1995 OPEN FORUM Abstracts
AIRWAY RESISTANCE AND LUNG VOLUMES ARE VALUABLE ADJUNCTS TO SPIROMETRY FOR ASSESSING REVERSIBLE OF AIRWAY OBSTRUCTION.
M SNOW RPFT, B ANDERSON RPFT/RRT, K KANDAL RRT AND R FALLAT MD CALIFORNIA PACIFIC MEDICAL CENTER, SAN FRANCISCO, CALIFORNIA
BACKGROUND: Airway Resistance (Raw) has been previously been shown to be more more sensitive than FEV1 for detecting reversible airways obstruction (RAO) and more strongly correlated with patient subjective response to aerosolized bronchodilators. Since specific types of airway obstruction are predominantly volume rather than flow responsive, we hypothesized that the different mechanisms for increasing resistance in Asthma, Cystic Fibrosis, Alpha- 1 Antitrypsin deficiency Emphysema and COPD may be reflected in the pattern of response.
Methods: Spirometric and body plethysmographic measurements were made before and 15 minutes after adminstration of aerosolized bronchodilators in 208 patients representing four distinct types of airway obstruction. Additionally, 35 patients with no evidence of airways obstruction were also assessed to provide a control. FEV1 and FVC responses were considered significant if they met ATS guidelines of 12% and > 200 m1 improvement while Lung Volume and Raw responses had to exceed two standard deviations from laboratory variability standards.
FEV1 FVC TLC RV RV/TLCRaw SRaw
ATS ATS (8%)(16%) (20%)(25%)(25%)
72 (53%) (29%) (15%) (39%) (21%)(75%)(81%)
COPD1721 9 145 2026
57 (30%) (37%) (20%) (25%) (9%) (35%)(45%)
Alpha-1 1320 5 202 1623
45 (29%) (44%) (11%) (44%) (16%)(36%)(51%)
Cystic Fib 9 63 169 1515
34 (26%) (18%) (9%)(47%) (26%)(44%)(44%)
Normal 024 122 8 1
35 (0%)(6%) (11%) (34%) (6%) (23%)(3%)
DISCUSSION: Relative sensitivity for FEV1 and SRaw are similar in normal subjects while SRaw provides significantly higher sensitivity for all categories. Alpha-1 and CF patients demonstrate more significant volume changes in FVC, RV and RV/TLC. Alpha-1 patients demonstrate significant increases in FVC with corresponding decreases in RV.
Conclusions: 1. SRaw and Raw provide increased sensitivity in detecting RAO in Asthmatics and CF patients. 2. FVC, RV and SRaw provide increased sensitivity in detecting RAO in Alpha-1 and COPD patients. 3. Lung Volumes and Airway Resistance provide additional information not available from spirometry.