Functional capacity evaluation

Functional Capacity - METs Matter

• MET (Metabolic Equivalent): A measure of oxygen consumption. 1 MET is the basal metabolic rate at rest.
• Assessing METs helps stratify perioperative cardiac risk. The key threshold is 4 METs.
  • < 4 METs: Poor functional capacity. (e.g., Activities of Daily Living, walking indoors)
  • ≥ 4 METs: Good functional capacity. (e.g., climbing a flight of stairs, cycling)

⭐ If a patient's functional status is uncertain, the Duke Activity Status Index (DASI) can be used. A score of <34 correlates with an inability to achieve 4 METs.

METs Scoreboard - Activity Power Levels

• 1 MET: Basal energy requirement at rest.
• < 4 METs (Poor): Light activities.
  • Self-care (dressing, eating).
  • Walking around the house.
  • Light housework (dishwashing).
• 4-10 METs (Good): Moderate activities.
  • Climbing one flight of stairs (~4 METs).
  • Running a short distance.
  • Heavy housework (scrubbing floors).
  • Moderate sports: golf, cycling, swimming.
• > 10 METs (Excellent): Strenuous activities.
  • Strenuous sports: singles tennis, basketball, skiing.

⭐ A key perioperative risk threshold is the inability to perform activities meeting a 4-MET demand. This often prompts further non-invasive cardiac testing before major surgery.

The 4-METs Rule - Go or No-Go?

• MET (Metabolic Equivalent of Task): A measure of exercise capacity. 1 MET is the resting metabolic rate.
• The 4-METs level is a crucial threshold in pre-operative cardiac risk assessment, gauging ability to withstand surgical stress.

• < 4 METs (Poor): Slow walking (2-3 mph), light housework, dressing.
• ≥ 4 METs (Good): Climbing a flight of stairs, brisk walking (4 mph), heavy housework, dancing.

⭐ Inability to climb two flights of stairs or walk four blocks (a surrogate for 4 METs) is a significant predictor of postoperative cardiopulmonary complications.

• Functional capacity is a key independent predictor of perioperative cardiac risk, measured in Metabolic Equivalents (METs).
• Poor capacity (<4 METs) is the inability to climb one flight of stairs or walk 4 blocks; it signals high risk.
• Good capacity (≥4 METs) often allows proceeding with surgery without further cardiac testing.
• Excellent capacity (>10 METs) involves strenuous activities like swimming or tennis.
• The Duke Activity Status Index (DASI) is a validated questionnaire to estimate METs.