Association of Passive Lung Insufflation Oxygen Fraction in Adult Patients on Cardiopulmonary Bypass with Postoperative Pulmonary Outcomes: A Retrospective Cohort Study

Abstract

Objectives: To determine whether F_IO₂ of passive lung insufflation during cardiopulmonary bypass correlates with postoperative pulmonary function.

Design: A retrospective, observational study SETTING: A single-center, university-affiliated, specialist cardiothoracic center in the United Kingdom.

Participants: Adult patients presenting for nonemergency, nontransplant cardiac surgery requiring cardiopulmonary bypass without the need for deep hypothermic circulatory arrest between January 1, 2018, and December 31, 2018.

Interventions: Passive insufflation of the lungs during cardiopulmonary bypass with fresh gas flow of varying F_IO₂. Patients were sorted retrospectively into low F_IO₂ (0.21-0.44), intermediate F_IO₂ (0.45-0.69), and high F_IO₂ (0.7-1.0) groups. The primary outcome was the difference between the PaO₂:F_IO₂ on the first postinduction blood gas and on the first blood gas recorded postoperatively in the intensive care unit (ICU) (delta PaO₂:F_IO₂). Secondary outcomes were ICU and hospital lengths of stay, requirement for respiratory support, and 30-day mortality.

Measurements and main results: Nine hundred patients were included in the authors' analysis (low F_IO₂ n = 307, intermediate F_IO₂ n = 459, high F_IO₂ n = 134). There was no significant difference in delta PaO₂:F_IO₂ among the groups (low F_IO₂ = 52.5 [-38.8 to 152.4], intermediate F_IO₂ = 71.8 [-39.4 to 165.1], high F_IO₂ = 60.2 [-19.2 to 184.0], p = 0.25). There were no significant differences among groups for any secondary outcomes.

Conclusion: Fresh gas flow with a low F_IO₂ delivered to the lungs without positive airway pressure during cardiopulmonary bypass was not associated with improved postoperative pulmonary function when compared to higher F_IO₂ levels.

Keywords: Cardiopulmonary bypass; outcome; passive lung insufflation; pulmonary function.