CPET as a diagnostic tool
I have seen some people post their CPET data but I think it's probably one of the more informative tests for helping people figure out their subtype/cause of exercise intolerance. They usually send you a summary report but will send you the raw data if you ask. With AI, it's been really helpful to break down to help hone in on what is most likely to be causing my symptoms.
Key CPET numbers (done at altitude ~5,280 ft):
- Peak VO2: 41.3 mL/kg/min (91% predicted)
- Anaerobic threshold (AT): 21.9 mL/kg/min (53% of peak) at HR 112
- O2 pulse (VO2/HR): rose to 17 mL/beat at AT, plateaued 16-18 through most of exercise, terminal rise to 18.7 (92% predicted)
- Peak HR: 191 (98% predicted)
- VE/VCO2 slope: 28.99 (normal, <30)
- SpO2: 97-99% throughout
- BP: 112/68 rest → 170/60 peak (normal)
- HR recovery: 191 → 192 at 8 sec, 194 at 17 sec, 181 at 37 sec, 174 at 47 sec (delayed)
- RER at peak: 1.15 (genuine max effort)
What the data ruled OUT:
Pulmonary vascular disease / pulmonary hypertension. Normal VE/VCO2 (26 at AT, 30 at peak; slope 28.99). Normal Vd/Vt. No exertional desaturation. PVD typically shows VE/VCO2 at AT ≥34 and elevated Vd/Vt.
Primary cardiac limitation (cardiomyopathy, chronotropic incompetence). Peak HR 98% predicted, O2 pulse peak 92% predicted, normal BP response. Pure cardiac limitation produces earlier O2 pulse plateau with lower absolute peak.
Pure deconditioning. Peak VO2 at 91% predicted is too preserved to explain functional symptoms by deconditioning alone. Deconditioning produces proportionally reduced values with normal curve shapes — not the O2 pulse plateau pattern.
Significant ventilatory inefficiency. Normal VE/VCO2 and ventilatory reserve.
What the data ruled IN (or strongly suggested):
Peripheral oxygen extraction limitation. The O2 pulse plateau from AT through most of exercise is the signature. In a normal system, O2 pulse continues rising throughout exercise. A plateau with otherwise preserved cardiopulmonary parameters localizes the problem to muscles' ability to extract/use oxygen. This is the mitochondrial/microvascular pattern.
Autonomic component (probable, layered on top). Elevated resting HR (93), delayed HR recovery (HR stayed at 191-194 for first 17+ seconds post-exercise), and low resting PETCO2 (25 mmHg, suggesting resting hyperventilation). Not diagnostic for POTS without orthostatic testing.
What the CPET CANNOT answer:
- Mitochondrial vs. microvascular within the peripheral extraction bucket (needs 31P-MRS or NIRS)
- POTS or specific autonomic patterns (needs orthostatic testing)
- Structural cardiac issues (needs echo)
- Severity of muscle pathology (Wüst's group does biopsy + respirometry)
- 2-day PEM-specific decline (single CPET only captures the first-day exertion)
Quick note some of my other data suggests mitochondrial issues as more of a thing than microvascular, so I am trying to target that more with treatment.