Introduction Cardiopulmonary Exercise testing (CPET) has become an important tool for perioperative assessment as it may identify patients at risk of postoperative cardiopulmonary complications. Older (1) recommended that an Anaerobic Threshold (AT)<11 or >11ml/min/kg can be used to stratify post-operative treatment in colorectal patients (ITU, HDU or ward). The BTS guidelines (2) recommend that a Peak VO2 (PVO2)<15 or >15ml/min/kg can be used as a risk assessment in thoracic surgical patients. However, CPET can be difficulty to carry out. This study was undertaken to determine whether selected lung function values correlated with CPET outcome, so that they could be used as an alternative to AT and PVO2.

Method 500 pre-operative colorectal (388) and oesophageal (112) patients attending the Lung Function Department were analysed. Spirometry and Gas Transfer were performed to assess lung function. CPET was performed on a cycle ergometer to calculate PVO2 and AT.

Results The area under the curve (AUC) of a Receiver Operating Curve (ROC) analysis was carried out on the 500 patients. This compared percent predicted FEV1, FVC, TLco and Kco values to PVO2 and AT.

Discussion Our findings indicated that analysis of lung function variables cannot reliably predict PVO2 or AT outcome. However, of the variables recorded, TLco was the best marker for predicting a PVO2>15ml/min/kg (0.721). When the cut-off for TLco was set at 80% predicted it had a sensitivity and 1-specificity of 62% and 24% respectively.

Interestingly, there was a significant correlation between AT and PVO2 (0.894), suggesting that AT can be used as a predictor of PVO2. If the cut-off for AT was set at 11ml/min/kg; the sensitivity was 91.7% and the 1-specificity 37.7%. However if the cut-off was adjusted to 12ml/min/kg; the sensitivity was 77.3% and the 1-specificity was 13.7%.

Conclusion These results suggest that in pre-operative assessment of patients undergoing thoracic surgery, an AT>12ml/min/kg could be used as an alternative measure if the patient was unable to achieve a PVO2>15ml/min/kg.

Reference

1. Older (1999). Cardiopulmonary exercise testing as a screening test for perioperative management of major surgery in the elderly. Chest; 116; 355–62.

2. BTS Guidelines on the selection of patients with lung cancer for surgery (2001). Thorax 56:89–108.