Pulmonary Function Testing in Asthmatic Children. Tests to Assess Outpatients During the Covid-19 Pandemic

Several Respiratory Societies have developed recommendations to protect patients and health care workers in pulmonary function laboratories during the current Covid-19 pandemic. Recommendations include restricting pulmonary function tests (PFTs) to those deemed essential, mainly spirometry and diffusion capacity measurements. However, spirometric maneuvers require forced expiration, which in turn induces cough and the release of droplets in the laboratory. Testing asthmatic children need caution; the clinical picture of worsening asthma or an asthma exacerbation substantially overlaps with Covid-19. Alternative PFTs provide useful clinical information on bronchial obstruction and response to bronchodilators in asthmatic children. Measurements of respiratory resistance (FOT, Rint) are easy to perform during tidal breathing. Quantifying the fractional concentration of exhaled nitric oxide (FENO), a biomarker of eosinophilic-airway inflammation, requires slow expiratory maneuvers. Multiple-breath washout (MBW) assesses ventilation distribution inhomogeneity during relaxed breathing and helps to evaluate small airways dysfunction in patients with severe asthma. Home PFTs with telemonitoring and remote feedback could support patients needing close surveillance. These tests can help clinicians to safely manage their pediatric patients until the risk of SARS-Cov-2 transmission can be minimized. We describe the main characteristics of the techniques, discuss their clinical application, and emphasize the need for standardized measures and devices, having in mind the unpredictable duration of this pandemic.