Prevalence of supranormal pulmonary function test values between a military and nonmilitary cohort

BACKGROUND: The study objective was to determine differences in the proportion of supranormal pulmonary function tests (PFTs) between active duty (AD) military personnel and a similar non-active duty (non-AD) population. Given the emphasis on cardiovascular fitness in the military, it has been hypothesized that regular exercise in this cohort leads to an increased proportion of supranormal PFTs. We hypothesized that a comparison of PFTs would identify no differences in the ratio of supranormal to normal PFTs between the AD and non-AD populations. METHODS: A retrospective chart review was conducted of all PFT studies at the Brooke Army Medical Center from 2006 to 2011. Studies were included with either an FVC or FEV₁ > 110% of predicted, with both values > 100% of predicted. A comparative analysis was performed for patients between 18 and 50 years of age based on AD status. Further analysis was performed on all ages to determine the distribution of supranormal findings in the entire study population. RESULTS: A total of 16,600 interpreted PFTs were queried. Of those, 4,303 (31.6%) were AD patients, and 9,306 (68.4%) were non-AD patients. From all of the PFTs reviewed, a total of 912 (6.7%) were identified as supranormal. When further analyzed, 381 (9.4%) of AD patients 18-50 years old were supranormal, 175 (12.4%) of non-AD patients 18-50 years old were supranormal, and 356 (4.7%) of non-AD patients older than 50 years were supranormal. CONCLUSIONS: This study revealed no significant difference in the proportion of supranormal-to-normal PFTs in an AD versus non-AD duty population of the same age range. Based on these findings, no assumption should be made that supranormal PFTs are more common in military personnel. Interpretation of normal PFTs in AD personnel undergoing evaluation should not differ from that in any typical patient.