Late Breaking Abstract - Combining CT and spirometry to determine hyperinflation in COPD patients for lung volume reduction eligibility

To determine eligibility for lung volume reduction (LVR) in COPD patients body plethysmography (BP) is the preferred method measuring hyperinflation. However, BP is technically complex and not widely available in many countries. We aimed to simplify the hyperinflation assessment by combining spirometry with quantitative analysis of an inspiratory chest CT (QCT), eliminating the need for BP. Patients from the Groningen severe COPD cohort were included, who underwent spirometry, BP, and CT on the same day. QCT total lung volume was compared to BP. The highest vital capacity (VC_spiro) was used to calculate RV_BP and RV_CT. We included 808 patients (62±7yrs, FEV1 29±9%pred). Mean VC was 3.00±0.92L. TLC_CT was 645±429ml lower than TLC_BP. RV_CT was 202±43%pred (RV/TLC 57.7±9%), while RV_BP was 236±46%pred (RV/TLC 60.5±8.2%). Bland-Altman plots showed a systematic difference between BP and CT, with underestimation of volume on CT. However, a strong significant association was found between RV%pred_BP and RV%pred_CT (pearson r=0.87). All p<0.001. Almost all patients with a RV%pred >150% and RV/TLC >55% on CT were eligble for LVR refferal. <fig><object-id>erj;64/suppl_68/PA2552/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> Figure. In conclusion, combining spirometry with inspiratory chest QCT analysis could be an effective tool for screening severe COPD patients for LVR. We would suggest to refer patient to a LVR expert center if CT derived RV is ≥150%pred and RV/TLC is ≥ 55%.