Pediatric Pulmonary Function Testing: Evidence‑Based Recommendations
1. Test Selection by Age and Developmental Capability
2. Clinical Indications
Asthma and Wheezing
Cystic Fibrosis
Chronic Neonatal Lung Disease
3. Technical Requirements
4. Measurement and Reporting Standards
5. Age‑Specific Physiological Considerations
6. Test‑Specific Pitfalls and Mitigation
7. Recommendations for Research Design
Pulmonary Function Testing in Children
Age-Specific Capabilities
- Children aged 3-6 years can successfully perform most pulmonary function tests that require only tidal breathing, including forced oscillation technique (FOT), interrupter resistance (Rint), specific airway resistance (sRaw), functional residual capacity (FRC) measurements, and multiple-breath washout (MBW) methods 4, 5, 6
- Spirometry requiring forced expiratory maneuvers is more challenging in preschool children because young children can typically blow either "hard" or "long" but frequently cannot do both simultaneously 7
- Children aged 6-7 years and older can reliably perform standard spirometry and peak flow measurements, as they can follow instructions and maintain the required effort throughout the maneuver 8, 9
- Standard adult-type pulmonary function testing becomes routinely feasible once children reach school age and can cooperate with voluntary respiratory maneuvers 4, 10
Critical Technical Considerations
- Specialized pediatric adaptations are essential because equipment designed for adults will produce inaccurate results in young children 6, 10
- Trained staff experienced in pediatric testing is mandatory to engage and encourage preschool children who have short attention spans and are easily distracted 4, 5
- The testing environment must be child-friendly with a bright, pleasant atmosphere and age-appropriate materials to help children feel at ease and improve performance 9
Test Selection by Age
- For children 3-5 years old, prioritize tidal breathing techniques (FOT, Rint, MBW) over forced expiratory maneuvers, as these require less active cooperation and are more likely to yield valid results 7
- Perform forced expiratory measurements after tidal measurements if attempting both, because it is easier to "wind up" young children than to calm them down afterward 7
- Avoid deep inhalation maneuvers in children with asthma during initial testing, as deep inhalation may change bronchial tone 7
Physiological Developmental Factors
- The FEV₁/FVC ratio in healthy 5-6 year olds is approximately 90-95% (even higher in younger children), which differs substantially from older children and adults, requiring age-specific interpretation 7
- Preschool children lack the chest wall muscle strength to maintain flow limitation to lung volumes as low as 90% of exhaled vital capacity, making FEV₀.₅ or FEV₀.₇₅ more appropriate outcome measures than FEV₁ 7
- Reference data from older subjects should never be extrapolated for use in children younger than 6 years, as this leads to misinterpretation 4
Common Pitfalls to Avoid
- Do not attempt testing during or within 3 weeks of a respiratory infection, as this will produce invalid baseline measurements 11
- Do not use sedation for preschool children, as they are generally too old for this approach used in infants, and testing under anesthesia is neither ethically acceptable nor physiologically relevant 5, 10, 12
- Do not test children in adult laboratories without pediatric accommodations, as this significantly reduces success rates and data quality 9
- Ensure oxygen saturation is above 95% before testing and have bronchodilator and resuscitation equipment immediately available 11
Quality and Interpretation Requirements
- Results must be expressed as z-scores (multiples of standard deviation from the mean) rather than percentages of predicted values for accurate interpretation in young children 4
- Operators must have access to raw data from equipment to allow investigation of age-appropriate algorithms and improve disease discrimination as knowledge evolves 6, 10
- Validation of reference data is essential by testing at least 30-50 healthy preschool children using identical techniques before applying results clinically 4