Airway resistance and characterization of airway obstruction

Abstract

Background: Airway obstruction occurs due to an increase in airway resistance, so the determination of Raw must be considered for the evaluation of its presence and severity classification especially in individuals with difficultty to perform forced maneuvres.

Aims: To determine the presence of airway obstruction according to FEV₁/FVC<70%, Raw≥0.240KPa/l/s and Raw≥0.380KPa/l/s criteria; Estimate the sensitivity and specificity of the Raw≥0.240KPa/l/s and Raw≥0.380KPa/l/s criteria; Classify the severity degree of airway obstruction according to FEV₁ and Raw.

Methods: Cross-sectional study. The sample included 579 individuals who performed spirometry and whole body plethysmography during 2019. For the detection of airway obstruction, the criteria mentioned above were considered. In the presence of airway obstruction defined by FEV₁/FVC ratio, its severity was established according to FEV₁% and when defined by Raw≥0.240KPa/l/s was based on Raw severity degrees.

Results: The Raw≥0.240KPa/l/s detected the presence of airway obstruction in 61.8% of individuals, the FEV₁/FVC<70% in 55.1% and Raw≥0.380KPa/l/s in 29.5%. The Raw≥0.240KPa/l/s showed a sensitivity of 79.9% and a specificity of 47.6% and the Raw≥0.380KPa/l/s of 59.2% e 92.7%, respectively. Relatively to airway obstruction severity, through FEV₁ analysis, 35.1% were mild, 18.5% moderate, 15.7% moderatly severe, 20.4% severe and 10.3% very severe. Through the Raw KPa/l/s analysis, 62.9% were mild, 26.5% moderate and 10.6% severe.

Conclusion: Raw showed a high capacity to identify airway obstruction and allowed to classify the obstruction severity, which should be valued in the study of individuals with suspected obstructive disease with difficulty of perform the spirometry