Paper
Oxygen therapy for pulmonary arterial hypertension: We need to rethink and investigate
Published Mar 8, 2020 · S. Green, D. Stuart
Respirology
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Abstract
Pulmonary arterial hypertension (PAH) is characterized by progressive increases in mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR), resulting in right ventricular failure and death. Primary treatment of PAH (Class 1) is based on the use of four classes of drugs in the form of monotherapy or combination therapy. Despite significant advances in drug-based treatment of PAH and improvements in survival rates, the prognosis for PAH patients remains poor. PAH drugs target mechanisms involved in vasodilation of pulmonary arterial vessels (Fig. 1A), but their vascular effects are not limited to the pulmonary circulation, probably contributing to side effects and limiting drug efficacy. Thus, there is a need for additional therapeutic approaches. In contrast to PAH drugs, oxygen is a potent and selective pulmonary vasodilator. Yet, the use of supplemental oxygen (i.e. O2 therapy) to treat PAH is often viewed as being outdated and ineffective. Recent guidelines do not recommend O2 therapy for PAH patients, except for the minority of patients who develop severe hypoxaemia (percent arterial O2 saturation <91%). These recommendations are based on a single negative finding and linked to the prescription of O2 therapy in chronic obstructive pulmonary disease (COPD) patients who develop severe hypoxaemia. As most PAH (Class 1) patients do not develop severe hypoxaemia, this rules out O2 therapy for most patients. But, does this recommendation accurately reflect the available clinical evidence and is it based on current scientific understanding of effects of alveolar O2 on pulmonary arterial vessels? With respect to clinical evidence of acute effects of O2 on the pulmonary circulation, we reviewed nine studies involving a total of 11 cohorts of PAH patients (paediatric and adult) exposed to 100% O2 for 15–30 min under right heart catheter conditions. All but one study showed that O2 significantly reduced PVR by ~20–30% and mPAP by
Oxygen therapy may be a valuable treatment option for pulmonary arterial hypertension, but current guidelines should reconsider its use for most patients.
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