Respiratory Admittance by Oscillometry in Children

Oscillometry is a pulmonary function testing technique that is well suited to children who have difficulty cooperating with conventional tests such as spirometry, as it is performed during spontaneous breathing and does not require specific respiratory maneuvers. In contrast, spirometry requires a deep inspiration followed by a forced and complete expiration.

Oscillometry provides a measure of respiratory impedance, which is the complex sum of respiratory resistance (Rrs) and respiratory reactance (Xrs). However, when the oscillatory signal is applied directly at the subject's airway opening, part of the flow signal may be lost due to cheek wall vibrations, resulting in an underestimation of Rrs. This underestimation may be more pronounced during bronchoconstriction, such as that induced by an exercise challenge test (ECT). This limitation may be overcome by calculating respiratory admittance (Ars), the inverse of respiratory impedance. When calculating the response to ECT, cheek wall admittance is cancelled out, potentially allowing a more accurate assessment of changes in respiratory mechanics during an ECT.

The hypothesis was that calculating Ars provides a more accurate assessment of changes in airway mechanics during an ECT.

Inclusion criteria

• Children aged 5 to 16 years
• Children addressed by the pediatric pulmonologist to an exercise challenge test between January 2023 and April 2026
• Children with interpretable and reproducible oscillometric measurements
• Children with interpretable and reproducible spirometric measurements

Exclusion criteria

• Children who performed only spirometric measurements
• Children who performed only oscillometric measurements
• Children whose oscillometric and spirometric measurements are non-interpretable
• Children whose oscillometric and spirometric measurements are non-reproducible