Impaired membrane lung CO<sub>2</sub> elimination: is it dead space, V/Q ratio or acidosis?

Bachmann, K; Berger, David

doi:10.1177/0267659120947379

Cited by 3 publications

(4 citation statements)

References 7 publications

(9 reference statements)

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“…V̇ co 2 is highly dependent on the V̇/Q̇̇ ratio and is thus dependent not only on blood flow but also on ventilation ( 19 ). This interferes with the precision of blood flow calculations, as the constructed mass balance equation is only applicable if the inflow and outflow gas content of both the ECMO and the lung are equal.…”

Section: Methodsmentioning

confidence: 99%

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Berger

Zwicker

Nettelbeck

et al. 2023

American Journal of Physiology-Lung Cellular and Molecular Phys

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Assessment of native cardiac output during extracorporeal circulation is challenging. We assessed a modified Fick principle under conditions such as deadspace and shunt in 13 anesthetized swine undergoing centrally canulated veno-arterial extracorporeal membrane oxygenation (V-A ECMO, 308 measurement periods) therapy. We assumed that the ratio of carbon dioxide elimination (V̇CO2) or oxygen uptake (V̇O2) between the membrane and native lung corresponds to the ratio of respective blood flows. Unequal ventilation/perfusion (V̇/Q̇) ratios were corrected towards unity. Pulmonary blood flow was calculated and compared to an ultrasonic flow probe on the pulmonary artery with a bias of 99 mL/min (limits of agreement -542 to 741 mL/min) with blood content VO2 and no-shunt, no-deadspace conditions, which showed good trending ability (least significant change from 82 to 129 mL). Shunt conditions led to underestimation of native pulmonary blood flow (bias -395, limits of agreement -1290 to 500 mL/min). Bias and trending further depended on the gas (O2, CO2), and measurement approach (blood content vs. gas phase). Measurements in the gas phase increased the bias (253 [LoA -1357 to 1863 mL/min] for expired V̇O2 bias 482 [LoA -760 to 1724 mL/min] for expired V̇CO2) and could be improved by correction of V̇/Q̇ inequalities. Our results show that common assumptions of the Fick principle in two competing circulations give results with adequate accuracy and may offer a clinically applicable tool. Precision depends on specific conditions. This highlights the complexity of gas exchange in membrane lungs and may further deepen the understanding of V-A ECMO.

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Section: Methodsmentioning

confidence: 99%

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Berger

Zwicker

Nettelbeck

et al. 2023

American Journal of Physiology-Lung Cellular and Molecular Phys

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“…Priming volume of the system was approximately 2.2 L. It was filled with a mixture of discarded human red blood cells and lactated Ringer’s solution in a ratio of 3:1 to reach a hemoglobin value of 8–10 g/L. 50–100 mmol of sodium bicarbonate were added to reach physiological pH values between 7.3–7.4 4 . Glucose 20% was added to keep glucose level above 5 mmol/l.…”

Section: Methodsmentioning

confidence: 99%

“…In a recent review, refinement of patient inclusion criteria, optimization of additional treatment strategies and weaning strategies were considered research fields of major importance for the ongoing improvement for patients on ECMO treatment 3 . The physiology of gas exchange and blood flow with two competing systems, the ECMO and the patient’s own heart and lung in parallel connection, is incompletely understood 4 . The goal of the treatment is to maintain tissue perfusion and gas exchange in order to gain time for recovery of native cardiac output (i.e.…”

Section: Introductionmentioning

confidence: 99%

Estimating cardiac output based on gas exchange during veno-arterial extracorporeal membrane oxygenation in a simulation study using paediatric oxygenators

Bachmann

Vasireddy

Heinisch

et al. 2021

Sci Rep

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Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy is a rescue strategy for severe cardiopulmonary failure. The estimation of cardiac output during VA-ECMO is challenging. A lung circuit ($${\dot{\text{Q}}}$$ Q ˙ Lung) and an ECMO circuit ($${\dot{\text{Q}}}$$ Q ˙ ECMO) with oxygenators for CO2 removal ($$\mathop {\text{V}}\limits^{.}$$ V . CO2) and O2 uptake ($$\mathop {\text{V}}\limits^{.}$$ V . O2) simulated the setting of VA-ECMO with varying ventilation/perfusion ($$\mathop {\text{V}}\limits^{.}$$ V . /$${\dot{\text{Q}}}$$ Q ˙ ) ratios and shunt. A metabolic chamber with a CO2/N2 blend simulated $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2. $${\dot{\text{Q}}}$$ Q ˙ Lung was estimated with a modified Fick principle: $${\dot{\text{Q}}}$$ Q ˙ Lung = $${\dot{\text{Q}}}$$ Q ˙ ECMO × ($$\mathop {\text{V}}\limits^{.}$$ V . CO2 or $$\mathop {\text{V}}\limits^{.}$$ V . O2Lung)/($$\mathop {\text{V}}\limits^{.}$$ V . CO2 or $$\mathop {\text{V}}\limits^{.}$$ V . O2ECMO). A normalization procedure corrected $$\mathop {\text{V}}\limits^{.}$$ V . CO2 values for a $$\mathop {\text{V}}\limits^{.}$$ V . /$${\dot{\text{Q}}}$$ Q ˙ of 1. Method agreement was evaluated by Bland–Altman analysis. Calculated $${\dot{\text{Q}}}$$ Q ˙ Lung using gaseous $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2 correlated well with measured $${\dot{\text{Q}}}$$ Q ˙ Lung with a bias of 103 ml/min [− 268 to 185] ml/min; Limits of Agreement: − 306 ml/min [− 241 to − 877 ml/min] to 512 ml/min [447 to 610 ml/min], r2 0.85 [0.79–0.88]). Blood measurements of $$\mathop {\text{V}}\limits^{.}$$ V . CO2 showed an increased bias (− 260 ml/min [− 1503 to 982] ml/min), clinically not applicable. Shunt and $$\mathop {\text{V}}\limits^{.}$$ V . /$${\dot{\text{Q}}}$$ Q ˙ mismatch decreased the agreement of methods significantly. This in-vitro simulation shows that $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2 in steady-state conditions allow for clinically applicable calculations of $${\dot{\text{Q}}}$$ Q ˙ Lung during VA-ECMO therapy.

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“…Bachman and Berger for their thoughtful insight into CO 2 clearance within the membrane lung. 1,2 We particularly appreciate the opportunity to discuss mechanisms in addition to dead-space as a rationale for reduced CO 2 clearance.…”

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confidence: 99%

Response to “Impaired membrane lung CO2 elimination: is it dead space, V/Q ratio, or acidosis?”

2020

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Impaired membrane lung CO₂ elimination: is it dead space, V/Q ratio or acidosis?

Cited by 3 publications

References 7 publications

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Estimating cardiac output based on gas exchange during veno-arterial extracorporeal membrane oxygenation in a simulation study using paediatric oxygenators

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Impaired membrane lung CO2 elimination: is it dead space, V/Q ratio or acidosis?

Cited by 3 publications

References 7 publications

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model

Estimating cardiac output based on gas exchange during veno-arterial extracorporeal membrane oxygenation in a simulation study using paediatric oxygenators

Response to “Impaired membrane lung CO2 elimination: is it dead space, V/Q ratio, or acidosis?”

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Impaired membrane lung CO₂ elimination: is it dead space, V/Q ratio or acidosis?