How effective is Cardiopulmonary Exercise Testing (CPET) in a hospital setting to assess a patient's fitness for surgery?

CPET Effectiveness for Preoperative Surgical Fitness Assessment

CPET is an effective and beneficial tool for preoperative risk assessment in high-risk patients undergoing elevated-risk surgery who have objectively reduced functional capacity (<4 METs), providing gold-standard measurement of cardiorespiratory fitness that predicts perioperative morbidity and mortality. 1

When CPET is Most Effective

Target Population for CPET:

• High-risk patients undergoing elevated-risk procedures (major abdominal, vascular, bariatric, thoracic surgery) with poor functional capacity (<4 METs) or unknown functional capacity 1
• Patients with FEV1 or DLCO <40% being considered for lung resection surgery 1
• Moderate- to high-risk surgical candidates where routine pulmonary function tests are insufficient 1

Predictive Value and Thresholds

Key CPET Parameters and Risk Thresholds:

Anaerobic Threshold (AT):

• AT <9-10 mL/kg/min predicts increased perioperative complications and mortality 1, 2
• AT <10.1 mL/kg/min independently predicts postoperative complications with 88% sensitivity and 79% specificity 3
• AT 9-11 mL/kg/min predicts 90-day to 3-year survival after hepatic surgery 2
• Optimal cutoff: AT 10.5 mL/kg/min for major morbidity prediction 4

Peak Oxygen Consumption (VO₂peak):

• VO₂peak <50-60% predicted associated with higher morbidity and mortality after lung resection 1
• VO₂peak <15 mL/kg/min predicts 90-day mortality after AAA repair 2
• VO₂peak <17.0 mL/kg/min predicts major morbidity after esophagectomy (70% sensitivity, 53% specificity) 4
• VO₂peak is an independent predictor of major postoperative morbidity (OR 0.85) 4

VE/VCO₂ Slope:

• VE/VCO₂ slope >35 is the single strongest predictor of mortality and complications in COPD patients (hazard ratio 5.14), with only 40% survival probability at 1 year 5
• This parameter predicts complications better than VO₂ alone in patients with chronic lung disease 5

Clinical Outcomes CPET Predicts

Proven Predictive Capabilities:

• All-cause morbidity (more comprehensive than cardiovascular complications alone) 1
• Postoperative mortality 1, 2, 3
• ICU admission requirements 2
• Hospital length of stay (26 vs 10 days in high vs low complication groups) 3
• Postoperative pulmonary complications 1, 6

Advantages Over Alternative Testing

CPET Superiority:

• Gold-standard assessment of physiological response to exercise providing objective functional capacity measurement 1
• Significantly improves outcome prediction compared to questionnaire-based assessments (VASI) alone 3
• Detects clinically occult heart disease not identified by standard pulmonary function tests 1
• Provides more reliable postoperative functional capacity estimates than PFTs, which routinely overestimate functional loss 1
• Diagnoses etiology of exercise intolerance (cardiac vs pulmonary pathology) to guide preoperative optimization 1

Comparison with Simpler Tests:

• 6-minute walk test and shuttle walk test are easier to perform but demonstrate variable correlation with CPET 1
• These simpler tests may be more effective at identifying exercise desaturation but lack the comprehensive physiological data CPET provides 1
• CPET provides additional physiological data beyond 6-minute walk test that supports its use in high-risk patients 1

Evidence Quality and Limitations

Important Caveats:

• Most perioperative CPET studies are retrospective and single-center with variable predictive precision 1
• Risk thresholds vary between cohorts and surgical procedures, requiring institutional validation 1
• Thresholds have evolved over time (AT decreased from 11 to 9-10 mL/kg/min) reflecting advances in surgical and perioperative practice 1
• Standardized conduct by trained personnel is essential for reliable results 1

Clinical Implementation

When CPET Provides Maximum Benefit:

• High-risk patients with objectively reduced functional capacity undergoing elevated-risk procedures where additional physiological data are needed to inform perioperative care 1
• Guides preoperative optimization and prehabilitation programs 1, 6
• Identifies "borderline" patients who might otherwise be excluded from potentially curative surgery 1
• Preoperative pulmonary rehabilitation based on CPET screening reduces postoperative complications (16.9% vs 83.3%) and improves fast-track recovery 6

When CPET is NOT Indicated:

• Low-risk patients with adequate functional capacity (≥4 METs) undergoing low-risk procedures 1
• Patients with contraindications: acute coronary syndrome, decompensated heart failure, severe aortic stenosis, uncontrolled arrhythmia, severe pulmonary hypertension 1

Practical Algorithm

For patients being considered for major surgery:

1. Assess baseline risk using validated risk tools and functional capacity
2. If high surgical risk + poor functional capacity (<4 METs) → Perform CPET 1
3. Interpret multiple parameters together: AT, VO₂peak, and VE/VCO₂ slope (especially in COPD patients) 5
4. Use CPET results to guide preoperative optimization and prehabilitation programs 1, 6
5. Prospective validation of algorithms has demonstrated morbidity and mortality reduced by one-half without unnecessarily excluding patients from surgery 1