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Effect of oxygenator type and bypass flow pattern on the P(a-ET)CO2 gradient
S E Opper1, E E Fibuch, R E Nelson
1Department of Anesthesiology, St Luke's Hospital Kansas City, MO 64111.
Journal of Cardiothoracic and Vascular Anesthesia
|February 1, 1992
Summary
Pulsatile flow during cardiopulmonary bypass helps maintain the P(a-ET)CO2 gradient, unlike nonpulsatile flow which tends to increase it. This finding is crucial for optimizing patient ventilation during cardiac surgery.
Area of Science:
- Cardiovascular Surgery
- Respiratory Physiology
- Biomedical Engineering
Background:
- Cardiopulmonary bypass (CPB) involves complex physiological changes.
- The P(a-ET)CO2 gradient, reflecting ventilation-perfusion matching, can be affected by CPB.
- Understanding factors influencing this gradient is vital for patient management.
Purpose of the Study:
- To investigate the impact of different cardiopulmonary bypass configurations on the P(a-ET)CO2 gradient.
- To compare the effects of pulsatile versus nonpulsatile flow and bubble versus membrane oxygenators.
- To analyze the influence of hemodynamic changes and bypass duration on P(a-ET)CO2.
Main Methods:
- A study involving 36 adult patients undergoing CPB.
- Patients were divided into three groups: bubble oxygenator with nonpulsatile flow (BN), bubble oxygenator with pulsatile flow (BP), and membrane oxygenator with nonpulsatile flow (MN).
- P(a-ET)CO2, PaCO2, and PETCO2 were measured pre- and post-bypass, along with hemodynamic parameters.
Main Results:
- The overall P(a-ET)CO2 gradient showed a non-significant trend to increase post-bypass.
- Pulsatile flow (group 2) demonstrated a significant correlation (r=0.85) with a stable P(a-ET)CO2 gradient.
- Nonpulsatile flow groups (1 and 3) showed an increase in the P(a-ET)CO2 gradient post-bypass.
- Hemodynamic changes and CPB duration did not significantly influence the P(a-ET)CO2 gradient.
Conclusions:
- Pulsatile flow during CPB is associated with a more stable P(a-ET)CO2 gradient compared to nonpulsatile flow.
- The type of oxygenator (bubble vs. membrane) did not independently affect the P(a-ET)CO2 gradient in this study.
- Pulsatile flow may be beneficial in maintaining ventilation-perfusion balance during CPB.