Selected cardiopulmonary exercise testing variables
| Peak Vo2 Highest oxygen uptake obtained (aerobic capacity) Values vary widely with age, sex, activity level, weight, and disease (< 20 mL/kg/min in elderly; > 90 in elite athletes) Nonspecific but starting point for interpretation and stratification Peak Vo2 ≥ 85% of predicted is generally favorable; ≤ 14 mL/kg/min carries a poor prognosis in heart failure (≤ 10 if on beta-blockers) Ventilatory threshold Point at which anaerobic metabolism increases Vo2 at ventilatory threshold typically is 40%–60% of peak Vo2 A low value is consistent with deconditioning or disease; a high value is consistent with athletic training VE/Vco2 slope Ventilatory volume/carbon dioxide output; reflects ventilatory efficiency Normal 25–30 May be slightly elevated in isolation in otherwise healthy elderly patients Elevated value reflects ventilatory inefficiency or ventilation-perfusion mismatch Values ≥ 34 indicate clinically significant cardiopulmonary disease (heart failure, pulmonary hypertension, chronic obstructive pulmonary disease Higher values = worse prognosis Peak respiratory exchange ratio (VCO2/Vo2) Reflects substrate metabolism Normal < 0.8 at rest; progressively increases during exercise Value > 1.1 signifies physiologically maximal response; lower value suggests submaximal effort Peak heart rate Varies with age, fitness level, use of beta-blockers Should increase linearly with ramped increase in work Peak rate ≥ 85% of predicted is generally favorable Heart rate reserve (Maximum heart rate – resting heart rate) divided by (predicted maximum heart rate – resting heart rate) Reflects chronotropic competence Normal ≥ 80% if not on beta-blocker; ≥ 62% if on beta-blocker; less than this = chronotropic incompetence Heart rate recovery Maximum heart rate minus rate at 1 minute recovery Recovery ≥ 12 bpm is normal; < 12 is abnormal across all populations; < 6 is threshold in heart failure scoring system | Vo2/work slope Oxygen uptake per unit of work Normal is 10 ± 1.5 mL/min/watt Validated with cycle ergometry; not valid with treadmill exercise, as unable to calculate specific unit of work A high slope reflects increased anaerobic demand or high oxygen cost, eg, in obesity or hyperthyroidism; low slope reflects increased anaerobic work, eg, in heart failure or coronary artery disease O2-pulse Oxygen delivered per heart beat; a surrogate for stroke volume Curvilinear increase with exercise Norms based on predicted peak Vo2 and peak heart rate; value ≥ 85% of predicted is favorable Blunted response or decline suggests ventricular failure; response can be falsely high if heart rate is blunted End-tidal Pco2 Reflects perfusion: better cardiac output = better CO2 diffusion In heart failure, values > 33 mm Hg at rest and > 36 mm Hg at ventilatory threshold are favorable; low values = poor prognosis Exercise oscillatory breathing Abnormal breathing pattern often seen in heart failure; no universal definition Sustained visible fluctuations in ventilations support a poorer prognosis Oxygen uptake efficiency slope Additional logarithmic model of ventilatory efficiency In heart failure, values < 1.4 carry a poor prognosis Peak respiratory rate Rarely exceeds 50/min High value suggests pulmonary limitation or exceptional effort Value < 30 suggests submaximal effort Peak Ve/Mvv Ventilatory reserve: peak exercise ventilations (VE) divided by predicted or measured maximum voluntaryventilations (Mvv) Normal: 15%–20% reserve in most people May be reduced or absent in elite athletes; reduced reserve suggests pulmonary limitation; excessive value suggests submaximal effort |
Adapted from information in references 4–7.