ANZCTR - Registration

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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]

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

respiratory failure post surgery

Condition category

Condition code

Respiratory

Other respiratory disorders / diseases

Diet and Nutrition

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]

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]

Change in end-expiratory lung impedance (EELI) as a surrogate for end-expiratory lung volume (EELV), measured by electrical impedance tomography (EIT).

Timepoint [1]

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]

Change in tidal variance as a surrogate for tidal volume, measured by EIT

Timepoint [1]

Secondary outcome [2]

Pa02:Fi02 ratio

Timepoint [2]

Blood gas analysis will be carried out at baseline, 1 hour, 3 hours and 6 hours, post initiation of HFN02.

Secondary outcome [3]

Change in Pac02

Timepoint [3]

Blood gas analysis will be carried out at baseline, 1 hour, 3 hours and 6 hours post initiation of HFN02.

Secondary outcome [4]

Incidence of post operative respiratory complications.

Timepoint [4]

30 days post operatively
Retrospective review of medical notes.

Secondary outcome [5]

Length of hospital stay

Timepoint [5]

Measured in days

Secondary outcome [6]

Patient comfort, measured by the modified Borg score

Timepoint [6]

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

Sex

Both males and females

Can healthy volunteers participate?

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

3/04/2017

Date of last participant enrolment

Anticipated

30/09/2017

Actual

Date of last data collection

Anticipated

31/10/2017

Actual

Sample size

Target

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

QLD

Recruitment hospital [1]

St Andrew's War Memorial Hospital - Brisbane

Recruitment postcode(s) [1]

4001 - Brisbane

Funding & Sponsors

Funding source category [1]

Charities/Societies/Foundations

Name [1]

Wesley Medical Research

Address [1]

Health and Medical Research Centre
Level 8, East Wing, The Wesley Hospital
451 Coronation Drive
Auchenflower
QLD 4066

Country [1]

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]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

The UnitingCare Health Human Research Ethics Committee

Ethics committee address [1]

UnitingCare Health Human Research Ethics Committee
The Wesley Hospital
PO Box 499
Auchenflower  Qld  4066

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

03/01/2017

Approval date [1]

21/02/2017

Ethics approval number [1]

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

Prof John Fraser

Address

Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001

Country

Australia

Phone

+61 7 3834 4444

Fax

john.fraser@health.qld.gov.au

Contact person for public queries

Name

Rachel Fulton

Address

Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001

Country

Australia

Phone

+61 7 3834 4444

Fax

r.fulton.04@aberdeen.ac.uk

Contact person for scientific queries

Name

John Fraser

Address

Intensive Care Unit
St Andrews War Memorial Hospital
457 Wickham Terrace,
Brisbane City
QLD 4001

Country

Australia

Phone

+61 7 3834 4225

Fax

john.fraser@health.qld.gov.au

No information has been provided regarding IPD availability

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

Source	Title	Year of Publication	DOI
Embase	High flow nasal oxygen after bariatric surgery (OXYBAR), prophylactic post-operative high flow nasal oxygen versus conventional oxygen therapy in obese patients undergoing bariatric surgery: Study protocol for a randomised controlled pilot trial.	2018	https://dx.doi.org/10.1186/s13063-018-2777-2
Embase	Prophylactic Postoperative High Flow Nasal Oxygen Versus Conventional Oxygen Therapy in Obese Patients Undergoing Bariatric Surgery (OXYBAR Study): a Pilot Randomised Controlled Trial.	2021	https://dx.doi.org/10.1007/s11695-021-05644-y

N.B. These documents automatically identified may not have been verified by the study sponsor.

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