Role of spirometry with flow volume loop in the diagnosis of upper airway obstruction: A study from the pulmonary medicine department of a tertiary care center

1 ABSTRACT INTRODUCTION Spirometry with flow volume loop (FVL) is an easy-to-use bed side test to determine upper airway obstruction (UAO). The study aimed to find the prevalence of UAO and the ability of visual and quantitative criteria to detect UAO. METHODS This was retrospective study conducted for a period of two years at the pulmonary medicine department of a tertiary care center to find the proportion of UAO cases among patients undergoing spirometry, to study the profile of UAO, and to investigated the utility of spirometric indices described for UAO. The demographic data, diagnosis, relevant imaging and bronchoscopy reports of patients were noted. 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), FIF50 <100 L/ min and qualitative features like flattening of inspiratory or expiratory loops, box-shaped loop and oscillations on the loop. RESULTS Mean age of the population was 43 years. Prevalence of UAO was 24 (3.1%). The most common cause of UAO was multinodular goiter (MNG) seen in 10 (39%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for Empey’s index were 62.5%, 89.4%, 15.7% and 98.6%, respectively. The sensitivity, specificity, PPV and NPV for qualitative criteria of flow volume loop (FVL) visual abnormalities were 95.6%, 99.7%, 91.6% and 99.8%, respectively. The sensitivity, specificity, PPV and NPV of FIF50 <100 L/min were 79.1%, 80.4%, 11.5% and 99.1%, respectively. Variable extrathoracic UAO was seen in 17, variable intrathoracic UAO in 4, while 3 cases had fixed UAO. CONCLUSIONS Spirometry with FVL is a simple and useful screening test for UAO.