Estimation of pulmonary blood flow from sinusoidal gas exchange during anaesthesia: A theoretical study

M. J. Turner; D. Weismann; G. G. Járos; A. B. Baker

Estimation of pulmonary blood flow from sinusoidal gas exchange during anaesthesia: A theoretical study

M. J. Turner^*, D. Weismann, G. G. Járos, A. B. Baker

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

Abstract

We simulated the use of simultaneous sinusoidal changes of inspired O₂ and N₂O (Williams et al., J Appl Physiol, 1994; 76: 2130-9) at fractional concentrations up to 0.3 and 0.7, respectively, to estimate FRC and pulmonary blood flow (PBF) during anaesthesia, using O₂ as an insoluble indicator. Hahn's approximate equations, which neglect the effect of pulmonary uptake and excretion on expiratory flow, estimate dead space and alveolar volume (V(A)) with systematic errors less than 10%, but yield systematic errors in PBF which are approximately proportional to F1(N)₂(O) in magnitude. A correction factor (I - P̄)^-1 for Hahn's equations for PBF (where P̄ is the mean partial pressure of the soluble indicator) reduces the dependence of PBF estimates on F1(N)₂(O), and the solution of equations describing the simultaneous mass balance of both indicators yields accurate results for a wide range of mean F1(N)₂(O). However, PBF estimates are sensitive to measurement errors and a third gas must be present to ensure that the indicator gases behave independently.

Original language	English
Pages (from-to)	371-378
Number of pages	8
Journal	British Journal of Anaesthesia
Volume	85
Issue number	3
Publication status	Published - 2000
Externally published	Yes

Keywords

Computers
Lung, blood flow
Lung, dead space
Lung, volume
Measurement techniques, pulmonary arterial

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title = "Estimation of pulmonary blood flow from sinusoidal gas exchange during anaesthesia: A theoretical study",

abstract = "We simulated the use of simultaneous sinusoidal changes of inspired O2 and N2O (Williams et al., J Appl Physiol, 1994; 76: 2130-9) at fractional concentrations up to 0.3 and 0.7, respectively, to estimate FRC and pulmonary blood flow (PBF) during anaesthesia, using O2 as an insoluble indicator. Hahn's approximate equations, which neglect the effect of pulmonary uptake and excretion on expiratory flow, estimate dead space and alveolar volume (V(A)) with systematic errors less than 10%, but yield systematic errors in PBF which are approximately proportional to F1(N)2(O) in magnitude. A correction factor (I - {\=P})-1 for Hahn's equations for PBF (where {\=P} is the mean partial pressure of the soluble indicator) reduces the dependence of PBF estimates on F1(N)2(O), and the solution of equations describing the simultaneous mass balance of both indicators yields accurate results for a wide range of mean F1(N)2(O). However, PBF estimates are sensitive to measurement errors and a third gas must be present to ensure that the indicator gases behave independently.",

keywords = "Computers, Lung, blood flow, Lung, dead space, Lung, volume, Measurement techniques, pulmonary arterial",

author = "Turner, {M. J.} and D. Weismann and J{\'a}ros, {G. G.} and Baker, {A. B.}",

year = "2000",

language = "English",

volume = "85",

pages = "371--378",

journal = "British Journal of Anaesthesia",

issn = "0007-0912",

publisher = "Oxford University Press",

number = "3",

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T1 - Estimation of pulmonary blood flow from sinusoidal gas exchange during anaesthesia

T2 - A theoretical study

AU - Turner, M. J.

AU - Weismann, D.

AU - Járos, G. G.

AU - Baker, A. B.

PY - 2000

Y1 - 2000

N2 - We simulated the use of simultaneous sinusoidal changes of inspired O2 and N2O (Williams et al., J Appl Physiol, 1994; 76: 2130-9) at fractional concentrations up to 0.3 and 0.7, respectively, to estimate FRC and pulmonary blood flow (PBF) during anaesthesia, using O2 as an insoluble indicator. Hahn's approximate equations, which neglect the effect of pulmonary uptake and excretion on expiratory flow, estimate dead space and alveolar volume (V(A)) with systematic errors less than 10%, but yield systematic errors in PBF which are approximately proportional to F1(N)2(O) in magnitude. A correction factor (I - P̄)-1 for Hahn's equations for PBF (where P̄ is the mean partial pressure of the soluble indicator) reduces the dependence of PBF estimates on F1(N)2(O), and the solution of equations describing the simultaneous mass balance of both indicators yields accurate results for a wide range of mean F1(N)2(O). However, PBF estimates are sensitive to measurement errors and a third gas must be present to ensure that the indicator gases behave independently.

AB - We simulated the use of simultaneous sinusoidal changes of inspired O2 and N2O (Williams et al., J Appl Physiol, 1994; 76: 2130-9) at fractional concentrations up to 0.3 and 0.7, respectively, to estimate FRC and pulmonary blood flow (PBF) during anaesthesia, using O2 as an insoluble indicator. Hahn's approximate equations, which neglect the effect of pulmonary uptake and excretion on expiratory flow, estimate dead space and alveolar volume (V(A)) with systematic errors less than 10%, but yield systematic errors in PBF which are approximately proportional to F1(N)2(O) in magnitude. A correction factor (I - P̄)-1 for Hahn's equations for PBF (where P̄ is the mean partial pressure of the soluble indicator) reduces the dependence of PBF estimates on F1(N)2(O), and the solution of equations describing the simultaneous mass balance of both indicators yields accurate results for a wide range of mean F1(N)2(O). However, PBF estimates are sensitive to measurement errors and a third gas must be present to ensure that the indicator gases behave independently.

KW - Computers

KW - Lung, blood flow

KW - Lung, dead space

KW - Lung, volume

KW - Measurement techniques, pulmonary arterial

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JO - British Journal of Anaesthesia

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