terminologies and ranges in CPET testing

$V_e$ : ventilatory volume or minute ventilation. Volume of air expired¹
$V_{O_2}$ : volume of oxygen obtained
peak $V_{O_2}$ : highest oxygen uptake. Max achievable uptake
- marker of aerobic capacity²
- generally ≥ 85% predicted. The higher the better
- ≤ 84% is deemed abnormal³
- < 20 mL/kg/min in elderly
- < 14 mL/kg/min = poor prognosis in heart failure
- ≤ 10 if on beta blockers
$V_{CO_2}$ volume of carbon dioxide expired. Typically increases with $V_{O_2}$ increases until ventilatory threshold is reached then increases more rapidly.⁴
$V_{O_2}\theta$ anaerobic threshold: point of anaerobic metabolism
- $V_{O_2}$ usually at 40-60% peak $V_{O_2}$
- high value: athletic training
- low value: deconditioning
$V_E\theta$ ventilatory threshold: point at which buffer system is not enough to keep up with CO2 production, blood pH falls. ETCO2 increases.⁵
$MVV$ : maximum voluntary ventilations
peak $V_e/MVV$ : ventilatory reserve
- 15-20%
- reduced in athletes
- otherwise reduced in pulmonary limitation
- high in submaximal effort
$V_e/V_{CO_2}$ slope: ventilatory efficiency, marker of V/Q mismatch. Increased slope = worse disease
- normal 25-30
- ≥ 34 = significant cardiopulmonary disease
$V_{O_2}/work$ slope: oxygen uptake per unit of work
- normal 10±1.5 mL/min/watt
- high slope: increased anaerobic demand, high O2 cost (obesity, hyperthyroidism)
- low slope: increased anaerobic work (heart failure, CAD)
$V_{O_2}/kg$ : low = maybe obesity related⁶

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