C108-03 Prevalence and Characteristics of Individuals With and Without Dysanapsis: The American Lung Association Lung Health Cohort

Abstract Rationale Dysanapsis is described as a spirometric pattern of reduced FEV1/FVC with normal FEV1 and FVC, (FEV1/FVC lower limit of normal (LLN) with FEV1 ≥ LLN and FVC ≥ LLN) and is thought to reflect reduced airway size relative to parenchymal size. Whether dysanapsis is a normal physiologic variant or indicates a propensity to lung disease is unclear. To gain further insight, we compared demographic and physiologic characteristics of healthy volunteers with and without dysanapsis enrolled in the Deep Lung Phenotyping (DLP) Ancillary Study of the American Lung Association Lung Health Cohort (LHC). Methods Healthy volunteers aged 25-35 years old with no history of lung disease other than mild asthma were recruited from participants in the LHC. We measured lung volumes by multiple breath nitrogen washout, diffusing capacity of the lung for carbon monoxide, and oscillometry. We compared demographic and physiologic characteristics of participants with and without dysanapsis as defined from spirometry. In particular, we were interested in comparisons of airway size to lung size, and explored novel oscillometry parameters R5/X5, R19/X5, and R19/TLC as possible ways of determining dysanapsis. Results We present data on 520 out of a planned 1000 participants who have so far completed the DLP study (Table 1). Relative to the LHC parent study (n = 2,958, median age 29 yrs, 63% female, median BMI 26 kg/m2, 37% current/former smoker, 9% with asthma), demographics are similar, but with a lower proportion of women in DLP. Dysanapsis is seen in 5.8% of participants in the DLP study. Spirometry variables are different between those with and without dysanapsis as expected based on the definition of dysanapsis (lower FEV1 and FEV1/FVC, higher FVC in those with dysanapsis). Among the other measurements, only R19 is found to be statistically different (higher) in those with dysanapsis and correlates with dysanapsis to a small degree (r = 0.126, p = 0.004). Conclusions Dysanapsis is found in 5.8% of individuals in the DLP study to date and is associated with higher central airway resistance as reflected by higher R19. These preliminary data suggest dysanapsis is primarily defined by narrowed central airways rather than elevated lung volumes or a peripheral lung process. The slightly higher prevalence of asthma in the dysanapsis group may indicate that dysanapsis is associated with asthma. This abstract is funded by: NHLBI, ALA-ACRC