Coexistence of upper airway obstruction on spirometry with flow volume loop in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) can arise from smoking and non-smoking causes. Spirometry with flow-volume loop (FVL) analysis is a simple and essential test not only for diagnosing COPD but also for detecting upper airway obstruction (UAO). Identifying the coexistence of UAO in COPD has important clinical implications. The present study was an independent analysis of spirometry data from COPD patients (ECARP/2022/124) over 2 years at a tertiary care center. Various spirometry parameters and FVL patterns were assessed, including visual loop flattening, forced expiratory flow at 50% of vital capacity, forced inspiratory flow at 50% of vital capacity ratio (FEF50/FIF50), FIF50, and Empey's index. Patients meeting ≥3 of 4 standard UAO criteria were classified as having UAO. A total of 193 COPD patients were included (mean age 56.3 years). Visual loop flattening was observed in 27% (7% inspiratory, 20% expiratory). The FEF50/FIF50 ratio was >1 in 17% and <0.3 in 44%, suggesting variable intrathoracic obstruction as the most common type of UAO. FIF50 <100 L/min was noted at 27.3%. Overall, 7.21% of patients met ≥3 of 4 diagnostic criteria for UAO. Thus, a significant subset of COPD patients demonstrated features of coexisting UAO. Routine spirometry with FVL analysis provides a valuable, noninvasive tool to identify this overlap, which may influence diagnosis, management, and patient outcomes.