Effect of Normobaric Hypoxia on Exercise Performance in Pulmonary Hypertension

Effect of a day-trip to altitude (2500 m) on exercise performance in pulmonary hypertension: randomised crossover trial

“…In addition to the lower P aCO 2 , the adaptive response was shown by the increased heart rate at rest and during exercise, resulting in a higher CO, as measured by echocardiography at rest and end-exercise at 2500 m versus 470 m. This resulted in an increased D aO 2 at rest, but not end-exercise at 2500 m versus 470 m. The increase in D aO 2 during cycling exercise was higher at 470 m compared to 2500 m, potentially contributing to the longer exercise time ( table 3 ). The similar D aO 2 at end-exercise in the presently investigated PH patients is in line with our previous study investigating PH patients under normobaric hypoxia versus ambient air, but also in PH patients breathing oxygen-enriched air [ 10 , 14 ].…”

“…The PAP was significantly higher at 2500 m versus 470 m both at rest and at end-exercise along with an increased CO, related to the increased heart rate, and a higher PVR at rest, but not end-exercise as assessed by echocardiography. The higher TRPG and PVR at rest suggests that the effect of HPV was present after >3 h at altitude, which is consistent with existing literature [ 33 , 34 ], although in previous studies PAP remained unchanged by exposing patients with pre-capillary PH to normobaric hypoxia for 20 min [ 12 ] and with consecutive CWRET [ 14 ] which was probably related to the shorter exposure. The similar change of the TRPG and CO with exercise at both altitudes resulted in an unchanged pressure–flow slope during exercise at 2500 m versus 470 m. Since a steeper increase in TRPG/CO slope was linked to worse survival, the similar slope found in our study may be a sign that a short-term exposure to a comparable altitude does not acutely harm the cardiopulmonary system; however, our study was not powered to firmly address safety in PH patients going to altitude [ 16 ].…”

“…In contrast, muscular and cerebral deoxygenation may well have contributed to exercise limitation at altitude, which is further supported by the significantly higher lactate. Our previous study in PH patients under short-term normobaric hypoxia showed comparable results [ 14 ]; however, COPD patients at similar altitude revealed a reduction in CTO and MTO [ 30 ].…”

“…Compared to patients with moderate to severe COPD experiencing a 54% reduction in CWRET-time at 2590 m [ 30 ], the corresponding reduction of 22.9% we observed in patients with PH at similar altitude was less pronounced, but similar to the reduction in CWRET time of 25.8% reported in elite cyclists at 2340 m [ 31 ]. Of interest, in a recent study in patients with PH exposed to normobaric hypoxia ( F IO 2 15%) for 30–60 min corresponding to an altitude equivalent of 2500 m we found that the CWRET cycling-time was reduced by 7% [ 14 ], i.e. to a lesser extent compared to patients in the current study exposed to a comparably reduced inspiratory oxygen partial pressure at real altitude, but for a considerably longer time of 6–7 h. In parallel, a pilot trial investigating nine patients with PAH/CTEPH at 2048 m found a reduction in 6MWD and CWRET-time compared to 490 m [ 32 ].…”

“…Overall, there is still insufficient scientific knowledge on pathophysiological changes of PH under hypoxic conditions and their clinical implications, which impedes adequate counselling of PH patients for their upcoming mountain journey [ 13 ]. In a recent study in patients with PH exposed to simulated altitude by breathing hypoxic air ( F IO 2 0.15, altitude equivalent 2500 m) we found that short-term exposure to normobaric hypoxia was well tolerated, but reduced median constant work-rate exercise test (CWRET) cycling time without significantly altering pulmonary haemodynamics by echocardiography and that PVR resulted as the best predictor for exercise time [ 14 ]. Tricuspid regurgitation pressure gradient (TRPG)/cardiac output (CO) ratio is an established measure to assess total pulmonary resistance and potential surrogate of PVR, especially during exercise, and was shown to predict survival in PH [ 15 , 16 ].…”