Correlation of Airway Hyper-responsiveness With Obstructive Spirometric Indices and FEV₁ > 90% of Predicted

Authors: Kotti, George H; Bell, David G; Matthews, Tokunbo; Lucero, Pedro F; Morris, Michael J

Source: Respiratory Care, Volume 57, Number 4, April 2012 , pp. 565-571(7)

Publisher: The Journal Respiratory Care Company

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Abstract:

BACKGROUND: Current published guidelines on spirometry interpretation suggest an elevated FVC and FEV₁ > 100% of predicted with an obstructive ratio may represent a physiological variant. There is minimal evidence whether this finding can be indicative of symptomatic airways obstruction. METHODS: Pulmonary function testing databases for a 4-year period were retrospectively reviewed. All technically adequate spirometry studies were included, based on these criteria: FEV₁ > 90% of predicted, and FEV₁/FVC below the lower limit of normal, based on 95th percentile confidence intervals. Clinical indications for testing were noted. Testing for post-bronchodilator response, lung volumes, and methacholine challenge tests were reviewed for evidence of airway hyper-responsiveness (AHR). Comparisons were made between symptomatic versus asymptomatic individuals and FEV₁ values less than or greater than 100% of predicted. RESULTS: A total of 280 studies were analyzed. During their clinical evaluation, 192 patients (69%) had post-bronchodilator spirometry recorded, 63 patients (23%) had lung volumes, and 36 patients (11%) completed methacholine challenge testing. Indications for spirometry included 193 symptomatic patients and 87 asymptomatic patients. Nearly 28% of patients with post-bronchodilator testing met criteria for AHR. No differences in AHR were found between the symptomatic and asymptomatic groups. The majority of patients (77%) with AHR had an FEV₁ < 100%, when compared to patients with an FEV₁ ≥ 100%. CONCLUSIONS: A normal FEV₁ > 90% of predicted with obstructive indices may not represent a normal physiological variant, as 28% of patients were found to have underlying AHR. These findings suggest that clinicians should evaluate for AHR, especially in symptomatic patients, even if the FEV₁ is > 90% of predicted.

Keywords: pulmonary function testing; normal FEV1; obstruction; airway hyper-responsiveness

Document Type: Research article

DOI: http://dx.doi.org/10.4187/respcare.01244

Affiliations: 1: Pulmonary Disease Service, Keesler Medical Center, Keesler Air Force Base, Biloxi, Mississippi, USA

Publication date: 2012-04-01

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