Is a Pulmonary Function Test (PFT) required for anesthesia clearance?

Is PFT Required for Anesthesia Clearance?

Pulmonary function testing (PFT) is NOT routinely required for anesthesia clearance in the general surgical population, but IS indicated for specific high-risk patients based on clinical factors including age ≥75 years, reduced exercise tolerance (MET <4), significant smoking history (≥20 pack-years), known respiratory disease, or when thoracic surgery is planned. 1, 2

General Anesthesia Clearance Guidelines

The American Society of Anesthesiologists does not recommend routine preoperative PFTs for most patients undergoing anesthesia 1. Studies examining routine pulmonary function testing found abnormal findings in 15.0-51.7% of cases, but changes in clinical management were not consistently reported, and no clear benefit to routine testing was demonstrated 1.

Specific Indications for Preoperative PFT

High-Risk Patient Populations Requiring PFT:

Age and Functional Status:

• Patients ≥75 years old should undergo targeted spirometry screening 2
• Patients with reduced exercise tolerance (MET <4) regardless of age 2
• These criteria detected previously unknown obstructive disorders in 35.2% of screened patients and impaired gas exchange in 27.6% 2

Respiratory Disease History:

• History of cigarette smoking ≥20 pack-years 1
• Cessation of smoking within the past 2 years or current smoking 1
• History of pneumonitis, COPD, or asthma 1
• Significant respiratory symptoms: cough, wheezing, dyspnea, rales on auscultation, or abnormal chest X-ray 1
• History of pleural drainage within the past 3 months 1

Neuromuscular Disease:

• All patients with neuromuscular disease at risk of respiratory complications should undergo PFT to assist with management decisions 1
• Testing should include FVC or SVC, MIP/MEP or SNIP, and peak cough flow (PCF) 1
• Patients with FVC ≤50% measured in seated upright position are at increased risk for respiratory complications 1
• Patients with FVC ≤30% are at high risk for complications and may require postoperative noninvasive ventilation 1

Thoracic Surgery Candidates:

• PFTs are essential for lung resection candidates, where preoperative testing has measurable benefit in predicting outcomes 3
• Postoperative predicted FEV1 and diffusing capacity are independent predictors of postoperative pulmonary complications after lobectomy 1
• For pneumonectomy candidates with central airway obstruction, quantitative perfusion scan combined with PFTs to calculate post-resection FEV1 is helpful 1
• Patients with marginal PFTs should undergo pulmonary exercise testing to calculate maximum oxygen consumption for surgical risk assessment 1

Recommended PFT Parameters

When PFTs are indicated, the following measurements should be obtained 1:

• Spirometry: FEV1/FVC ratio and FEV1 as percentage of predicted
• Lung volumes: Forced vital capacity (FVC) or slow vital capacity (SVC)
• Respiratory muscle strength: Maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), or sniff nasal inspiratory pressure (SNIP)
• Cough effectiveness: Peak cough flow (PCF)
• Gas exchange: Diffusing capacity for carbon monoxide (DLCO) in selected patients 1

Critical Thresholds:

For neuromuscular disease patients:

• Postbronchodilator FEV1/FVC >70% or FEV1 >50% of predicted is recommended 1
• PCF <270 L/min or MEP <60 cm H2O indicates increased risk due to impaired cough 1
• DLCO <50% (moderate impairment) or <40% (severe impairment) may preclude certain therapies 1

Patients NOT Requiring Routine PFT

The following do NOT require routine preoperative PFTs 1, 3:

• Healthy patients undergoing non-thoracic surgery
• Patients without respiratory symptoms or risk factors
• Patients undergoing coronary artery bypass grafting (insufficient evidence for benefit) 3
• Non-surgical candidates (PFTs should be excluded from routine testing) 1

Timing Considerations

• For patients with neuromuscular disease at risk of respiratory failure, PFTs should be performed at minimum every 6 months, adjusted based on disease progression rate 1
• After major thoracic, abdominal, or head surgery, waiting times before PFT can often be reduced to <3 weeks with modern less invasive surgical techniques, rather than the traditional 6-week recommendation 4

Clinical Decision Algorithm

1. Screen all patients for age ≥75, MET <4, smoking history ≥20 pack-years, respiratory symptoms, or neuromuscular disease 1, 2
2. If any risk factors present: Order spirometry with FVC, MIP/MEP or SNIP, and PCF 1, 2
3. If thoracic surgery planned: PFTs are mandatory regardless of symptoms 1, 3
4. If neuromuscular disease: PFTs required with specific thresholds for anesthesia risk stratification 1
5. If no risk factors and non-thoracic surgery: PFTs are not indicated 1

Common Pitfalls

• Avoid routine testing in low-risk patients: This increases costs without improving outcomes 1
• Don't use PFTs in isolation: Clinical context, including exercise tolerance and symptoms, must guide decision-making 1, 2
• Don't delay necessary surgery for borderline PFT results: Consult pulmonology for optimization strategies rather than canceling surgery 1
• Recognize that normal PFTs don't eliminate risk: Postoperative complications are multifactorial 2, 5