# Preoperative Predictors of Exercise-Induced Hypoxemia Following Lung Cancer Surgery

## TL;DR

This study identifies Brinkmann's index and lung diffusion capacity as preoperative predictors of exercise-induced hypoxemia after lung cancer surgery.

## Contribution

The study introduces Brinkmann's index and %DLCO as novel preoperative risk markers for postoperative exercise-induced hypoxemia.

## Key findings

- Higher Brinkmann's index and lower %DLCO were significantly associated with postoperative exercise-induced hypoxemia.
- Physical function and sarcopenia were not significantly linked to postoperative hypoxemia.
- Brinkmann's index and %DLCO showed moderate predictive accuracy with AUCs of 0.702 and 0.671, respectively.

## Abstract

Objective: This study aimed to identify preoperative predictors of postoperative exercise-induced hypoxemia (EIH) in patients undergoing lung cancer surgery, with a particular focus on physical function and sarcopenia.

Methods: This single-center, retrospective study included 200 patients who underwent lung resection and perioperative rehabilitation for primary lung cancer between January 2020 and December 2021. The exclusion criteria were incomplete clinical data, no preoperative rehabilitation, and in-hospital death. Postoperative EIH was defined as a ≥4% drop in peripheral oxygen saturation (SpO2) during the six-minute walk test (6MWT) prior to discharge. Background characteristics, pulmonary function, physical function, and surgical factors were compared. Multivariate logistic regression was used to examine associations between preoperative variables and postoperative EIH. Additionally, receiver operating characteristic (ROC) curve analysis was conducted to assess the predictive performance of variables identified as significant predictors in the multivariate analysis.

Results: After applying the exclusion criteria, a total of 157 patients were ultimately included and divided into a non-EIH group (n=124) and an EIH group (n=33). Significant differences were observed between the two groups in history of interstitial lung disease, Brinkmann’s index, first second of forced expiratory volume (FEV₁), FEV₁/forced vital capacity (FVC), percentage diffusing capacity of the lungs for carbon monoxide (%DLCO), and resting SpO₂ (p < 0.05 for all). In contrast, no significant differences were found in preoperative physical function or the presence of sarcopenia. In multivariate analysis, higher Brinkmann's index/100 (odds ratio (OR): 1.110; 95% confidence interval (CI): 1.030-1.170; p = 0.003) and lower %DLCO (OR: 0.976; 95%CI: 0.960-0.992; p = 0.004) were associated with a higher likelihood of postoperative EIH. ROC analysis showed that Brinkmann's index/100 had an area under the curve (AUC) of 0.702 and %DLco an AUC of 0.671, with cutoff values of 7.50 and 103.8%, respectively.

Conclusion: Although preoperative physical function and sarcopenia were not significantly associated with the development of postoperative EIH, both Brinkmann's index and %DLCO were associated with increased risk, suggesting their potential utility as preoperative risk markers. These findings may help inform perioperative risk stratification and guide rehabilitation planning for patients undergoing lung cancer surgery. Limitations include the single-center retrospective design, small sample size, possible unmeasured confounders, undetermined optimal cutoff value, and lack of outcome validation related to postoperative EIH.