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Trial registered on ANZCTR

Registration number

ACTRN12616000531415

Ethics application status

Approved

Date submitted

20/04/2016

Date registered

26/04/2016

Date last updated

17/01/2024

Date data sharing statement initially provided

25/07/2019

Type of registration

Prospectively registered

Titles & IDs

Public title

High flow humidified nasal oxygenation in pregnant women

Scientific title

Efficacy of high flow humidified nasal oxygenation in healthy pregnant women and in women undergoing caesarean section under general anaesthesia

Secondary ID [1]

None

Universal Trial Number (UTN)

U1111-1182-1418

Trial acronym

The HINOP Study

Linked study record

Health condition

Health condition(s) or problem(s) studied:

Pregnancy

Oxygenation

Condition category

Condition code

Anaesthesiology

Anaesthetics

Reproductive Health and Childbirth

Childbirth and postnatal care

Intervention/exposure

Study type

Interventional

Description of intervention(s) / exposure

In this prospective study we aim to recruit two groups of women. Each woman will be placed on a hospital bed in an optimally ramped position and with a right lateral pelvic wedge to minimise aortocaval compression. Baseline vital signs will be measured. Whilst the woman is breathing room air (FiO2 21%) a tightly fitting face mask will be applied by a trained investigator (anaesthetist, anaesthetic registrar, medical student, or nurse) and a good seal and ideal fitting will be determined by observing the capnography trace. The face mask will then be removed. High flow humidified nasal cannulae (Optiflow (Trademark)) will then be inserted into the woman’s nostrils by the trained investigator (anaesthetist, anaesthetic registrar, trained medical student, or nurse). Humidification will be set at 44 mg/l and oxygen concentration will be 100%. The oxygen flow will be commenced (first 30 seconds at 30 l.min-1, then next 150 seconds at 50 l.min-1). Each woman will be instructed to take deep breaths. At the end of three minutes the woman will be asked to hold her breath in inspiration while the nasal cannulae are quickly removed and the tightly fitting face mask (connected to 6 l.min-1 air FiO2 100%) will be applied. The woman will then be asked to exhale normally and breathe normally. The second group of women will be those who are undergoing general anaesthesia for caesarean section. Each woman will be placed on a hospital bed in an optimally ramped position and with a right lateral pelvic wedge to minimise aortocaval compression. Baseline vital signs will be measured. A tightly fitting face mask (connected to at least 6 l.min-1 oxygen (at the discretion of the treating anaesthetist) FiO2 100%) will be applied by the anaesthetist or anaesthetic registrar and a good seal obtained (indicated by capnography trace). Once the woman’s FetO2 reaches 90% or at the discretion of the anaesthetist/anaesthetic registrar, general anaesthesia will be induced with cricoid pressure applied. The face mask will then be removed. High flow humidified nasal cannulae (Optiflow (trademark)) will then be inserted into the woman’s nostrils by the trained investigator (anaesthetist, anaesthetic registrar, medical student, or nurse). Humidification will be set at 44 mg/l and oxygen concentration will be 100%. The oxygen flow will be commenced at 70 l.min-1. Chin lift and jaw thrust will be performed. At the discretion of the treatment anaesthetist once muscle relaxation deemed to have taken effect tracheal intubation will be attempted and oxygenation and ventilation will occur once successful. (the Apnoeic oxygenation group). After successful intubation of the trachea has been achieved nasal humidified oxygenation will cease and the nasal cannulae will be removed.

Intervention code [1]

Prevention

Intervention code [2]

Treatment: Other

Comparator / control treatment

The comparator group is the Pre-oxygenation group. Each woman will be placed on a hospital bed in an optimally ramped position and with a right lateral pelvic wedge to minimise aortocaval compression. Baseline vital signs will be measured. Whilst the woman is breathing room air (FiO2 21%) a tightly fitting face mask will be applied trained investigator (anaesthetist, anaesthetic registrar, medical student, or nurse) and a good seal and ideal fitting will be determined by observing the capnography trace. The face mask will then be removed. High flow humidified nasal cannulae (Optiflow™) will then be inserted into the woman’s nostrils by the trained investigator (anaesthetist, anaesthetic registrar, medical student, or nurse). Humidification will be set at 44 mg/l and oxygen concentration will be 100%. The oxygen flow will be commenced (first 30 seconds at 30 l.min-1, then next 150 seconds at 50 l.min-1). Each woman will be instructed to take deep breaths. At the end of three minutes the woman will be asked to hold her breath in inspiration while the nasal cannulae are quickly removed and the tightly fitting face mask (connected to 6 l.min-1 air FiO2 21%) will be applied. The woman will then be asked to exhale normally and breathe normally and the peak FetO2 and time to achieve FetO2 of 21% will be recorded.

Control group

Active

Outcomes

Primary outcome [1]

Pre-oxygenation group - End-tidal oxygen fraction measured by the end tidal gas analyser on the anaesthetic machine

Timepoint [1]

After three minutes of pre-oxygenation with high flow humidified nasal oxygenation.

Primary outcome [2]

Apnoeic oxygenation group - Lowest oxygen saturation level measured by the pulse oximeter

Timepoint [2]

Pulse oximetry (oxygen saturation monitor) monitoring will be continuous and this is displayed and recorded continuously. The lowest recorded oxygen saturation during the time from completion of routine pre-oxygenation until 5 minutes after successful tracheal intubation will be the numerical data point recorded.

Secondary outcome [1]

Pre-oxygenation group - Comfort level of the standard face mask and the high flow nasal cannuale assessed using a 5-Point Likert Scale.

Timepoint [1]

At completion of the study protocol

Eligibility

Key inclusion criteria

Pre-oxygenation group - Pregnant women at term ( greater than or equal to 36 weeks gestation)
Apnoeic oxygenation group - Any pregnant woman undergoing general anaesthesia caesarean section

Minimum age

18 Years

Maximum age

40 Years

Sex

Females

Can healthy volunteers participate?

Yes

Key exclusion criteria

Significant nasal pathology

Study design

Purpose of the study

Prevention

Allocation to intervention

Non-randomised trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

N/A

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

N/A

Masking / blinding

Open (masking not used)

Who is / are masked / blinded?

Intervention assignment

Other

Other design features

In this prospective study we aim to recruit two groups of women. The first group of women will be those who will electively undertake high flow humidified nasal oxygenation in order to examine this technique in the setting of pre-oxygenation (the Pre-oxygenation group). The second group of women will be those who are undergoing general anaesthesia for caesarean section and will have high flow humidified nasal oxygenation after induction of anaesthesia in the setting of apnoeic oxygenation (the Apnoeic oxygenation group).

To examine the use of high flow humidified nasal oxygenation for pre-oxygenation we aim to determine the FetO2 in 80 term pregnant women at the end of a protocolised pre-oxygenation method with a high flow humidified nasal cannulae system (Optiflow (trademark)). We aim to assess whether this new technique is able to obtain FetO2 of greater than or equal to 90% after three minutes of pre-oxygenation.

To examine the use of high flow humidified nasal oxygenation for apnoeic oxygenation we aim to recruit women undergoing general anaesthesia caesarean section and use our routine pre-oxygenation technique supplemented with high flow nasal oxygenation immediately after pre-oxygenation and during tracheal intubation and measure oxygen saturation levels and times until successful intubation of the trachea.

Phase

Not Applicable

Type of endpoint/s

Efficacy

Statistical methods / analysis

Pre-oxygenation group
A sample of 80 women will be recruited. This is a pragmatic sample size based on the four months (16 weeks) of recruiting by Dr P Tan. It is anticipated that recruitment will take place in hours on weekdays. Approximately 25 women undergo elective caesarean section each week and with an approximate 20% recruitment rate, 80 women will be recruited during this time. [The previous and only study examining pre-oxygenation in pregnant women had a sample size of only 20 women.] Our hypothesis is that end-tidal oxygen values of equal to or greater than 90% can be achieved in at least 80% of term pregnant women after three minutes of oxygenation using high flow humidified nasal oxygenation.

Apnoeic oxygenation group
For the apnoeic oxygenation study it is anticipated that at least 20% of the women undergoing general anaesthesia caesarean section will be recruited to this study over a one year period (30 women). This is based on the following estimates of numbers - approximately 7500 women give birth with a conservative 25% caesarean section rate of which 8% are performed under general anaesthesia. Information about the study protocol will be disseminated within the anaesthetic department and operating theatres, and experience with nasal oxygenation will increase in the department over the first few months of the pre-oxygenation study thereby facilitating participant enrolment in the study. Our hypothesis is that high flow humidified nasal oxygenation can prevent a desaturation (SpO2) value of greater than 92% in 100% of women prior to successful intubation of the trachea

Recruitment

Recruitment status

Recruiting

Date of first participant enrolment

Anticipated

19/08/2016

Actual

19/08/2016

Date of last participant enrolment

Anticipated

31/12/2024

Actual

Date of last data collection

Anticipated

31/01/2025

Actual

Sample size

Target

110

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

VIC

Recruitment hospital [1]

The Royal Women's Hospital - Parkville

Funding & Sponsors

Funding source category [1]

Hospital

Name [1]

The Royal Women's Hospital

Address [1]

Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria, Australia 3052

Country [1]

Australia

Primary sponsor type

Hospital

Name

The Royal Women's Hospital

Address

Department of Anaesthesia, The Royal Women’s Hospital,
Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria, Australia 3052

Country

Australia

Secondary sponsor category [1]

None

Name [1]

N/A

Address [1]

N/A

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

The Royal Women's Hospital Human Research Ethics Committee

Ethics committee address [1]

The Royal Women’s Hospital, 
Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria,  Australia 3052

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

04/05/2016

Approval date [1]

02/08/2016

Ethics approval number [1]

Summary

Brief summary

One of the most serious complications of general anaesthesia in pregnant women is hypoxic brain injury and fetal and/or maternal death related to difficulty oxygenating a pregnant woman. This is due to inability of the anaesthetist to intubate the trachea and ventilate a pregnant woman because of the changed anatomy and physiology of pregnant women leading to the known problem of the difficult obstetric airway. The latest obstetric airway management guidelines by the Obstetric Anaesthetists’ Association (OAA) & Difficult Airway Society (DAS) discuss the importance of pre-oxygenation in managing pregnant women undergoing general anaesthesia as it increases oxygen reserve in the lungs during apnoea. The guidelines recommend that the end-tidal oxygen fraction (FetO2) of equal to or greater than 90%, indicating effective lung denitrogentation, should be achieved prior to induction of anaesthesia. The current way anaesthetists pre-oxygenate pregnant women undergoing general anaesthesia is to use a tight fitting face mask to deliver 100% inspired oxygen. The new guideline also states an alternative method. The guidelines states that nasal oxygenation, to facilitate bulk flow of oxygen to the alveoli could be considered as part of  
1.	Pre-oxygenation - A pre-oxygenation method and 
2.	Apnoeic oxygenation - A technique to increase apnoeic time. 
The guideline suggests that the anaesthetist should consider attaching nasal cannulae with 5 l.min-1 oxygen flow before starting pre-oxygenation, to maintain bulk flow of oxygen (O2) during intubation attempts, or attach nasal oxygenation after pre-oxygenation during the apnoeic period. There is also mention of humidified high flow nasal oxygenation however no data exists in pregnant women as to its safety or efficacy or acceptability by pregnant women. It is possible that a new pre-oxygenation technique, using high flow humidified nasal oxygen, may have an application in pregnant women however before this new pre-oxygenation technique is considered, it should be equivalent (at least) to the current available technique in terms of safety and efficacy i.e. be able to obtain FetO2 of at least 90% after three minutes of pre-oxygenation. Currently there are no studies reporting FetO2 values in pregnant women with high-flow humidified nasal oxygen delivery systems and no studies reporting the use of nasal high flow oxygen to increase apnoea times therefore it is unclear whether humidified high flow nasal oxygenation, is safe and beneficial in pregnant women. 

In this prospective study we aim to recruit two groups of women. The first group of women will be those who will electively undertake high flow humidified nasal oxygenation in order to examine this technique in the setting of pre-oxygenation (Pre-oxygenation group). The second group of women will be those who are undergoing general anaesthesia for caesarean section and will have high flow humidified nasal oxygenation after induction of anaesthesia.

Trial website

N/A

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

A/Prof Alicia Dennis

Address

Department of Anaesthesia, The Royal Women’s Hospital,
Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria, Australia 3052

Country

Australia

Phone

+61 3 8345 2381

Fax

+61 3 8345 2379

alicia.dennis@thewomens.org.au

Contact person for public queries

Name

Alicia Dennis

Address

Department of Anaesthesia, The Royal Women’s Hospital,
Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria, Australia 3052

Country

Australia

Phone

+61 3 8345 2381

Fax

+61 3 8345 2379

alicia.dennis@thewomens.org.au

Contact person for scientific queries

Name

Alicia Dennis

Address

Department of Anaesthesia, The Royal Women’s Hospital,
Locked Bag 300, Corner Grattan Street and Flemington Road, Parkville, Victoria, Australia 3052

Country

Australia

Phone

+61 3 8345 2381

Fax

+61 3 8345 2379

alicia.dennis@thewomens.org.au

Data sharing statement

Will individual participant data (IPD) for this trial be available (including data dictionaries)?

Yes

What data in particular will be shared?

Spreadsheet of de-identified participant characteristics, baseline vital sign data, respiratory data during the experiment

When will data be available (start and end dates)?

1st April 2020 - likely time of publication of data
No end date determined

Available to whom?

The data will be available as a supplementary file to the publication therefore will be available to readers of the particular journal

Available for what types of analyses?

As the data will be raw data the anaylses that will be able to be performed on the data will be at the discretion of the reviewing researchers

How or where can data be obtained?

The data will be available as a supplementary file to the publication

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 humidified nasal pre-oxygenation in pregnant women: The HENOP1 Study.	2018
Embase	High-flow humidified nasal preoxygenation in pregnant women: a prospective observational study.	2019	https://dx.doi.org/10.1016/j.bja.2018.08.015

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

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Documents added automatically