Sleep Abnormalities and Treatment in Emphysema

Abstract

Sleep abnormalities are common in severe emphysema, and include poor sleep quality, the development of nocturnal oxygen desaturation, and the presence of coexistent obstructive sleep apnea. With lower baseline oxygenation and abnormal respiratory mechanics in patients with severe emphysema, alterations in ventilatory control and respiratory muscle function that normally occur during sleep can have profound effects, and contribute to the development of sleep abnormalities. The impact on quality of life, cardiopulmonary hemodynamics, and overall survival remains uncertain. In addition, treatment for chronic obstructive pulmonary disease and its effect on sleep abnormalities have demonstrated conflicting results. More recently, as part of the National Emphysema Treatment Trial, lung volume reduction surgery has been shown to improve both sleep quality and nocturnal oxygenation in emphysema. Although indications for performing an overnight polysomnogram in patients with emphysema have been debated, recommendations have been presented. Future studies investigating disease mechanism and response to therapy in patients with sleep abnormalities and severe emphysema are warranted.Keywords: emphysema; sleep; hypoventilation; apnea; oxygenation Patients with severe emphysema commonly have distinct abnormalities related to sleep that include poor sleep quality (1-4) and the development of nocturnal oxygen desaturation (NOD) (1,(3)(4)(5)(6)(7)(8). Patients with emphysema often complain of difficulty with initiating and maintaining sleep (3), and objective measurements have demonstrated increased sleep latency, decreased total sleep time, and an increased number of nocturnal arousals (1-4). These findings contribute to the excessive daytime sleepiness and early morning awakenings reported in these patients (9-11). As part of the National Emphysema Treatment Trial (NETT), sleep quality and nocturnal oxygenation have been examined in patients with severe emphysema who were being evaluated for lung volume reduction surgery (LVRS) (4, 12).Episodes of NOD are more pronounced during REM sleep (2, 5-7), and can develop despite an awake Pa O 2 . 60 mm Hg. Although predictors for the development of NOD have been identified (3,7,8,(13)(14)(15)(16)(17)(18), its effect on pulmonary hemodynamics and overall survival are still uncertain. In addition, patients with emphysema with coexistent obstructive sleep apnea (OSA), often referred to as the ''overlap syndrome,'' also demonstrate NOD. This review examines the physiological variables that affect sleep quality and nocturnal oxygenation in severe emphysema. In addition, therapeutic interventions, including LVRS, and their impact on sleep quality and overall survival are reviewed. Finally, limitations in the current literature and open questions that remain to be answered are discussed. PHYSIOLOGICAL ALTERATIONS DURING SLEEPVentilation is normally controlled by a combination of two systems: a metabolic system responsible for the automatic changes directly related to gas exchange, and a beha...

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