ERS 2022: Lung Function Testing from Preschool Age to Adolescence: Are we Done with Spirometry?
In this session, experts discussed different lung function tests applicable from preschool age to adolescence by reviewing the most recent technical changes and the clinical use of these techniques, exploring the accuracy of respiratory mechanics measurements in the assessment of bronchial reactivity in asthmatic children, and the clinical applications of oscillometry in children.
Interrupter technique: The measurement of airway resistance using the interrupter resistance (Rint) technique has become an increasingly popular lung function test in pediatric respiratory medicine. Rint is an easy tidal breathing technique measuring respiratory resistance. Reliable reference values are available for 3-13 years old children. Epidemiological studies have demonstrated that annual average air pollution exposure between 4 and 8 years was not associated with a change in Rint between 4 and 8 years. In another large prospective study at 6 years of age, Rint was significantly associated with BMI. Rint in wheezy children is higher than that in non-wheezy children.
Despite the large intersubject variability of baseline Rint, it can detect effects of environmental exposures or conditions (obesity) but can be a poor predictor of disease at the individual level. Rint is a sensitive marker of bronchodilator response (BDR). A minimum of 400 µg of salbutamol should be given to assess BDR using Rint. Rint can be used during a bronchial challenge in addition to an oxygenation index.
Oscillometry: Oscillometry is assessed using an external oscillatory signal applied to the mouth. Oscillometry in children is easy to perform. Patients should be breathing relaxed and stable, seated in an upright posture with correct head position, cheek support, mouthpiece seal and tongue position.1,2 The recommended thresholds for positive bronchodilator responses in children are -40% in Rrs5, +50% in Xrs5 and -80% in the area of reactance (AX).
There is increasing evidence for the prognostic value of bronchodilator testing using oscillometry in symptomatic children and adults to support its use as a clinical test. Spirometry and oscillometry are not directly comparable in individual children and may reflect different aspects of lung function.3 The sensitivity of oscillometry in detecting BDR varies in different studies, but it has been suggested to be more sensitive than spirometry because of no "deep inspiration" effect.4-6 Oscillometry helps discriminate disease populations from healthy control subjects. Evidence suggests that most of the clinical application of oscillometry is in children with asthma. Evidence for long-term clinical utility needs to be studied.
Multiple breath washout techniques: Steps in the successful development of multiple breath washout (MBW) techniques
1. MBW equipment became accessible for widespread use
2. Validation of the equipment. The validation was moved beyond analyzer accuracy to develop a system to check performance in test settings with functional residual capacity (FRC) as an accuracy marker.
3. As a primary outcome measure, MBW became feasible on a grand scale- European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN) endorsement.
4. Beneficial effects of interventions in the preschool age range
5. Beneficial effects of interventions in infants
6. Life cycle inventory analysis (LCI) reference data in a rapidly moving field
7. Understanding the effect of inert gas choice
8. Understanding when to use MBW-It is not the test for all cystic fibrosis patients
9. Integrating tests into clinical care
10. The impact of ongoing validation
Multiple breath washout (MBW) has taken significant steps towards integration into routine clinical use.
It compliments but does not replace spirometry in cystic fibrosis. It should be used in early lung disease settings, but clinical care integration requires further understanding of how it should direct care. Ongoing efforts to reduce testing time whilst maintaining sensitivity will remain important.
Spirometry: Interpretation of pulmonary function tests (PFTs) should be based on good quality tests. Interpretation of PFTs must consider a level of uncertainty related to:
- Lung function changes in individuals over time
- Pre-test probability of disease
- Appropriateness of reference population
Interpreting PFT results must always consider the inherent biological variability, the uncertainty of the test result and the clinical signs and symptoms of the individual patient. Home spirometry decreases barriers to performing spirometry, allows spirometry with telehealth visits, and has the potential to reduce patient burden. Challenges to home spirometry include access, data quality accuracy and variability, adherence, and training. Improved error detection may improve accuracy. Home spirometry is feasible in individuals with asthma and cystic fibrosis.
European Respiratory Society (ERS) International Congress 2022, 3rd-6th Sept. 2022, Barcelona
