Smeets M, Brunekreef B, Dijkstra L, Houthuijs D. Lung growth of preadolescent children. Eur Respir J 1990; 3: 91–96.

The study sample consisted of 420 children of 6-11 yrs in age. There were 206 boys and 214 girls. The children were from a study on the relationship between indoor air pollution and respiratory health, in which repeated observations were made over a 2.5 yr period.
In 1984, the parents of 997 children were invited to let their children participate. The children were 6-9 yrs old, and the parents were contacted through ten schools located in four small, non-industrial communities in the south-east of The Netherlands. Of the 997 contacted, 832 (84%) were granted permission. In 1986, the parents of 702 of these children were again contacted for a follow-up study. Of the original 832, 88 had left the area, and 42 could not be included because their school refused to participate. Of the 702, 614 were allowed to participate in the follow-up study (88%).
Pulmonary function of all of the children was measured in the schools by trained technicians, using Vicatest-5 rolling-seal spirometers coupled with a microcomputer. Forced expiratory manoeuvres were performed whilst sitting, without a nose-clip. Each child was required to perform at least five acceptable forced expirations from a maximum of eight attempts. FVC, FEV₁, peak expiratory flow (PEF), maximal expiratory flow when x% remains to be exhaled (MEF_x%) and maximal mid-expiratory flow (MMEF) were recorded at each effort. In this report. results for FVC, FEV₁, PEF and MMEF only will be discussed. Selection of the lung function values out of the five measuremenls occurred according to the recommendations made for adults [9] and adolescents [10]. Lung function values were corrected to body temperature, pressure and saturation (BTPS). Details of the protocol are given elsewhere [11]. Tests were performed in the fall of 1984, in the spring of 1985, in the fall of 1986 and again in the spring of 1987. Acceptable data were obtained for 85-89% of all of the children on each of the four occasions. Of the 614 children included in the follow-up study, 420 (68%) had acceptable data on all four occasions. If the capacity to perform an acceptable test were uncorrelated between occasions, only 52% (0.85⁴) to 63% (0.89⁴) of the children would have been expected to have acceptable data on each occasion.
A respiratory symptoms questionnaire [12] was completed by the parents of the children, and the reported prevalence of respiratory symptoms was no different in the 420 children with full pulmonary function data compared to the prevalence in the total group of 614 children. The prevalence of chronic cough was 3.3% in the group of 420 children, and 2.5% in the group of 614 children. The prevalence of chronic wheeze was 4.6 and 4.7%, respectively. The prevalence of attacks of shortness of breath with wheeze was 3.1 and 3.0%, respectively. The analysis was restricted to the 420 children with full data, as for them pulmonary function growth could be calculated most reliably.
At the time of the lung function lest, standing height and weight were measured in stockinged feeL. Age at each examinalion was computed exactly (in yrs) by dividing the difference between birth date and day of measurement (days) by 365.25.

References

10. Schrader PC, Quanjer PhH, Borsboom G. Wise ME. Selection of variables from maximum expiratory flow-volume curves. Bull Eur Physiopathol Respir. 1981, 19,43-49.
11. Houthuijs D, Remijn D, Brunekreef R, Koning R de. Estimation of maximum expiratory flow-volume variables in children. Pediatr Pulmonol 1989.6, 127-132.
12. Florey C du V, Leeder SR. Methods for cohort studies of chronic airflow limittation. WHO Regional Publications, European Series no. 12, 1982.
 

Houthuijs D, Remijn D, Brunekreef R, Koning R de. Estimation of maximum expiratory flow-volume variables in children. Pediatr Pulmonol 1989.6, 127-132.

Study Design

The study population consisted of 794 Caucasian children, 6-9 years old, from ten primary schools in five non-industrial communities of the southeastern Netherlands. They participated in a longitudinal study on the effects of indoor air pollution on respiratory health. Pulmonary function testing of all children was performed twice between September 20 and October 31, 1984, and between April 15 and May 10, 1985. During both periods, a total of 118 children performed a repeat pulmonary function test up to 4 days after the first one, to assess the reproducibilily of the measurements. Using the data from this study, we have evaluated: 1) whether the minimum number of acceptable maneuvers should be three or five; 2) the optimal number of attempts; and 3) the best of seven different methods for the selection of MEFV variables from multiple maneuvers.
 

Procedure and Instrumentation

The pulmonary function testing was done with two dry spirometers between 9:00 a.m. and 3:00 p.m. at school by four trained teehnicians. The children invited for a second testing during the same period were selected at random from those who had performed the first test acceptably. The second test could take place on the same day or 1-4 days later. Children with repeated measurements in September or October 1984 were excluded from the reproducibility tests in April and May 1985.
The procedure of pulmonary function testing was according to the protocol of the Working Party for Standa4rdization of Lung Function Tests of the European Community for Coal and Steel (ECCS)⁶ with adjustments based on the recommendations in the American Thoracic Society (ATS) guidelines¹ and the studies in children, adults and teenagers.^2,3,4 Standing height with stockinged feet and weight were measured. The children performed the tests in the siuing position; no nose clip was used. The children were instructed by the technician and were allowed to practice the maneuver twice. The technician tried to obtain five acceptable curves. A maximum of eight attempts was allowed, or the pulmonary function test was considered unacceptable. Acceptability was judged by observation of the children during the forced expiratory maneuver and by visual inspection afterward of the volume-time chart trace obtained. The criteria for a technically acceptable blow were those recommended by the ATS and the ECCS.^1,6 Briefly: maximum inhalation; no hesitation at the start, followed by a maximum effort: no early termination of the maneuver; no coughing during the blow; no obstruction of the flow by the tongue, and no leak in the system; all of these help produce a smooth continuous curve. During the test three to five children were watching the performance of their classmate, to minimize the need for instructions before the start of the test.
The Vicatest VCT-5 dry spirometer (Mijnhardt, Bunnik, The Netherlands) measures the FVC, FEV1, peak expiratory flow (PEF), forced expiratory flows when 75%, 50%, and 25% of the FVC remains to be exhaled (FEF_75%, FEF_50%, and FEF_25%) anf forced expiratory flow between 25% and 75% (FEF_25-75%). The spirometer meets the requirements recommended by the ATS and the ECCS.^1,6 The Vicatest VTC-5 has a processor that computes the MEFV variables correcting for ambient temperature, There is no temperature recording inside the spirometer; therefore Ihe spirometers were frequently flushed with room air to keep them at room temperature. The results were transferred to a HP 85-A personal computer. The MEFV variables of acceptable blows, the serial number of the attempt, and the anthropometrie data of the children were recorded on tape. Afterwards, the MEFV variables were corrected for barometric pressure, which completed the body temperature, ambient pressure, saturated (BTPS) correction. The performance of the spirometers was checked three times a day using a Jones CS-400 calibrator.

References

 
1. Gardner RM (chairman). Snowbird Workshop on Standardization of Spirometry: ATS Statement. Am Rev Respir Dis 1979; 119: 831-838.
2. Taussig LM (chairman). Standardization of lung function testing in children. Proceedings and recommendations of the GAP conference Committee, Cystic Fibrosis Foundation. J Pediatr 1980; 97: 668-676.
3. Peslin R, Bohadana A. Hannhart B, Jardin P. Comparison of various methods for reading maximal expiratory flow-volume curves. Am Rev Respir Dis 1979; 119: 271-278.
4. Schrader PC, Quanjer PH, van ZOmeren BC, DeGroodt EG, Wever AMJ, Wise ME. Selection of variables from maximum expiratory flow-volume curves. Bull Eur Physiopath Respir 1983; 19: 43-49.
6. Quanjer PH (editor). Standardized lung function testing: Report of working party, European Community for Coal and Steel. Bull Eur Physiopath Respir 1983; 19 (suppl. 5): 1-95.