Measuring lung function is particularly challenging in preschool children (2-5 years old) and physiologic measurements are often put off until the child reaches the school age. Yet, having some information on lung function may be extremely important at this age for clinical and research reasons [4,5].
Active participation in the collection and interpretation of lung function tests in preschool children in an ambulatory setting using the interrupter technique (Rint) and the forced oscillation technique (FOT) or lung function tests available for this particular age group. Technical aspects, including calibration, will also important for measurement of lung function test in this particular age .
In many of the hospital in developing country no expertise in the field of lung functions testing in preschool children. So, need for especial attention to perform advanced lung function tests for clinical/research purposes and potentially improve the training of other pediatric pulmonologists in pulmonology department.
Assessment of lung function in preschool children is difficult. Techniques which require active patient cooperation are difficult to perform and frequently give unreliable result .
The interrupter technique (Rint) is one of the few lung function tests that have been developed for assessment of airway caliber in young children. With this technique, measurement of the resistance of the respiratory system can be carried out quickly; with minimal cooperation of the child . The method is particularly suitable for subject who cannot undertake standard lung function tests, such as preschool children and schoolchildren who are unable to undertake spirometry. Commercial equipment for measuring Rint is now available. Undertaking the test is not complicated, even in a busy environment, and so it is possible to measure Rint outside specialist center .
Rint is measuring now using two commercial devices (Micro lab 4000 and Microprint, Micro Medical Ltd, Gillingham, UK). In both device flows is measured immediately before valve closure. Pressure is measured in both using a two-point linear back extrapolation method [4,7].
Technique to measure Rint
- Measurement will be made with the child seated, breathing through a mouthpiece and bacterial filter, nose clip in situ, and cheeks supported.
- Occlusion should be made with a valve closing less than 10 millisecond and lasting for 100 milliseconds.
- Occlusion will be triggered by a flow sheet to coincide with Peak expiratory flow (PEF) and will be made during expiration.
- Ten occlusions will be recorded, with the aim of retaining a minimum of five acceptable maneuvers.
- The median of all technically acceptable occlusions will be accepted.
The forced oscillation technique (FOT) is another most suitable device requires minimal patient cooperation and is ideally suited to subject unable to perform voluntary forced expirations. The FOT has been used in research studies for several decades and more recently, its use in clinical practice has been advocated, as reviewed by Oostven and colleagues .
The FOT is a noninvasive technique performed during tidal breathing that is relatively easy to apply in preschool children. An external pressure wave applied, usually at the mouth and the resulting pressure –flow relationship is analyzed in terms of respiratory impedance. The latter express the impediment to flow in the respiratory system that include both fractional losses and elastic and inertial loads .
Respiratory impedance spectra (Zrs), yielding Rrs and Xrs as a function of frequency, were obtained using commercially available equipment (12M, Chess Medical, Belgium) based on the specification of Landseer and coworkers in accordance with European Respiratory Society guidelines. The forced oscillatory signal is a pseudorandom signal consisting of frequency components between 4 and 48 Hz with a measurement period of 8 seconds [4,9].
Technique of FOT: 1
- The child will be seated, breathing through a mouthpiece, and wear a nose clip with the cheeks and mouth floor firmly supported.
- An acquisition period will cover several breathing cycles, typically lasting 8-16 seconds
- Three to five measurement will be performed.
- Result will be reported as the mean of the three to five measurements and a CV will be calculated from the SD to mean ratio [4,9].
The interrupter technique (Rint) and the forced oscillation technique (FOT) or other lung function tests available for this particular age group may help to improve clinical, training and research potential for respiratory physician and reduce the respiratory illness among the children in globe.
- Lopez AD (1993) Causes of death in industrial and developing countries: estimates for 1985–1990. In: Jamison DT et al., Eds.Disease control priorities in developing countries. Washington, DC, Oxford Medical Publications 3: 35–50.
- World Health Organization (2013) Global surveillance, prevention and control of chronic respiratory diseases: a comprehensive approach. Geneva: World Health Organization; 2013.World Health Organization. Chronic respiratory disease, asthma. 2013. Geneva: World Health Organization; 2013.
- World Health Organization. Chronic respiratory disease, asthma. 2013. Geneva: World Health Organization; 2013.
- Lombardi E (2007) Pulmonary function test in preschool children. Am J Respir Crit Care Med 175: 1304-1345.
- Lombardi E, Sly PD ,Concutelli G (2001) Reference value of interrupter respiratory resistance in healthy preschool white children. Thorax 56: 691-695.
- Merkus PJFM, Arets HGM, Josten T, Siero A (2002) Measurement of interrupter resistance: reference values for children 3-13 years of age. Eur Respir J 20: 907-911.
- McKenzie SA, Chan E, Dundas I (2002) Airway resistance measured by the interrupter technique: normative data for 2-10 years old of three ethnicities. Arch Dis Child 87: 248-251.
- Hall GL, Sly PD, Fukushima T (2007) Respiratory function in healthy young children using forced oscillations. Thorax 62: 521-526.
- Thamrin C, Gangell CL, Udomittipong K (2007) Assessment of Bronchodilator responsiveness in preschool children using forced oscillations. Thorax 62: 814-819.