Improved olfaction under continuous positive airway pressure therapy

ISRCTN ISRCTN11128866
DOI https://doi.org/10.1186/ISRCTN11128866
Secondary identifying numbers EKNZ 2014-335
Submission date
04/10/2016
Registration date
12/10/2016
Last edited
08/11/2023
Recruitment status
No longer recruiting
Overall study status
Completed
Condition category
Signs and Symptoms
Prospectively registered
Protocol
Statistical analysis plan
Results
Individual participant data

Plain English summary of protocol

Background and study aims
Obstructive sleep apnoea (OSA) is a common condition in which the upper airways (wind pipe) collapse repeatedly during sleep, stopping the flow of air into the lungs. This prevents the sufferer from being able to breathe properly while they are asleep, causing excessive sleepiness throughout their waking hours. OSA is usually treated using a continuous positive airway pressure (CPAP) machine. This involves the patient wearing a face mask during sleep which is connected to the machine which supplies a constant steam of air to help keep the airways open. Although this therapy has been using for decades now, it is not known whether it affects a patient’s sense of smell. This study consists of two parts, in the first part the aim of this study is to find out whether sense of smell changes as a result of undergoing CPAP as part of standard care. In the second part, participants receiving CPAP are randomly allocated to continue with treatment or have the pressure of the device lowered (so it is no longer as effective) in order to see if this impacts on sense of smell.

Who can participate?
Adults with moderate to severe OSA who suffer from daytime sleepiness

What does the study involve?
In the first part of the study participants attend a study visit at which they complete a questionnaire about their sleepiness and sense of smell. Their sense of smell is then tested by asking participants to smell a number of scent dispensing smells. Following this, participants begin standard CPAP therapy as part of their usual care. Three months later, participants attend a second study visit at which time the questionnaires and smell tests are repeated in order to find out if CPAP has had an effect on their sense of smell and how tired they are during the day.
In the second part of the study, participants able to stick to the CPAP therapy in the first part of the study are randomly allocated to one of two groups. Those in the first group continue with their standard CPAP therapy for three weeks, those in the second group have the pressure of the CPAP device lowered for three week so it is no longer working as well. At the start of this treatment period and then after three weeks, participants complete questionnaires and smell tests in order to assess their sense of smell and how tired they are during the day.

What are the possible benefits and risks of participating?
There are no direct benefits or risks involved for those participating in this study.

Where is the study run from?
Cantonal Hospital Aarau (Switzerland)

When is the study starting and how long is it expected to run for?
February 2014 to August 2016

Who is funding the study?
Research Council of the Cantonal Hospital Aarau (Switzerland)

Who is the main contact?
Dr Sarosh Irani
siran@gmx.ch

Contact information

Dr Sarosh Irani
Scientific

Clinic of Pulmonary and Sleep Medicine
Cantonal Hospital Aarau
Tellstrasse 25
Aarau
CH-5001
Switzerland

Phone +41 (0)62 838 44 70
Email siran@gmx.ch

Study information

Study designPart 1: Observational cohort study; Part 2: Randomized controlled trial
Primary study designObservational
Secondary study designCohort study
Study setting(s)Hospital
Study typeTreatment
Participant information sheet Not available in web format, please use the contact details to request a patient information sheet
Scientific titleSignificant improvement of olfactory performance in sleep apnea patients after three months of nasal continuous positive airway pressure therapy
Study objectivesThe aim of this study is to assess the sense of smell before initiation of nasal continuous positive airway pressure (CPAP) and after three months treatment, in moderate and severe obstructive sleep apnea (OSA) patients.
Ethics approval(s)Ethics Committee of the Nordwest- und Zentralschweiz, 18/11/2014, ref: EKNZ 2014-335
Amendment approved: 19/05/2016
Health condition(s) or problem(s) studiedOlfactory performance in moderate and severe sleep apnea patients
InterventionPart 1:
Participants attend a study visit at which they undergo several investigations. Firstly, a questionnaire concerning sleepiness and self-estimated quality of the own olfaction has to be answered which takes about five minutes. Secondly, sense of smell is tested with the aid of a standardized test battery. This test battery contains 112 odour-dispensing pens to evaluate odour threshold, odour discrimination and odour identification. These pens are exposed to the nose of the patient in a specific order. The test takes about 40 minutes.
During the same visit patients then begin standard CPAP therapy as part of their usual care. This involves adaptation of a suitable nasal mask and instruction of the patient how to use and to maintain the CPAP device and the humidifier.

After three months, participants attend another study visit at which they undergo the same procedure of testing the sense of smell and answering the same questionnaire as during the initial study visit. Furthermore, after these tests a download of the therapy data are discussed with the patient and a check of the CPAP device is performed. This follow up visit takes about 90 minutes.

Part 2:
Participants who show a sufficient therapy adherence during the first follow up visit are randomized to one of two groups using block randomization if they agree to take part to the second study part and give written informed consent. Sufficient therapy adherence is defined as applying the CPAP therapy in 70% of the nights at least 4 hours CPAP use per night.

Group 1: Patients maintain under unchanged CPAP therapy for three weeks (maintenance group)
Group 2: Therapy pressure of the CPAP device is set to a sub therapeutic pressure of 4 centimeter of water for three weeks (sham group).

Follow up for all participants involves testing of sense of smell and answering the study questionnaire much like they did at the follow up visit. The visits take place at the outpatients department of the Cantonal Hospital Aarau, Switzerland.
Intervention typeDevice
Pharmaceutical study type(s)
PhaseNot Applicable
Drug / device / biological / vaccine name(s)-
Primary outcome measurePart 1:
Self-estimated olfaction is measured using a visual analogue scale (VAS) at baseline and 3 months.

Part 2:
Self-estimated olfaction is measured using a visual analogue scale (VAS) at baseline and 3 weeks.
Secondary outcome measuresPart 1:
1. Odor threshold, odor discrimination, odor identification and the summarized value of these three tests threshold, discrimination and identification overall score (TDI) are measured with the aid of a standardized test battery (sniffin’sticks) at baseline and 3 months
2. Daytime sleepiness is measured using the Epworth sleepiness scale (ESS) at baseline and 3 months

Part 2:
1. Odor threshold, odor discrimination, odor identification and the summarized value of these three tests threshold, discrimination and identification overall score (TDI) are measured with the aid of a standardized test battery (sniffin’sticks) at baseline and 3 weeks
2. Daytime sleepiness is measured using the Epworth sleepiness scale (ESS) at baseline and 3 weeks
Overall study start date05/02/2014
Completion date16/08/2016

Eligibility

Participant type(s)Patient
Age groupAdult
Lower age limit18 Years
SexBoth
Target number of participants30
Total final enrolment35
Key inclusion criteria1. Outpatients of our department of pulmonary and sleep medicine
2. Age 18 years and over
3. Suffer from daytime sleepiness
4. Show moderate to severe OSA (apnea hypopnea index (AHI) ≥ 15 per hour) in a respiratory sleep study
Key exclusion criteria1. Lack of written informed consent
2. Insufficient knowledge of the German language
3. Known disease of the nasal cavity or sinuses, or topical nasal therapy usage
Date of first enrolment19/11/2014
Date of final enrolment15/07/2015

Locations

Countries of recruitment

  • Switzerland

Study participating centre

Cantonal Hospital Aarau
Clinic of Pulmonary and Sleep Medicine
Tellstrasse 25
Aarau
CH-5001
Switzerland

Sponsor information

Cantonal Hospital Aarau
Hospital/treatment centre

Tellstrasse
Aarau
CH-8057
Switzerland

Phone +41 62 838 44 72
Email pneumologie@ksa.ch
ROR logo "ROR" https://ror.org/056tb3809

Funders

Funder type

Research council

Research Council of the Cantonal Hospital Aarau

No information available

Results and Publications

Intention to publish date31/12/2016
Individual participant data (IPD) Intention to shareNo
IPD sharing plan summaryNot expected to be made available
Publication and dissemination planPlanned publication of study results in a medical journal.
IPD sharing planThe participant level data will not be made available at the request of the approving ethics committee.

Study outputs

Output type Details Date created Date added Peer reviewed? Patient-facing?
Basic results 10/10/2016 13/10/2016 No No
Results article results 03/02/2017 Yes No
Protocol (other) 03/02/2017 08/11/2023 No No

Additional files

ISRCTN11128866_BasicResults_10Oct2016.docx
Uploaded 13/10/2016

Editorial Notes

08/11/2023: Protocol and total final enrolment added.
06/02/2017: Publication reference added.
13/10/2016: The basic results summary file has been uploaded.