Abstract Background Cardiac surgery performed via median sternotomy frequently leads to postoperative impairments in respiratory mechanics and heterogeneous ventilation distribution. Optimizing ventilatory strategies during the perioperative period may minimize these changes. Noninvasive ventilation (NIV) is recommended to improve functional lung volume and promote more homogeneous regional ventilation. However, the short-term impact of inspiratory positive airway pressure (IPAP) adjustment on perioperative regional ventilation remains unclear. Objective To compare the short-term effects of adjusted IPAP levels during pre- and postoperative NIV on regional lung ventilation distribution in patients undergoing elective cardiac surgery. Methods An experimental repeated-measures study was conducted in adults undergoing elective cardiac surgery via median sternotomy. Electrical impedance tomography (EIT) was used to assess end-expiratory lung impedance variation (ΔEELI), anteroposterior ventilation distribution (VAP), and regional ventilation across four regions of interest (ROI1-ROI4). Vital signs and NIV parameters were recorded at six time points: M1 (preoperative, before NIV), M2 (preoperative, during NIV), M3 (preoperative, 30 min after NIV withdrawal), M4 (postoperative, before NIV), M5 (postoperative, during NIV), and M6 (postoperative, 30 min after NIV withdrawal). Patients were assigned to Group 1 (IPAP +1 cmH2O) or Group 2 (IPAP +2 cmH2O) relative to their preoperative setting. Results Significant time effects were found for VAP (p = 0.010, effect size = 0.98), ROI2 (p = 0.007, effect size = 0.98), and ROI3 (p = 0.008, effect size = 0.95). A significant time-by-group interaction was observed for ROI2 (p = 0.031, effect size = 0.96), indicating that the higher IPAP adjustment (+2 cmH2O) altered the temporal pattern of regional ventilation. Post-hoc comparisons showed that Group 2 exhibited a greater increase in ROI2 ventilation during and after NIV (mean change +0.12 ± 0.04) compared with Group 1 (+0.06 ± 0.03), corresponding to a mean difference of + 0.06 (95% CI 0.02-0.10, p = 0.018). ROI1 and ROI4 remained stable across time (p 0.10). No between-group differences were found for ΔEELI or VAP amplitude. Conclusions Short-term NIV led to measurable and reversible changes in thoracic expansion and regional ventilation patterns during the perioperative period of cardiac surgery. An IPAP increase of + 2 cmH2O enhanced mid-lung recruitment (ROI2) and redistributed ventilation from ventral to central-dorsal regions, suggesting a dose-dependent physiological response without hemodynamic compromise. These findings highlight the clinical relevance of individualized inspiratory pressure adjustment to optimize postoperative ventilation. This abstract is funded by: Brazilian research agencies: CNPq 303988/2025-8; FACEPE APQ-1020-4.08/25; CAPES 001; UFPE PROPG PRO-Equipamentos e PROPESQI-PARQUETEC ACADEMIA
Campos et al. (2026) studied this question.