Martin A. King

Health-related quality of life in narcolepsy

Narcolepsy is a chronic sleep disorder characterised by symptoms of excessive daytime sleepiness and cataplexy. The aim of this study was to describe the health‐related quality of life of people with narcolepsy residing in the UK. The study comprised a postal survey of 500 members of the UK narcolepsy patient association, which included amongst other questions the UK Short Form 36 (SF‐36), the Beck Depression Inventory (BDI), and the Ullanlinna Narcolepsy Scale (UNS). A total of 305 questionnaires were included in the final analysis. The results showed that the subjects had significantly lower median scores on all eight domains of the SF‐36 than normative data, and scored particularly poorly for the domains of role physical, energy/vitality, and social functioning. The BDI indicated that 56.9% of subjects had some degree of depression. In addition, many individuals described limitations on their education, home, work and social life caused by their symptoms. There was little difference between the groups receiving different types of medication. This study is the largest of its type in the UK, although the limitations of using a sample from a patient association have been recognised. The results are consistent with studies of narcolepsy in other countries in demonstrating the extensive impact of this disorder on health‐related quality of life.

Periodic limb movement in a community population detected by a new actigraphy technique

BACKGROUND Periodic limb movements (PLMs) have been studied in both community and sleep clinic populations using polysomnography. An alternative detection method is actigraphy. Our aims were to determine the frequency of PLMs, measured by actigraphy in a community sample, and to assess the relationships of PLMs with age, gender, and reported sleep-related symptoms. METHODS Volunteers had bilateral foot actigraphy (Cambridge Neurotechnology) at home and completed sleep questionnaires. Actigraphy was scored for PLMs per hour in bed (PLMI) and statistical analysis performed to assess possible associations. RESULTS PLMI (mean of two nights) ranged from 0 to 60.3 and 37% of the sample had a PLMI> or =5. Men had significantly higher PLMIs than females (P=0.003) but PLMI was not correlated with age. There was a modest but significant correlation between subjectively reported restless leg severity and PLMI (r=0.238; P=0.003), but none with reported sleepiness. CONCLUSIONS This actigraphy technique is a practical and reliable tool for community studies. A large proportion of this community sample, particularly men, had PLMs. PLMI was not correlated with age or Epworth Sleepiness Score.

Treatment of ventilatory failure in the Prader-Willi syndrome

Hypercapnic respiratory failure is a common cause of death in the Prader-Willi syndrome. Its relationship to sleep-disordered breathing has not been established and there are no reports of its successful treatment. We have retrospectively reviewed the records of four patients with the syndrome, who developed ventilatory failure. Daytime arterial blood gas tensions and overnight oximetry traces before and during treatment were compared. Each patient had severe sleep-disordered breathing in association with daytime ventilatory failure. The median overnight mean arterial oxygen saturation (Sa,O2) was 82% and the median minimum was only 41.5%. Initial treatment was with nasal intermittent positive pressure ventilation, and in each case the daytime arterial blood gas tensions were normalized. The patients were maintained on nasal continuous positive airway pressure at night after discharge. Compliance has been good, and at last follow-up (after a median of 4.8 yrs) the daytime arterial gas tensions remained normal, while the median overnight mean arterial oxygen saturation was 95.5% and the median minimum was 84.5%. This study of patients with the Prader-Willi syndrome shows that daytime ventilatory failure is associated with sleep-disordered breathing. It can be reversed with nocturnal noninvasive ventilation and maintenance treatment with continuous positive airway pressure is well tolerated, with no deterioration in respiratory parameters.

Choosing a negative pressure ventilation pump: are there any important differences?

Five negative pressure ventilator pumps were assessed to determine whether there were any differences in performance which were likely to be of clinical importance. The pumps tested were the NEV-100 (Lifecare Inc.), the Negavent Respirator DA-1 (Dima Italia), the Thompson Maxivent (Puritan Bennett), the CCP-001 and Newmarket pumps (Si-Plan Electronics Research Ltd). A patient model was employed to investigate the relationship between the pressure waveform of each pump and the tidal volume generated, the stability of performance on a continuous 8 h test, and the response to a change in leak. On the continuous tests, the stability was better than +/- 1% for the inspiratory/expiratory (I:E) ratio and rate, and better than +/- 10% for the peak negative pressure for all of the pumps. The Negavent and NEV-100 pumps generated a square wave of pressure and for the same peak negative pressure produced a tidal volume up to 30% greater than the CCP-001 and the Newmarket pumps, which produced a half sine wave. The Maxivent produced an intermediate waveform, with a plateau at peak negative pressure but a curved decay back to atmospheric pressure. It is argued that if the pressure of the pumps producing a half sine wave is made more negative to compensate and produce an equivalent tidal volume, they are more likely to induce upper airway obstruction. The leak compensation of the NEV-100 and Negavent pumps was nearly complete but took several breaths to develop, the CCP-001 and Newmarket pumps had a very rapid compensation but this was less complete, whilst the Maxivent has no mechanism for leak compensation. From these results, it seems that in patients liable to upper airway obstruction the NEV-100 and Negavent pumps would be advantageous, whilst when rapidly changing leaks impair the efficiency of negative pressure ventilation the CCP-001 and Newmarket pumps would be preferable. The Maxivent pump seems to offer no advantages.