Hooray for the V<scp>a</scp>/TLC and D<scp>l</scp><sub>CO</sub>/V<scp>a</scp>

Hansen, James E.

doi:10.1164/ajrccm.187.1.107

Cited by 2 publications

(1 citation statement)

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“…25 As expected, in emphysema where there is a high degree of heterogeneous ventilation, VA/TLC underestimates total lung volume 37 and, conversely, is a good reflection of the amount of nonemphysematous lung on CT. 27 Although studies describing the relationship between VA and TLC go back many years, 23 there has recently been renewed interest in the VA/TLC as a measure of VH. 18,38,39 VH is well described in asthma and plays an important role in abnormal gas exchange. 40 However, it is unclear how VH is linked to AR.…”

Section: Discussionmentioning

confidence: 99%

Relationship between the baseline alveolar volume‐to‐total lung capacity ratio and airway responsiveness

2014

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Background and objective Ventilation heterogeneity (VH) has been linked to airway responsiveness (AR) based on various measures of VH involving inert gas washout, forced oscillation and lung imaging. We explore whether VH at baseline, as measured by the simple ratio of single breath alveolar volume to plethysmographically determined total lung capacity (VA/TLC), would correlate with AR as measured by methacholine challenge testing. Methods We analyzed data from spirometry, lung volumes, diffusing capacity and methacholine challenge to derive the VA/TLC and the dose-response slope of FEV1 (DRS-FEV1) during methacholine challenge from 136 patients. We separated out airway closure vs. narrowing by examining the DRS for FVC (DRS-FVC) and the DRS for FEV1/FVC (DRS-FEV1/FVC), respectively. Similarly, we calculated the DRS for sGaw (DRS-sGaw) as another measure of airway narrowing. We performed statistical analysis using Spearman rank correlation and multifactor linear regression using a backward stepwise modeling procedure. Results We found that the DRS-FEV1 correlated with baseline VA/TLC (rho = −0.26, p < 0.01), and VA/TLC and FEV1 were independently associated with DRS-FEV1 (R2 = 0.14, p = 0.01). In addition, VA/TLC was associated with both airway narrowing and closure in response to methacholine. Conclusions These results confirm that baseline VA/TLC is associated with AR, and reflects both airway closure and airway narrowing following methacholine challenge.

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