Airway resistances deteriorate following spirometry in asthma and COPD patients

Abstract

Introduction: Spirometry is the most commonly used pulmonary function test. However, the forced expiratory manoeuvre itself may affect airway physiology. Aim: We investigated the effect of spirometry on airway impedance (resistance and reactance) as assessed by impulse oscillometry (IOS). Methods: IOS parameters were measured by IOS system (IOS, Jaeger Master Screen, Jaeger Co, Wurzburg, Germany) in 12 mild asthmatics , 10 mild COPD patients, and 12 healthy volunteers before and after spirometry for 60 minutes, including airway resistance at 5 and 20 Hz (R5, R20 respectively), airway reactance at 5 Hz (X5), dependence of resistance from 5 to 20 Hz (R5-20), resonant frequency (Fres), and low-frequency reactance area (AX). Results: Following the spirometric manoeuvre, airway resistances (R5, R20) were significantly increased in COPD and asthmatic patients (p=0.004, p=0.04 respectively). Whereas airway reactance (X5) was significantly increased in only COPD patients (p=0.009). Contrary to patients with lung disease, healthy volunteers presented a significant decrease in airway resistance immediately after spirometry (p=0.01). Conclusion: The forced expiratory manoeuvre of spirometry may increase airway resistances in COPD and asthmatic patients contrary to healthy volunteers where resistances decreased. An important practical clinical message is physicians should undertake oscillometry before spirometry.