Emphysema is characterised by airflow limitation that is a result of both loss of elastic recoil and small airways disease. It is poorly responsive to medical therapy. Lung volume reduction coils improve symptoms and lung function in the short term. However their mechanism of action and medium term effectiveness is not fully understood.
Methods
A randomised controlled study consisting of thirty patients with severe chronic obstructive pulmonary disease was performed. Control patients crossed over to the treatment arm at 12 months. The primary outcome was 6 minute walk distance at 12 months. Changes in spirometry, lung volumes, computed tomography measured lung volumes and gas trapping were also assessed. In a small subgroup of patients detailed physiological characterization was performed to assess changes in airways resistance, ventilation heterogeneity and lung elastic recoil.
Results
In the randomised study at 12 months, there was no significant difference in 6 minute walk distance between treatment and controls (between group difference 25m, 95% CI -40 to 59, p = 0.7028). There was a trend to improvement in symptoms measured by SGRQ score (-6.53 points, 96% CI -17 to 0.2, p = 0.0589) and significant improvements in FRC (-0.41L, 95% CI -0.86 to -0.1, p = 0.0077). Including the crossovers there were 4 patient deaths (13.3%). Target lobe volume at both inspiration and expiration was reduced with no overall change in gas trapping. Airways resistance by plethysmography did not change significantly. There was no significant change in elastic recoil.
Conclusions
Treatment with lung volume reduction coils is effective at reducing lung volume
and may achieve its effect through volume loss. There could also be an effect through elastic recoil as there was a non-significant trend towards an increase after the intervention. There appears to be no effect on airways resistance. Careful patient selection is required as there is a risk of death following treatment.