A simple method for correcting single breath total lung capacity for underestimation.

Loiseau, Alain; Loiseau, Patrick; Saumon, Georges

doi:10.1136/thx.45.11.873

Cited by 6 publications

(6 citation statements)

References 18 publications

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“…On that account in apparently normal subjects this method underestimates the true volumes to a slight degree; in healthy subjects the intraindividual coefficient of variation is about 8% [71]. In subjects with airflow limitation, the underestimation of the true lung volume may become very large due to uneven distribution of inhaled gas; however, a partial correction for this can be made when the slope of the alveolar plateau (phase Ill) is recorded simultaneously [71,84].…”

Section: Single Breath Nitrogen Methodsmentioning

confidence: 99%

“…Useful information can also be derived from assessing 1LC by different methods in the same patient In healthy subjects TLC assessed by the single breath helium dilution method (see § 3.7.2) is somewhat smaller (down to 83%) than when assessed with the multi-breath technique [71,84,85]. The difference can be accentuated in patients with asthma even during a period when no airflow limitation is detected, indicating abnormal unevenness of ventilation distribution.…”

mentioning

confidence: 99%

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Lung volumes and forced ventilatory flows

Quanjer¹,

Tammeling²,

Cotes³

et al. 1993

European Respiratory Journal

4,584

982

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Section: Single Breath Nitrogen Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Lung volumes and forced ventilatory flows

Quanjer¹,

Tammeling²,

Cotes³

et al. 1993

European Respiratory Journal

4,584

982

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“…We used 85% as the lower limit of normal of VA/TLC . A low VA/TLC reflects VH, as supported by data showing that a low VA/TLC correlates with an increased inert gas phase III slope, and VA as an estimate of TLC can be corrected for the degree of VH or airflow limitation . As expected, in emphysema where there is a high degree of heterogeneous ventilation, VA/TLC underestimates total lung volume and, conversely, is a good reflection of the amount of non‐emphysematous lung on CT .…”

Section: Discussionmentioning

confidence: 62%

“…18 In health, complete distribution of the inert gas during the brief 10-s breath-hold of the DLCO test provides VA and TLC values that are essentially equal (VA/ TLC ≥ 85%); 19 however, as VH increases, gas distribution during the measurement is reduced so that VA underestimates TLC (VA/TLC < 85%). Heterogeneous ventilation, as measured by reduced VA/TLC, is typically seen in patients with airways disease such as asthma and COPD, [18][19][20][21][22][23][24][25][26][27][28] although the association of VA/TLC to AHR is unknown.…”

Section: Introductionmentioning

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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“…T CO is the product of lung volume and the Krogh factor (K CO ), which is the uptake of CO per unit of time, per unit of pressure difference and per unit of lung volume. This means that the difference between the RB and the SB estimates of volume, which is caused by unequal ventilation [6, 7, 8], influences the relation between the RB and SB T CO in a direct way, irrespective of the distribution of diffusion in the lung. To eliminate this effect of unequal ventilation we compared K CO measured with the RB method and with the SB method instead of comparing the RB and SB T CO .…”

Section: Introductionmentioning

confidence: 99%

Rebreathing K<sub>CO</sub> and Single Breath K<sub>CO</sub> Measured at the Same Mean Alveolar Volume Reveal a Physiological Relationship between Unequal Diffusion and Unequal Ventilation in Normal Subjects

Jansons

Fokkens²,

Tweel³

et al. 2000

Respiration

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Background: The single breath (SB) method for determining the transfer factor for carbon monoxide is influenced by an unequal distribution of diffusion and ventilation. The rebreathing (RB) method is thought not to be influenced by these inequalities. Therefore, a comparison of the results of the two methods enables us to investigate unequal ventilation and diffusion. We have previously shown that even in normal subjects unequal ventilation influences the relation between the transfer factor as measured by the RB method and by the SB method. Objectives: To investigate to what extent unequal diffusion influences the relation between the RB and SB transfer factor in normal subjects. Methods: Measurements were performed in 8 normal subjects. Differences in alveolar volume as measured by the RB and SB method were prevented from influencing the results by comparing the RB and SB transfer factor per liter of alveolar volume, i.e. the RB and SB Krogh factor, instead of the RB and SB transfer factor. The effect of the known dependence of the Krogh factor on inspired volume was prevented by measuring the SB Krogh factor at an inspired volume equal to the mean inspired volume of the RB measurement. This SB Krogh factor was compared with the RB Krogh factor calculated as the quotient of the RB transfer factor and the mean alveolar volume during the RB measurement. Results: This RB Krogh factor was always larger than the corresponding SB Krogh factor. The difference was significant (p = 0.006). A high percentage (80%) of the variance in the quotient of the two Krogh factors, which can be considered as a parameter for unequal diffusion, was explained by the variance in the quotient of the mean RB volume and the corresponding SB volume. The latter quotient is a measure of unequal ventilation. Conclusions: The finding suggests a physiological relation between unequal diffusion and unequal ventilation. A plausible explanation was found in the decrease of the Krogh factor with an increasing ratio of inspired volume to residual volume for each part of the lung separately. The consequence is that in the absence of unequal ventilation the RB transfer factor is equal to the SB transfer factor measured at an inspired volume equal to the mean RB inspired volume.

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A simple method for correcting single breath total lung capacity for underestimation.

Cited by 6 publications

References 18 publications

Lung volumes and forced ventilatory flows

Lung volumes and forced ventilatory flows

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

Rebreathing K<sub>CO</sub> and Single Breath K<sub>CO</sub> Measured at the Same Mean Alveolar Volume Reveal a Physiological Relationship between Unequal Diffusion and Unequal Ventilation in Normal Subjects

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