Spirometric tests in children
| Spirometric tests can be performed in children from age 6 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.
Index |
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.
References:
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.