103. Risk Factors for Home Oxygen Therapy at Discharge for DIEP Flap Reconstruction in Colorado

PURPOSE: Postoperative hypoxemia can occur more frequently in patients undergoing general anesthesia in high-altitude areas1. Once hypoxemia is identified, supplemental oxygen therapy becomes necessary to maintain normal blood oxygen saturation levels, which are crucial for effective wound healing and microvascular anastomosis2. At the University of Colorado Hospital, located at an elevation of 5,404 feet3, patients undergoing deep inferior epigastric perforator (DIEP) flap reconstruction often require home oxygen therapy at discharge. The purpose of this study was to identify risk factors associated with the need for new home oxygen therapy in this high-altitude patient population. METHODS: A retrospective review was conducted on patients who underwent DIEP flap reconstruction. Our primary outcome was the need for new home oxygen therapy at discharge, indicated for patients with a blood oxygen saturation level of ≤88% during the postoperative admission period4. We compared patients who required home oxygen therapy with those who did not, using a chi-square test or Fisher’s exact test for categorical variables, and a two-sample t-test or Wilcoxon rank-sum test for continuous variables. Additionally, we performed both univariate and multivariable logistic regression analyses to assess associations between home oxygen use and various factors, including demographics, comorbidities, and perioperative variables. Model calibration was evaluated using the area under the receiver operating characteristic curve and the Hosmer-Lemeshow test. A p-value of ≤0.05 was considered statistically significant. RESULTS: We reviewed a total of 530 patients who underwent either unilateral (34%) or bilateral (66%) breast reconstruction from 2012-2022. Ninety patients (17%) were discharged on new home oxygen therapy. There was a significant difference in median (IQR) preoperative oxygen saturation levels between the home oxygen use and non-home oxygen use cohorts (95% (94-96%) vs 96% (94-97%) respectively, p= 0.001). After adjusting for potential covariates, oxygen requirement at discharge was significantly associated with age (OR: 1.03, 1.00-1.06, p= 0.03), a BMI >30 kg/m2 (OR: 2.23, 0.91-5.44, p= 0.02), and bilateral flap reconstruction (OR: 3.56, 1.65-7.70, p= 0.001). CONCLUSIONS: Older age, a BMI above 30 kg/m2, and bilateral reconstruction were identified as significant risk factors for the need for home oxygen therapy following DIEP flap reconstruction at high-altitude. Data from this study can inform the development of quality improvement guidelines aimed at enhancing patient outcomes in high-elevation medical centers. Future studies will compare these findings with those from sea-level centers to better understand the impact of altitude as a risk factor in surgical recovery.