| Category of cause of dyspnea | CPET characteristics |
| Ventilatory | - Low peak VO2 (<85% predicted), despite good effort
- Inability to fully recruit VT (less than twice the baseline)
- Rapid, shallow breathing, or other abnormal breathing pattern
- Elevated VE resulting in reduced breathing reserve (<11 L)
- Elevated VE versus VCO2 slope (>30 to 32) or nadir of VE/VCO2 curve (>32 to 34)
- Dynamic hyperinflation with low inspiratory capacity
- Abnormal flow-volume loops during exercise
|
| Cardiac | - Low peak VO2 (<85% predicted), despite good effort
- Accelerated heart rate at high work loads
- Low O2 pulse and early plateau (<80% predicted)
- ECG changes of ischemia or arrhythmia
- Excessive BP response, especially diastolic BP (>20 mmHg above baseline) indicative of peripheral vascular disease
- Elevated VE versus VCO2 slope, or nadir of VE/VCO2 curve
- Decreased OUES (slope of VO2 versus logVE)
- Exercise oscillatory ventilation (oscillation in the VE versus time curve)
|
| Pulmonary vascular | - Low peak VO2 (<85% predicted), despite good effort
- Decrease in PaO2 or SpO2 with exercise
- Widening of A-a difference >35
- Failure of ratio of VD to VT to decrease
- Elevated VE versus VCO2 slope, or nadir of VE/VCO2 curve
- Low O2 pulse and early plateau
|
| Metabolic | - Low peak VO2 (<85% predicted), despite good effort
- Low AT (<40% predicted maximal VO2)
- Normal cardiovascular, ventilatory, and gas exchange responses
- Decreased OUES (slope of VO2 versus logVE)
|
| Deconditioning | - Low peak VO2 (<85% predicted), despite good effort
- Low AT (<40% predicted maximal VO2)
- Normal cardiovascular, ventilatory, and gas exchange responses
|
