Regional pulmonary perfusion and V/Q in awake and anesthetized-paralyzed man

Landmark, Sandra J.; Knopp, T. J.; Rehder, Kai; Sessler, Alan D.

doi:10.1152/jappl.1977.43.6.993

Cited by 55 publications

(27 citation statements)

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“…O 2,A , determined for a given breath, was about 13%, independent of the selection of t 1 . This suggests that the existence of different F A O 2 values in different alveolar districts (West 1962;Landmark et al 1977), as well as their possible sequential emptying (Meyer et al 1983), do not seem to have any systematic effects on the alveolar gas transfer as determined by algorithm G, at least under the present experimental conditions.…”

Section: Discussionmentioning

confidence: 52%

“…This may not be true. Indeed, the ventilation/perfusion ratio varies over the lung (West 1962;Landmark et al 1977), implying the existence of different F A O 2 values in different alveolar districts and the gas fractions assessed at the mouth depend critically on the breathing pattern, namely on the ventilation and on the expired volume (Meyer et al 1983). These findings imply that the gas fractions assessed at the mouth during expiration would be truly representative of alveolar gas fractions if, and only if, the regional outflows from any given region of the lung are proportional to its volume, which is not necessarily so (Cortese et al 1976).…”

Section: Discussionmentioning

confidence: 99%

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New perspectives in breath-by-breath determination of alveolar gas exchange in humans

Capelli

Cautero

Prampero

2001

Pfl�gers Archiv European Journal of Physiology

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Alveolar gas transfer over a given breath (i) was determined in ten subjects at rest and during steady-state cycling at 60, 90 or 120 W as the sum of volume of gas transferred at the mouth plus the changes of the alveolar gas stores. This is given by the gas fraction (FA) change at constant volume plus the volume change (deltaVAi) at constant fraction i.e. VAi-1(FAi-FAi-1)+FAi x deltaVAi, where VAi-1 is the end-expiratory volume at the beginning of the breath. These quantities, except for VAi-1, can be measured on a single-breath (breath-by-breath) basis and VAi-1 set equal to the subject's functional residual capacity (FRC, Auchincloss model). Alternatively, the respiratory cycle can be defined as the interval elapsing between two equal expiratory gas fractions in two successive breaths (Grønlund model G). In this case, Ft1 = Ft2 and thus the term VAi-1 (FAi-FAi-1) vanishes. In the present study, average alveolar O2 uptake (VO2,A) and CO2 output (VCO2,A) were equal in both approaches whereby the mean signal-to-noise ratio (S/N) was 40% larger in G. Other approaches yield steady state S/N values equal to that obtained in G, although they are based on the questionable assumption that the inter-breath variability of alveolar gas transfer is minimal. It is concluded that the only promising approach for assessing "true" single-breath alveolar gas transfer is that originally proposed by Grønlund.

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Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

New perspectives in breath-by-breath determination of alveolar gas exchange in humans

Capelli

Cautero

Prampero

2001

Pfl�gers Archiv European Journal of Physiology

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“…This is associated with increased ventilation of superior regions with persistence of the normal vertical gradient of blood flow (Landmark, Knopp, Rehder & Sessler, 1977;Chevrolet, Martin, Flood, Martin & Engel, 1978). These results support the findings reported here in spontaneously breathing patients with bilateral diaphragm paralysis.…”

Section: Discussionmentioning

confidence: 99%

Regional Lung Function in Bilateral Diaphragmatic Paralysis

et al. 1980

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1. The distribution of regional function in the lungs of six patient with bilateral diaphragmatic paralysis was investigated by continuous inhalation and infusion of the radioactive gases 81mKr and 85mKr during tidal breathing. 2. In the supine and right lateral decubitus postures the vertical distribution of ventilation per unit alveolar volume was less in the dependent zones, the reverse of that found in normal subjects. In the upright posture ventilation was slightly decreased at the lung base. Perfusion per unit alveolar volume was more uniformly distributed than normally in the upright posture, and decreased from superior to inferior in the supine posture. In the lateral decubitus posture, perfusion of the lower lung was greater than that of the upper. Ventilation/perfusion ratios were more uniformly distributed in the patients than in normal subjects, except in the right lateral decubitus posture. 3. Alterations in the distribution of ventilation may be explained in terms of the altered mechanical interaction of chest wall, mediastinal and abdominal contents, with selective use of intercostal and accessory muscles. The effects on the distribution of blood flow are probably related to the low end-expiratory lung volume.

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“…This may not hold true. Indeed: (1) the ventilation-perfusion ratio varies over the lung (West 1962;Landmark et al 1977), implying the existence of different F A O 2 values in different alveolar districts; and (2) the gas fractions assessed at the mouth depend critically on the breathing pattern, namely on the ventilation and on the expired volume (Meyer et al 1983). These findings imply that the gas fractions assessed at the mouth during expirations would be truly representative of alveolar gas fractions if, and only if, the regional outflows from any given region of the lung were proportional to its volume, a fact which is not necessarily true (Cortese et al 1976).…”

Section: Alveolar Gas Transfer At Steady-state: Gr Versus Aumentioning

confidence: 99%

New acquisitions in the assessment of breath-by-breath alveolar gas transfer in humans

2003

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We summarise recent results obtained in testing some of the algorithms utilised for estimating breath-by-breath (BB) alveolar O2 transfer (VO2A) in humans. VO2A is the difference of the O2 volume transferred at the mouth minus the alveolar O2 stores changes. These are given by the alveolar volume change at constant O2 fraction (FAiO2 DeltaVAi) plus the O2 alveolar fraction change at constant volume [V(Ai-1)(FAi-F(Ai-1))O2], where V(Ai-1) is the alveolar volume at the beginning of the breath i. All these quantities can be measured BB, with the exception of V(Ai-1), which is usually set equal to the subject's functional residual capacity (FRC) (Auchincloss algorithm, AU). Alternatively, the respiratory cycle can be defined as the time elapsing between two equal O2 fractions in two subsequent breaths (Grønlund algorithm, GR). In this case, FAiO2= F(Ai-1)O2 and the term V(Ai-1)(FAi-F(Ai-1))O2 disappears. BB alveolar gas transfer was first determined at rest and during exercise at steady-state. AU and GR showed the same accuracy in estimating alveolar gas transfer; however GR turned out to be significantly more precise than AU. Secondly, the effects of using different V(Ai-1) values in estimating the time constant of alveolar O2 uptake (VO2A) kinetics at the onset of 120 W step exercise were evaluated. VO2A was calculated by using GR and by using (in AU) V(Ai-1) values ranging from 0 to FRC +0.5 l. The time constant of the phase II kinetics (tau2) of VO2A increased linearly, with V(Ai-1) ranging from 36.6 s for V(Ai-1)=0 to 46.8 s for V(Ai-1)=FRC+0.5 l, whereas tau2 amounted to 34.3 s with GR. We concluded that, when using AU in estimating VO2A during step exercise transitions, the tau2 value obtained depends on the assumed value of V(Ai-1).

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Regional pulmonary perfusion and V/Q in awake and anesthetized-paralyzed man

Cited by 55 publications

References 0 publications

New perspectives in breath-by-breath determination of alveolar gas exchange in humans

New perspectives in breath-by-breath determination of alveolar gas exchange in humans

Regional Lung Function in Bilateral Diaphragmatic Paralysis

New acquisitions in the assessment of breath-by-breath alveolar gas transfer in humans

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