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The effect of high pressure on microporous membrane oxygenator failure
Y Tamari1, A J Tortolani, M Maquine
1Department of Surgery, North Shore University Hospital, Manhasset, NY 11030.
Abstract:
A retrospective study to determine the relationship between early microporous membrane oxygenator (MMO) failure and blood pressure at the MMO outlet (Pmo) was conducted using data collected with 19 dogs (22 +/- 1 kg, mean +/- SEM) undergoing routine normothermic cardiopulmonary bypass. Because gas flow was maintained at a high level, it could not be used to control CO2 exchange. Instead, blood PCO2 was controlled by adding CO2 to the sweep gas. Blood PO2 was controlled as suggested by the manufacturer, by adjusting the %O2 in the gas phase (g). Blood flow was 2575 +/- 54 ml/min; Pmo ranged from 173 to 790 mm Hg; and hematocrit was 33 +/- 1%. O2 exchange was calculated from blood gas parameters. Changes in the diffusion potential of O2 (delta PO2) and CO2 (delta PCO2) and MMO performance (P, taken as oxygen exchange normalized to a diffusion potential of 100 mm Hg) indicated MMO failure. Initial values, taken within 60 min of bypass initiation, were compared to final values taken at 226 +/- 9 min of bypass. Despite higher final delta PO2 (411 +/- 9 vs. 538 +/- 19 mm Hg, p less than 0.0001 paired t-test) and delta PCO2 (18.6 +/- 2.4 vs. 30.5 +/- 4.7 mm Hg, p less than 0.0017), arterial blood PO2 decreased (159 +/- 15 to 89 +/- 6 mm Hg, p less than 0.0005) and PCO2 increased (36.4 +/- 1.5 to 46.1 +/- 3.0 mm Hg, p less than 0.0039), and the performance decreased [24.5 +/- 1.1 to 20.1 +/- 0.7 (ml/min)/(100 mm Hg), p less than 0.0001].(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
High outlet pressure in microporous membrane oxygenators (MMO) during cardiopulmonary bypass is linked to decreased oxygen transfer and potential device failure. This study in dogs suggests monitoring MMO outlet pressure is crucial for safe and effective gas exchange.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Respiratory Physiology
Background:
- Microporous membrane oxygenators (MMOs) are vital for gas exchange during cardiopulmonary bypass.
- Early detection of MMO failure is critical to prevent patient complications.
- Blood pressure at the MMO outlet (Pmo) is a potential indicator of MMO performance.
Purpose of the Study:
- To investigate the relationship between early microporous membrane oxygenator (MMO) failure and blood pressure at the MMO outlet (Pmo).
- To identify Pmo as a predictor of MMO performance degradation during cardiopulmonary bypass.
Main Methods:
- A retrospective analysis of data from 19 dogs undergoing normothermic cardiopulmonary bypass.
- Monitoring of blood gas parameters, including PCO2 and PO2, and MMO outlet pressure (Pmo).
- Calculation of oxygen exchange and MMO performance (P) based on diffusion potentials (delta PO2, delta PCO2).
Main Results:
- Despite increased diffusion potentials for O2 and CO2, arterial PO2 decreased and PCO2 increased over time.
- MMO performance (P) significantly decreased from initial to final bypass values.
- A correlation between higher Pmo and diminished MMO gas exchange capacity was observed.
Conclusions:
- Elevated blood pressure at the MMO outlet (Pmo) is associated with reduced oxygen transfer efficiency.
- Monitoring Pmo may serve as an early warning sign for impending MMO failure during cardiopulmonary bypass.
- Further research is warranted to establish Pmo thresholds for predicting MMO dysfunction.