PURPOSE:Improvement in spirometry after bronchodilator administration (BD) is characteristic of obstructive airway diseases, such as asthma. However, one occasionally encounters a restrictive pattern on testing that improves after BD. The aim of this study was to determine the total lung capacity (TLC) of patients with this reversible restrictive defect.
METHODS:Patients with restrictive spirometry who had a bronchodilator study were identified by review of all PFTs done at the Oklahoma City VAMC between January 2004 and August 2006. Restriction was defined as a decreased FVC (based on the values predicted for age, height and gender), with a normal FEV1/FVC. Responsiveness to BD was defined as an improvement in FEV1 and/or FVC of at least 12% and 200 ml. Clinical records of these patients were reviewed and those with follow up TLC measurements were analyzed.
RESULTS:A total of 2344 PFTs were reviewed, with 1593 undergoing BD including 84 patients (4%) who had a restrictive pattern and BD evaluation. Thirty three of 84 (39%) patients had a response to bronchodilator, with a moderately decreased prebronchodilator FVC (2.85+0.7 L, 65+11% of the predicted) including 8 (24%) with subsequent plethysmographic lung volume measurements. There was no difference between patients who underwent plethysmography, and those who did not, in terms of their clinical presentation, demographics, or baseline spirometry. In the former group, the mean TLC and RV averaged 92+12% and 122+32% of the predicted, respectively. The TLC was less than the lower limit of normal in only 2 patients. The DLCO averaged 65+15% of the predicted.
CONCLUSION:Reversible restrictive pattern appears to be a variant of obstructive lung disease in which complete closure of terminal lung units by contraction of alveolar ducts leads to low FVC despite a normal TLC.
CLINICAL IMPLICATIONS:In symptomatic patients, a therapeutic trial of BD may be of potential benefit.
DISCLOSURE:Ross Michel, No Financial Disclosure Information; No Product/Research Disclosure Information