On Treatment but Still Sleepy

Cause and Management of Residual Sleepiness in Obstructive Sleep Apnea

Sandrine H. Launois; Renaud Tamisier; Patrick Lévy; Jean-Louis Pépin


Curr Opin Pulm Med. 2013;19(6):601-608. 

In This Article

Residual Sleepiness in Treated Obstructive Sleep Apnea Patients

Low CPAP compliance, inadequate CPAP titration leading to residual respiratory events and sleep fragmentation, mask or mouth leaks, complex sleep apnea, behaviorally induced insufficient sleep syndrome (BIISS), depression, sedative medication use and undiagnosed coexisting sleep disorders are the most common explanations for persistent sleepiness.[16,17] In our experience, these potential causes of sleepiness on CPAP often coexist. Thus, each factor has to be thoroughly and systematically evaluated through clinical evaluation, CPAP device report examination, sleep log, actimetry and polysomnography (PSG) on CPAP.

Regarding CPAP compliance, a crucial issue is what CPAP usage can be considered adequate to alleviate sleepiness. The optimal duration of CPAP use actually differs depending on the chosen outcome measures of vigilance:[18] there is a dose–response relationship between various outcome measurements and hours of use, with optimal Epworth score, Multiple Sleep Latency Test (MSLT) and FOSQ scores obtained with 4, 6 and 7.5 h/night, respectively.[18] Whether this relationship reflects a correlation between sleepiness and total sleep duration or residual nocturnal respiratory events during part of the night has never been examined. Some patients tend to use CPAP irregularly, alternating periods of good compliance and periods of CPAP discontinuation.[8] This may affect overall daytime alertness as acute, short-term CPAP withdrawal is associated with a rapid return of subjective and objective sleepiness,[19,20] though not consistently.[21]

Particular attention should be paid to mild sleep deprivation, as it is often ignored or minimized by patients. Sleep log or actimetry can help quantify sleep curtailment. If BIISS appears to contribute to sleepiness, a trial of sleep extension should be recommended as a first step.

CPAP effective pressure is determined by manual in-lab titration or automatic titration with an automatic positive airway pressure device.[22] Regardless of the titration mode, residual respiratory events may persist at the chosen effective pressure in up to 25% of patients.[23,24,25] The presence of residual events is associated with a 4-point difference in the Epworth score between patients with and without persistent apneas and hypopnea.[23] Most CPAP devices now provide daily and mean residual apnea–hypopnea indices (AHIs), and this parameter has to be evaluated carefully in the management of OSA patients still sleepy on CPAP. However, in a patient with persistent sleepiness, a full night PSG on CPAP is necessary to confirm that the chosen pressure is adequate, particularly in rapid eye movement (REM) sleep and in the supine position, and to rule out complex sleep apnea. The PSG will also evaluate sleep architecture, the presence of leaks that may lead to sleep fragmentation and may be coupled with MSLT to rule out central hypersomnia. In a recent study of residual sleepiness patients, two of 20 patients met the criteria for central hypersomnia.[26] Periodic leg movements (PLMs) are commonly cited as a potential cause of persistent sleep fragmentation and sleepiness in OSA patients. However, a comparison between OSA patients with and without persistent sleepiness showed no significant difference in PLM index after 1 year of CPAP treatment.[27]

Even after sleep hygiene improvement, optimization of CPAP treatment and comorbid sleep disorders and depression management, some compliant CPAP users still experience EDS and can be considered as suffering from true residual sleepiness.

Interestingly, the concept of residual sleepiness has not been applied thus far to patients correctly treated with an oral appliance. There may be several reasons: better compliance with oral appliance than with CPAP leading to less residual sleepiness; smaller percentage of initially sleepy patients treated with oral appliance than with CPAP; and a switch to CPAP if EDS has not improved enough with oral appliance. As these appliances have become a widespread alternative to CPAP, this issue deserves to be carefully examined in future studies.