Relevant data from studies used to demonstrate the reviews conclusions
| First author [ref.] and parameter | HVS suspects | Controls | p-value |
| Kinnula [28] | n=10 | n=10 | |
| Resting PaCO2 kPa | 4.10±0.60 | ND | |
| Resting pH | 7.46±0.06 | ND | |
| VeqCO2 at 40–50 W exercise | 41.8±6.00 | 30.0±3.30 | 0.01 |
| Jack [29] | n=23 | n=23 | |
| Resting PaCO2 kPa | 3.87±0.60 | ND | |
| VeqCO2 at 40 W exercise | 38.4±5.70 | 28.9±2.50 | ND |
| Brat [19] | n=29 | n=29 | |
| Resting arterial PaCO2 kPa | 4.80 (4.40–4.93) | 4.80 (4.53–5.07) | 0.44 |
| Resting arterial pH | 7.45 (7.43–7.47) | 7.44 (7.43–7.45) | 0.07 |
| Peak exercise PaCO2 kPa | 3.87±0.53 | 4.67±0.40 | <0.01 |
| Peak exercise arterial pH | 7.47 (7.46–7.50) | 7.40 (7.37–7.42) | <0.01 |
| Resting d/VT | 0.21±0.11 | 0.22±0.10 | 0.77 |
| Peak exercise d/VT | 0.18±0.05 | 0.13±0.06 | <0.01 |
| VeqCO2 at rest | 38.0 (33.0–44.0) | 37.0 (32.0–40.0) | 0.31 |
| VeqCO2 at peak exercise | 38.0 (35.0–43.0) | 31.0 (27.0–34.0) | <0.01 |
| V′E/V′CO2 slope | 37.0 (33.0–34.0) | 27.0 (24.0–30.0) | <0.01 |
| Troosters [30] | n=24 | n=20 | |
| NQ scores | 30.3±9.70 | 7.90±5.20 | <0.001 |
Data are presented as mean±sd or median (interquartile range), unless otherwise stated. HVS: hyperventilation syndrome; PaCO2: arterial carbon dioxide tension; VeqCO2: ventilatory equivalent for carbon dioxide; d/VT: ratio of dead space volume to tidal volume; ND: not disclosed in study. V′E/V′CO2 slope: gradient of the V′E (abscissa) and V′CO2 (ordinate) slope; NQ: Nijmegen Questionnaire.