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Updated: Jun 10, 2026
Protocol and Guidelines for Point-of-Care Lung Ultrasound in Diagnosing Neonatal Pulmonary Diseases Based on International Expert Consensus
Published on: March 6, 2019
Potential misinterpretation of infant lung function unless prospective healthy controls are studied
Sooky Lum1, Ah-Fong Hoo, Georg Hulskamp
1Portex Unit, Respiratory Physiology and Medicine, UCL, Institute of Child Health, London, UK. s.lum@ich.ucl.ac.uk
Insights
Interpreting infant lung function tests using old equations can lead to misdiagnosis. New reference data or equipment-specific equations are crucial for accurate assessment in infant pulmonary function testing.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Medical Device Evaluation
Background:
- Pulmonary function tests (PFTs) are vital for diagnosing infant lung diseases.
- Existing reference data for infant PFTs are limited, hindering accurate interpretation.
- Commercial equipment advancements necessitate updated reference equations.
Purpose of the Study:
- To evaluate the validity of current published reference equations for infant forced expiratory flow-volume (FEFV) data.
- To assess the impact of using these equations on interpreting PFT results in infants with lung disease.
- To determine the need for updated reference data for infant PFTs.
Main Methods:
- FEFV maneuvers were performed on healthy infants and those with cystic fibrosis (CF) using Jaeger Masterscreen BabyBody equipment.
- Results were initially analyzed using Z-scores based on published reference equations.
- Multilevel modeling was employed to adjust for differences in healthy infants and analyze CF patient data.
Main Results:
- Published equations significantly underestimated FEFV outcomes in healthy infants (e.g., mean Z-score difference of -1.4 for V (maxFRC)).
- Adjustments using multilevel modeling brought mean Z-scores within predicted ranges for healthy infants.
- Using published equations, 41-45% of CF infants' results were deemed "abnormal"; this decreased to 20-28% after adjustment.
Conclusions:
- Reliance on outdated published equations can lead to misinterpretation of infant lung function.
- This misinterpretation can negatively affect research findings and clinical management of infant lung diseases.
- Establishing equipment-specific reference data or using contemporary control groups is essential for accurate infant PFT interpretation.
Unlabelled:
SUMMARY RATIONALE: Reliable interpretation of pulmonary function tests relies on appropriate reference data, which remain very limited for infants.
Objectives:
This study aimed to assess the validity of published reference equations for forced expiratory flow-volume (FEFV) data in infants when using current, commercially available equipment, and how this could impact on interpretation of results from infants with lung disease.
Methods:
The Jaeger Masterscreen BabyBody (v4.67) equipment was used to perform partial and raised volume FEFV maneuvers in healthy infants and those with cystic fibrosis (CF). Results were initially expressed as Z-scores using published reference equations. Multilevel modeling was used to calculate differences, if any, from predicted scores in healthy infants.
Results:
Data were available from 66 healthy full term infants on 89 test occasions; [median (range) postnatal age 49.4 (12-101) weeks. All FEFV outcomes were significantly lower than predicted, with mean (SD) Z-score differences of -0.4 (1.1) for FVC; -0.6 (1.0) for FEV(0.5); -1.0 (1.0) for FEF(25-75) and -1.4 (1.1) for V'(maxFRC). After adjustments using multilevel modeling, mean Z-scores were within 0.1 (SD approximately 1.0) predicted for all outcomes in healthy infants. Among 50 infants with CF, studied on 85 test occasions, results were "abnormal" (<-1.96 Z-scores) on 35 (41%) and 37 (45%) test occasions for FEV(0.5) and FEF(25-75), respectively, when using published equations. This fell to 24 (28%) and 20 (24%), respectively, after adjustment.
Conclusions:
Dependence on published equations for interpreting FEFV data in infants may lead to misinterpretation of lung function status, which could impact adversely both in the research setting and on clinical management. Use of a contemporary control group or establishment of equipment-specific reference data is essential for meaningful interpretation of infant lung function data.
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