PURPOSE:FEV1 /FVC is useful in evaluating obstructive airways disease in school age children. As preschool children can perform reliable spirometry but have short expiratory times, FEV1 cannot always be determined. Furthermore, when measurable, FEV1 /FVC is higher than described in older children. As FEV0.5/FVC and FEV0.75/FVC have been proposed as alternative measures, we aimed to describe these ratios in our population and determine if they could be surrogates for FEV1 /FVC in this age group.
METHODS:Our study population consisted of healthy Caucasian children aged 3 to 5 years attending 11 daycare centers in the Eastern Townships of Quebec. Measurements were obtained as per ATS guidelines using the Ms Pneumo spirometer (Jaeger). FEVx (where x could be one second or less) was calculated from the curve showing the highest sum of FEVx + FVC.
RESULTS:143 children were tested of which 128 (62M, 66F) performed successful spirometry. Forced expiration was maintained longer than 1 and 0.75 seconds in 107(48M, 59F) and 123(59M, 64F) subjects respectively. FEV0.5 was obtained in all 128. Mean values (±SD) are reported for males and females respectively. FEV1 /FVC was 92.6(±4.9) and 95.05(±5.1), p=0.01; FEV0.75/FVC was 87.8 (±7.0) and 90(±6.4), p=NS; FEV0.5/FVC was 76.43(±9.0) and 78(±8.4), p= NS; FEV1 was 1.20(±0.02) and 1.11(±0.02), p=0.007 and FVC was 1.31(±0.14) and 1.18(±0.14) p=0.001. FEV0.75/FVC and FEV0.5/FVC correlated to FEV1/FVC (r=0.91 p<0.0001 and r=0.85 p<0.0001 respectively), while FEV0.75 and FEV0.5 correlated to FEV1(r=0.98 p<0.0001 and r=0.94 p<0.0001 respectively).
CONCLUSION:We report normative data from our population for ratios of FEV1,FEV0.75 and FEV0.5 with respect to FVC. The lower limits of normal can be determined as 1.96 SD below the mean. Due to the better correlation, we propose that FEV0.75/FVC be used preferentially to FEV0.5/FVC as an alternative to FEV1/FVC. The usefulness of these reference values would have to be tested in future with respect to obstructive airways disease.
CLINICAL IMPLICATIONS:Predicted values for these volume ratios are likely to be helpful in appropriately interpreting clinical spirometry values.
DISCLOSURE:Mario Dumas, No Financial Disclosure Information; No Product/Research Disclosure Information