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

Objectives To determine whether FIO2 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 FIO2. Patients were sorted retrospectively into low FIO2 (0.21-0.44), intermediate FIO2 (0.45-0.69), and high FIO2 (0.7-1.0) groups. The primary outcome was the difference between the PaO2:FIO2 on the first postinduction blood gas and on the first blood gas recorded postoperatively in the intensive care unit (ICU) (delta PaO2:FIO2). 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 FIO2 n = 307, intermediate FIO2 n = 459, high FIO2 n = 134). There was no significant difference in delta PaO2:FIO2 among the groups (low FIO2 = 52.5 [–38.8 to 152.4], intermediate FIO2 = 71.8 [–39.4 to 165.1], high FIO2 = 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 FIO2 delivered to the lungs without positive airway pressure during cardiopulmonary bypass was not associated with improved postoperative pulmonary function when compared to higher FIO2 levels.