Lung vascular volumes in cystic fibrosis patients before and after Elexacaftor-Tezacaftor-Ivacaftor (ETI) therapy

<bold>Rationale:</bold> Low attenuation regions (LAR) in CF lung disease reflects trapped air and hypoperfusion secondary to hypoxic pulmonary vasoconstriction. <bold>Aim:</bold> To assess changes in LAR and lung arterial and venous blood volumes before and after introduction of ETI. <bold>Hypothesis:</bold> ETI results in a reduction of LAR, higher small (0.2-1mm) arterial and venous volumes and a reduction in upstream (>2mm) arterial volume. <bold>Methods:</bold> 9 CF patients, age 35(26-39) years, (M2,F7) underwent broncho alveolar lavage and an ins- and expiratory chest CT scan before, and on ETI therapy 1.5 years later. CTs were automatically analysed (LungQ V.3.0.1, Thirona, Nijmegen, NL). LungQ-VERA assesses LAR (%total lung volume). LungQ-AVX assesses arterial and venous blood volumes (%total lung blood volume) in bins of: 0.2-1, 1-2, >2 mm. <bold>Results:</bold> On ETI, LAR reduced by 42% (23.94(6.30-41.36)% to 13.95(1.87-23.31)% (p=0.028)). Blood volumes (Table). <bold>Conclusions:</bold> ETI therapy results in: reductions in LAR and higher venous blood volumes. The trend in higher small (0.2-1mm) arterial volume and reduced upstream (>2 mm) arterial volume suggest improved arterial perfusion and a reduction in pulmonary arterial pressure. <table-wrap><object-id>erj;64/suppl_68/PA5257/T1</object-id><object-id>T1</object-id><object-id>t1</object-id><table><colgroup><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td>Variable</td><td> Pre-ETI, Blood volume (%) Median (SD) </td><td> On-ETI, Blood volume (%) Median (SD) </td><td> Statistics, P-value </td></tr><tr><td>Arteries 0.2-1 mm</td><td>4.97 (1.364)</td><td>7.07 (1.58)</td><td>U = 21, p = 0.094</td></tr><tr><td>Arteries 1-2 mm</td><td>11.68 (2.45)</td><td>9.73 (1.08)</td><td>U = 55, p = 0.222</td></tr><tr><td>Arteries >2 mm</td><td>42.11 (7.76)</td><td>37.38 (4.56)</td><td>U = 62, p = 0.063</td></tr><tr><td>Veins 0.2-1 mm</td><td>3.04 (0.88)</td><td>4.47 (0.84)</td><td>U = 18, p = 0.040</td></tr><tr><td>Veins 1-2 mm</td><td>6.84 (1.40)</td><td>8.17 (1.07)</td><td>U = 13, p = 0.014</td></tr><tr><td>Veins >2 mm</td><td>28.91 (5.19)</td><td>33.62 (3.73)</td><td>U = 18, p = 0.040</td></tr></tbody></table></table-wrap>