Condition category
Nervous System Diseases
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Not provided at time of registration

Trial website

Contact information



Primary contact

Prof Neil Douglas


Contact details

Department of Respiratory Medicine
Second Floor
Royal Infirmary of Edinburgh
51 Little France Crescent
EH16 4SA
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Randomised controlled trial of variable-pressure versus fixed-pressure continuous positive airway pressure (CPAP) treatment for patients with obstructive sleep apnoea/hypopnoea syndrome (OSAHS)


Study hypothesis

Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a common illness affecting approx 4% of middle-aged men and 2% of middle aged women, who most frequently complain of symptoms of snoring and breathing pauses during sleep and daytime sleepiness. OSAHS is caused by relaxation of the upper airway during sleep, predisposing the airway to narrowing and eventual collapse. The restoration of airway patency is achieved by short arousals from sleep to allow breathing before sleep ensues again. The treatment of choice for OSAHS is continuous positive airway pressure (CPAP), which is a mechanical treatment involving the patient wearing a nasal mask during sleep, through which is blown a gentle airstream that splints the upper airway open, preventing collapse, breathing pauses, sleep disruption and dips in oxygenation.

This randomised controlled cross-over trial will seek to determine whether OSAHS patients on variable-pressure CPAP (AutoSet Spirit™) for six weeks have better outcomes over fixed-pressure CPAP for:
1. Patients' treatment preference
2. Patient-orientated function on treatment (objective and subjective sleepiness, quality of life, vigilance, side-effects, symptoms)
3. Clinician-orientated treatment success (CPAP use, CPAP pressure, residual Apnoea-Hypopnea Index [AHI], mask leak)
4. Direct economic costs (staff and patient time, equipment costs)
5. Indirect economic benefits (health utility/quality-adjusted life years [QALYs])

Ethics approval

Lothian NHS Board, Lothian Local Research Ethics Committee 04, approved on 17 February 2005 (ref: 04/S1104/41)

Study design

Randomised double-blind (patients and researchers) cross-over single-centre trial

Primary study design


Secondary study design


Trial setting


Trial type


Patient information sheet


Obstructive sleep apnoea/hypopnoea syndrome (OSAHS)


This is a randomised double-blind cross-over trial with 6 weeks of fixed-pressure continuous positive airways pressure (CPAP) and 6 weeks of variable-pressure CPAP. The first two weeks of each treatment was taken as a wash-out period.

Eligible patients will be identified during the Dept of Sleep Medicine's weekly clinical review of cases, where full casenotes and investigations are available to ascertain inclusion and exclusion criteria. Consecutive eligible patients will be approached with information on the study and asked to consent to participation. Excluded or declining patients in the series will have reasons for these recorded for later post-hoc comparison with the recruited patient group.

Consenting patients will receive CPAP education and mask-fitting as per our usual practice and automated CPAP titration using Spirit units, to determine therapeutic pressure for fixed-pressure CPAP (95th centile of pressure profile, unless adjusted by clinical staff for technical reasons). Patients will be asked to complete Epworth and SF-36® Health Survey just before titration, as a contemporaneous measure of pre-treatment status. After titration study, all patients will be issued with a Spirit unit set in the appropriate treatment mode (fixed- or variable-pressure CPAP) for home use over the first 6 week treatment limb.

At the end of each 6 week treatment limb, patients are asked to attend with their Spirit CPAP units for a 3 hour session of testing, including breaks, and collecting the following measurements:
1. Objective sleepiness: Two 40-min Oxford Sleep Resistance (OSLER) tests (sleep resistance task)
2. Subjective sleepiness Epworth sleepiness scale
3. Vigilance Physiological vigilance test (PVT)
4. Symptom ratings Nocturnal and daytime symptoms
5. Health-related quality of life SF-36® Health Survey
6. CPAP side effects Edinburgh side-effects checklist
7. CPAP use and efficacy of Spirit CPAP units' memory (final 4 weeks):
7.1. CPAP use
7.2. CPAP pressure
7.3. Mask leak
7.4. Residual AHI on CPAP
8. At the last session patients will also be asked to rate treatment preference: variable-pressure or fixed-pressure CPAP

Intervention type



Phase IV

Drug names

Primary outcome measure

Patient preference, recorded once at trial end and assessed using a chi-square test.

Secondary outcome measures

1. Patient-orientated effectiveness of treatment (sleepiness, symptoms, side-effects)
2. Physiologically-orientated effectiveness of CPAP (AHI, CPAP pressure, CPAP use)

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Both males and females, between 18 and 70 years of age
2. CPAP naïve patients
3. Epworth Sleepiness Scale (ESS) >10 OR history of troublesome sleepiness when driving
4. AHI >15 on polysomnography or AHI/respiratory disturbance index (RDI) >25 on limited sleep study

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Severe neurological deficit sufficient to compromise CPAP usability or understanding
2. Significant co-morbidity (severe or unstable respiratory, neurological, metabolic or cardiac disease)
3. Co-existing sleep disorder such as narcolepsy, periodic limb movement syndrome
4. Contra-indications to CPAP use including recent pneumothorax

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Department of Respiratory Medicine
EH16 4SA
United Kingdom

Sponsor information


Lothian NHS Board (UK)

Sponsor details

Lothian Local Research Committee 04
Deaconess House
148 Pleasance
United Kingdom

Sponsor type




Funder type


Funder name

ResMed Ltd (Australia) (ref: RESPMED052)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2010 results in

Publication citations

  1. Results

    Vennelle M, White S, Riha RL, Mackay TW, Engleman HM, Douglas NJ, Randomized controlled trial of variable-pressure versus fixed-pressure continuous positive airway pressure (CPAP) treatment for patients with obstructive sleep apnea/hypopnea syndrome (OSAHS)., Sleep, 2010, 33, 2, 267-271.

Additional files

Editorial Notes