What is the predicted postoperative lung function in a patient with an FEV1 (Forced Expiratory Volume in 1 second) of 1.8 L undergoing a right upper lobe lobectomy using the segment counting method?

Predicted Postoperative FEV1 for Right Upper Lobe Lobectomy

Using the segment counting method with a preoperative FEV1 of 1.8 L and removing 3 segments (right upper lobe), the predicted postoperative FEV1 is approximately 1.52 L.

Calculation Method

For lobectomy, the anatomic segment counting method is the recommended approach rather than perfusion scanning, which is reserved for pneumonectomy 1.

The formula is:

• PPO FEV1 = preoperative FEV1 × (19 - segments removed) / 19 1

For this patient:

• Preoperative FEV1 = 1.8 L
• Right upper lobe = 3 segments 1
• Total lung segments = 19 1

Calculation: 1.8 L × (19 - 3) / 19 = 1.8 L × 16/19 = 1.52 L 1

Clinical Context and Risk Stratification

This patient's preoperative FEV1 of 1.8 L exceeds the 1.5 L threshold that allows proceeding directly to surgery without additional testing for lobectomy 1. However, the calculated PPO FEV1 of 1.52 L warrants further evaluation.

The predicted postoperative value should be expressed as a percentage of predicted normal values to properly assess surgical risk 1. Without knowing this patient's predicted normal FEV1, definitive risk stratification cannot be completed, but the absolute value of 1.52 L is above the historical 800 mL minimum threshold 1.

Risk Assessment Framework

• If PPO FEV1 >60% predicted: Low risk - proceed with surgery 1
• If PPO FEV1 30-60% predicted: Moderate risk - perform low-technology exercise testing (stair climb or shuttle walk) 1
• If PPO FEV1 <30% predicted: High risk - requires cardiopulmonary exercise testing and consideration of limited resection 1, 2

Important Clinical Caveats

The segment counting formula consistently underestimates actual postoperative FEV1 3, 4. Research demonstrates that:

• For lobectomy patients, the predicted value underestimates actual postoperative FEV1 by approximately 250 mL 3
• At 3 months post-lobectomy, measured FEV1 is typically 8% higher than predicted, increasing to 13% higher at 12 months 5
• Patients with severe COPD (FEV1 ≤60% predicted and FEV1/FVC ≤0.6) may actually improve their FEV1 after upper lobectomy due to removal of hyperinflated, poorly functioning tissue 6

This means the actual postoperative FEV1 for this patient will likely be approximately 1.77 L (1.52 L + 0.25 L) rather than the calculated 1.52 L 3.

Additional Required Testing

This patient requires measurement of DLCO (diffusing capacity) and calculation of predicted postoperative DLCO using the same segment counting formula 1. Both PPO FEV1 and PPO DLCO must be >40% predicted for acceptable risk, as these are independent prognostic factors for perioperative complications 1.

Oxygen saturation on room air should also be measured, as SaO2 <90% indicates increased risk 1, 2.