SESSION TYPE: Physiology/PFTs/ Rehabilitation Posters
PRESENTED ON: Wednesday, October 24, 2012 at 01:30 PM - 02:30 PM
PURPOSE: Background: Spirometry is used to identify restrictive processes and estimate their severity. Total lung capacity (TLC) measured via plethysmography or nitrogen wash out. It is considered the gold standard for characterizing restrictive thoracic disease. In 2005, the ATS guidelines recommended that the forced expiratory volume in one second (FEV1) be used to grade restrictive deficits on spirometry, rather than the previously used forced vial capacity (FVC). It is unclear which of the two parameters more accurately reflects the TLC.
METHODS: Methods: The Vmax spirometry database at our institution was searched for all studies where TLC was determined by plethysmography over the past 10 years. Any patient with coexisting obstruction was excluded. The severity of restriction was graded using the reduction of the percent predicted volume of TLC, FEV1, and FVC according to ATS guidelines. Grades were then compared across all three measures using the kappa statistic to measure agreement.
RESULTS: Results: A total of 456 studies matching the inclusion criteria were identified. The mean age for the group was ±, 236 (51.6%) were male, and the majority was Caucasian (49.7%) or African American (29.1%). The severity of restriction was mild-to-moderate in 77.5%, 72.6%, and 65.1% when graded using TLC, FEV1, and FVC respectively. Agreement in severity was poor for TLC and both FVC (kappa=0.24; p<0.001) and FEV1 (kappa=0.25, p<0.001).
CONCLUSIONS: Conclusions: Both FVC and FEV1 tend to over-estimate the severity of restriction graded using TLC measured via plethysmography. Neither measure is particularly accurate in characterizing severity, and neither measure is superior to the other.
CLINICAL IMPLICATIONS: Spirometry must be used with caution when grading the severity of restrictive pulmonary disease.
DISCLOSURE: The following authors have nothing to disclose: Sean Roark, Aaron Holley, Timothy Quast
No Product/Research Disclosure InformationWalter Reed National Military Medical Center, North Bethesda, MD