Value of spirometry in diagnosis and staging of airflow limitation

Abstract

Rationale Using ventilatory flow limitation (VFL) as a new and simple way to grade chronic obstructive pulmonary disease (COPD) severity accurately. Aim of the work Accurate measurement of airflow limitation in COPD patients and correlation between standard forced expiratory volume in 1 s (FEV1) and VFL as an accurate measurement of airflow limitation. Patients and methods This study included 50 patients, 40 patients with COPD from outpatient clinic of Chest Department of Asyut University Hospital and 10 control persons were enrolled into our study. Measurement of spirometric data was taken (FEV1, forced vital capacity, FEV1/forced vital capacity) and patients were classified according to GOLD 2017 into mild, moderate, severe, and very severe COPD. Patients in our study were classified into two groups: group I: mild and moderate, group II: severe and very severe COPD. Tidal flow-volume loop was drawn by plotting exercise tidal flow-volume loop inside maximal flow-volume loop. Assessment of airflow limitation was done by measuring VFL: percent from tidal volume (Vt) that expiratory airflows meet or exceed the maximal expiratory flow. End expiratory lung volume (EELV) was measured from exercise tidal flow-volume loop. Results All very severe COPD patients had severe VFL. While severe COPD patients who had severe VFL were only 27.3%. The remaining 72.27% of severe COPD patients had moderate VFL. All mild and moderate COPD patients had mild VFL. Patients were classified into three categories: (a) with mild VFL for mild and moderate COPD grades, (b) with moderate VFL for severe COPD grade, (c) with severe VFL for very severe COPD grade. The increase in EELV during exercise is linked to the occurrence of VFL. EELV is increased to mean value of 618 ml in group II and just 240 ml in group I. Group II had significantly higher (P < 0.0001) VFL and EELV. Conclusion VFL and EELV are specific indices for airway obstruction in COPD patients and are correlated to the degree of severity.