These data tend to support in concept the report by Reinert and Trendelenburg in 1971. They examined two patients, one normal and the other with COPD. Using an integrated pneumotachograph linked to the exhalation port of the body plethysmograph, they found that FRC shifted by 300 and 500 ml in these two subjects, respectively. They […]

Differences in effort could affect the determination of RV and TLC. Along this line, the mean difference was reduced when the unlinked TLC was compared with the maximal, rather than mean, linked TLC. This likely reflects the use of the (maximal) vital capacity on the separate spirometer for calculation of the unlinked TLC. The maximal […]

In support of the unlinked approach, the variability of FRC was less than that of RV and TLC, which demonstrated 95 percent confidence interv als of ± 629 and 517 ml, respectively. The coefficients of variation for RV and TLC were 11.0 percent and 4.0 percent, respectively, which might argue that TLC was most reproducible. […]

The relationship between differences in TLC and ERV (unlinked-linked) is shown in Figure 3. Differences in mean ERV correlated negatively with the differences between mean linked TLC and unlinked TLC (r= -0.518, p<0.001) as well as the maximal linked TLC and unlinked TLC (r = – 0.550, p<0.001). These differences may be separated into four […]

Differences between linked and unlinked values exceeded the 95 percent interval (629 ml) in only 7.3 percent of RV determinations (Table 2). However, differences exceeded the respective 95 percent confidence interval in 20.0 percent of mean TLC determinations and 11.8 percent of maximal TLC determinations by the linked method (Table 2). There was a tendency […]

The 95 percent confidence interval for FRC determinations was 402 ml, with a coefficient of variation (CV) of 4.5 percent. Similar analysis of linked determinations of RV and TLC revealed the 95 percent confidence intervals to be 629 ml and 517 ml, corresponding to CVs of 11.0 percent and 4.0 percent, respectively When we examined […]

As an indication that the FRC represented during unlinked spirometry was not reliably the same as that measured in the box, we examined the relationship between differences (unlinked-linked) in ERV and TLC. We reasoned that the pattern of the relationship would suggest whether differences reflected an altered effort or a shift in FRC. This may […]