Outcomes of CPAP treatment in a sleep laboratory specialized in neuropsychiatry

The rapidly increasing number of sleep laboratories implicates their specialization into various fields of sleep medicine. In our sleep laboratory that specializes in neuropsychiatry, patients with the symptoms typical for the obstructive sleep apnea/hypopnea syndrome (OSAHS) were routinely redirected to a local respiratory clinic. Some patients, however, admitted to our center for other reasons revealed OSAHS in nocturnal polysomnography. The purpose of this retrospective study was to assess the outcome of CPAP in treating the sleepiness in this group of patients. Our material consisted of 36 patients who started CPAP therapy due to OSAHS diagnosed in our laboratory in the year 2000 and who came for a routine checkup in 2001. The sleepiness was assessed by using the Epworth Sleepiness Scale (ESS). After CPAP, the mean group ESS score decreased from 10.9 +/-4.4 to 8.5 +/-4.3 points (P<0.01). Some patients showed, however, persisting excessive sleepiness (PTS) after CPAP, defined as ESS >or=12. We overviewed the documentation of those patients in search for the possible causes of PTS. We identified the following causes: narcolepsy - 1 patient, insufficient CPAP pressure - 1 patient, low CPAP compliance, fewer than 2 h/night, - 2 patients. In 5 other patients we found CPAP compliance to be between 2.0 and 4.5 h/night, which is less likely to be the cause of PTS. In 1 patient no cause was identified. Our patients showed relatively mild sleepiness before CPAP and only a slight improvement under CPAP. The CPAP noncompliance seems the most prevailing reason for CPAP failure, but in some patients the cause of PTS could not be unraveled by using standard diagnostic tools and some additional measures are to be employed to resolve the issue.