2001 OPEN FORUM Abstracts
BRONCHIAL PROVOCATION TESTING INMILITARY APPLICANTS WITH HISTORY OF CHILDHOOD ASTHMA: DO PRE-CHALLENGE SPIROMETRYRESULTS PREDICT THE OUTCOME OF BRONCHIAL PROVOCATION TESTING?
Rikki S. Bruinsma, RRT, CPFT, St.LukeÕs Hospital, Jacksonville, FL.
Background: The St. LukeÕsHospital Pulmonary Lab was contracted by the local Military Entrance ProcessingStation (MEPS) in 1997 to perform methacholine challenge testing on 71 militaryapplicants who had indicated a history of childhood asthma or asthma-like symptoms.The results of the tests were reviewed to determine if there were significantdifferences in the pre-methacholine challenge Forced Expiratory Volumes (FVC),Forced Expiratory Volumes, one-second (FEV1), FVC/FEV1 ratio and Peak ExpiratoryFlow Rates (PEF) to establish if a positive response to the bronchial provocationtesting could be predicted.
Method: A retrospective reviewof the results of bronchial provocation studies was performed on military applicantsfrom 1997 through 2000. Testing was performed using the MedGraphicsâ BreezePFPulmonary Function Softwareª. ATS criteria was used to certify all reportedresults. Each applicant included in the review performed a minimum of threepre-challenge FVC maneuvers. Sixty-three applicants met Mayo Clinic protocolfor high dose methacholine challenge testing by achieving an FEV1 ³ 70% of predictedvalue. Each of these applicants then received one breath of 25mg methacholine.Following a 3-minute wait time, post-challenge FVC maneuvers were obtained.If there was < a 20% decrease in an applicantÕs FEV1, up to 4 additional breathsof 25mg methacholine were given. Following an additional 3-minute wait time,FVC maneuvers were again repeated. A 20% or greater decline in pre-challengeFEV1 results indicated a positive study.
Results: The following tableoutlines the results, comparing those who had < a 20% decline in their FEV1results to those who had a ³ 20% decline:
|Population With ³ 20% decrease in FEV1||Population With < 20% decrease in FEV1|
|Sample Size (Male / Female)||18 (12 / 6)||45 (34 / 11)|
|Mean Age, years (± SD)||20.3 (± 3.8)||19.8 (± 3.1)|
|Mean Pre FVC (% pred ± SD)||96.3% (± 10.4)||92.7 % (± 9.1)|
|Mean Pre FEV1 (% pred ± SD)||96.7% (± 10.5)||88.5 % (± 8.2)|
|Mean Pre FEV1 / FVC % (± SD)||85% (± 5.1)||81% (± 5.7)|
|Mean Pre PEF (% pred ± SD)||113% (± 16.5)||107 % (± 14.6)|
Using the F-Test with a 95% confidencelevel, results show no significant differences in the pre-challenge FVC (p=.23),FEV1 (p=.09), FEV1/FVC (.33) or PEF (.25) test results to indicate whether ornot a particular MEPS applicant may or may not have a 20% or greater responseto bronchial provocation testing using methacholine.
Conclusion: Based on the results,prediction of positive methacholine challenge testing in the military applicantwho presents with a history of childhood asthma can not be made based on pre-challengespirometry values.