Different measures of ventilatory efficiency in preoperative cardiopulmonary exercise testing are useful for predicting postoperative complications in abdominal cancer surgery.

BACKGROUND

Ventilation as a function of elimination of CO during incremental exercise (VE/VCO slope) has been shown to be a valuable predictor of complications and death after major non-cardiac surgery. VE/VCO slope and partial pressure of end-tidal carbon dioxide (PetCO) are both affected by ventilation/perfusion mismatch, but research on the utility of PetCO for risk stratification in major abdominal surgery is limited.

AIM

We aimed to determine the correlation between VE/VCO slope and PetCO measured during preoperative cardiopulmonary exercise testing (CPET) and its association with major cardiopulmonary complications (MCPCs) or death following oesophageal and other major abdominal cancer surgeries.

METHOD

In a retrospective cohort of 116 patients undergoing preoperative CPET 2008-2023, VE/VCO slope and PetCO (kPa) were recorded. The main outcome was MCPC during hospitalisation or death ≤90 days of surgery. We determined threshold values for each measure, corresponding to 90% specificity, using receiver operating characteristics analysis.

RESULTS

A strong negative correlation was found between PetCO after a 5-minute warm-up and VE/VCO slope (Pearson r = -.88). In oesophagus cancer, VE/VCO slope >38 and PetCO < 4.1 kPa (30.8 mmHg) were both significant thresholds for the main outcome. For other major abdominal surgery patients, threshold analyses were non-significant. The area under the curve to predict outcome was similar using VE/VCO slope (0.70, 95% confidence interval 0.51-0.89) as compared to PetCO (0.71, 0.53-0-90).

CONCLUSION

Both preoperative VE/VCO slope and PetCO could identify subjects with a very high risk of complications following oesophageal resection, with similar prognostic utility. PetCO can be measured with simpler equipment and could therefore be useful when CPET is not available.