TLNO/TLCOratio is not the end of the road

Martinot, Jean-Benoît; Guénard, H.

doi:10.1183/09031936.00012314

Cited by 6 publications

(3 citation statements)

References 10 publications

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“…However, caution should be exercised when looking at the ratio alone, since an apparently normal value could result from both DLNO and DLCO being low, and in addition a low ratio could of course either result from a low value of DLNO or a high value of DLCO, while the opposite could apply to a high ratio. Furthermore, the scatter of the normal values for the ratio is rather large (mean±SD 4.4±0.24), and for patients the scatter of values is also found to be large [39,40]. Obviously, this might result in difficulties differentiating between normal and pathological values.…”

Section: Dlno/dlcomentioning

confidence: 93%

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Reference equations for pulmonary diffusing capacity of carbon monoxide and nitric oxide in adult Caucasians

et al. 2018

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The aim of this study was to determine reference equations for the combined measurement of diffusing capacity of the lung for carbon monoxide (CO) and nitric oxide (NO) (). In addition, we wanted to appeal for consensus regarding methodology of the measurement including calculation of diffusing capacity of the alveolo-capillary membrane () and pulmonary capillary volume (). was measured in 282 healthy individuals aged 18-97 years using the single-breath technique and a breath-hold time of 5 s (true apnoea period). The following values were used: 1) specific conductance of nitric oxide (θ)=4.5 mL·mL·min·mmHg; 2) ratio of diffusing capacity of the membrane for NO and CO (/)=1.97; and 3) 1/red cell CO conductance (1/θ)=(1.30+0.0041·mean capillary oxygen pressure)·(14.6/Hb concentration in g·dL).Reference equations were established for the outcomes of , including and and the calculated values and Independent variables were age, sex, height and age squared.By providing new reference equations and by appealing for consensus regarding the methodology, we hope to provide a basis for future studies and clinical use of this novel and interesting method.

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Section: Dlno/dlcomentioning

confidence: 93%

“…This has led researchers who previously regarded θNO to be infinite to consider it finite with a value of 4. [4,6,39].…”

Section: θCo θNo and αmentioning

confidence: 99%

Reference equations for pulmonary diffusing capacity of carbon monoxide and nitric oxide in adult Caucasians

et al. 2018

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“…On theoretical basis, θ NO /θ CO ratio ( k ) cannot be lower than the DL NO /DL CO ratio which maximal published value in healthy human is 6·5 (Martinot and Guénard, ). θ CO recommended value in normoxia is about 0·58 (Forster, ) as the recent consensus on θ NO led to a value of 4·5 (both values in ml gas × min −1 × mmHg −1 ml −1 blood).…”

Section: Reconsidering the ‘Classic’ Roughton–forster (Rf) Equationmentioning

confidence: 99%

Nitrogen monoxide and carbon monoxide transfer interpretation: state of the art

Martinot

Guénard

Dinh-Xuan

et al. 2015

Clin Physio Funct Imaging

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Just a few clinicians routinely measure the subcomponents of the lung diffusing capacity for Carbone monoxide (DL ). This is because the measurement of membrane and blood conductances for CO (Dm and Db = θ × V , respectively) by the classic Roughton and Forster method is complicated and time consuming. In addition, it mistakenly assumes a close relationship between alveolar oxygen partial pressure (PAO ) and mean intracapillary oxygen partial pressure (PcapO ) which is the true determinant of specific conductance of haemoglobin for CO (θ ). Besides that, the critical multistep oxygenation method along with different linear equations relating 1/θ to PcapO gave highly scattered Dm and V values. The Dm and V can also be derived from a simultaneous measurement of DL and DL with the blood resistance for NO assumed to be negligible. However, recent in vitro and in vivo experiments point towards a finite value of θ (about 4·5 ml × ml × min × mmHg ). Putting together the arguments and our clinical data allows us to report here the state of the art in partitioning the CO diffusing capacity into its constitutive components, with the goal to encourage further studies examining the sensitivity of Dm and V to alterations observed in parenchymal diseases.

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Modeling of Gas Exchange in the Lungs

Sapoval¹,

Kang²,

Dinh-Xuan³

2020

Comprehensive Physiology

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This overview presents the recent progress in our understanding of gas transfer by the lungs during the respiratory cycle and during breath holding. Different phenomena intervene in gas transfer, convection and diffusion in the gas, dissolution, diffusion across the alveolar-capillary membrane, diffusion across blood plasma, and finally diffusion and reaction with hemoglobin inside blood cells. The different gases, O 2 , CO, and NO, have very different reaction times with hemoglobin ranging from a few microseconds to tens of milliseconds. This is leading to different outcomes.For O 2 , the solutions to the coupled nonlinear gas and blood equations are obtained at the acinus level. They include the fact that the acinar internal ventilation is strongly heterogeneous due to the arborescent structure. Also, in the dynamic calculation, one takes care of the delay between the start of inhalation and arrival of fresh air in the acinus. This "dead" time is the dynamic equivalent of the dead space ventilation.The question of the dependence of Vo 2 on ventilation and perfusion takes a different form. The results show that Vo 2 is not only a function of the ventilation/perfusion ratio but also depends on the variables: acinar ventilation VE ac and perfusion Q ac . The ratio VE ac /Q ac roughly determines arterial O 2 saturation and arterial and alveolar O 2 partial pressure.The classic Roughton-Forster interpretation of DLCO (separation between independent membrane and blood resistance) was a mathematical conjecture. It was shown recently that this conjecture was violated. This article presents an alternative interpretation that uses time concepts instead of resistance.

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T_LNO/T_LCOratio is not the end of the road

Cited by 6 publications

References 10 publications

Reference equations for pulmonary diffusing capacity of carbon monoxide and nitric oxide in adult Caucasians

Reference equations for pulmonary diffusing capacity of carbon monoxide and nitric oxide in adult Caucasians

Nitrogen monoxide and carbon monoxide transfer interpretation: state of the art

Modeling of Gas Exchange in the Lungs

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