Preoperative Pulmonary Function for Surgery
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Direct answer
Two numbers — the predicted postoperative (ppo) FEV1 and the predicted postoperative DLCO — decide whether a patient can safely lose a lobe or a lung: values above 60 per cent predicted are low risk and need no further testing, values between roughly 30 and 60 per cent are intermediate and warrant exercise testing (stair climb or formal cardiopulmonary exercise testing with VO2 max), and values below about 30 per cent predict prohibitive risk for major resection. The ppo value is calculated by subtracting the functional segments removed (using the 19-segment model, each segment worth about 5.3 per cent of total function) from the preoperative FEV1. Assessment sits inside a wider bundle — smoking cessation, treatment of infection and obstruction, inspiratory muscle training and cardiac evaluation — because deaths after lung resection are as often cardiac as respiratory.
What you must remember
- Segment counting: both lungs have 19 bronchopulmonary segments (right 10, left 8–9); ppo FEV1 = preoperative FEV1 × (19 − segments removed)/19 — for a lobectomy expect roughly a 20–25 per cent reduction, much larger for pneumonectomy.
- Thresholds in common guidelines: ppo FEV1 and ppo DLCO above 60 per cent — low risk, proceed; 30–60 per cent — intermediate, add exercise testing; below 30 per cent — very high risk for standard major resection, consider sublobar resection, stereotactic radiotherapy or chemoradiation.
- DLCO measures gas exchange and predicts postoperative complications and mortality independently of FEV1 — a low DLCO with a normal FEV1 is still high risk.
- Low-technology exercise tests: stair climbing — climbing more than about 22 m (some centres say 5 flights) suggests acceptable risk, while inability to climb two flights or under about 12 m flags very high risk; the 6-minute walk and shuttle test are alternatives.
- Cardiopulmonary exercise testing: VO2 max above 15–20 mL/kg/min indicates low risk, below 10 mL/kg/min high risk — the gold standard when ppo values fall in the intermediate band.
- Risk reduction bundle before any thoracic (and indeed upper abdominal) surgery: smoking cessation (ideally 4–8 weeks, with even shorter abstinence improving carboxyhaemoglobin), bronchodilator optimisation of COPD, treating infection, inspiratory muscle training and physiotherapy, epidural or regional analgesia planned to permit early mobilisation and coughing.
- Cardiac assessment is inseparable: lung cancer patients carry smoking-related coronary disease; arrhythmia (especially atrial fibrillation after pneumonectomy), ischaemia and right heart strain after major resection drive perioperative death — risk of atrial fibrillation is highest in the first 2–3 days.
- Benchmark operative mortality: lobectomy under about 3 per cent in fit patients; pneumonectomy several-fold higher, with right pneumonectomy the riskiest.
A worked example
A 66-year-old man with a 40 pack-year smoking history has a 3 cm right lower lobe squamous carcinoma; his FEV1 is 62 per cent predicted and DLCO 55 per cent. He climbs three flights of stairs without stopping. Reason it out: a right lower lobectomy removes five segments, so ppo FEV1 = 62 × 14/19 ≈ 46 per cent, and ppo DLCO ≈ 40 per cent — both in the 30–60 per cent intermediate band. That mandates further testing, not refusal: a stair climb beyond the threshold (or a formal CPET showing VO2 max above 15 mL/kg/min) supports proceeding with lobectomy. Contrast a second patient whose ppo FEV1 computes to 24 per cent for the required pneumonectomy: even with a reassuring exercise test, that figure predicts very high mortality — the discussion shifts to lobectomy if oncologically acceptable, sleeve resection, or non-operative treatment. Both patients additionally get the risk-reduction bundle: smoking stopped now (never postpone cancer surgery indefinitely for perfect abstinence), bronchodilators, chest physiotherapy taught preoperatively, and a plan for epidural analgesia — because the postoperative complication chain (pain, poor cough, retention of secretions, atelectasis, pneumonia, respiratory failure) is interruptible at every link.
Where students slip
The recurring error is quoting a single absolute FEV1 (for example "FEV1 over 1.5 litres for lobectomy, over 2 for pneumonectomy") without converting to ppo percentages — examiners now expect the ppo method and the 60/30 thresholds. The second is forgetting DLCO entirely, though it independently predicts mortality. The third is answering "FEV1 low — deny surgery" when the correct answer is a staged algorithm that ends in sublobar resection or radiotherapy options; risk assessment exists to choose the right operation, not to end the conversation.
Frequently asked questions
How is predicted postoperative FEV1 calculated?
ppo FEV1 = preoperative FEV1 × (19 − number of bronchopulmonary segments resected)/19, based on 19 functional lung segments.
What ppo FEV1 or DLCO values are considered low risk for lung resection?
Above 60 per cent predicted; values below 30 per cent indicate very high risk, and 30–60 per cent requires further exercise-based assessment.
Which exercise tests stratify intermediate-risk patients?
Stair climbing (over about 22 m acceptable; under about 12 m very high risk), 6-minute walk, and formal CPET where VO2 max above 15–20 mL/kg/min supports surgery and below 10 opposes it.
Why is DLCO assessed separately from FEV1?
DLCO reflects alveolar-capillary gas exchange and predicts postoperative respiratory and cardiac complications independently — a patient with normal airflow but poor DLCO remains high risk.
How long before surgery should smoking be stopped?
Ideally at least 4–8 weeks, though any abstinence reduces carboxyhaemoglobin and improves oxygen delivery.