Within-subject difference in FRC measured by multiple breath nitrogen washout (FRC_N2) and body plethysmography (FRC_pleth).

<p>The mean within-subject difference FRC_N2—FRC_pleth decreased after the three tissue N₂ excretion equations were applied to washout data from healthy and CF populations.</p

Correcting for tissue nitrogen excretion in multiple breath washout measurements - Fig 6

<p><b>Relationship between the contribution of tissue N₂ to LCI_N2 and length of washout calculated at a) the traditional 2.5% washout cut-off and b) the 5% washout cut-off.</b> The contribution of tissue N₂ to LCI_N2 calculated at the 2.5% cut-off (LCI_uncorr−LCI_Cournand) increased as washout time increased. However, this relationship was no longer observed at the earlier 5% cut-off.</p

Summary of tissue nitrogen correction equations.

<p>Summary of tissue nitrogen correction equations.</p

Relationship between the contribution of tissue N₂ to FRC_N2 and the difference between FRC as measured by MBW_N2 and MBW_SF6.

<p>FRC_N2 became disproportionately greater than FRC_SF6 as the contribution of tissue N₂ estimated by the within-subject difference FRC_N2—FRC_Cournand increased.</p

Estimates of tissue N₂ contribution to MBW outcomes at the 2.5% washout cut-off.

<p>Values are presented as the mean within-subject difference (95% CI) of the uncorrected–corrected MBW_N2 outcome. Outcomes were corrected by applying either the Cournand or Lundin tissue N₂ excretion equations.</p

Characteristics of study participants.

<p>Values are presented as mean (SD) unless otherwise indicated. P value indicates group difference between health and CF.</p

Average slopes of the second half of all uncorrected, Lundin-corrected and Cournand-corrected FRC_N2/breath number curves (depicted graphically in Fig 4) for healthy subjects and those with CF.

<p>Average paired difference (uncorrected-corrected) in absolute and relative (percent of uncorrected slope) terms are shown. Data are expressed as mean 95% confidence interval) unless otherwise stated.</p

Effect of applying Lundin and Cournand correction equations to previously published observational MBW data.

<p>Data are shown as pre-treatment and post-treatment LCI with paired treatment effect. Values are presented as mean (SD) unless otherwise indicated.</p

Within-subject difference between uncorrected LCI_N2 and LCI_N2 corrected for tissue N₂ excretion (LCI_Cournand) at different washout cut-offs.

<p>The difference was progressively smaller when calculated at earlier cut-offs of the washout in both health and CF.</p

Tissue N₂ excretion equations used for correction of MBW_N2 measurements.

<p>The three equations used to estimate the volume of N₂ excreted from the body tissues are plotted over a 7 minute time period. The Cournand 1941 equation was adjusted for a constant excretion rate and plotted for a subject with the average body size of the subjects measured in the Lundin 1953 study. The ATS/ERS equation calculates the volume of tissue N₂ excreted using Cournand’s 1941 equation standardized to a 7 minute washout for all subjects.</p