Nocturnal hypercapnia with daytime normocapnia in patients with advanced pulmonary arterial hypertension awaiting lung transplantation

A narrative review on the management of patients awaiting lung transplantation in Japan

Background and Objective

The number of lung transplantations performed in Japan is increasing, and post-transplant outcomes are relatively favorable. A major concern is the extremely long waiting time and the high mortality rate on the waitlist. The management of patients before transplantation is very important and essential for further improvement of outcomes. In this review, we summarize the management of patients awaiting lung transplantation in Japan.

Methods

A literature search was conducted via PubMed in November 2022 using the following keywords: lung transplantation, waiting, management, recipient, and Japan. Peer-reviewed academic journal articles published in English were also included.

Key Content and Findings

A growing number of studies have evaluated the management of pre-transplant patients. This includes infection control, vaccination, respiratory disease-specific treatment, malignancy, nutrition, rehabilitation, psychosocial assessment, and health-related quality of life (HRQOL) for patients on the waitlist. Each is important, and various evaluation methods and strategies to improve outcomes have been reported.

Conclusions

Proper and multifaceted management of pretransplant patients is extremely important to reduce the mortality of candidates for lung transplantation. Integrated management is crucial to the success and survival of lung transplant recipients.

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?

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

Sleep-related breathing disorders, including sleep apnea and hypoxemia during sleep, are common in pulmonary arterial hypertension, but the underlying mechanisms remain unknown. Overnight fluid shift from the legs to the upper airway and to the lungs promotes obstructive and central sleep apnea, respectively, in fluid-retaining states. The main objective was to evaluate if overnight rostral fluid shift from the legs to the upper part of the body is associated with sleep-related breathing disorders in pulmonary arterial hypertension. In a prospective study, a group of stable patients with idiopathic, heritable, related to drugs, toxins, or treated congenital heart disease pulmonary arterial hypertension underwent a polysomnography and overnight fluid shift measurement by bioelectrical impedance in the month preceding or following a one-day hospitalization according to regular pulmonary arterial hypertension follow-up schedule with a right heart catheterization. Results show that among 15 patients with pulmonary arterial hypertension (women: 87%; median (25-75th percentiles); age: 40 (32-61) years; mean pulmonary arterial pressure 56 (46-68) mmHg; pulmonary vascular resistance 8.8 (6.4-10.1) Wood units), two patients had sleep apnea and eight (53%) had hypoxemia during sleep without apnea. The overnight rostral fluid shift was 168 (118-263) mL per leg. Patients with hypoxemia during sleep had a greater fluid shift (221 (141- 361) mL) than those without hypoxemia (118 (44-178) mL, p = 0.045). In conclusion, this pilot study suggests that hypoxemia during sleep is associated with overnight rostral fluid shift in pulmonary arterial hypertension.