Reversal of Nocturnal Periodic Breathing in Primary Pulmonary Hypertension After Lung Transplantation

Precapillary Pulmonary Hypertension and Sleep-Disordered Breathing: Is There a Link?

Among patients with sleep apnea the reported prevalence of precapillary pulmonary hypertension (PH) has varied largely, depending on patient selection, disease definition, and associated conditions, in particular chronic pulmonary disease. However, in the absence of comorbidities, PH seems to be rare in patients with sleep apnea. Conversely, sleep-related breathing disorders have been commonly found in patients with PH and they have been associated with an impaired quality of life. Since sleep-related breathing disorders may affect the pulmonary circulation and vice versa, patients with sleep-related breathing disorders should be evaluated for risk factors, symptoms and clinical signs of PH and right ventricular heart failure and patients with PH should be evaluated for sleep apnea. Therapeutic options for patients with sleep apnea and PH may include supplemental oxygen, drugs and positive pressure ventilation. Both nocturnal oxygen administration and acetazolamide have been shown to improve sleep apnea in patients with PH. In addition, oxygen therapy also improved exercise performance. Further studies are needed to corroborate the efficacy of these and other treatments.

Central sleep apnea

Neurophysiologically, central apnea is due to a temporary failure in the pontomedullary pacemaker generating breathing rhythm. As a polysomnographic finding, central apneas occur in many pathophysiological conditions. Depending on the cause or mechanism, central apneas may not be clinically significant, for example, those that occur normally at sleep onset. In contrast, central apneas occur in a number of disorders and result in pathophysiological consequences. Central apneas occur commonly in high-altitude sojourn, disrupt sleep, and cause desaturation. Central sleep apnea also occurs in number of disorders across all age groups and both genders. Common causes of central sleep apnea in adults are congestive heart failure and chronic use of opioids to treat pain. Under such circumstances, diagnosis and treatment of central sleep apnea may improve quality of life, morbidity, and perhaps mortality. The mechanisms of central sleep apnea have been best studied in congestive heart failure and hypoxic conditions when there is increased CO2 sensitivity below eupnea resulting in lowering eupneic PCO2 below apneic threshold causing cessation of breathing until the PCO2 rises above the apneic threshold when breathing resumes. In many other disorders, the mechanism of central sleep apnea (CSA) remains to be investigated.

Central sleep apnea

Central apnea is caused by temporary failure in the pontomedullary pacemaker generating breathing rhythm, which results in the loss of ventilatory effort, and if it lasts 10 seconds or more it is defined as central apnea. This article reviews current knowledge on central sleep apnea.

Recognition and management of complex sleep-disordered breathing

PURPOSE OF REVIEW

The recent rapid evolution of our understanding of the mechanisms involved in control of respiration during sleep has yielded new insights to guide our care of difficult-to-treat sleep apnea patients with complex sleep-disordered breathing. This review will describe these recent advances in the literature and suggest a model for their incorporation into clinical practice.

RECENT FINDINGS

Control of respiration during sleep shows amplified instability relative to that seen during wake in these difficult patients. Baseline (eupneic) carbon dioxide levels as well as the responsiveness of the ventilatory system to changes in carbon dioxide are all-important in this relative instability. Furthermore, the instability seen during sleep varies widely across sleep states. A further refinement of our definition of stable and unstable sleep has been developed that directly informs our understanding of the control of respiration across a night of sleep.

SUMMARY

Complex sleep-disordered breathing is a distinct form of sleep apnea. It has recognizable characteristics that are present without, and often worsened during, positive airway pressure treatment. Both sleep state stability and the behavior of the respiratory control system contribute to this complexity. It is only with a clear understanding of the factors contributing to complex sleep-disordered breathing that implementation of truly effective clinical therapy can be achieved for this disorder, which to date is poorly controlled.