The purpose of our study is to establish whether domiciliary use of the Airvo warm passover humidifier can reduce the number of exacerbations in patients with respiratory insufficiency. Participants must have a diagnosis of chronic obstructive pulmonary disease (COPD) and be in long term oxygen therapy (LTOT). The following questions will be investigated:

Do outpatients receiving long term oxygen therapy benefit if this is delivered through an Airvo humidification system. The proposed benefits under investigation are:

1. a reduction in the number of exacerbations and thus hospital admissions?
2. an increase in quality of life (QOL)?
3. an improved lung function and thus increased physical activity?

Experience at Aalborg University Hospital's Department of Pulmonary Medicine (Lungemedicinsk Afdeling) in Denmark gives rise to a renewed interest in the investigation of the properties and effects of humidification in COPD patients in LTOT. For the last 5 years, the department has discharged fibrosis patients with oxygen flow > 6 l/min with a warm mist humidifier. The initiative has given clear indication that infection ratios can be reduced and the QOL increased. Many COPD patients experience improved oxygen saturation when oxygen treatment for respiration insufficiency is given with warm humidification.

Previous studies have typically concerned other patient categories and involved the use of cold-water humidifiers. To increase air moistening, the temperature must be raised as moisture absorption capability increases with temperature. The 2009 study of Rea et al. (9) examined the effect of warm humidification on COPD and bronchiectasis patients, who used a warm humidifier (MR 880) on average for two hours per day. LTOT was not an inclusion criterion in the study, and the severity of COPD varied. Despite the relatively short time of use the study demonstrated the beneficial effect of humidification on exacerbation frequency.

Our study therefore aims to examine the effect of using warm humidification as a minimum during the night - preferably for 8 hours.

In addition to their usual oxygen apparatuses, the treatment group will have an Airvo warm humidifier installed in the home. Their respiratory gas flow setting will be increased to 20-25 l/min based on patient preference; then the peripheral saturation readings will form the basis for adjusting the oxygen flow rate.

The control group will continue receiving the standard oxygen therapy prescribed by the department.

For the study to achieve the desired power, 190-200 patients across the two groups are required Appendix 3). Patients must have been diagnosed with severe/very severe COPD and be receiving long-term domiciliary oxygen treatment (LTOT)

For all participants, the following procedure will be adhered to:

1. Metrics at inclusion:

   • Demographic data

   • Pulmonary function measurement using spirometry

   • Exacerbations (by number of)

     • hospitalisation days in past year (data extracted from AS400)
     • antibiotics courses and prednisolone courses in past year (from prescription database)
     • exacerbations/self-treatment plans launched

   • 6-minute walk test

   • QOL measurement (St George's Respiratory Questionnaire)

   • Artery puncture (Airvo group only)

2. Metrics in project period at 1, 3, 6 and 9 months:

   Patients will be contacted by telephone on a date agreed in advance.

   • QOL measurement (St George's Respiratory Questionnaire). Form completed only after 6 months; sent to patient in advance.
   • Number of exacerbations/self-treatment plans launched

3. Metrics at project period completion (at 12 months):

Patients will be called in for an outpatient visit to the department

• Pulmonary function measurement (spirometry)

• St George's Respiratory Questionnaire (sent to patient prior to interview)

• 6-minute walk test

• Exacerbations in project period (by number of)

  • hospitalisation days in past year (data extracted from AS400)
  • antibiotics courses and prednisolone courses in past year (from prescription database)
  • exacerbations/self-treatment plans launched

Analysis and statistical processing of project data will be performed by statistician Hans Hockey of Biometricmatters Ltd, Hamilton, New Zealand. Power calculations based on anonymised data extracts from AS400 have already been performed.

Consultation with Mr Hockey has clarified that "events" and "visits" are synonymous terms. In the appendix the term "events" will be used, to indicate the number of contacts with the hospital.

According to Mr Hockey, risk time will be calculated as "the period of time for which a patient is at risk of the event being considered". Risk time thus corresponds to the time that the patient participates in the trial. The trial period is 12 months, but drop-out due to death or withdrawal for any other reasons is to be expected. All data will be included in the study, including data on dropouts.

This project protocol has been approved by the North Denmark Region scientific ethical committee (N-20110057).

Inclusion Criteria:

• have severe/very severe COPD diagnosis
• have had chronic respiratory insufficiency for at least 3 months and be in steady oxygen therapy (LTOT) with a minimal supplement of 1 litre of oxygen per minute for at least 16 hours per day
• understand and accept oral and written information in Danish
• be capable of handling the Airvo warm humidifier after instruction.

Exclusion Criteria:

• Comorbidity (known malignant disease, terminal illness, dementia, uncontrolled mental illness)
• Bronchiectasis without simultaneous COPD diagnosis
• Treatment with BiPAP in the home
• Affected level of consciousness
• Smoking status change during project period.