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Pulmonary hypertension (PH) is a condition of raised pulmonary artery pressure (PAP), which may be secondary to a number of causes, one of which is sleep disordered breathing (SDB). When PH complicates SDB, it carries a significant burden of morbidity and mortality due to the risk of progression to right ventricular failure over time. This narrative review will cover the definition and classification of PH, and explore the epidemiology of PH in SDB. The mechanisms by which the two conditions are linked will be reviewed. Repetitive hypoxia with or without hypercapnia alongside frequent arousals can result in important metabolic and pulmonary vascular consequences for the left and right heart. MEDLINE was used to search for all relevant articles and abstracts published from January 1960 to October 2019 inclusive (in all languages). Current best practice in the investigation and management of PH complicating SDB will be reviewed. Important diagnostic investigations and when to consider and screen further for PH in patients with SDB will be discussed. Optimal disease management must include control of SDB with therapy.Additional treatment options will be reviewed. Areas for further research will be highlighted.

Pulmonary hypertension (PH) is a recognised and significant complication of chronic lung disease (CLD) and hypoxia (referred to as group 3 PH) that is associated with increased morbidity, decreased quality of life and worse survival. The prevalence and severity of group 3 PH varies within the current literature, with the majority of CLD-PH patients tending to have non-severe disease. The aetiology of this condition is multifactorial and complex, while the prevailing pathogenetic mechanisms include hypoxic vasoconstriction, parenchymal lung (and vascular bed) destruction, vascular remodelling and inflammation. Comorbidities such as left heart dysfunction and thromboembolic disease can further confound the clinical picture. Noninvasive assessment is initially undertaken in suspected cases (e.g.cardiac biomarkers, lung function, echocardiogram), while haemodynamic evaluation with right heart catheterisation remains the diagnostic gold standard. For patients with suspected severe PH, those with a pulmonary vascular phenotype or when there is uncertainty regarding further management, referral to specialist PH centres for further investigation and definitive management is mandated. No disease-specific therapy is currently available for group 3 PH and the focus of management remains optimisation of the underlying lung therapy, along with treating hypoventilation syndromes as indicated.