Figures
- FIGURE 1
The minute ventilation (V′E)/carbon dioxide production (V′CO2) relationship slope in two pulmonary arterial hypertension patients. In (a) the physiological behaviour of ventilation during exercise is preserved in spite of hyperventilation, such that two slopes can be recognised around the respiratory compensation (RC) point (slope 1 (S1)=40.4 and slope 2 (S2)=55.1). In (b) a single slope characterises the V′E/V′CO2 relationship.
- FIGURE 2
The minute ventilation (V′E)/carbon dioxide production (V′CO2) relationship slope in a patient with pulmonary arterial hypertension and preserved physiological behaviour of the V′E/V′CO2 relationship during exercise. In the first part of exercise, the V′E/V′CO2 slope is high and the V′E-axis intercept is close to zero. This means that dead space ventilation progressively increases during exercise. After the end of isocapnic buffering, i.e. at the respiratory compensation (RC) point, the slope becomes steeper and the V′E-axis intercept becomes severely negative showing that dead space ventilation severely increases toward the end of exercise. Reproduced from [32] with permission.
- FIGURE 3
Difference of oxygen uptake efficiency (OUE; oxygen uptake (V′O2)/minute ventilation (V′E)) plateau between a typical pulmonary arterial hypertension (PAH) patient and a “normal” control subject. In normal subjects, OUE typically increases during exercise from rest to plateau and then gradually decreases until the end of exercise. It then further decreases in the immediate recovery period and begins stabilising after about 2 min. In PAH patients, OUE changes in a similar way to control subjects but is always lower than in controls in the transition from rest to the end of exercise. Reproduced from [48] with permission.
Tables
- TABLE 1
Cardiopulmonary exercise test (CPET) determinants of prognosis in risk assessment
CPET parameters Low Risk (<5%) Intermediate risk (5–10%) High risk (>10%) Peak V′O2 mL·kg−1·min−1 >15 11–15 <11 Peak V′O2 % predicted >65 65–35 <35 V′E/V′CO2 slope <36 36–45 >45 V′O2: oxygen uptake; V′E : minute ventilation; V′CO2: carbon dioxide production; V′E/V′CO2 slope: slope of the relationship between V′E and V′CO2.
- TABLE 2
Common cardiopulmonary exercise test findings in patients with pulmonary arterial hypertension
Reduced parameters Increased parameters Peak V′O2 VD/VT during exercise (>30%) WR PA–aO2 differences during exercise (up to 45 mmHg or over) O2 pulse V′O2/WR PETCO2 at rest PETCO2 at AT O2 saturation during exercise (drop >3% without PaCO2 rise) V′O2: oxygen uptake; VD: dead space volume; VT: tidal volume; WR: work rate; PA–aO2: alveolar–arterial oxygen tension difference; PETCO2: end-tidal carbon dioxide tension; AT: anaerobic threshold; PaCO2: arterial carbon dioxide tension.
- TABLE 3
Resting and exercise values in normal subjects and primary pulmonary hypertension (PPH) patients categorised according to severity of reduction in cardiopulmonary exercise test (CPET) aerobic capacity
Values Normal# (n=20) Mild PPH (n=3) Moderate PPH (n=14) Severe PPH (n=22) Very Severe PPH (n=14) Peak V′O2 % predicted range 82–132 65–79 50–64 35–49 <35 Peak V′O2 % predicted 101±19 70±4 58±4 42±5 27±4 Peak V′O2 mL·min−1·kg−1 29.5±6.6 14.5±3.3 12.5±2.2 11.2±2.6 8.1±1.7 AT % predicted 104±16 85±7 75±10 57±9 41±7 AT mL·min−1·kg−1 16.3±3.9 10.4±2.3 9.7±1.3 8.7±2.2 6.8±1.3 Peak O2 pulse % predicted 108±25 86±11 73±8 56±11 39±5 Peak HR % predicted 96±13 83±12 80±8 77±12 70±13 ΔV′O2/ΔWR mL·min−1·W−1 9.6±0.9 8.3±0.5 7.0±1.5 6.0±1.0 5.6±1.3 V′E/V′CO2 at AT % predicted 99±12 142±22 149±21 161±25 219±76 V′E/V′CO2 at AT absolute 29±4 43±6 45±7 46±8 62±20 V′E/V′CO2 slope % predicted 88±11 164±49 148±27 141±32 215±123 V′E/V′CO2 slope absolute 25±3 49±14 45±9 40±10 60±32 Peak V′E % MVV 70±15 63±19 54±9 47±11 43±16 MRT s 12±10 34±9 37±14 47±13 64±15 mPAP mmHg 48±17 63±14 70±18 57±17 CO L min−1 5.1±1.1 4.4±1.4 3.5±1.0 3.8±1.2 PVR mmHg·L−1·min−1 8±4 15±8 18±5 14±6 NYHA symptom class 2.0±0.4 2.5±0.5 2.8±0.6 3.3±0.4 V′O2: oxygen uptake; AT: anaerobic threshold; HR: heart rate; WR: work rate; V′E: minute ventilation; V′CO2: carbon dioxide production; MVV: maximum voluntary ventilation; MRT: mean response time of V′O2 during unloaded cycling; mPAP: mean pulmonary arterial pressure; CO: cardiac output; PVR: pulmonary vascular resistance; NYHA: New York Heart Association; V′E/V′CO2 slope: slope of the relationship between V′E and V′CO2; V′E/V′CO2 at AT: ratio of ventilation to carbon dioxide output at AT; ΔV′O2/ΔWR: increase in oxygen uptake per increase in work rate. #: each CPET parameter is significantly different for all PPH patients compared to that of normal control subjects (p<0.001). Data is reproduced from [20] with permission.
