Spirometric tests in children
|Spirometric tests can be performed in children from age 3 year. Patience is required, particularly in young and inexperienced children, to obtain satisfactory FVC maneuvers; in a sizeable percentage of children this is not achieved. Therefore the tests must meet high standards:|
|•||the tests should be administered by professionally trained personnel used to dealing with children and capable of making them feel at ease|
|•||patience, time pressures should not play a role, otherwise measurements usually fail|
|•||clear and simple instructions|
|•||a quiet room adapted to children, so that the child is not distracted by minor details|
|•||all equipment should be suitable for children, such as the chair, the mouthpiece and location of equipment at a suitable height|
|•||equipment is usually designed for adults and subsequently used for children. However, for children it is most desirable that|
|•||FVC maneuvers can be visualized on line on a screen or other device|
|•||the scaling of FVC can be adjusted for children, because otherwise it is difficult to assess the quality of flow-volume curves and correct performance of maneuvers.|
|•||the FVC maneuvers can be visualized immediately, so that technically unsatisfactory maneuvers can be recognized and an extra effort can be made to obtain a satisfactory maneuver.|
|•||on these accounts a lung function laboratory for adults is often not ideally suited for measurements in children.|
|•||particularly in young children it is difficult to obtain both a satisfactory FEV1 and FVC in one maneuver. The ATS recommendation to select the curve with the highest sum of FEV1 and FVC is therefore not suitable in children. The flow-volume curve should instead be a ‘composite curve’. This entails constructing a flow-volume curve from acceptably performed FVC maneuvers with the largest FVC on the X-axis, and on the Y-axis the largest peak expiratory flow, and the largest flow selected from curves the FVC of which differed less than 5% from the largest FVC. This does not degrade the quality of the measurement, as this method leads to greater reproducibility than with curves with the largest sum of FEV1 and FVC. Children with asthma are usually well trained in lung function testing; as a result the within subject variation in FEV1 and in FVC is 5% or less.|
|•||In children and in adolescents the largest FEV1 and the largest FVC are selected from 3 technically satisfactory maneuvers. The largest FEV1 and FVC should not differ by more than 5% or 100 mL (the larger of the two) from the next largest one. (However, do take note of the table below).|
It is important that, while you instruct and encourage the patient and handle the equipment, you keep an eye on the patient in order to be able to assess subject cooperation.
Inspection of flow-volume curves may yield important information: reproducible shape, sharp peak, uninterrupted exhalation, complete exhalation indicated by gradual drop of flow to zero rather than sudden drop. Pain, stress incontinence and poor understanding may lead to unsatisfactory maneuvers.
In general the above adult-based goals for spirometry test performance are met by children and adolescents according to Enright et al., who do recommend age-specific criteria for time to PEF so as to improve the reproducibility of PEF values. Arets et al. were more critical.
Enright et al. (9-18 yr)
Arets et al. (5-19 yr)
|Back-extrapolated volume||<5% of FVC||<0.12 L (<15 yr), < 0.15 L (>15 yr)|
|Time to PEF||<160 ms||no time criterion, judge by eye 'rapid rise to peak flow'|
|End-of-test volume||<60 mL|
|Forced expiratory time||> 6 s||>1 s (<8 yr), >2 s (>15 yr)|
|ΔFVC||<200 mL and <5%||<5%|
|ΔFEV1||<200 mL and <5%||<5%|
|ΔPEF||< 1.0 L/s and < 15%|
Ad Arets et al.
- Arets et al. suggested – probably rightly so - not to discard curves too easily based on time criteria. Within certain limits, the time to reach PEF is probably not critical to obtain reasonable PEF values, and it is highly unlikely that differences in FEV1 or FVC due to a slightly slower rise time to PEF will be clinically relevant.
- Forced expiratory time criterion: this should probably not be applied too strictly: Healthy children < 8 yrs of age usually have a very short expiration time. Sometimes they can exhale FVC within 1 second, even making it impossible to obtain FEV1. Hence, it should be regarded with some common sense: by visual inspection of the flow-volume curve the experienced investigator can judge whether expiration was complete or not.
An ATS/ERS Working Group issued the following recommendation for pulmonary function testing in preschool children:
- The flow–volume curve ideally should be presented to the operator in real time with the ability to also view the volume–time trace. Alternatively, the operator should be able to view the previous flow–volume curve before the next expiration attempt.
- The following indices from each spirometry attempt should be available to the operator before the next attempt: FVC, FEV in t seconds (FEVt), back-extrapolated volume (VBE), and the point at which flow ceases, presented as a proportion of peak expiratory flow (PEF).
- If it is the subject’s first attempt at spirometry, a period of training is essential. The child should be familiarized with the equipment and technician.
- Interactive computerized incentives may be used to encourage the maneuver, but these are not mandatory. If incentives are to be used, then a volume-driven incentive, or a flow- and volume-driven incentive must be used when maneuvers are to be recorded.
- Posture and noseclip use should be recorded and reported.
- The operator should observe the child closely to ensure there is no leak, and that the maneuver is performed optimally.
- A minimum of three maneuvers should be recorded, but no maximum number is stipulated.
- Both volume–time and flow–volume curves should be visually inspected. The attempt should be excluded if the flow–volume curve does not demonstrate a rapid rise to peak flow, and a smooth descending limb, without evidence of cough or glottic closure.
- If the VBE is greater than 80 ml, or 12.5% of FVC, then the curve should be reinspected, but need not necessarily be excluded.
- If cessation of flow occurs at greater than 10% of peak flow, then this maneuver should be classified as showing premature termination. It may be possible to report timed expiratory volumes from such a maneuver, but FVC and forced expiratory flows should not be reported.
- The highest FEVt and FVC should be reported, after examining data from all of the usable curves, even if they do not come from the same curve.
- The starting point for FEVt should be determined by back extrapolation.
- The method of identifying best flows should be recorded and reported. If flows are to be reported from the “best” maneuver, then this should be identified as that with the highest sum of FEV0.5 and FVC.
- Ideally, the subject should produce at least two acceptable curves, where the second highest FVC and FEVt are within 0.1 L or 10% of the highest value, whichever is greater. If a single satisfactory maneuver is recorded, then these results should not be excluded simply because of poor repeatability. The number of technically satisfactory maneuvers and the repeatability results should always be reported.
Enright PL, Linn WS, Avol EL, Margolis HG, Gong H, Peters JM. Quality of spirometry test performance in children and adolescents. Chest 2000; 118: 665-671.
Arets HGM, Brackel HJL, van der Ent CK. Forced expiratory manoeuvres in children: do they meet ATS and ERS criteria for spirometry? Eur Respir J 2001; 18: 655-660.
Beydon N, Davis SD, Lombardi E, Allen JL, Arets HGM, Aurora P, et al. on behalf of the American Thoracic Society/European Respiratory Society Working Group on Infant and Young Children Pulmonary Function Testing. An Official American Thoracic Society/European Respiratory Society Statement: Pulmonary Function Testing in Preschool Children. Am J Respir Crit Care Med 2007; 175: 1304–1345.