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The Maximum Expiratory Flow-Volume Curve with Air and a Low ...

The Maximum Expiratory Flow-Volume Curve with Air and a Low ...

Table 7-Sum of Squared

Table 7-Sum of Squared Deviations by Component Parts for Visoj’ Source Sum Squares DF MS F Between subjects 3589.722 8 448.715 20.1 1 Between days within subject 11671.111 27 432.263 Between days 918.130 3 306.043 0.68 Days by subje(’tS 10752.981 24 448.041 13.48* Between time within (lays within subjects 14081.779 36 391.161 Between time 87.414 1 87.414 0.25 Time by subject 1508.531 8 188.566 8.51 Time by day Time bs’ subject l)y day 1462.278 11023.556 3 24 487.426 459.315 1.06 15.49* Between observers within time within days within subjects 5264.665 144 36.560 Between observers 557.287 2 278.644 12.49* Observers by subjects 426.019 16 26.626 1.20 Observers by day 153.565 6 25.594 1.16 Observers by time 378.392 2 189.196 8.54* Observers by subjects by time 493.414 16 30.838 1.41 Observers by subjects by day 1641.574 48 34.199 1.57* Observers by day by time 191.472 6 31.912 1.41 Observers 1)y subject by day by time 1422.942 48 29.645 1.36* Residual 9433.334 432 21.836 Total 44040.611 *Significant (P

Table 9-Pooled Mean Squares b Source and by Measurement Source Vo V5o VisoV Days within sU1)jects 1.894 1632.148 432.26 Time Xsubject 1 . 1 1 5 2064.241 177.327 Time Xsubject Xday 1 . 143 1916. 105 462.438 Observer Xsubject 0. 146 56.606 54.628 Observer Xsuhject Xday 0.084 69.742 33.243 Observer Xsubject Xtim’ 0.053 72.273 48.434 (Thserver Xsubject Xday Xtime 0.038 86.076 29.897 Residual 0.017 5.042 21.836 cause problems in the interpretation of the results of such a study. This study documented the subject and observer variability of V5o, AV50, and VisoV as performed by the method described. From this study, an estimate can be made of the magnitude of changes required to show significant differences in these measurements when following changes in experimental or disease situations. It was shown that the variability during and between days for all three tests was not consistent and that it is not necessary to perform subsequent tests at the same time of day when making progress assessments. However, the poor reproducibility within subjects greatly limits the usefulness of the V5o and VisoV. APPENDIX The statistical model used initially was an analysis of variance using a cross-classified design15 with four factors-subject, day, time, and observer. Subject and observer were random effects, and all tests or readings involved the same ten persons and the same three observers. Day and time were treated as cross-classified fixed effects, since all subjects were tested on a first, second, and third day and one month later as well as in the morning and afternoon. The results are shown in Tables 5 through 7. The F tests for significance were performed using as denominators the mean squares with appropriate expected components. The four-way interaction was tested first and was found to be statistically significant. Next, the three-way interaction was tested and nonsignificant components dropped from the expected mean squares. Three-way interaction effects were pooled ( by adding the sum squares and then dividing by the combined degrees of freedom) when their expected mean squares were identical after dropping off nonsignificant components. These pooled mean squares were used as denominators for the testing of two-way interactions, etc. This pooling had little effect on the F tests. Table 8 shows the modified expected mean squares after removing nonsignificant components. The results of the pooling are shown in Table 9. Since no main effect was shown of day ( ie, practice or learning effect ) , of time ( ic, morning vs afternoon effect ) , or of day-by-time interaction, the model was revised and the analysis redone. The new model then consisted of the hierarchal random effects ( ie, subject, day within subject, and time within day within subjects ) and the random crossclassified effect of the observer differences. This model is described in Table 10. All sum squares, mean squares, and degrees of freedom for the different effects were obtained from the SPSS statistical package. Table 10-Expected Mean Squares-Second Model Source Test* Expected Mean Squares Between subjects Vo, Vo notda+not an +flOaT +flt(lao +nt a120 +flao + a, Between days within sul)jects not an +nocri’ +nt a#{241}o +flaTo + Between times within days within subjects V5o, Vu, VisoV noa+nao+u Between ol)servers within times within days within subjects Between observers Observer X subject Observer xday ()bserver Xtime ObserverXsubject Xtime Observer X SU1)ject X day Observer Xday Xtime Observer Xsubject Xday Xtime VisoV TbO, VisoV . Va V50, VisoV na+nao+nao +no4o + a, ntdso5 +nt(hrO +nt aj,o+n o4o + cr, flt(l oo +nt crbo +n afo + a, nt ao +n ao + no4o+ a,’ n4o+ a nt ajo + 0 ajo + a, flao+ a, n ajo + a, Resi(lual a, *Test for vhih till’ source was statistically significant. For ahl)reviations, see Table 4. CHEST, 80: 1, JULY, 1981 MAXIMUM EXPIRATORY FLOW.VOLUME CURVE 29 Downloaded From: http://publications.chestnet.org/ on 05/16/2014

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