Clinical comparison of one in vitro and three in-line blood gas P(O<sub>2</sub>) sensors during cardiopulmonary bypass

Poslad, S J; Pearson, D. T.; Murray, Alan

doi:10.1088/0143-0815/8/3/004

Cited by 4 publications

(1 citation statement)

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“…The major advantage of continuous in-line blood gas measurement is standardization of the blood gas control technique,17 but there is also evidence that in-line techniques are more accurate. [18][19][20] An ideal system will use in-line monitors with electrical outputs to allow automated data collection by computer.…”

Section: Measurement Techniquesmentioning

confidence: 99%

Monitoring oxygenator gas exchange performance

1994

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IntroductionThe oxygenator plays a pivotal role in clinical cardiopulmonary bypass (CPB). Poor control of gas exchange in the oxygenator can lead to significant patient morbidity and may even be lethal. 1 Although CPB has become widespread, characterization of oxygenator gas exchange from data recorded in the clinical environment remains difficult because there is no well accepted technique. In contrast to laboratory assessment, the interdependent quantities which influence gas exchange during CPB are prone to rapid and often unpredictable fluctuation. Figure 1 shows the variability in some of these quantities measured during a complete CPB.This paper reviews assessment of gas exchange in oxygenators during clinical CPB, with discussion of the issues raised and recommendations for future studies.Gas exchange .Respiratory exchange of 02 and C02 involves both diffusion and chemical reactions with blood. The mechanisms of gas transport and gas exchange in the lungs have been extensively reviewed by Roughton.2 Gas transport is governed by the convection-diffusion equation which is based on Fick's Law. This equation takes a flowing element of blood and balances the rate of accumulation of gas in the element against both diffusion into the element and chemical reaction within the element.&dquo;5 The concentration profiles of 02 and C02 within the oxygenator blood compartment can be obtained by solving the convection-diffusion equation and can demonstrate, for example, enhanced gas exchange due to turbulent blood flow.6 Measurement of concentration profiles during CPB is impractical at present, but overall gas exchange can be measured from the difference in gas content between inputs and outputs of either the gas compartment or the blood compartment, taking into account the gas or blood flowrates.The 02 content of blood is the sum of dissolved 02 and chemically bound 02. Dissolved 02 is the product of 02 partial pressure (P02) and 02 solubility. The solubility of 02 in blood varies with temperature: at 37°C it is 0.023 ml/dl/kPa whereas at 28°C it is 0.026 ml/dl/kPa. The solubility at a particular temperature can be estimated using an empirical formula.7 Chemically bound 02 is the product of the percentage saturation of haemoglobin (S02), the haemoglobin concentration [Hb] and the quantity of 02 that binds with a specified amount of haemoglobin. The volume of 02 (ml) which will bind with 1 g of Hb is sometimes called the Huffner factor. A theoretical value of 1.39 ml/g can be obtained, but a lower value is at NANYANG TECH UNIV LIBRARY on June 22, 2015 prf.sagepub.com Downloaded from 164 Figure 1 Variability of conditions during clinical cardiopulmonary bypass. All quantities recorded simultaneously during evaluation of a Cobe CML2 oxygenator.37 found experimentally and 1.34 ml/g is commonly used. Both P02 and S02 are related by the oxyhaemoglobin dissociation curve (OHDC). It is possible to calculate values of S02 from the measurements of P02,7 but this approach is vulnerable to errors unless S02 exceeds 90%,s.9 so it...

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Section: Measurement Techniquesmentioning

confidence: 99%

Monitoring oxygenator gas exchange performance

1994

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A clinical evaluation of the Bentley 10B and Bentley 10Plus bubble oxygenators

et al. 1988

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During clinical hypothermic cardiopulmonary bypass (CPB) in 20 adult patients, the ability of the perfusionist, using an alphastat acid-base blood gas management technique, to control blood gas values has been evaluated in the Bentley 10B and Bentley 10Plus bubble oxygenators. Superior flexibility in control of the blood gas values to within a defined target range (PaO2 20 ± 3.3 kPa, PaCO2 5.3 ± 0.6 kPa) with significantly improved control of PaO2 was demonstrated in the Bentley 10Plus when compared with the Bentley 1 0B. The percentage of values when both PaCO2 and PaO2 were within the target range was higher in the Bentley 10Plus (14%) than in the Bentley 10B (11 %). The incorporation of an Integral gas proportioning valve in the Bentley 10Plus oxygenator offers a degree of independence of control of PaO 2 and PaCO2 which is unique in a bubble oxygenator. When the two oxygenator groups were compared, the rise in plasma haemoglobin was significantly less (p<0.005) in the Bentley 10Plus but no significant differences could be demonstrated between the two groups with respect to alteration in other formed blood elements (platelets or white blood cells) or in gaseous microemboli production.

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