• transcutaneous PCO2
  
• transcutaneous PO2
  
• Oxygen saturation
  

• Respiratory Disturbance Index
  
• Desaturation Index
  
• MSLT
  
• arterial PO2
  
• arterial PCO2
  
• Hypercapnic Ventilatory Response
  
• total sleeping time
  
• sleep latency
  
• percentage REM- and nREM-sleep of total sleep time
  
• number of arousals
  
• number of apneas during sleep
  
• number of hypopneas during sleep
  
• Epworth Sleeping Score
  
• Dyspnea Visual Analog Score
  

Rationale: More than 50% of patients with chronic obstructive pulmonary disease (COPD) have sleep complaints characterised by longer latency to falling asleep, more frequent arousals and awakenings, generalised insomnia and/or excessive daytime sleepiness. Sleep disturbance seems to be more severe with advancing disease and substantially reduces patients' quality of life. The sleep complaints are due to dyspnea, chronic cough, sputum production, hypoxaemia and hypercapnia during the night. One of the available therapies for these patients is the prescription of hypnotics (like benzodiazepines).

However, it is thought that in patients with COPD sleep medication may produce adverse respiratory effects due to suppression of the cerebral respiratory drive. In our practice, we never encounter any adverse respiratory effect of an hypnotic in patients with COPD. There have been several trials in COPD patients studying these potentially adverse effects. The results of these studies are inconsistent, relative older hypnotics are used and there are several methodological limitations. Furthermore, in none of these studies transcutaneous PCO2 or PO2 was monitored. Temazepam is nowadays the sedative of first choice in the medical treatment of sleep complaints.

Aim: primary: studying the effects of temazepam on the respiratory function during daytime and at night in patients with severe COPD. Secondary: studying the effects of temazepam on the sleep quality and sleep structure and on the objective and subjective sleepiness during daytime and at night in patients with COPD.

Study design: double blind, placebo-controlled, cross-over randomised clinical trial.

Treatment: 10 mg temazepam or placebo during seven consecutive nights.

Endpoints: Primary: difference in PtcCO2, PtcO2 and oxygen saturation during sleep after 1 week temazepam compared to placebo. Secondary: Respiratory Disturbance Index, Desaturation Index and Hypercapnic Ventilatory Response, percentage REM/nREM-sleep and total effective sleep time, Multiple Sleep Latency Test and the Epworth Sleeping Score.