PURPOSE: American Thoracic Society guidelines state an abnormal inspiratory loop may indicate the presence of upper airway obstruction. We evaluated the incidence of consistently abnormal inspiratory FVLs, the subsequent clinical evaluation if completed, and whether choosing the best inspiratory and expiratory efforts based on FVL analysis changes the interpretation of spirometry and the calculation of mid-flow ratios (FEF50/FIF50).
METHODS: Spirometry data was collected retrospectively over one year. 123 patients with abnormal inspiratory FVLs were identified. All breathing trials were reviewed to determine consistency of the inspiratory effort. The best inspiratory effort indices were compared to evaluate changes in interpretation and FEF50/FIF50. Charts were reviewed to determine the clinical evaluation, if any, of the abnormal FVL and associated conditions.
RESULTS: Of 123 patients identified, 47 had consistently abnormal and 22 had partially consistent abnormal FVLs. Only 21(17%) of these patients underwent an evaluation with vocal cord disorders(VCD) diagnosed in 10 patients(48%) and other conditions in 5 patients(24%). Associated conditions included gastroesophageal reflux 49(40%), asthma 23(19%), obstructive sleep apnea 16(13%), and allergic rhinitis 10(8%). Using the best inspiratory FVL to choose the trial for interpretation, there was an increase in mild restrictive changes from 25 to 36 and in mild obstruction changes from 0 to 4. The FEF50/FIF50 ratio decreased from 3.07 +/- 1.63 to 1.77 +/- 1.15. The number of patients with a ratio greater than 2.2 decreased from 75 to 29.
CONCLUSION: Abnormal inspiratory FVLs are commonly seen on spirometry. They often indicate an inconsistent effort and all trials should be evaluated to determine the best loop used for analysis. When there is a consistent abnormality of the inspiratory FVL, an evaluation is often not pursued though vocal cord abnormalities were commonly found.
CLINICAL IMPLICATIONS: Spirometry technicians should be trained to obtain consistency in both the inspiratory and expiratory FVL. If inspiratory FVL abnormalities are reproducible, an evaluation for functional and anatomic upper airway obstruction is indicated.
DISCLOSURE: James Sterner, No Financial Disclosure Information; No Product/Research Disclosure Information