133Xenon ventilation scan as a functional assessment in bronchiectasis

Mucus impaction in the airways impairs ventilation and exercise tolerance in patients with bronchiectasis. Parameters for evaluating the ventilatory dynamic change have been limited by variable cofactors. We developed a tool to evaluate the changes directly on images of a ventilation scan.

We used a 133Xenon ventilation washout scan to assess the time of half clearance (T1/2) of the regions of interest (ROIs) corrected by that of a control area (CA) as T1/2ROI/CA. We then compared the ventilation washout scan with high-resolution computer tomography (HRCT) scoring to assess the severity of bronchiectasis, as well as conducting 6-minute walking tests or spirometry for the evaluation of the clinical response to a 3-day course of chest physiotherapy. Nine patients with bronchiectasis and mucus hypersecretion were enrolled in this study.

The functional impairments by mucus impaction or air trapping were well documented in the ventilation washout scan, which not only provided an anatomical image but also dynamic profiles. The ratios of T1/2ROI/CA were significantly correlated to the corresponding scoring of HRCT (3.45 +/- 0.85 vs 7.50 +/- 1.51, r2 = 0.61, p = 0.023, n = 8). The improvement in T1/2ROI/CA (from 3.45 +/- 0.85 to 2.60 +/- 0.59, p = 0.022, n = 9) was paralleled by an increase in the 6-minute walking test (from 310.4 +/- 43.2 m to 352.4 +/- 45.1 m, p = 0.028, n = 7).

The 133Xenon scan may be used to evaluate the heterogeneity of ventilation abnormalities and the efficacy of clinical therapy directly in patients with bronchiectasis.