View Abstract

A3908 - Increasing the Resolution of COPD Definition: Using Lung Volumes to Identify At-Risk Smokers with Preserved Spirometry
Author Block: S. Zeng1, B. Bos2, A. Tham3, M. Arjomandi4; 1University of California San Francisco, San Francisco, CA, United States, 2Radboud University Medical Center, Nijmegen, Netherlands, 3University of Southern California, Los Angeles, CA, United States, 4Univ of California San Francisco, San Francisco, CA, United States.
Background: Current definition of COPD is based on Spirometry. Many current and former smokers who do not meet the spirometric criteria for COPD diagnosis (post-bronchodilator FEV1/FVC and FEV1 ≥lower limit of normal) have respiratory symptoms suggestive of obstructive lung disease. Air trapping is manifestation of obstructive lung disease. However, its significance in those with preserved spirometry is unclear.
Objective: To determine whether lung volume measurements including residual volume (RV), total lung capacity (TLC) and air trapping (defined as RV/TLC) could identify smokers with preserved spirometry who are at greater risk for morbidity and mortality.
Methods: We retrospectively interrogated the United States Veterans Affairs (VA) electronic health records through the nationwide VA Informatics and Computing Infrastructure (VINCI) database and identified 7,961 smokers with preserved spirometry who had full pulmonary function test (PFT including plethysmography) between 1985-2017, and examined their records starting the time of their first full PFT for association of RV/TLC with clinical diagnosis of COPD, respiratory exacerbations, healthcare utilization, and mortality in adjusted models.
Results: Air trapping was prevalent with 29.4% having RV/TLC above the upper limit of normal (ULN), and varied widely across the range of observed FEV1/FVC and FEV1 (average span of 47±11% and 42±7%, respectively). Despite having documented preserved spirometry, patients with RV/TLC above ULN were more likely to have a clinical diagnosis of COPD (odds ratio [95% confidence interval] of 1.49 [1.34-1.66]) and higher number of prescribed respiratory medications per year (0.18 [0.09-0.26]). They also had higher annual rate of office visits (0.27 [0.17-0.37]), hospitalizations (0.04 [0.02-0.05]) and ICU admissions (0.005 [0.001-0.008]) with COPD diagnosis, and higher all-cause mortality (1.39 [1.28-1.51]). Even when RV/TLC was within normal limits, patients with relatively high RV/TLC (above the median of 35.7%) were more likely to be diagnosed with COPD (1.34 [1.17-1.55]), higher annual rate of hospital admissions (0.02 [0.01-0.04]), and higher averaged hazard rate of death (1.26 [1.12-1.42]).
Conclusion: In this cohort of patients from nationwide Veterans Health Administration with smoking history but preserved spirometry, air trapping was common and predicted adverse respiratory outcomes and mortality. Incorporating lung volume measurement in definition of COPD may improve its ability to identify at-risk patients.