Hypoxemia during sleep and overnight rostral fluid shift in pulmonary arterial hypertension: a pilot study

Sleep-related disorders in patients with precapillary pulmonary hypertension

Precapillary pulmonary hypertension (PcPH) is associated with the development of sleep-related disorders and impairment of sleep quality. With growing recognition of the clinical relevance of sleep-related conditions in PcPH, this narrative review seeks to discuss the spectrum of disorders encountered in clinical practice, pathophysiological mechanisms linking PcPH with sleep-related disorders, and potential therapeutic considerations. Current evidence demonstrates a higher prevalence of impaired sleep quality, sleep-disordered breathing, sleep-related hypoxia, and restless leg syndrome in patients with PcPH. These sleep-related disorders could further lead to impairment of quality of life in a patient population with already a high symptom burden. Recent data suggest that sleep-related hypoxia is strongly linked to worse right ventricular function and higher risk of transplantation or death. However, limited studies have investigated the role of oxygen therapy or positive airway pressure therapy improving symptoms or outcomes. Abnormal iron homeostasis is highly prevalent in PcPH and may contribute to the development of restless legs syndrome/periodic limb movement of sleep. To improve sleep management in PcPH, we highlight future research agenda and advocate close collaboration between pulmonary hypertension specialists and sleep physicians.

Relationship between obstructive sleep apnea and pulmonary hypertension: past, present and future

INTRODUCTION

Obstructive sleep apnea (OSA) is a widely prevalent condition with consequent multiple organ systems complications. There is consensus that OSA is associated with negative effects on pulmonary hemodynamics but whether it contributes to development of clinical pulmonary hypertension (PH) is unclear.

AREAS COVERED

In this review, we (1) highlight previous studies looking into the possible bidirectional association of OSA and PH, focusing on those that explore clinical prognostic implications, (2) explore potential pathophysiology, (3) discuss the new metrics in OSA, (4) describe endo-phenotyping of OSA, (5) recommend possible risk assessment and screening pathways.

EXPERT OPINION

Relying only on symptoms to consider a sleep study in PH patients is a missed opportunity to detect OSA, which, if present and not treated, can worsen outcomes. The potential prognostic role of sleep study metrics such as oxygen desaturation index (ODI), hypoxic burden (HB) and ventilatory burden (VB) in OSA should be studied in prospective trials to identify patients at risk for PH. AHI alone has not provided clarity. In those with PH, we should consider replacing ambulatory overnight pulse oximetry (OPO) with home sleep studies (HST). In PH patients, mild OSA should be sufficient to consider PAP therapy.

Sleep-Disordered Breathing in Adults with Precapillary Pulmonary Hypertension: Prevalence and Predictors of Nocturnal Hypoxemia

PURPOSE

To evaluate the frequency of sleep-disordered breathing (SDB) and predictors of the presence of nocturnal desaturation in adults with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension.

METHODS

Outpatients with a hemodynamic diagnosis of precapillary pulmonary hypertension who underwent portable polysomnography were evaluated. Diagnosis and severity of SDB were assessed using three well-established respiratory disturbance index (RDI) thresholds: 5.0/h, 15.0/h, and 30.0/h, while nocturnal hypoxemia was defined by the average oxygen saturation (SpO₂) < 90%. Multiple linear regression analysis evaluated the potential relationships among explanatory variables with the dependent variable (average SpO₂ values), with comparisons based on the standardized regression coefficient (β). The R-squared (R²; coefficient of determination) was used to evaluate the goodness-of-fit measure for the linear regression model.

RESULTS

Thirty-six adults were evaluated (69.4% females). The majority of the participants (75.0%) had SDB (26 with obstructive sleep apnea [OSA] and one with central sleep apnea [CSA]); while 50% of them had nocturnal hypoxemia. In the linear regression model (R² = 0.391), the mean pulmonary artery pressure [mPAP] (β - 0.668; p = 0.030) emerged as the only independent parameter of the average SpO₂.

CONCLUSION

Our study found that the majority of the participants had some type of SDB with a marked predominance of OSA over CSA, while half of them had nocturnal desaturation. Neither clinical and hemodynamic parameters nor the RDI was a predictor of nocturnal desaturation, except for mPAP measured during a right heart catheterization, which emerged as the only independent and significant predictor of average SpO₂.

Development and Validation of a Nomogram for Predicting Obstructive Sleep Apnea in Patients with Pulmonary Arterial Hypertension

PURPOSE

Patients with pulmonary arterial hypertension (PAH) are at high risk for obstructive sleep apnea (OSA), which may adversely affect pulmonary hemodynamics and long-term prognosis. However, there is no clinical prediction model to evaluate the probability of OSA among patients with PAH. Our study aimed to develop and validate a nomogram for predicting OSA in the setting of PAH.

PATIENTS AND METHODS

From May 2020 to November 2021, we retrospectively analyzed the medical records of 258 patients diagnosed with PAH via right-heart catheterization. All participants underwent overnight cardiorespiratory polygraphy for OSA assessment. General clinical materials and biochemical measurements were collected and compared between PAH patients with or without OSA. Lasso regression was performed to screen potential predictors. Multivariable logistic regression analysis was conducted to establish the nomogram. Concordance index, calibration curve, and decision curve analysis were used to determine the discrimination, calibration, and clinical usefulness of the nomogram.

RESULTS

OSA was present in 26.7% of the PAH patients, and the prevalence did not differ significantly between male (29.7%) and female (24.3%) patients. Six variables were selected to construct the nomogram, including age, body mass index, hypertension, uric acid, glycated hemoglobin, and interleukin-6 levels. Based on receiver operating characteristic analysis, the nomogram demonstrated favorable discrimination accuracy with an area under the curve (AUC) of 0.760 for predicting OSA, exhibiting a better predictive value in contrast to ESS (AUC = 0.528) (P < 0.001). Decision curve analysis and clinical impact curve analysis also indicated the clinical utility of the nomogram.

CONCLUSION

By establishing a comprehensive and practical nomogram, we were able to predict the presence of OSA in patients with PAH, which may facilitate the early identification of patients that benefit from further diagnostic confirmation and intervention.

The association between sleep-related breathing disorders and pre-capillary pulmonary hypertension: A chicken and egg question

The level of knowledge about a direct link between sleep-related breathing disorders and pre-capillary pulmonary hypertension (PH) is low and there is a chicken and egg question to know which disease causes the other. On one hand, sleep-related breathing disorders are considered as a cause of group 3 PH, in the subgroup of patients with hypoxemia without lung disease. Indeed, isolated sleep-related breathing disorders can lead to mild pre-capillary PH on their own, although this is rare for obstructive sleep apnea and difficult to establish for obesity-hypoventilation syndrome, the evolution towards PH being observed especially in the presence of respiratory comorbidities. The hemodynamic improvement under treatment with continuous positive airway pressure or non-invasive ventilation also argues for a causal link between pre-capillary PH and sleep-related breathing disorders. On the other hand, patients followed for pre-capillary PH, particularly pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension, develop more sleep-related breathing disorders than the general population, especially sleep hypoxemia, central sleep apnea in patients with severe PH and obstructive sleep apnea in older patients with higher body mass index. The main objective of this article is therefore to answer two main questions, which will then lead us to discuss the bilateral link between these diseases: are sleep-related breathing disorders independent risk factors for pre-capillary PH and does pre-capillary PH induce sleep-related breathing disorders? In other words, who is the chicken and who is the egg?