Accuracy of Impulse Oscillometry in Airway Dysfunction

Background: The purpose of this study was to calculate and compare the specificity and sens itivity of impulse oscillometry (lOS) as a new technique in the detection of airways dysfunction by means of a simple pulmonary function test in chemical warfare injured cases sufferin g from respiratory dise ases . Methods: The study was performed prospectively in 100 patients, who complained of dyspnea as a result of sulfur mustard gas exposure in the Iran-Iraq war , between 1981 and 1988 . Following a physical examination, lOS and spirometery wer e performed for all the patients. Then, the specificity and sens itivity of lOS parameters were calculated and compared with those of spirometery. Results: With a routine cut- off point, R at 5Hz and R at 20Hz have a sensitivity and specificity of 48 .9%, 70.4% and 40.0% and 85.2%, respe ctively. With a normal cut-off point of R at5Hz= 240 or R at20Hz= 180 or x at5Hz= -0. 20 kpal//s , there is a 100% specificity (PPV= 100%). Conclusion : While lOS is a new , cooperation independent technique and specific in the detection of airways dysfunction, it is less sensitive than spirometery in spotting small airways obstructions. lOS is a good diagnostic method in the detection of pulmonary involvements in uncooperative patients.