MINI-SYMPOSIUM: LUNG FUNCTION IN PRESCHOOL CHILDRENInert gas washout in preschool children
Section snippets
INTRODUCTION
Over the last 10 years studies have shown that it is possible to measure lung function in many preschool children (3–6 years) using incentive spirometry,1 by measurements of airway resistance with the forced oscillation2 or the interrupter technique,3 or as specific resistance during tidal breathing in a body-box.4 Spirometry may be more informative but requires active co-operation in contrast to the resistance measurements that require tidal breathing only. On theoretical grounds it can be
MULTIPLE-BREATH WASHOUT AND OTHER GAS-MIXING TESTS
The effectiveness of ventilation distribution and gas mixing cannot be measured using oxygen (O2) or carbon dioxide (CO2) because these gases participate in the gas exchange across the alveolo–capillary membrane. Several inert gases, e.g., nitrogen (N2), argon (Ar), helium (He) and sulphur hexafluoride (SF6), are suitable for this purpose, however, because they have a relatively low solubility in blood and other tissues and can be easily be measured with fast responding analysers (Table 1).
This
EQUIPMENT AND PROCEDURES
Hardware for breath-by-breath MBW systems includes a gas analyser and a flow meter, measuring the inert gas concentration and the inspiratory and expiratory flows close to the mouth. In addition a device for delivering gas mixtures, a suitable inert marker gas mixture and a computer with a data acquisition board are needed. Fig. 1 shows a 3-year-old child performing a MBW while watching a video film. She wears a facemask sealed with therapeutic putty and connected to a pneumotachometer. The gas
REFERENCE VALUES
Only a few MBW studies including healthy subjects between aged 2–6 years have been published. Interestingly, reference values for LCI are similar across the age range from infancy to adolescence with a narrow distribution. This makes the MBW test even more clinically useful and this feature is particularly helpful when doing longitudinal follow-up of patients. LCI values obtained in healthy preschool children have been published by Aurora et al. using a SF6 MBW method.9 These reference values
CLINICAL INTERPRETATION
An abnormally elevated LCI indicates uneven ventilation distribution, which can be the result of generalised peripheral airway obstruction or more focal airway disease associated with reduced regional ventilation. Studies in children with CF show that abnormal ventilation distribution is seen in the majority of patients with normal spirometry findings.9, 22, 23 In preschool children with CF, the MBW is a more sensitive method than both airway resistance measurements and spirometry in detecting
AVAILABILITY
Unfortunately, no MBW systems adapted for preschool children are today commercially available except for the ultrasound method. A task force group within the ATS (American Thoracic Society) and ERS (European Respiratory Society) will present standards for lung function testing methods and procedures in preschool children in a near future. Hopefully that will encourage manufacturers to start producing MBW systems of good quality at affordable prices.
CONCLUSIONS
Multiple-breath inert gas washout tests can be performed successfully in almost all children aged 3–6 years because they involve only normal tidal breathing. There is evidence that this test is more sensitive to airway involvement than spirometry or airway resistance measurements in preschool children with CF, suggesting that it may have a clinical role. It can be presumed that the MBW test is a more sensitive test also in other airway disorders that involve the peripheral airways in young
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Cited by (53)
High inspired oxygen fraction impairs lung volume and ventilation heterogeneity in healthy children: a double-blind randomised controlled trial
2019, British Journal of AnaesthesiaCitation Excerpt :FRC was calculated by dividing the net amount of nitrogen exhaled during the washout by the difference in end-tidal gas concentrations from the beginning to the end of washout.14 To characterise the ventilation heterogeneities, LCI was obtained by counting the number of FRC turnovers required to reduce the end-tidal concentration of nitrogen to 1/20th (LCI5) and 1/40th (LCI2.5) of the starting concentrations.14 During each assessment, FRC and LCI measurements were performed in reproducible duplicates, and the average values were used for further analysis.
Early lung disease in infants with cystic fibrosis. Diagnostic tools and possible therapeutic pathways
2016, Revue des Maladies RespiratoiresAlternative outcomes for the multiple breath washout in children with CF
2015, Journal of Cystic FibrosisFrequency dependence of capnography in anesthetized rabbits
2014, Respiratory Physiology and NeurobiologyCitation Excerpt :The multiple-breath washout of inert gases or of nitrogen by oxygen identifies the contribution of inhomogeneous ventilation to the obstructive lung disease (Gustafsson, 2005). The lung clearance index has thus been shown to be an early detector of lung function abnormalities in cystic fibrosis (Gustafsson, 2005; Robinson et al., 2010). With either method however, an airtight mask-to-face seal is mandatory for valid interpretation, and sedation may be required beyond a few months of age.
Lung function measurement with multiple-breath-helium washout system
2013, Medical Engineering and PhysicsCitation Excerpt :The lung clearance index (LCI) has been commonly used as a measure of lung health and is defined as the total expired volume during washout divided by the FRC, for a fall in tracer gas concentration to 2.5% of the initial value [35–37]. It has been shown that the LCI is more sensitive than the spirometry in cystic fibrosis (CF) adults, and its mean value has been measured 13.1 ± 3.8 in CF patients and a much lower mean value of 6.7 ± 0.4 in normal subjects [26,34–39,43–45]. Other studies have also shown the increasing LCI with the age [34] and a higher range of LCI in emphysematous patients [40].
Sensitivity of multiple breath washout to detect mild-to-moderate asthma in adolescence
2019, Journal of Allergy and Clinical Immunology: In Practice