Factors Affecting Regional Distribution of Ventilation and Perfusion in the Lung

Bryan, A. C.; Bentivoglio, Lamberto G.; Beerel, Frederick R.; Macleish, H.; Zidulka, A.; Bates, David V.

doi:10.1097/00132586-196512000-00004

Cited by 34 publications

(42 citation statements)

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“…If the cardiac output of the erect subjects was high because of anxiety during the control measurement, relative apical perfusion would have been elevated (15). During posthypoxia the subjects may have been more relaxed and relative perfusion of the lung bases would then be higher.…”

Section: Resultsmentioning

confidence: 99%

Regional pulmonary blood flow in sitting and supine man during and after acute hypoxia

Dawson¹

1969

J. Clin. Invest.

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A B S T R A C T Regional pulmonary blood flow was measured by external counting of intravenously injected 'Xe during 20 min of breathing 14.2% oxygen and during 20 min of recovery from hypoxia. 16 normal human volunteers were studied, nine sitting and seven supine. During hypoxia there was a slight but significant increase in relative perfusion of the upper portions of the lungs in both the sitting and supine subjects. During recovery from hypoxia, blood flow distribution differed significantly from the control. The erect subjects showed increased relative perfusion of the lung bases and the supine subjects showed increased relative perfusion of the upper zones.Comparison of the distribution of inhaled and intravenously injected isotope showed that in the sitting subjects the altered distribution during hypoxia tended to make alveolar oxygen tension more uniform. In the supine subjects, however, the shift in blood flow increased the perfusion of the regions with the lowest ventilation/ perfusion, tending to accentuate uneven alveolar oxygen tension. Therefore it does not seem that the altered blood flow distribution during hypoxia was due to selective vasoconstriction in the regions of lowest alveolar oxygen tension, but rather that vasoconstriction was greatest in the lower lung zones because the vessels there are more responsive to hypoxia. During mild acute hypoxia, vasoconstrictor tone does not seem to effectively match ventilation and perfusion.The altered distribution of pulmonary blood flow during recovery from hypoxia suggests the occurrence of posthypoxic vasodilation. Failure to consider this possibility may lead to erroneous interpretation of pulmonary hemodynamic measurements made after the inspired oxygen concentration has been changed.

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Section: Resultsmentioning

confidence: 99%

Regional pulmonary blood flow in sitting and supine man during and after acute hypoxia

Dawson¹

1969

J. Clin. Invest.

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“…Regional differences in gas exchange in humans in the upright position are characterized by relatively better ventilation than perfusion (low PCO 2 ) in the top, and relatively better perfusion than ventilation at the bottom (high PCO 2 ) [19]. During a deep breath, inspired air preferentially goes to the expanding lower lung [20][21][22][23]. This means an increased ventilation/perfusion ratio in the basal part of the lung with increased CO 2 dilution.…”

Section: Discussionmentioning

confidence: 99%

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve

Kars¹,

Bogaard²,

Stijnen³

et al. 1997

Eur Respir J

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The slope of phase 3 and three noninvasively determined dead space estimates derived from the expiratory carbon dioxide tension (PCO 2 ) versus volume curve, including the Bohr dead space (VD,Bohr), the Fowler dead space (VD,Fowler) and pre-interface expirate (PIE), were investigated in 28 healthy control subjects, 12 asthma and 29 emphysema patients (20 severely obstructed and nine moderately obstructed) with the aim to establish diagnostic value.Because breath volume and frequency are closely related to CO 2 elimination, the recording procedures included varying breath volumes in all subjects during self-chosen/natural breathing frequency, and fixed frequencies of 10, 15 and 20 breaths·min -1 with varying breath volumes only in the healthy controls.From the relationships of the variables with tidal volume (VT), the values at 1 L were estimated to compare the groups. The slopes of phase 3 and VD,Bohr at 1 L VT showed the most significant difference between controls and patients with asthma or emphysema, compared to the other two dead space estimates, and were related to the degree of airways obstruction. Discrimination between no-emphysema (asthma and controls) and emphysema patients was possible on the basis of a plot of intercept and slope of the relationship between VD,Bohr and VT. A combination of both the slope of phase 3 and VD,Bohr of a breath of 1 L was equally discriminating. The influence of fixed frequencies in the controls did not change the results.The conclusion is that Bohr dead space in relation to tidal volume seems to have diagnostic properties separating patients with asthma from patients with emphysema with the same degree of airways obstruction. Equally discriminating was a combination of both phase 3 and Bohr dead space of a breath of 1 L. The different pathophysiological mechanisms in asthma and emphysema leading to airways obstruction are probably responsible for these results.

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“…These findings are supported by basic pulmonary physiology, which demonstrates that differences in regional ventilation are the result of variation in vertical pleural pressure, and that these differences are influenced by gravity [17][18][19][20][21][22][23] .…”

Section: Discussionmentioning

confidence: 67%

Influência da variação dos decúbitos laterais na deposição pulmonar de aerossol

Alcoforado¹,

Filho²,

Brandão³

et al. 2011

Rev. bras. fisioter.

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Factors Affecting Regional Distribution of Ventilation and Perfusion in the Lung

Cited by 34 publications

References 0 publications

Regional pulmonary blood flow in sitting and supine man during and after acute hypoxia

Regional pulmonary blood flow in sitting and supine man during and after acute hypoxia

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve

Influência da variação dos decúbitos laterais na deposição pulmonar de aerossol

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