Table 1.

Suggested target values for key cardiopulmonary exercise testing variables (cycle ergometry) [1, 5–7, 10, 11, 15]

Variable	Target value	Abnormal
Peak ${\dot{\text{V}}\text{O}}_2$ (exercise capacity)	≥ 85% based on ${\dot{\text{V}}\text{O}}_2$ pred. or > 20 mL O2/min/kg	< 85%/ < 70%/ < 50% (mild/moderate/severe)
${\dot{\text{V}}\text{O}}_2$/WR (aerobic capacity)	≥ 9–10 mL/min/watt1	≤ 8 mL/min/watt
${\dot{\text{V}}\text{O}}_2$ at AT	≥ 40–80% pred. $\dot{\text{V}}\text{O}$ (usually 50–65% of peak ${\dot{\text{V}}\text{O}}_2$)	< 40%/ < 30%/ < 25% (mild/moderate/severe)
Blood pressure	Increase by 10 mmHg per 30 watts	Decrease, inadequate increase
O2 pulse (${\dot{\text{V}}\text{O}}_2$/HR)2	≥ 80%	< 70% pred. during peak exercise
Heart rate reserve (HRR)	≥ 85% pred. (< 15 bpm)	< 85% predicted (but wide range)
Breathing reserve (BR)	≥ 15–20% (or ≥ 11–15 L/min)	< 15–20% (or < 11–15 L/min)
Breathing frequency (BF)	≤ 50/min	≥ 60/min
EqCO2 at AT	25–30 at AT, ≤ 40 after AT	≥ 35 at AT, > 40 after AT;
EqO2 at AT	20–30 at AT, ≤ 40 after AT	≥ 35 at AT, > 40 after AT
$\dot{\text{V}}\text{E}/{\dot{\text{V}}\text{CO}}_2$ slope	25–30 (slightly lower than EqCO2 at AT)	≥ 35 or < 20
RER	≥ 1.05 (ill) or ≥ 1.1 (healthy); > 1.1–1.5 in recovery phase; at rest: > 0.7, < 1.0	< 1 (peak exercise)
PETCO2 (≈ PACO2 ≈ PaCO2)	> 35 mmHg (at rest); > 40 mmHg (during exercise)	< 33 mmHg (at rest), < 3 mmHg increase or > 50 mmHg (peak exercise)
PETO2 (≈ PAO2)	≥ 90 mmHg (at rest), 20–30 mmHg increase during exercise	Lack of increase or decrease during exercise
P(A-a) O23	20 mmHg (at rest); 30 mmHg (during exercise)	> 35 mmHg
P(a-ET) CO24	At rest: minimally positive; during exercise: slightly negative	> 5 mmHg

a arterial, A alveolar, AT anaerobic threshold, bpm beats/minute, CO₂ carbon dioxide, Eq ventilatory equivalent, ET end-tidal, HR heart rate, O₂ oxygen, P pressure, pred. predicted, RER respiratory exchange rate, $\dot{\text{V}}\text{E}/{\dot{\text{V}}\text{CO}}_2$ ventilatory equivalent for carbon dioxide, ${\dot{\text{V}}\text{O}}_2$ oxygen uptake, WR work rate

¹Peak ${\dot{\text{V}}\text{O}}_2$ in obesity should be expressed as L/min or referenced to weight predicted

²O₂ pulse (V̇O₂/HR) peak exercise values vary widely by the same factors that affect normal peak ${\dot{\text{V}}\text{O}}_2$ and HR (e.g., age, body size, gender, Hb concentration, work rate, fitness level)

³P(A-a)O₂ indicates efficacy of O₂ uptake. PAO₂ is calculated using the alveolar air formula (requires PaCO₂ from blood gas analysis [BGA]), PaO₂ is also determined using BGA

⁴P(a-ET)CO₂ indicates efficacy of CO₂ output to the alveoli: PACO₂ is measured as PETCO₂; PaCO₂ is determined by BGA. P(a-ET)CO₂ is slightly positive at rest due to V/Q inhomogeneities (poorly perfused upper lung areas with impaired CO₂ production, PaCO₂ > PACO₂), and negative due to hyperventilation during exercise (PaCO₂ < PACO₂ [difference approximately 4 mmHg])