Original ArticleSleep apnea in precapillary pulmonary hypertension☆
Introduction
It is well-known that precapillary pulmonary hypertension (PH) can occur as a consequence of untreated obstructive sleep apnea (OSA) [1]. In contrast, breathing while asleep has been less extensively investigated in patients with PH. Pilot studies have found that nocturnal oxygen desaturation is common in PH and that these patients may show both OSA and central sleep apnea (CSA). Minai et al. reported significant nocturnal hypoxemia unrelated to apneas/hypopneas in 30 out of 43 patients with PH [2]. Our group was the first to describe CSA closely resembling Cheyne-Stokes respiration in congestive heart failure (CSR-CHF) in six out of 20 patients with idiopathic pulmonary arterial hypertension (IPAH) [3]. In a subsequent study, Ulrich and colleagues observed sleep apnea (mainly CSA) in 17 out of 38 patients with different etiologies of PH [4].
Up until now, the prevalence of sleep-disordered breathing has not yet been investigated in a larger patient cohort with an ascertained diagnosis of PH. Furthermore, the clinical significance of sleep apnea in PH remains to be clarified, although, a negative impact on daytime well-being and disease prognosis may be suspected. With this background, the aims of the present study were to determine the prevalence of sleep-related breathing disorders in PH, to evaluate the frequency of OSA versus CSA in these patients and to identify patient characteristics linked to the presence of sleep-disordered breathing. Finally, we planned to investigate if sleep apnea in PH is related to daytime sleepiness and the severity of the disease. For these purposes, we performed a single-center, prospective polygraphic study in 169 patients of whom the diagnosis of PH had been established by prior right heart catheterisation.
Section snippets
Patient recruitment
The patients participating in the present study were prospectively enrolled at the Pulmonary Hypertension Unit of the University of Giessen Lung Center, Germany. The main inclusion criterion was the presence of PH with a mean pulmonary artery pressure (PAP) at rest of ⩾25 mm Hg. Furthermore, the patients had to be clinically stable in NYHA classes II or III. Exclusion criteria were the following: pulmonary venous hypertension (pulmonary capillary wedge pressure [PCWP] >15 mm Hg), age <18 or >80
Patient characteristics
The patient characteristics are summarized in Table 1, Table 2. The mean age of all patients was 61.3 years and approximately two thirds of them were females. On an average, the patients had normal body weight (mean BMI: 27.2 kg/m2). The majority of them were in NYHA class III. Mean PAP measured at rest was 43.3 mm Hg indicating quite severe PH.
About half of the patients already took vasodilator drugs and were under long-term oxygen therapy. Patients with IPAH were younger, had more severe PH and
Discussion
This is the first study evaluating the prevalence of sleep apnea in a large cohort of patients with a diagnosis of precapillary PH based on right heart catheterisation. Using an AHI cutoff value of >10/hour, we found that about every fourth patient with PH suffered from sleep-disordered breathing. Of the total of 169 patients studied, 27 patients (i.e. 16.0%) had OSA and 18 patients (i.e. 10.6%) had CSA. On an average, the severity of sleep-disordered breathing was only mild-to-moderate. It
Limitations
It should be acknowledged that our study has some limitations. First, we did not include a control group without PH. Nevertheless, it may be justified to compare our data to those from studies evaluating the prevalence of sleep-disordered breathing in the community. As the patients studied were predominantly females with an average BMI lying in the normal range, the prevalence of OSA can be considered to be increased [16]. The same is true for CSA, which has been reported to occur at a markedly
Conclusions
In summary, at least every fourth patient with precapillary PH suffers from mild-to-moderate sleep apnea. Both OSA and CSA seem to occur more frequently in PH than in the general population. The same factors as those which are known to be predictive for the presence of OSA and CSR-CHF, can be found in PH patients with sleep-disordered breathing. The clinical significance of sleep apnea in PH warrants further study.
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2012.11.013.
Acknowledgement
We thank Ute Flechtner and Cornelia Hecker for their excellent technical assistance in performing the sleep studies.
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This manuscript contains parts of the MD thesis of J. Eckermann. The study was supported by an unrestricted research grant from Actelion Pharmaceuticals, Freiburg, Germany.