RESUMO
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.