Table 4– Capillary carbon dioxide tension (Pc,CO2) and expiratory gases at rest and during maximal exercise
ParameterRestMaximal exercise
ControlIPAHCTEPHANOVA p-valueControlIPAHCTEPHANOVA p-value
Subjects n372116372116
Pc,CO2 mmHg38.1 (32.0–42.1)31.7### (24.1–37.6)32.8### (27.1–38.2)<0.00137.5 (27.4–44.2)31.6### (22.8–39.0)29.5### (22.8–40.7)<0.001
PET,CO2 mmHg35.8 (26.5–44.7)27.2*,### (20.4–35.0)22.7### (20.3–35.1)<0.00139.4 (26.3–48.3)28.3**,### (16.5–38.9)19.7### (13.8–34.0)<0.001
Pc−ET,CO2 mmHg2.3 (-4.8–8.1)4.4*** (0.9–9.0)8.6### (3.0–13.7)<0.001-1.9 (-5.7–6.2)4.1***,### (0.0–8.8)9.3### (3.3–13.1)<0.001
VD/VT %42 (13–64)46** (29–61)58### (39–66)<0.00123 (5–51)35***,### (19–52)49### (29–57)<0.001

  • Data are presented as median (range), unless otherwise stated. IPAH: idiopathic pulmonary arterial hypertension; CTEPH: chronic thromboembolic pulmonary hypertension; PET,CO2: end-tidal carbon dioxide tension; Pc–ET,CO2: capillary to end-tidal carbon dioxide gradient (Pc,CO2 – PET,CO2); VD: dead space volume (calculated according to Bohr’s formula); VT: tidal volume. ###: p<0.001 for difference from control; *: p<0.05 for difference between IPAH and CTEPH; **: p<0.01 for difference between IPAH and CTEPH; ***: p<0.001 for difference between IPAH and CTEPH.