What are the requirements for pre‑operative pulmonary clearance, including history, physical examination, investigations (chest radiograph, arterial blood gas, spirometry with FEV1 and DLCO), and management based on FEV1 and DLCO percentages?

Preoperative Pulmonary Clearance Requirements

All patients being considered for lung resection surgery should undergo both spirometry (FEV1) and DLCO measurement regardless of baseline lung function, with predicted postoperative (PPO) values calculated to stratify surgical risk. 1

History and Physical Examination

Critical Historical Elements

• Smoking history: Quantify pack-years (≥20 pack-years triggers mandatory spirometry) 1
• Recent smoking status: Document if cessation within past 2 years or currently smoking 1
• Respiratory disease history: Prior pneumonitis (including treatment-related), COPD, asthma, or interstitial lung disease 1
• Cardiac risk factors: Ischemic heart disease, angina, arrhythmias, or prior myocardial infarction require cardiac stress testing 1
• Recent interventions: Pleural drainage within past 3 months 1

Physical Examination Findings

• Respiratory symptoms: Cough, wheezing, dyspnea, or rales on auscultation 1
• Oxygen requirement: Patients requiring continuous supplemental oxygen preoperatively are not surgical candidates 1
• Exercise tolerance: Assess functional capacity as this guides need for cardiac evaluation 1

Required Investigations

Spirometry (FEV1)

• Measure in all patients with post-bronchodilator values 1
• Normal threshold: FEV1 >80% predicted generally requires no further testing if DLCO also >80% 1
• Calculate PPO FEV1 using anatomic segment counting method for lobectomy: PPO FEV1 = preoperative FEV1 × (19 - segments removed)/19 1, 2
• For pneumonectomy, use perfusion scanning method instead 1

DLCO Measurement

• Mandatory in all patients regardless of FEV1 value, as 40% of patients with normal FEV1 (>80%) have abnormal DLCO (<80%) 1, 3
• Poor correlation between FEV1 and DLCO (correlation coefficient <0.5) justifies systematic measurement 1, 3
• Calculate PPO DLCO using same segment counting formula as FEV1 1, 2
• DLCO is a stronger predictor of postoperative complications and mortality than FEV1, even in patients without airflow limitation 1, 4, 5, 3

Chest Radiograph

• Evaluate for abnormal parenchymal lung disease, which warrants DLCO measurement 1
• Identify pleural effusions requiring drainage consideration 1

Arterial Blood Gas

• Oxygen saturation: SaO2 <90% on room air indicates increased risk 2
• Assess for baseline hypoxemia requiring optimization 1

Risk Stratification Algorithm Based on PPO Values

Low Risk (Proceed to Surgery)

• PPO FEV1 >60% predicted AND PPO DLCO >60% predicted 1, 2
• No additional testing required 1

Moderate Risk (Requires Exercise Testing)

• PPO FEV1 30-60% predicted OR PPO DLCO 30-60% predicted 2
• Perform low-technology exercise testing (6-minute walk test, stair climbing, or shuttle walk test) 1
• If 6-minute walk distance <80% predicted for age/sex or oxygen saturation drops <90% during test, patient should not receive surgery 1

High Risk (Requires Specialized Evaluation)

• PPO FEV1 <30% predicted OR PPO DLCO <30% predicted 2
• Cardiopulmonary exercise testing with VO2max measurement 1
• Consider alternative therapies: SBRT, limited resection (wedge/segmentectomy), or lung volume reduction surgery combined with resection 1
• Pulmonology consultation mandatory 1

Historical Threshold (Context)

• PPO FEV1 and PPO DLCO >40% predicted was historically considered acceptable risk, though selected patients below this threshold can undergo surgery safely with modern techniques 1, 2
• PPO DLCO <40% is associated with increased perioperative risk and mortality 1

Special Considerations

Patients with Severe COPD

• FEV1 <1.5 L may require chronic inhaled steroids and/or bronchodilators 1
• Post-bronchodilator FEV1/FVC >70% OR FEV1 >50% predicted recommended 1
• Consider VATS approach, which shows improved outcomes compared to thoracotomy in severe COPD 1

Cardiac Clearance

• Left ventricular ejection fraction >45% required on echocardiogram 1
• Patients with acceptable exercise tolerance receive only ECG 1
• Limited exercise capacity warrants noninvasive cardiac testing 1

Common Pitfalls

• Do not skip DLCO measurement in patients with normal FEV1—this misses 40% of patients with impaired gas exchange who are at increased risk 1, 3
• Immediate postoperative FEV1 (day 1) is only 71% of PPO value, reaching 93% by day 7—current PPO calculations predict function at 1-3 months, not the critical early period 1
• DLCO <60% predicts increased perioperative risk even with normal spirometry 5, 3