Pulmonary Function Testing in Pre-schoolers

Rationale And Clinical Challenges

Recurrent wheezing affects 20 to 30 percent of Indian preschoolers, frequently predicting persistent asthma by school age.
Traditional spirometry fails in over half of children under six years due to short attention spans, poor cooperation, and inability to perform maximal forced maneuvers reliably.
Objective testing is required to prevent systemic over-treatment or under-treatment with inhaled corticosteroids.
Recent advances prioritize effort-independent techniques, achieving 80 to 95 percent feasibility in trained centers.

IOS superimposes small pressure oscillations (5 to 35 Hz) onto spontaneous tidal breathing via a mouthpiece.
It non-invasively calculates respiratory system impedance, enabling early detection of peripheral airway obstruction that traditional spirometry misses.
Feasibility exceeds 90 to 96 percent in awake preschoolers without requiring sedation.

Parameter	Clinical Significance
R5	Total airway resistance.
R20	Large airway resistance.
R5-R20	Small airway dysfunction and peripheral airway obstruction.
X5	Reactance, indicating airway distensibility and presence of air trapping.
AX	Reactance area, which correlates strongly with poor asthma control and future exacerbations.
Fres	Resonant frequency.

A positive bronchodilator response requires a 25 to 30 percent drop in R5 or normalization of z-scores.
IOS abnormalities at age four strongly predict active asthma and impaired lung capacity at school age.

Measures the Lung Clearance Index to identify ventilation inhomogeneity.
Multicenter trials report success rates exceeding 92 percent in the preschool demographic.
An elevated Lung Clearance Index (greater than 7.5 to 8.0) accurately predicts persistent wheezing and cystic fibrosis progression before spirometric changes occur.

Digital spirometers utilize artificial intelligence quality control combined with gamified visual incentives to enhance acceptability to over 85 percent in cooperative four to six-year-olds.
The American Thoracic Society and European Respiratory Society 2025 technical updates accept FEV0.75 (Forced Expiratory Volume in 0.75 seconds) if there is no cough or glottic closure during the maneuver.

Diagnosis remains primarily clinical for children aged five years and under.
IOS and Multiple-Breath Washout are explicitly recommended in specialist settings for persistent symptoms to assess disease control and guide therapy escalation.

Endorses Impulse Oscillometry in pediatric pulmonology clinics specifically for preschool wheezing evaluation.
Objective testing is mandated for refractory cases prior to initiating long-term inhaled controllers or biologic therapies.
Integration with school health programs and National Clean Air Programme pilots is emphasized for early chronic respiratory disease detection.