Source: International Congress 2015 – Lung function: exploring the boundaries of the respiratory system
Disease area: Airway diseases

Abstract

Rationale: Traditionally, spirometry defines the presence and severity of airway disease in Alpha-1 Antitrypsin Deficiency (AATD). However, it requires maximal effort and FEV1 is not a sensitive marker of early disease. Emerging data suggest that small airways disease is the earliest pathological change in the AATD lung. We assessed specific airway resistance indices as non-volitional markers of early disease.Methods: Retrospective lung function data were collected from AATD patients with normal spirometry (n=69) and mild to severe airflow obstruction (n=185). FEV1 %Pred, FEV1/FVC and Kco %Pred were plotted against %Pred Specific Total Resistance (sRtot), Specific Effective Resistance (sReff) and Specific Resistance -0.5 to +0.5 L/s (sR0.5). Relationships were visually assessed and, where appropriate, curvilinear relationships were logged and analysed by linear regression.Results: Curvilinear relationships were observed for spirometry and specific airways resistance. FEV1 %Pred correlated with %Pred sRtot (r² = 0.66, p < 0.001), sReff (r² = 0.70, p < 0.001) and sR0.5 (r² = 0.65, p < 0.001). Similar correlations were observed for FEV1/FVC and %Pred sRtot (r² = 0.53, p < 0.001), sReff (r² = 0.58, p < 0.001) and sR0.5 (r² = 0.52, p < 0.001). Kco did not correlate with any measure of airway resistance.Conclusions: Although spirometry and specific resistance correlated well, visual assessment of the data suggests that spirometry becomes abnormal earlier in the disease. Physiologically, this is logical as resistance is measured during tidal breathing and may not detect airflow limitation in the small airways until disease is better established.This research is funded by The Alpha-1 Foundation.


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Citations should be made in the following way:
James Stockley (Birmingham, United Kingdom), James Stockley, Laura Smith, Brendan Cooper, Robert Stockley, Elizabeth Sapey. Specific airway resistance as a marker of early disease in alpha-1 antitrypsin deficiency. Eur Respir J 2015; 46: Suppl. 59, 960

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