The Clinical Characteristics of Patients With Pulmonary Hypertension Combined With Obstructive Sleep Apnoea

Lu Yan; Zhihui Zhao; Qing Zhao; Qi Jin; Yi Zhang; Xin Li; Anqi Duan; Qin Luo; Zhihong Liu


BMC Pulm Med. 2021;21(378) 

In This Article

Study Background

Pulmonary hypertension (PH) refers to a clinical syndrome involving pulmonary vascular structural and functional changes caused by various aetiologies, leading to a progressive increase in pulmonary vascular resistance and eventually causing right heart failure or even death. Its aetiology is complex, and the clinical symptoms are diverse, with a high rate of misdiagnosis and mortality.[1] PH is characterized by a mean pulmonary artery pressure (mPAP) ≥ 25 mmHg (1 mmHg = 0.133 kPa)[1] measured by right heart catheterization (RHC) at sea level and at rest. The mPAP of a normal adult at rest is 14.0 ± 3.3 mmHg, and its upper limit does not exceed 20 mmHg.[2] Critical PH was once defined as mPAP = 21–24 mmHg.[3] At the 6th World Symposium on Pulmonary Hypertension (WSPH) in 2018, some experts suggested that the PH haemodynamic diagnostic criteria should be revised to mPAP > 20 mmHg,[4] but due to controversy about the cut-off points, there is still a lack of relevant studies on patients with mPAP between 21 and 24 mmHg in China. Therefore, this guideline does not adopt this diagnostic criterion.[5]

According to pathological manifestations, haemodynamic characteristics, and clinical diagnosis and treatment strategies, PH is divided into five categories: ① pulmonary arterial hypertension (PAH); ② pulmonary hypertension caused by left heart disease; ③ pulmonary hypertension caused by hypoxia and/or lung disease; ④ chronic thromboembolic pulmonary hypertension; and ⑤ pulmonary hypertension caused by multiple mechanisms and/or unknown mechanisms. In recent decades, advances in targeted drug therapy have greatly improved the prognosis of PAH. Because of improved diagnostic methods, the number of patients diagnosed with PH has significantly increased. The United States Registry to Evaluate Early and Long-term pulmonary and Arterial Hypertension Disease Management (REVEAL registry) reported that the 5-year survival rate of patients with PAH was still only 61.2%.[6]

Obstructive sleep apnoea (OSA) is characterized by recurrent episodes of partial or complete collapse of the upper airway during sleep, resulting in reduced (hypopnoea) or absent airflow (apnoea) that lasts for at least 10 s and is associated with either cortical arousal or a fall in blood oxygen saturation.[7] OSA, which is present in approximately 25% of adults in the United States, is the leading cause of excessive daytime drowsiness, as well as a cause of reduced quality of life, impaired job performance, and increased risk of motor vehicle collisions.[7]

OSA is associated with an increased incidence of hypertension, type 2 diabetes mellitus, atrial fibrillation, heart failure, coronary heart disease, stroke, and death.[8,9] OSA can be diagnosed by either home- or laboratory-based sleep testing, and effective treatments are available. Dumitrascu et al. studied 169 patients with precapillary PH and found 27 patients with OSA.[10] OSA is very common in patients with PH and is associated with disease progression, but the mechanism linking them remains unclear.[11–13]

OSA is more common in patients with than without PH. It is currently believed that OSA can cause precapillary PH, which belongs to category III PH, or it can exist as a comorbidity of PH, and the combination of the two has a poor prognosis. In the past, it was generally believed that OSA was mechanistically related to PH, but PH was only seen in a small number of patients with OSA, and their degree of correlation was generally mild. Therefore, OSA is often overlooked in the diagnosis, risk stratification, and treatment of PH. Additionally, there is a lack of research on the relationship between OSA and PH in China. We designed this single-centre study to understand the incidence and clinical characteristics of OSA in patients with pulmonary hypertension in China.