MINI-SYMPOSIUM: LUNG FUNCTION IN PRESCHOOL CHILDREN
Spirometry in the pre-school age group

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Summary

Spirometry is a widely used lung-function test in school-aged children and adults. It can also be used to test lung function in the pre-school population, provided that they are tested in a child-friendly setting, by experienced paediatric-orientated personnel and in a way that is congruent with their development. Accurate results can be obtained provided care and attention are paid to applying quality-control criteria suitable for this age group. The biggest challenge is to make the testing fun.

Section snippets

INTRODUCTION

Spirometry is used to record a forced expiratory vital capacity (FVC), the maximal volume that can be forcibly expired after inspiration to total lung capacity (TLC), as a volume–time plot. From this volume–time plot, timed forced expiratory volumes can also be calculated (FEVt). The most widely used is the forced expiratory volume in 1 s (FEV1), but volumes expired in 0.5 or 0.75 s (FEV0.5 and FEV0.75) can also be measured. Normal values for these have been developed in young children as by 1 s

LABORATORY ENVIRONMENT AND STAFF

No child will cooperate with any test if they feel intimidated so as with any other paediatric setting the laboratory needs to be child friendly. A child-sized table and chairs, with crayons and pictures to colour in is an important step to reassuring the child that what follows will be fun. The most important asset is a respiratory technician/tester who is child friendly and can quickly gain the child's trust. They must also be able to teach and encourage the child in an age-appropriate

TEACHING THE FORCED EXPIRATORY MANOEUVRE

Spirometry requires a forced expiratory manoeuvre which requires:

  • a full inspiration to total lung capacity,

  • a forceful, i.e. hard and fast, expiration,

  • and continues to residual volume (RV), which is the hardest step as expiring beyond functional residual capacity (FRC) is uncomfortable.

All this needs to be as a single, smooth manoeuvre. The average 3.5-year-old, however, has a developmental level that will process and carry out three-step commands only.1 This means that the forced expiratory

BREATH-ACTIVATED COMPUTER ANIMATION PROGRAMS (INCENTIVES)

Several of the spirometry manufacturers have developed breath-activated computer animation programs to use during testing. It is, however, very important that the animation program used is appropriate for both the child's age and the step being taught. For example, Jaeger has an animation program using candles (Fig. 1). This is appropriate for most ages, but only encourages peak expiratory flow; there is no incentive to encourage prolongation of the expiration down to residual volume. For this

REWARD AND POSITIVE RE-INFORCEMENT

Each manoeuvre takes a few seconds, many less than 1 s; so most children will happily perform 15 blows within a 5-min period. Once the tester is satisfied that several maximal effort blows have been achieved then the child can be rewarded. This can be done by reducing the difficulty so the child achieves the target or letting them choose an animation program from those available. Many laboratories also have a supply of stickers to give out as a further reward. Lastly, it is important to

REFUSALS

If a child refuses to participate, ask the parents to perform the manoeuvre first. If the child still refuses, praise and reward them and re-book the appointment. At this next appointment, most children will understand what will happen and that they will be rewarded and so happily participate.

There are a few children who have developmentally not reached the level necessary (usually the 3-year-olds) to ensure maximal effort despite appropriate teaching and encouragement. Again, time will solve

ACCEPTING MANOEUVRES (BLOWS) DURING THE TEST

During the test it is important to watch the child. Any blows where the child has not inspired to total lung capacity should be rejected. This also applies to any blows where the child has coughed or huffed. Blows should also be rejected if the tester feels the child has not tried maximally or not expired down to residual volume. Written comments on the child's effort and cooperation are useful in the subsequent analysis and for future tests.

QUALITY CONTROL AND INSPECTION OF FLOW–VOLUME AND TIME–VOLUME CURVES (LOOPS)

Saved loops need careful examination for acceptability and the flow–volume and time–volume curves for each blow need to be inspected together (Figure 2, Figure 3, Figure 4). Visual inspection is very important and may provide evidence of airways obstruction even before analysis of the results (Fig. 5).

REPORTING OF RESULTS

The best loop is that with the highest sum of FVC and FEV0.5 [as FEV0.5 is the commonest FEVt to be recorded in this age group, with fewer achieving forced expiratory times (FET) longer than 1 s]. The flows, MEF25, MEF50, MEF75 and MMEF, are taken from the best loop. The highest values for FEV0.5, FEV0.75, FEV1 and FVC are taken from any of the technically acceptable loops.

REPRODUCIBILITY

The number of loops within 10% of the sum of FVC and FEV0.5 of the best loop is also recorded. If there are no loops within 10% then this is not a reason for reporting a test failure. The percentage difference of the second best loop in this case should also be reported.

EUROPEAN RESPIRATORY SOCIETY (ERS) AND AMERICAN THORACIC SOCIETY (ATS) GUIDELINES

There are several studies that assess what pre-school children can achieve2, 3, 4, 5, 6, 7 in relation to standards for school age children and adults,8, 9 but as yet there are no published guidelines for standards of spirometry testing in the pre-school age group, though a joint ERS–ATS statement is due to be published soon.

REFERENCE PREDICTION EQUATIONS

Several groups have now published reference equations,10, 11, 12 which allow calculation of z-scores and percent predicted values from an individual child's results (Table 1).

POTENTIAL CLINICAL USES

Like spirometry in the older age groups, it is hoped that spirometry in the pre-school age group will aid diagnosis, prognostication and monitor response to treatment, but data are limited at present.

CONCLUSIONS

The pre-school age can no longer be regarded as the ‘Cinderella years’ with regard to lung-function testing. It is now widely recognised that these children can cooperate and perform to the best of their ability provided that they are tested in a suitable environment, by sympathetic testers and taught in an age-appropriate way. Most importantly they need encouragement, positive reinforcement and reward for their efforts.

To ensure accurate reporting of results careful scrutiny of the child

PRACTICE POINTS

  • Pre-school children can perform spirometry.

  • The lung function laboratory needs to be a child-friendly environment.

  • Personnel need to be experienced and suitably trained for testing children in an age-appropriate manner.

  • If breath-activated computer animation programs are used they need to be appropriate for the child and ultimately encourage a forced expiration down to residual volume.

  • Quality-control criteria need to be applied while inspecting flow–volume and volume–time curves to exclude

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