iPFT results
As a group, iPFT results in the SARS-CoV-2 group showed normal lung volumes, normal lung compliance (Crs) and normal airway resistance (Raw) (table 2). Expiratory flows in the SARS-CoV-2 group were mildly decreased, mainly when assessing flows from the tidal expiratory flow-volume curve (median (IQR) V̇maxFRC=60 (37-80) %predicted).
When comparing the SARS-CoV-2 group to controls, no differences in tidal breathing measurements, lung volumes, compliance nor resistance were found. The SARS-CoV-2 group demonstrated slightly better expiratory flows when compared to the control, mainly for low lung volumes (median (IQR) FEF85%=75 (48-98) in the SARS-CoV-2 group Vs. FEF85%=58 (43-77) in controls, p=0.035) (table 2).
Categorization according to iPFT pattern and bronchodilator responsiveness, showed no significant difference between the SARS-CoV-2 group and the controls, neither in the occurrence of different iPFT patterns, nor in the iPFT results (table 3). The majority of infants tested in both groups demonstrated an obstructive iPFT pattern (63% of the SARS-CoV-2 group and 66% of the controls, p=0.776) and only a minority showed normal iPFT results (31% of the SARS-CoV-2 group and 15% of the controls, p=0.074). Infants in the SARS-CoV-2 group with an obstructive lung disease pattern had similar iPFT results to controls.
Assessment of bronchodilator responsiveness (BDR) was available in 335 infants from our cohort (7 from the SARS-CoV-2 group and 328 controls). A positive BDR was present in 21% of the SARS-CoV-2 group and 22% of controls (p=0.904), see table 3.
In the SARS-CoV-2 group, abnormal pulmonary function tests were not associated with a personal or familial history of atopy nor with exposure to second-hand smoke. Data regarding atopy and second-hand smoke exposure were not sufficiently available for the control group.