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Trial registered on ANZCTR


Registration number
ACTRN12617000694314
Ethics application status
Approved
Date submitted
10/05/2017
Date registered
15/05/2017
Date last updated
15/05/2017
Type of registration
Retrospectively registered

Titles & IDs
Public title
Prophylactic post-operative high flow nasal oxygen therapy versus conventional oxygen therapy in obese patients undergoing bariatric surgery: a randomised controlled pilot study
Scientific title
Prophylactic post-operative high flow nasal oxygen therapy versus conventional oxygen therapy in obese patients undergoing bariatric surgery: a randomised controlled pilot study
Secondary ID [1] 291887 0
None
Universal Trial Number (UTN)
Trial acronym
OXYBAR
High flow nasal OXYgen after BARiatric surgery
Linked study record
None

Health condition
Health condition(s) or problem(s) studied:
Obesity 303181 0
respiratory failure post surgery 303182 0
Condition category
Condition code
Respiratory 302624 302624 0 0
Other respiratory disorders / diseases
Diet and Nutrition 302672 302672 0 0
Obesity

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Pre-operative management of the patient will be consistent with current surgical best practice and at the discretion of the responsible surgeon. The method and conduct of general anaesthesia will be at the discretion of the responsible anaesthetist. Given the nature of the surgery, all patients will undergo endotracheal intubation and mechanical ventilation.

Extubation will occur in theatre and all patients (control and intervention) will receive 6l of oxygen via Hudson face mask. They will then be transferred to the ICU.

Baseline measurements will be undertaken when the patient has achieved a Richmond agitation and sedation score (RASS) of -2 or greater. After baseline measurements have been recorded patients randomised to the intervention group will be managed with supplemental oxygen delivered at a FiO2 of 0.5 and a flow rate of 50 L/min via the Airvo (Trademark) 2 High Flow Nasal Oxygen device (Fisher & Paykel, New Zealand). Oxygen therapy will be titrated to maintain peripheral oxygen saturations (SpO2) =95%. This will be achieved by increasing or decreasing the FiO2 delivered. A constant flow rate of 50 L/min should be maintained for the duration of the study period. The study period will last for 6 hours following initation of HFN02.
Intervention code [1] 298002 0
Treatment: Devices
Comparator / control treatment
Pre-operative management and the conduct of general anaesthesia will be the same as that for the intervention group.

During recovery from general anaesthesia patients will be managed with supplemental oxygen delivered at 6 L/min via a Hudson mask. Oxygen therapy will be titrated to maintain peripheral oxygen saturations (SpO2) =95%. If after an initial period of stabilisation in the ICU, patients consistently achieve or exceed the SpO2 target, therapy may be titrated downwards (including the use of conventional nasal cannulae). A minimum of 2 L/min of supplemental oxygen should be maintained for the duration of the study period.
Control group
Active

Outcomes
Primary outcome [1] 302033 0
Change in end-expiratory lung impedance (EELI) as a surrogate for end-expiratory lung volume (EELV), measured by electrical impedance tomography (EIT).
Timepoint [1] 302033 0
A 2 minute continuous EIT recordings will be carried out as a baseline, with all patients receiving 6L of oxygen via Hudson face mask.
Further 2 minute EIT recordings will be carried out at 15 mins, 30 mins, 60 mins, 3 hours and 6 hours following initiation of HFN02.
Secondary outcome [1] 334574 0
Change in tidal variance as a surrogate for tidal volume, measured by EIT
Timepoint [1] 334574 0
A 2 minute continuous EIT recordings will be carried out as a baseline, with all patients receiving 6L of oxygen via Hudson face mask.
Further 2 minute EIT recordings will be carried out at 15 mins, 30 mins, 60 mins, 3 hours and 6 hours following initiation of HFN02.
Secondary outcome [2] 334652 0
Pa02:Fi02 ratio
Timepoint [2] 334652 0
Blood gas analysis will be carried out at baseline, 1 hour, 3 hours and 6 hours, post initiation of HFN02.
Secondary outcome [3] 334653 0
Change in Pac02
Timepoint [3] 334653 0
Blood gas analysis will be carried out at baseline, 1 hour, 3 hours and 6 hours post initiation of HFN02.
Secondary outcome [4] 334654 0
Incidence of post operative respiratory complications.
Timepoint [4] 334654 0
30 days post operatively
Retrospective review of medical notes.
Secondary outcome [5] 334655 0
Length of hospital stay
Timepoint [5] 334655 0
Measured in days
Secondary outcome [6] 334656 0
Patient comfort, measured by the modified Borg score
Timepoint [6] 334656 0
Measured at baseline, 1 hour, 3 hours and 6 hours after initiation of HFN02.

Eligibility
Key inclusion criteria
Age >18 yrs
BMI >32 kg/m2
Undergoing a laparoscopic bariatric procedure for weight reduction
Minimum age
18 Years
Maximum age
No limit
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
Age <18 yrs
Refusal of informed consent
Any contraindication to HFN02 therapy (see below)
Chest circumference too large for EIT belt (Chest > 75cm in diameter from left to right mid-axillae)

Contraindications to HFN02
Epistaxis
Significant facial trauma
Base of skull fracture
Nasal obstruction; e.g. nasal fracture, tenacious secretions, tumour

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation concealment will be maintained using sequentially numbered sealed opaque envelopes. Envelopes will be prepared by an independent person. Each envelope will contain a unique patient identifier code and will allocate the participant to either the intervention group (HFN02) or the control group (standard oxygen therapy).
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Randomisation will be achieved using a computer-generated random number table.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Parallel
Other design features
The theatre team will be blinded to the allocation. Due to the research design, neither the individual collecting data nor patient can be blinded to treatment allocation.
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
QLD
Recruitment hospital [1] 7979 0
St Andrew's War Memorial Hospital - Brisbane
Recruitment postcode(s) [1] 15954 0
4001 - Brisbane

Funding & Sponsors
Funding source category [1] 296383 0
Charities/Societies/Foundations
Name [1] 296383 0
Wesley Medical Research
Address [1] 296383 0
Health and Medical Research Centre
Level 8, East Wing, The Wesley Hospital
451 Coronation Drive
Auchenflower
QLD 4066
Country [1] 296383 0
Australia
Primary sponsor type
Hospital
Name
St Andrews War Memorial Hospital
Address
547 Wickham Terrace,
Brisbane City
QLD 4001
Country
Australia
Secondary sponsor category [1] 295331 0
None
Name [1] 295331 0
Address [1] 295331 0
Country [1] 295331 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 297621 0
The UnitingCare Health Human Research Ethics Committee
Ethics committee address [1] 297621 0
UnitingCare Health Human Research Ethics Committee
The Wesley Hospital
PO Box 499
Auchenflower Qld 4066
Ethics committee country [1] 297621 0
Australia
Date submitted for ethics approval [1] 297621 0
03/01/2017
Approval date [1] 297621 0
21/02/2017
Ethics approval number [1] 297621 0
UCH HREC 1709

Summary
Brief summary
Obesity, defined as a body mass index (BMI) > 30 kg/m2, has almost doubled since 1980, with more than 671 million people worldwide now classified as obese. Health problems associated with obesity impact on quality of life and impose a significant cost burden to the health service. The total financial cost of obesity is estimated to be $8.3 billion.

Obesity is difficult to treat. Diet, exercise and medications being only modestly effective in aiding weight loss. In selected individual’s, bariatric surgery may offer a means of achieving long-term weight loss, improved health and cost reduction.

The physiological and pathological changes that arise from obesity predispose to post-operative respiratory complications. Excess pressure exerted by an increased amount of fat tissue on the chest wall and in the abdomen, leads to collapse and closure of small airways within the lungs. This collapse of the small airways is worsened still by general anaesthesia and lying flat both of which are a requirement for surgery. This collapse persists longer into the postoperative period in the obese when compared to the non-obese population.

High flow nasal oxygen therapy (HFN02) has been established as treatment for respiratory failure in infants and neonates. Its use has also become more prevalent in the adult population over the last decade, with an expanding list of clinical applications.

High flow nasal cannula (HFNC) are designed to deliver a predetermined amount of heated and humidified oxygen to a patient. HFNC deliver oxygen at a much higher flow rate than a conventional face mask or nasal cannula, up to 70L/min vs 6L/min.

The use of high flow nasal oxygen (HFN02) has been shown to improve the clearance of mucus from the airways, reduce the amount of energy used to breath, deliver a more accurate and reliable amount of oxygen to the lungs, and provide a degree of positive pressure into the lungs. The provision of positive pressure has been shown to increase the lung volume, this suggests that small airways that were previously closed are splinted open by the pressure provided.

All of the positive effects of HFN02 outlined above are of potential benefit to obese patients in the postoperative period. Of particular interest is the provision of positive pressure which helps open up collapsed small airways. By carrying out our proposed study we hope to determine the impact that HFN02 has on postoperative lung volumes when compared to standard oxygen therapy.

Lung volumes, specifically end expiratory lung volume (EELV) can be measured using electrical impedance tomography (EIT). EIT is a radiation free functional imaging modality invented over 30 years ago. It is non-invasive and can be used in real time at the patient’s bedside to assess lung volume changes. EIT has been successful validated against a number of other imagining and measurement modalities.

It consists of 16 paired electrodes attached to a belt that is placed around the patient’s chest usually between the 4th/5th or 5th/6th rib. It then feeds back information about the patient’s volumes lungs as they breath to a computer for analysis. Both numerical measurements and images are produced.



Hypotheses
In obese, adult patients, undergoing laparoscopic surgery for weight reduction, prophylactic post-operative HFN02 therapy will increase EELV, improve respiratory function and reduce respiratory morbidity in the post-operative period

Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 74618 0
Prof John Fraser
Address 74618 0
Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001
Country 74618 0
Australia
Phone 74618 0
+61 7 3834 4444
Fax 74618 0
Email 74618 0
john.fraser@health.qld.gov.au
Contact person for public queries
Name 74619 0
Dr Rachel Fulton
Address 74619 0
Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001
Country 74619 0
Australia
Phone 74619 0
+61 7 3834 4444
Fax 74619 0
Email 74619 0
r.fulton.04@aberdeen.ac.uk
Contact person for scientific queries
Name 74620 0
Prof John Fraser
Address 74620 0
Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001
Country 74620 0
Australia
Phone 74620 0
+61 7 3834 4225
Fax 74620 0
Email 74620 0
john.fraser@health.qld.gov.au

No data has been provided for results reporting
Summary results
Not applicable