Sequelae of bronchoscopic lung volume reduction with endobronchial valves evaluated with quantitative VQ SPECT CT and quantitative CT-a sub analysis of the EMPHYSISE study.

BACKGROUND

Bronchoscopic lung volume reduction with endobronchial valves (BLVR-EBV) is a proven symptomatic treatment for advanced emphysema. Conflicting findings on the lobar effects post-treatment are noted in the literature. Our inhouse software for quantitative ventilation/perfusion scan (qVQ) with single photon emission computed tomography (SPECT) and low-dose computed tomography (CT) quantifies lobar ventilation radioactivity (Vent%), perfusion radioactivity (Perf%) and volume (Vol%) as percentages of total lung; and the product of lobar ventilation and perfusion per unit volume, as an index of differential contribution to total lung function [VQ capacity differential index (VQCDI)]. We coined other indices to evaluate: parenchymal function [VQ differential index (VQDI) = (Vent%/Vol%) × (Perf%/Vol%)]; and lobar gas trapping (VQCDI/Vol%). We evaluated lobar changes post BLVR-EBV using these qVQ parameters and emphysema ratio % (ER%) from quantitative CT (qCT).

METHODS

Pre and post BLVR-EBV qVQ and qCT were performed in a study (EMPHYSISE) with a primary aim of evaluating cardiopulmonary remodelling. A multidisciplinary panel determined the treatment indication and target lobe (TL) selection. Post-treatment cardiopulmonary exercise test (CPET) and pulmonary function test (PFT) were included. Pre- vs. post-BLVR-EBV qVQ and qCT parameters were analysed with the Wilcoxon signed-rank test for significant differences. The mean difference of Vent%, Perf%, Vol% of each lobe evaluated the redistribution to non-treated lobes; Vent%/Vol% and Perf%/Vol% evaluated the dilutional effect of increased volume; VQCDI, VQCDI/Vol% and VQDI evaluated lobar functional changes.

RESULTS

Ten of 13 participants had pre- and post- (<12 months) BLVR-EBV qVQ. TL: 4 left upper lobe (LUL), 5 left lower lobe (LLL), 1 combined right upper lobe (RUL)/right middle lobe (RML). Post-BLVR-EBV CPET in 9 and PFT in 9. All ten achieved at least 1 treatment response threshold. All paired comparisons reached statistical significance except for 3 pairs. For TL: marked reduction of all indices, even with subtotal collapse as low as 27.7% Vol% reduction. The ipsilateral untreated lobe (IUL): received highest volume, ventilation and perfusion redistributions (mean increases of >61%), mild dilution in ventilation but not perfusion; highest mean VQCDI increase (11%); minor mean VQCDI/Vol% worsening (-0.1); mild mean VQDI worsening (-0.2); highest mean ER% improvement (-3.5%). In the contralateral lung, the lower lobe (C-LL) had: highest redistributions (>19%); minor ventilation and perfusion dilution; the highest VQCDI improvement (+4.2%); minor VQCDI/Vol% worsening (-0.05); minor VQDI worsening (-0.1); mild ER% improvement (-0.6%).

CONCLUSIONS

Our study indicates that following BLVR-EBV, the TL suffers marked functional decline even with subtotal collapse. IUL benefits the most functionally. C-LL benefits the most in the contralateral lung. By implication, pre BLVR-EBV assessment using qVQ and qCT should ideally target the most diseased lobe that is paired with the healthiest IUL to maximise functional outcome. Further larger studies with longer follow-up would be beneficial.