SESSION TITLE: COPD Epidemiology & Physiology Posters
SESSION TYPE: Poster Presentations
PRESENTED ON: Saturday, March 22, 2014 at 01:15 PM - 02:15 PM
PURPOSE: Common techniques used to measure lung volumes may yield inaccurate results in patients with large bullae. Plethysmography may overestimate while gas dilution may underestimate functional lung volumes. Auto Smart Segmentation (SS) is used by radiation physicists to accurately map lung portions receiving radiation therapy. It uses contouring methodology to trace and accurately measure volume of contoured anatomic structures. Hypothesis. Contouring of bullae on thoracic Computed Tomography (CT) and digital subtraction of contoured volumes using SS will yield accurate lung volumes unaffected by technical limitations or patient effort.
METHODS: Using standard plethysmography, we measured static lung volumes before and after bullectomy. We also used SS on pre-operative CT to digitally subtract volume of the bullae to determine whether the resulting measurements would accurately predict functional lung volumes and match post-operative volumes measured plethysmographically. Resected tissue was examined histologically to determine whether functional lung tissue may have been resected.
RESULTS: Pre-operative pulmonary function tests (PFT’s) revealed obstructive pattern with FEV1/FVC=54%, TLC 7.98L (135% predicted) and FRC 3.7L (110% of predicted). Post-operative PFT’s revealed unexpected restriction with FEV1/FVC=77%, TLC 3.77L (64% predicted) and FRC 2.3L (69% predicted). When resting lung volumes were measured using SS on pre-operative CT with contouring of bullae and digital subtraction, the volume of bullous-free lung parenchyma was 1.94L. Post-operative resting lung volume using the same methodology was 2.5 L, accounting for some post-bullectomy expansion. These volumes represent the FRC, are reduced, and reflect pre-existing restrictive lung disease. Post-operative restrictive pattern was not related to resection of lung tissue since pathologic examination of resected specimen revealed only a thin membrane with no parenchyma.
CONCLUSIONS: This patient had restrictive lung disease masked by the bullae and not diagnosed by plethysmography. Auto SS, which analyzes the content of CT images and delineates anatomic structures, can provide more accurate lung volume measurements and physiologic diagnosis.
CLINICAL IMPLICATIONS: We propose the use of this technique in patients with bullae, especially during preoperative evaluation for bullectomy, to get more accurate assessment of pulmonary function.
DISCLOSURE: The following authors have nothing to disclose: Basim Dubaybo, Sikandar Ansari
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