INDEXES OF UPPER AIRWAY-OBSTRUCTION IN PATIENTS WITH SIMULTANEOUS CHRONIC AIR-FLOW LIMITATION

In patients with chronic airflow limitation (CAL), the detection of up per airway obstruction (UAO) by analysis of forced flows can be diffic ult due to the masking of conventional UAO indices. We analyzed five i ndices: maximum inspiratory flow at 50% of forced vital capacity (FIF5 0), the ratio of maximum expiratory to inspiratory flow at 50% of forc ed vital capacity (FEF(50)/FIF50), the ratio FEV(1)/PEFR, the ratio FE V(1) to forced expiratory volume in 0.5 s (FEV(1)/FEV(0.5)), and the r atio maximum voluntary ventilation (MVV)/FEV(1), to determine their us efulness in evaluating patients with simultaneous UAO and CAL. One hun dred and thirty-seven patients participated: 54 had UAO alone, 23 pres ented simultaneous UAO and CAL and 60 suffered from CAL with no eviden ce of UAO. The patients with UAO and CAL on the average presented fewe r abnormal indices and these were less severely altered. Twenty-seven of the 60 with CAL alone presented at least one abnormal index, but in no case were more than two present. FEF(50)/FIF50 and FEV(1)/PEFR wer e significantly less sensitive in patients with both UAO and CAL than in those with UAO alone (35 vs. 85% and 52 vs. 72%, respectively). In all patients the most specific indices (100%) were FEF(50)/FLF(50) and MVV/FEV(1). The index MVV/FEV(1) was the most accurate in patients wi th UAO and CAL. We conclude that when patients with CAL present 3 or m ore abnormal UAO indices, or have FEF(50)/FIF50 greater than or equal to 1 or MVV/FEV(1) less than or equal to 25, the possibility of simult aneous UAO must be strongly considered.