Diffusion of Gases Across the Alveolar Membrane

Forster, R. E.

doi:10.1002/cphy.cp030405

Cited by 55 publications

(58 citation statements)

References 107 publications

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“…Nevertheless, there are several uncertainties in this calculation of Vc. There are seven separate equations [15], differing in slope and intercept, for the expression 1/HCO5a?PO 2 + b, all measured in vitro under different experimental conditions, with a being a temperature and pHdependent coefficient linked to the reaction of CO with Hb. b is related to l, the ratio of the permeability of the red blood cell membrane to the interior of the cell, but may also depend on stagnant layers of plasma adjacent to the cell [16].…”

Section: Dmco and Vc From Simultaneous Single Breathmentioning

confidence: 99%

TheT_L,NO/T_L,COratio in pulmonary function test interpretation

Hughes

Lee

2012

Eur Respir J

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The transfer factor of the lung for nitric oxide (TL,NO) is a new test for pulmonary gas exchange. The procedure is similar to the already well-established transfer factor of the lung for carbon monoxide (TL,CO). Physiologically, TL,NO predominantly measures the diffusion pathway from the alveoli to capillary plasma. In the Roughton-Forster equation, TL,NO acts as a surrogate for the membrane diffusing capacity (DM). The red blood cell resistance to carbon monoxide uptake accounts for ,50% of the total resistance from gas to blood, but it is much less for nitric oxide.TL,NO and TL,CO can be measured simultaneously with the single breath technique, and DM and pulmonary capillary blood volume (Vc) can be estimated. TL,NO, unlike TL,CO, is independent of oxygen tension and haematocrit. The TL,NO/TL,CO ratio is weighted towards the DM/Vc ratio and to a; where a is the ratio of physical diffusivities of NO to CO (a51.97). The TL,NO/TL,CO ratio is increased in heavy smokers, with and without computed tomography evidence of emphysema, and reduced in the voluntary restriction of lung expansion; it is expected to be reduced in chronic heart failure. The TL,NO/TL,CO ratio is a new index of gas exchange that may, more than derivations from them of DM and Vc with their in-built assumptions, give additional insights into pulmonary pathology.

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Section: Dmco and Vc From Simultaneous Single Breathmentioning

confidence: 99%

TheT_L,NO/T_L,COratio in pulmonary function test interpretation

Hughes

Lee

2012

Eur Respir J

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“…Following the in vitro work of CARLSEN and COMROE [7], hNO is 4.5 mmHg?min -1 and the FORSTER [5] recommended value for hCO in normoxia is 0.58 mmHg?min -1 , the ratio of these conductances (hNO/hCO) would be 7.7. It can be demonstrated using the ROUGHTON and FORSTER [4] equation for the two gases that the TLNO/TLCO ratio cannot be greater than hNO/hCO, i.e.…”

Section: Tlno/tlco Ratio Is Not the End Of The Roadmentioning

confidence: 98%

“…The answer is well known: we do not know the right values of the carbon monoxide and nitric oxide conductance of haemoglobin (specific conductance (h)), which are necessary to the calculation of Vc and Dm. However, although we thought in 1987 that the conductance for nitric oxide could be taken as infinite [3], we have since changed our minds, as, at that time, we used the recommended carbon monoxide specific conductance of ROUGHTON and FORSTER [4], which was incorrect, as explained later by FORSTER [5]. The work of BORLAND et al [6] added experimental arguments leading us to consider that the conductance of nitric oxide has a finite value.…”

Section: Tlno/tlco Ratio Is Not the End Of The Roadmentioning

confidence: 99%

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T_LNO/T_LCOratio is not the end of the road

Martinot

Guénard

2014

Eur Respir J

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“…They have used the 1957 value for y CO ; Forster states that his 1957 value is incorrect and that the 1987 value should be used instead. 6 Magini et al have assumed that DL NO ¼ Dm NO i.e. that y NO is infinity, a view originally asserted by the Bordeaux group.…”

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confidence: 99%

Confusion in reporting pulmonary diffusing capacity for nitric oxide and the alveolar-capillary membrane conductance for nitric oxide

Zavorsky

Borland

2014

Eur J Prev Cardiolog

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We read with interest the paper by Magini and colleagues on the measurement of pulmonary diffusing capacity for nitric oxide in patients with heart failure (ejection fraction<40%).1 In their study they report pulmonary diffusing capacity and the individual components of pulmonary diffusing capacity in 50 patients with heart failure (65 years of age), and 50 control subjects (61 years of age). We feel that there are two problems with this paper that warrant discussion. First, the mean values for pulmonary diffusing capacity for nitric oxide (DL NO ) for the healthy subjects are too low, and second, both their alveolar-membrane conductances (Dm NO and Dm CO ) and pulmonary capillary blood volume (Vc) calculations, and hence conclusions, are incorrect.First, the values for DL NO for the healthy volunteers appear too low. If we assume that the women's and men's mean height in the healthy volunteers was 163 and 173 cm, respectively, then the mean DLNO values should be 96-113 and 140-154 ml/min/mm Hg, for women and men, respectively.2,3 The combined average for DL NO should be then 118-133 ml/min/mm Hg. The author's mean values of 89 ml/min/mm Hg for the healthy volunteers are 25-33% lower than predicted. However, their values for pulmonary diffusing capacity for carbon monoxide (DL CO ) were correct and the healthy volunteers was close to 100% of that predicted.2,3 Thus, if the mean DL NO in the control group is under-predicted by at least 25%, then the DL NO values in the heart failure patients could be under predicted by !25% too. Since DL NO and DL CO are measured simultaneously, and DL CO values were appropriate (close to 100% of those predicted), there must be some mathematical error in the calculation of DL NO and/or their breath-hold time was too short. The breath-hold time should be 5-10 s, 4 and it seems that their breath-hold time varied between 2-4 s.Second, in the discussion they state ''Vcap was unchanged, and the DL NO /DL CO ratio was 4.1 in healthy subjects and 4.4 in heart failure patients.'' Hughes and Van der Lee 5 have elegantly illustrated how DL NO /DL CO is a proxy for Dm/Vc so the only way for the patients in this study to have an unchanged Vc and a raised DL NO /DL CO is for them to have a higher Dm than the normal controls! Clearly Magini et al.'s calculations of Vc (and Dm) are wrong. They have used the 1957 value for y CO ; Forster states that his 1957 value is incorrect and that the 1987 value should be used instead.6 Magini et al. have assumed that DL NO ¼ Dm NO i.e. that y NO is infinity, a view originally asserted by the Bordeaux group.7 Nitric oxide transfer is now known to increase with hemolysis in vitro 8 and with addition of a cell-free blood substitute in vitro and in vivo 9 indicating that y NO is finite and that DL NO < Dm NO . We and the Bordeaux group 10 recommend using the values for y NO and y CO derived from rate constants measured using the Continuous Flow Rapid Reaction apparatus at the University of Pennsylvania. 11 We have recalculated Magini et al.'s data using these ...

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Diffusion of Gases Across the Alveolar Membrane

Cited by 55 publications

References 107 publications

TheT_L,NO/T_L,COratio in pulmonary function test interpretation

TheT_L,NO/T_L,COratio in pulmonary function test interpretation

T_LNO/T_LCOratio is not the end of the road

Confusion in reporting pulmonary diffusing capacity for nitric oxide and the alveolar-capillary membrane conductance for nitric oxide

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Diffusion of Gases Across the Alveolar Membrane

Cited by 55 publications

References 107 publications

TheTL,NO/TL,COratio in pulmonary function test interpretation

TheTL,NO/TL,COratio in pulmonary function test interpretation

TLNO/TLCOratio is not the end of the road

Confusion in reporting pulmonary diffusing capacity for nitric oxide and the alveolar-capillary membrane conductance for nitric oxide

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Product

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TheT_L,NO/T_L,COratio in pulmonary function test interpretation

TheT_L,NO/T_L,COratio in pulmonary function test interpretation

T_LNO/T_LCOratio is not the end of the road