Revisiting the role of Spirometry in the diagnosis of upper airway obstruction

Abstract

Deepthi Laldayal, Unnati Desai, Jyotsna M Joshi Introduction: Spirometry with flow volume loop perhaps remains the least utilized test to determine upper airway obstruction (UAO), reflecting our rather diminished understanding of the subject. Aim: To find the proportion of UAO cases among patients undergoing spirometry in a tertiary care pulmonary department. To investigate the utility of various spirometric indices described for UAO and their ability to differentiate between extrathoracic and intrathoracic UAO. Methods: In a two years study period, the demographic data, diagnosis, relevant imaging and bronchoscopic reports of patients were noted. All spirometries were reviewed for three quantitative and three qualitative indices. These comprised of Empey’s Index, ratio of the flow at the mid-point of the forced expiratory manoeuvre to the flow at the mid-point of the forced inspiratory manoeuvre (FEF50/FIF50) Results: 770 spirometries were analyzed, with a mean age of population of 43 years. 24 patients of UAO resulting in a proportion of 3.1%. Flow volume loop changes were able to differentiate extra and intrathoracic location in all cases. FEF50/ FIF50 value could accurately differentiate extrathoracic versus intrathoracic obstruction in 83.3%. Conclusion: Our study demonstrated higher sensitivity and specificity for all the spirometric indices in comparison to earlier studies.