Pulmonary Function Testing and Upper Airway Disorders: Analysis From the STAMPEDE III Database.
Upper airway disorders such as vocal cord dysfunction (VCD) may present in a similar manner to asthma. Identifying and differentiating between underlying asthma and VCD may significantly affect treatment options. This study reanalyzed the comprehensive pulmonary function data obtained from the STAMPEDE III study to compare findings in patients diagnosed with either asthma, airway hyperreactivity, and VCD.
The STudy of Active duty Military for Pulmonary Disease Related to Environmental Deployment Exposures (STAMPEDE) III was a prospective, observational study of active duty military with post-deployment exertional dyspnea. All patients underwent spirometry with bronchodilator response, impulse oscillometry (IOS), methacholine challenge testing, and exercise laryngoscopy. Several diagnostic categories from the STAMPEDE III study included asthma, airway hyperreactivity (AHR), and upper airway disorders. The results of the pulmonary function testing, flow volume loop (FVL), and impulse oscillometry (IOS) were directly compared between the 3 diagnostic groups.
Flow volume loop abnormalities were found in all groups. The forced inspiratory flow at 50% of the vital capacity (FIF50%) was lower in the VCD group at 4.43 ± 1.90 but not significant. Evaluation of the forced expiratory flow to force inspiratory flow (FEF50%/FIF50%) ratio was lower in the asthma group <1.0 and favored expiratory obstruction. Comparison of the FEF50%/FIF50% ratio for those patients with truncated inspiratory FVL (1.29 ± 0.6 vs. 1.19 ± 0.84 vs. 1.34 ± 0.53) also showed no differences. From the IOS data, baseline resistance at 5 Hz (R5% predicted) and resistance at 20 Hz (R20% predicted) values were significantly elevated in the asthma group (177.6 ± 52.5% and 149.3 ± 36.2%, respectively) compared to the VCD group (136.1 ± 48.7% and 126.4 ± 40.4%, respectively), P = .001 and P = .016. R5-R20 values were different in all 3 groups where asthma was the highest (1.44 ± 0.87) vs. VCD (0.81 ± 0.82) vs. AHR (0.49 ± 0.40). A significant difference was also noted with reactance at 5 Hz (X5)where asthma was the lowest (-1.93 ± 0.92) vs. VCD (-1.47 ± 0.77) vs. AHR (-1.07 ± 0.34).
While baseline spirometry and FVL do not readily differentiate asthma and VCD, the findings on IOS suggested differences between these patients. The use of IOS should be incorporated into the evaluation of patients with suspected VCD due to measurements of inspiratory impedance.
The STudy of Active duty Military for Pulmonary Disease Related to Environmental Deployment Exposures (STAMPEDE) III was a prospective, observational study of active duty military with post-deployment exertional dyspnea. All patients underwent spirometry with bronchodilator response, impulse oscillometry (IOS), methacholine challenge testing, and exercise laryngoscopy. Several diagnostic categories from the STAMPEDE III study included asthma, airway hyperreactivity (AHR), and upper airway disorders. The results of the pulmonary function testing, flow volume loop (FVL), and impulse oscillometry (IOS) were directly compared between the 3 diagnostic groups.
Flow volume loop abnormalities were found in all groups. The forced inspiratory flow at 50% of the vital capacity (FIF50%) was lower in the VCD group at 4.43 ± 1.90 but not significant. Evaluation of the forced expiratory flow to force inspiratory flow (FEF50%/FIF50%) ratio was lower in the asthma group <1.0 and favored expiratory obstruction. Comparison of the FEF50%/FIF50% ratio for those patients with truncated inspiratory FVL (1.29 ± 0.6 vs. 1.19 ± 0.84 vs. 1.34 ± 0.53) also showed no differences. From the IOS data, baseline resistance at 5 Hz (R5% predicted) and resistance at 20 Hz (R20% predicted) values were significantly elevated in the asthma group (177.6 ± 52.5% and 149.3 ± 36.2%, respectively) compared to the VCD group (136.1 ± 48.7% and 126.4 ± 40.4%, respectively), P = .001 and P = .016. R5-R20 values were different in all 3 groups where asthma was the highest (1.44 ± 0.87) vs. VCD (0.81 ± 0.82) vs. AHR (0.49 ± 0.40). A significant difference was also noted with reactance at 5 Hz (X5)where asthma was the lowest (-1.93 ± 0.92) vs. VCD (-1.47 ± 0.77) vs. AHR (-1.07 ± 0.34).
While baseline spirometry and FVL do not readily differentiate asthma and VCD, the findings on IOS suggested differences between these patients. The use of IOS should be incorporated into the evaluation of patients with suspected VCD due to measurements of inspiratory impedance.
Authors
Stoffel Stoffel, Newton Newton, Houle Houle, Moore Moore, Sjulin Sjulin, Morris Morris
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