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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The effect of oxygen on passive inspiratory flow in the apnoeic patient.
Scientific title
The effect of oxygen versus air on passive inspiratory flow rate in women undergoing an elective gynaecological procedure requiring intubation when rendered apnoeic under general anaesthesia.

Secondary ID [1] 282371 0
Universal Trial Number (UTN)
Trial acronym
Apnoeic Flow Study
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Passive inspiratory flow in the apnoeic patient 288953 0
Condition category
Condition code
Anaesthesiology 289285 289285 0 0

Study type
Description of intervention(s) / exposure
When patient is rendered apnoeic under general anaesthesia, each patient will be with administered oxygen first for ten minutes or less(when SpO2 less than91%), and then with air for ten minutes or less(when SpO2 less than91%).

The flow rate of both oxygen and air will be measured during period of apnoea.

Under normal circumstances the patient will be ventilated when rendered apnoeic. However, we are looking into the physiology of air and oxygen flow in an apnoeic patient.

Oxygen ( 5L/min) and air (5L/min) will be administered over a period of 10 minutes or when patient's pulse oximetry falls below 91%.(which ever occurs first).

Both oxygen and air will be delivered by Anaesthetic machine to patient via the endotracheal tube.

This study occurs at the start of anaesthesia and willll be terminated before the start of surgery.
Intervention code [1] 287003 0
Other interventions
Comparator / control treatment
Control group

Primary outcome [1] 289396 0
Flow rate of oxygen and air is measured with Eco-medics Vmax 26 flow meter which uses high frequency ultrasonic waves to measure small gas flows in neonates.
Timepoint [1] 289396 0
When flow rate stabilises or at 10 minutes (maximum).
Secondary outcome [1] 302394 0
Timepoint [1] 302394 0

Key inclusion criteria
Healthy female patients admitted for elective gynaecologycal procedure requiring intubation.

ASA 1-2 patients only.

Body mass index (BMI) between 20 and 35kg per metre square.
Minimum age
18 Years
Maximum age
70 Years
Can healthy volunteers participate?
Key exclusion criteria
Patient refusal.
BMI >35.
Oxygen saturation(peripheral) of less than 95% at room air.
Patients with chronic respiratory disease e.g. asthma.
Patients with features of difficult airway.

Study design
Purpose of the study
Educational / counselling / training
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Subject will be recruited in the Gynaecology Pre-admission clinic on a voluntary basis. All subjects will receive oxygen first followed by air.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Single group
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Univariate data will be expressed as mean(plus minus standard deviation) for parametric data and median(range) for non-parametric data.

Analysis will be done using student's unpaired t-test, Mann-Whitney sum rank test(continuous data), Chi-square test and Fisher Exact (categorical data) as appropriate.

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 923 0
King Edward Memorial Hospital - Subiaco
Recruitment postcode(s) [1] 6771 0
6008 - Subiaco

Funding & Sponsors
Funding source category [1] 287140 0
Self funded/Unfunded
Name [1] 287140 0
Address [1] 287140 0
Country [1] 287140 0
Primary sponsor type
King Edward Memorial Hospital
374, Bagot Road
WA 6008
Secondary sponsor category [1] 285909 0
Name [1] 285909 0
Address [1] 285909 0
Country [1] 285909 0

Ethics approval
Ethics application status
Ethics committee name [1] 289140 0
WNHS Ethics Committee
Ethics committee address [1] 289140 0
Ethics Secretary
Room 134
Level 1, Children’s Clinical Research Facility
Princess Margaret Hospital
Cnr Hamilton Street & Roberts Road
Subiaco WA 6008
Ethics committee country [1] 289140 0
Date submitted for ethics approval [1] 289140 0
Approval date [1] 289140 0
Ethics approval number [1] 289140 0

Brief summary
When you receive a general anaesthetic for your operation, you will be asleep also unable to breath for yourself. Therefore, a breathing tube is inserted in your windpipe to allow the anaesthetist to assist your breathing while the surgeon operates.

This study aims to determine the rate at which your lungs ‘suck in’ (or inspire) air while you are asleep and not breathing.This is possible with a continuous opening from your lungs to oxygen source. We believe that if the composition of the air being sucked into your lungs is all oxygen than it will continue to flow at a constant rate but if the composition of air is the same as in the room (20% oxygen) then the flow rate will tail off (like slowly turning off a tap). Computer programs and our understanding of the biology of people suggest this would be the case. However, we have no proof of this at present.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 39446 0
Dr Lip Yang Ng
Address 39446 0
Department of Anaesthesia and Pain Medicine
King Edward Memorial Hospital
374, Bagot Road
WA 6008
Country 39446 0
Phone 39446 0
+61(8) - 9340 2222
Fax 39446 0
+61(8) - 9340 2227
Email 39446 0
Contact person for public queries
Name 39447 0
Dr Lip Yang Ng
Address 39447 0
Department of Anaesthesia and Pain Medicine
King Edward Memorial Hospital
374, Bagot Road
WA 6008
Country 39447 0
Phone 39447 0
+61(8) - 9340 2222
Fax 39447 0
+61(8) - 9340 2227
Email 39447 0
Contact person for scientific queries
Name 39448 0
Dr Lip Yang Ng
Address 39448 0
Department of Anaesthesia and Pain Medicine
King Edward Memorial Hospital
374, Bagot Road
WA 6008
Country 39448 0
Phone 39448 0
+61(8) - 9340 2222
Fax 39448 0
+61(8) - 9340 2227
Email 39448 0

No information has been provided regarding IPD availability
Summary results
No Results