercise tolerance, has not been adequately studied. Methods Forty-eight patients with moderate to massive unilateral pleural effusion documented by chest radiograph were included in this prospective hospital-based study. The six-minute walk test (6-MWT), modified Borg dyspnoea scale, forced vital capacity (FVC), and forced expiratory volume in the first second (FEV1) were analysed before and 24 hours after the removal of pleural fluid. Pleural pressure was monitored during aspiration using over-dampened water manometer. Results The average fluid removed was 605.63 ± 74.94 mL. Following thoracentesis, 6-MWT, FVC, and FEV1 values increased (p < 0.05), whereas modified Borg dyspnoea scale decreased (p < 0.05). Statistical correlations (p < 0.001) between pleural fluid aspirated and FVC (r = 0.49) and pre-aspiration dyspnoea score were correlated with pre-aspiration pleural pressure with a Spearman's coefficient of rank correlation (ρ) 0.738 and a p-value of <0.001, suggesting a strong positive correlation and significant correlation. Conclusion The correlation between pre-aspiration pleural pressure and dyspnoea score in patients with pleural effusion is likely attributable to the effects of increased pleural pressure on the function of respiratory muscles, including the diaphragm and chest wall muscles, as well as increased stimulation of lung or chest wall mechanoreceptors or both. Following aspiration, the improvement in dyspnoea and effort intolerance is largely because of the reduction in pleural pressure and the subsequent relief of respiratory muscle dysfunction, which is not fully explained by the improvement in lung volumes.