No red cell resistance to NO? I think not!

Zavorsky, Gerald S.

doi:10.1152/japplphysiol.00240.2010

Cited by 16 publications

(16 citation statements)

References 26 publications

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“…This is similar to that initially reported by Carlsen and Comroe in 1958 (8). However, it has been estimated that DL NO would not need to be adjusted unless the hemoglobin concentration is Ͻ8 g/dl (50). This is apparent in the data reported by Borland et al (6) and in keeping with previous observation that changes in hemoglobin concentrations like measured in the present study would not be expected to affect DL NO (42).…”

Section: Discussionsupporting

confidence: 88%

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Bisschop

Martinot

Leurquin‐Sterk³

et al. 2012

Journal of Applied Physiology

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de Bisschop C, Martinot J, Leurquin-Sterk G, Faoro V, Guénard H, Naeije R. Improvement in lung diffusion by endothelin A receptor blockade at high altitude. J Appl Physiol 112: 20 -25, 2012. First published October 6, 2011 doi:10.1152/japplphysiol.00670.2011.-Lung diffusing capacity has been reported variably in high-altitude newcomers and may be in relation to different pulmonary vascular resistance (PVR). Twenty-two healthy volunteers were investigated at sea level and at 5,050 m before and after random double-blind intake of the endothelin A receptor blocker sitaxsentan (100 mg/day) vs. a placebo during 1 wk. PVR was estimated by Doppler echocardiography, and exercise capacity by maximal oxygen uptake (V O2 max). The diffusing capacities for nitric oxide (DLNO) and carbon monoxide (DLCO) were measured using a single-breath method before and 30 min after maximal exercise. The membrane component of DLCO (Dm) and capillary volume (Vc) was calculated with corrections for hemoglobin, alveolar volume, and barometric pressure. Altitude exposure was associated with unchanged DLCO, DLNO, and Dm but a slight decrease in Vc. Exercise at altitude decreased DLNO and Dm. Sitaxsentan intake improved V O2 max together with an increase in resting and postexercise DLNO and Dm. Sitaxsentan-induced decrease in PVR was inversely correlated to DLNO. Both DLCO and DLNO were correlated to V O2 max at sea level (r ϭ 0.41-0.42, P Ͻ 0.1) and more so at altitude (r ϭ 0.56 -0.59, P Ͻ 0.05). Pharmacological pulmonary vasodilation improves the membrane component of lung diffusion in high-altitude newcomers, which may contribute to exercise capacity. altitude; hypoxia; lung diffusion; gas exchange; exercise capacity; pulmonary vascular resistance; pulmonary capillary pressure; pulmonary hypertension BOTH THE MEMBRANE AND THE capillary components of lung diffusing capacity have been shown to be increased in highaltitude residents (10,13,15,25). Increased lung diffusing capacity at high altitude allows for the preservation of gas exchange in the presence of a decreased ventilatory response at exercise (15). High-altitude newcomers do not benefit from this adaptation (10,15,25) and, accordingly, depend on increased ventilation to maintain pulmonary gas exchange (15,45).Previous studies on lung diffusing capacity at high altitudes calculated the membrane and capillary components of alveolocapillary transfer of carbon monoxide (CO) using measurements at ambient air and increased inspired PO 2 (10,13,15,25). This approach rests on the PO 2 dependence of , the blood's specific transfer conductance of CO, in the Roughton and Forster equation, which states that 1/DL CO ϭ 1/Dm ϩ 1/ Vc where DL CO is the diffusing capacity of the lung for CO, Dm its membrane component, and Vc the capillary blood volume (37). Thus changing as by increasing or decreasing inspired PO 2 allows for the calculation of Dm and Vc from a simple system of two equations with two unknowns. However, changing inspired PO 2 might also change pulmonary vascular tone, cardiac output, ...

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Section: Discussionsupporting

confidence: 88%

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Bisschop

Martinot

Leurquin‐Sterk³

et al. 2012

Journal of Applied Physiology

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“…Because this rate is significantly faster than θ CO , θ NO has been considered infinite, such that the lung diffusing capacity for NO (DL NO ) is equal to D M,NO . Recently, however, the assumption that θ NO is effectively infinite compared to θ CO has been debated (Borland et al, 2014; Borland et al, 2010; Zavorsky, 2010), with some groups using an experimentally-derived, finite value of 4.5 (min*mmHg) −1 for θ NO (Borland et al, 2010; Carlsen and Comroe, 1958). However, the use of a finite θ NO remains somewhat controversial and for several reasons discussed in detail later in this manuscript ( see 4.7 Discussion , “ Assumption that θ NO is infinite ”) we have chosen to maintain the assumption that θ NO is infinite, as shown in the equations below:

\frac{1}{{italicDL}_{italicNO}} = \frac{1}{D_{M, NO}} + \frac{1}{θ_{NO} * V_{C}}

θ_{NO} \approx \infty

\frac{1}{{italicDL}_{italicNO}} = \frac{1}{D_{M, NO}} + \frac{1}{\infty}

\frac{1}{{italicDL}_{italicNO}} = \frac{1}{D_{M, NO}}

{DL}_{NO} = D_{M, italicNO}

…”

Section: Introductionmentioning

confidence: 99%

Optimizing the calculation of D M,CO and V C via the single breath single oxygen tension DL CO/NO method

Coffman

Taylor

Carlson

et al. 2016

Respiratory Physiology & Neurobiology

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Alveolar-capillary membrane conductance (DM,CO) and pulmonary-capillary blood volume (VC) are calculated via lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θCO) and the DM,NO/DM,CO ratio (α-ratio), are controversial. This study systematically determined optimal θCO and α-ratio values to be used in the single-FiO2 method that yielded the most similar DM,CO and VC values compared to the ‘gold-standard’ multiple-FiO2 method. Eleven healthy subjects performed single breath DLCO/DLNO maneuvers at rest and during exercise. DM,CO and VC were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θCO equations and a range of previously reported α-ratios. The RP θCO equation (Reeves and Park, Respiration physiology 88:1–21, 1992.) and an α-ratio of 4.0–4.4 yielded DM,CO and VC values that were most similar between methods. The RP θCO equation and an experimental α-ratio should be used in future studies.

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“…This is correct in the strictest sense: theoretically and in clinical practice lung nitric oxide transfer does not vary with the haematocrits routinely encountered [3,4]. However, if seriously low haemoglobin concentrations (,8 g?dL -1 ) are generated in the laboratory this can be shown to reduce the blood nitric oxide conductance [5].…”

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confidence: 88%

TheT_LNO/T_LCOratio in pulmonary function test interpretation

Borland

2013

Eur Respir J

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] provide an excellent review of transfer factor of the lung for nitric oxide (TLNO)/transfer factor of the lung for carbon monoxide (TLCO) and highlight this ratio as a new lung function test in its own right. Perhaps we ''TLNO enthusiasts'' have overplayed TLNO as a route to DM (membrane diffusing capacity) and to Vc (lung capillary volume) over the past three decades rather than thinking of it as a part of this ratio. HUGHES and VAN DER LEE [1] have rightly argued that TLNO/TLCO reflects DM/Vc and a, the ratio of nitric oxide/carbon monoxide diffusivity.

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No red cell resistance to NO? I think not!

Cited by 16 publications

References 26 publications

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Optimizing the calculation of D M,CO and V C via the single breath single oxygen tension DL CO/NO method

TheT_LNO/T_LCOratio in pulmonary function test interpretation

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No red cell resistance to NO? I think not!

Cited by 16 publications

References 26 publications

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

Optimizing the calculation of D M,CO and V C via the single breath single oxygen tension DL CO/NO method

TheTLNO/TLCOratio in pulmonary function test interpretation

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TheT_LNO/T_LCOratio in pulmonary function test interpretation