Too big to breathe: predictors of respiratory failure and insufficiency after open ventral hernia repair.

Introduction: Increased intra-abdominal pressure in open ventral hernia repair (OVHR) is hypothesized to contribute to postoperative respiratory insufficiency (RI) or failure (RF). This study examines the impact of abdominal volumes on postoperative RI in OVHR.
Methods: OVHR patients with preoperative CT scans were identified. 3D volumetric software measured hernia volume (HV), subcutaneous volume (SQV), and intra-abdominal volume (IAV). The ratio of hernia to intra-abdominal volume (HV:IAV) was calculated. A principal component analysis was performed to create new component variables for collinear volume and hernia variables.
Results: There were 1178 OVHR patients with preoperative CT scans. Demographics included a mean BMI of 34.2 ± 7.7 kg/m ² , age of 58.5 ± 12.4 years, and 57.8% were female. RI occurred in 8.3% of patients, including 4.0% requiring > 24 h respiratory support with ezPAP, CPAP, or biPAP (RI), and 4.3% requiring intubation (RF). Patients who developed RI had a higher BMI (33.8 ± 7.5 vs. 38.2 ± 9.1 kg/m ² , p < 0.0001), older age (58.1 ± 12.5 vs. 62.8 ± 10.4 years, p = 0.0001), larger defects (140.9 ± 128.4 vs. 254.0 ± 173.9 cm ² , p < 0.0001), HV (865.8 ± 1200.0 vs. 2005.6 ± 1791.7 cm ³ , p < 0.0001), and HV:IAV (0.26 ± 0.45 vs. 0.53 ± 0.58, p < 0.0001). Three PC variables accounted for 85% of variance: hernia volume PC consists primarily of HV (61.8%), ratio HV:IAV (57.7%), and defect size (50.1%) and accounts for 38.3% variance. Extra-abdominal volume PC consists primarily of SQV (63.7%) and BMI (60.8%) and accounts for 32.5% variance. Intra-abdominal volume PC is primarily IAV (75.8%) and accounts for 14.9% variance. In multivariate analysis, predictors of RI included asthma and COPD (OR 4.04, CI 1.82-8.96), hernia PC (OR 1.47, CI 1.48-1.98), EAV PC (OR 1.24, CI 1.04-1.48), increased age (OR 1.04, CI 1.01-1.06), and diabetes (OR 1.8, CI 1.11-2.91). Component separation, fascial closure, contamination, and panniculectomy were not associated with RI.
Conclusion: The impact of defect size, BMI, HV, SQV, IAV, and HV:IAV on respiratory insufficiency after OVHR is collinear. Patients with large defects and a large ratio of HV:IAV (greater than 0.5) are also at significantly increased risk of RI after OVHR. While BMI impacts these parameters, it is not directly predictive of postoperative RI.