Fluctuations of Required CPAP Related
to Sleep Stage and Body Position
H. Hein, B. Müllauer and H. Magnussen

Sixteen patients—one woman and 15 men—aged 51±9 years (mean±standard deviation), body mass index (BMI) 33±8 kg/m², apnea/hypopnea index at diagnosis 50±28/h, on long term nasal CPAP therapy (pressure: 10.7±2.1 cm H₂O) were examined. We titrated CPAP manually and continuously throughout the night to obtain the lowest possible pressure value. The lowest pressure needed was 5.9±2.3 cm H₂O, the highest 10.8±3 cm H₂O. With the exception of two cases, maximum pressure was necessary during REM and when the patient was in the supine position. Statistical analysis revealed that the required CPAP level was significantly higher in the supine position than in the lateral position (p=0.02). Manual regulation of pressure did not increase the number of arousals. The observed variations in the "splinting" pressure required supports the use of nasal CPAP devices with auto-titration rather than constant pressure CPAP devices.

PCO Syndrome and Sleep-related Breathing Disorders
A Case Study
Martin Konermann, Sabine Peine, Hilka Rehling and Berthold Rawert

A study was conducted on two female patients long suffering from progressive daily somnolence and a decrease in physical performance. Both patients were considerably overweight and had been since childhood, and both had a history of severe menstrual disorders. The patients were childless, despite one of the female's exhaustive attempts to conceive. Each patient suffered from hypertestosteronemia, a metabolic syndrome, obstructive sleep apnea at polysomnography, and an obesity-related hypoventilation syndrome. Diagnoses of PCO Syndrome, metabolic syndrome, overlap syndrome (obstructive sleep apnea and obesity-related hypoventilation) were established. One patient received nocturnal nCPAP treatment and the other received nBiPAP treatment. The PCO Syndrome was treated by applying a combination of estrogen and gestagen. Polysomnographic findings and a daily sense of well-being were considerably improved with therapy.

The Effects of Short Daytime Naps
for Five Consecutive Days
Mitsuo Hayashi, Hirokazu Fukushima and Tadao Hori

The aim of the present study was to examine the effects of short naps (less than 20 min) at noon for \five consecutive days. Seven young adults (21-24 yrs) who had normal sleep-wake habits without habitual daytime napping participated in both the Nap and the No-nap conditions. During the Nap week between Monday and Friday, the subjects went to bed at 12:40 and were awakened at 13:00. During the No-nap week, they read a newspaper, sitting on a semi-reclining chair during that time. Subjective sleepiness and fatigue were evaluated immediately before and after napping and twice in the mid-afternoon (14:40 and 16:30). A visual detection task was also performed in the mid-afternoon. The subjects took a nap for approximately 12 min every five days. Sleep inertia occurred even after such a short nap. However, it was reduced as a function of days and became similar to the No-nap week on the fourth day. In the mid-afternoon, sleepiness was suppressed by not only taking a nap, but also taking it continuously for three days or more. These findings suggest that even a short nap of less than 20 min would cause sleep inertia, however, it would have positive effects upon mid-afternoon sleepiness. Furthermore, the effects of a short nap are enhanced by taking it for more than three consecutive days.

Cognitive Dysfunction in Sleep-related
Breathing Disorders: A Meta-analysis
Stephany Fulda and Harmut Schulz

Sleep related breathing disorders (SRBD) are usually associated with impaired daytime functioning. The magnitude of this impairment might vary for different neuropsychological functions. Our objective was to assess cognitive dysfunction in SRBD patients. Different medical and psychological databases (Evidence Based Medicine, Medline, Embase, PsychInfo, PsychLit, The Eric Database, BiblioSleep) were searched (last search, December 2000). The reference lists of articles were checked and several journals and conference proceedings were hand-searched. We selected all observational studies comparing patients with an established diagnosis of SRBD to non-sleep disordered control groups, to clinical control groups, or to population norms on neuropsychological or psychometric performance measures, including computer-assisted tests and driving simulators. We rated the quality of each study according to criteria of external validity, internal validity, statistical validity, and the level of evidence. Outcome measures were classified according to a taxonomy of neuropsychological functions and statistically analyzed using meta-analytical techniques. Fifty-four studies reporting cognitive functioning of SRBD patients were reviewed. A total of 1,635 patients were compared with 1,737 control subjects. Twenty-eight studies provided adequate statistics and were integrated further. SRBD patients showed moderate to large reductions in mental flexibility, visual delayed-memory retrieval, and driving simulation performance (pooled effect size estimates ranged from 0.61 to 0.72). Small to moderate reductions were found for focused and sustained attention, verbal delayed-memory retrieval, verbal fluency and composite measures of general intellectual functioning (pooled effect size estimates ranged from 0.17 to 0.51). No difference was observed for divided attention, concept formation and reasoning, and verbal or visual immediate-memory performance. Data integration was not undertaken in the areas of attention-span and motor functions due to large between-study heterogeneity, and in the areas of perception, alertness, selective attention, vigilance, constructional performance, learning performance, executive functions and verbal and performance IQ measures due to insufficient data. Our conclusions were that cognitive performance of SRBD patients was impaired, yet there are remarkable differences between various neuropsychological functions and subfunctions. The integrated data show convincingly that disordered breathing during sleep is a risk factor for cognitive functioning during the daytime.