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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
A comparison of the rate of rise of transcutaneous carbon dioxide during apnoeic oxygenation in microlaryngoscopy using transnasal humidified rapid insufflation ventilatory exchange (THRIVE) versus low flow tracheal insufflation: a randomised control trial
Scientific title
A comparison of the rate of rise of transcutaneous carbon dioxide during apnoeic oxygenation in microlaryngoscopy using transnasal humidified rapid insufflation ventilatory exchange (THRIVE) versus low flow tracheal insufflation: a randomised control trial
Secondary ID [1] 302598 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
laryngeal pathology 319481 0
carbon dioxide rate of rise 319482 0
Condition category
Condition code
Anaesthesiology 317446 317446 0 0
Respiratory 317447 317447 0 0
Other respiratory disorders / diseases

Study type
Description of intervention(s) / exposure
This study will involve patients undergoing elective microlaryngoscopy procedures under care of ENT and anaesthetics. These patients will be randomised on day of surgery using simple randomisation, assigning patients to one of two anaesthetic techniques;

ARM 1: Trans-nasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE)
Those patients enrolled into the THRIVE arm will be induced with high flow nasal cannula attached but not yet turned on. As surgery begins, they will have their face masks removed and high flow O2 at 100% 70L started via Optiflow THRIVETM apparatus (Fisher and Paykel Healthcare Ltd, Auckland, New Zealand).
ARM 2: Low Flow Intra-tracheal Oxygen Insufflation (Lo-Flo)
Those patients enrolled into the Lo-Flo arm will be induced. After face mask ventilation and waiting suitable time for paralysis, a low flow oxygen catheter will be passed through the glottic opening to sit mid tracheal level using standard intubating equipment (direct or indirect laryngoscopy). After this oxygen catheter has been place, the patient will be ventilated using face mask ventilation until the surgical start point. At this point, face mask will be removed and oxygen catheter attached to oxygen wall outlet will be started at 0.5L/min.

The maximal allowable time for either apnoea technique will have a 30 minute cut off point.

There will be 45 patients will be randomised into each trial arm.
As the patient arrives in the holding bay prior to their operation, the transcutaneous carbon dioxide (TcCO2) monitor will be connected to the patient. Upon entering the operating room, routine anaesthetic monitoring will be established. The patient will be pre-oxygenated using an appropriately size face mask until the end tidal oxygen (EtO2) > 70 mmHg. The patient will be induced with propofol 1-2mg/kg and/or propofol infusion (target controlled infusion or mg/hr), 0.1mcg-0.4mcg/kg/min remifentanil infusion and paralysed using a muscle relaxant.

Ventilation of the patient will occur using face mask technique until appropriate degree of paralysis and up to immediate commencement of surgery.

This study will be powered to show a true “no difference” in the rate of rise of TcCO2 between the two anaesthetic techniques.
Intervention code [1] 318882 0
Treatment: Devices
Comparator / control treatment
ARM 1: Trans-nasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE)
Control group

Primary outcome [1] 325482 0
Rate of rise of TcCO2 per unit time
Timepoint [1] 325482 0
Time zero will be the moment that the surgical laryngoscope first enters the patient’s oral cavity. TcCO2 is recorded continuously and electronically by the Sentec TcCO2 device. The TcCO2 will be measured every minute. The rate of CO2 rise will be calculated over the operative time period.
Secondary outcome [1] 388089 0
Maintenance of oxygenation
Timepoint [1] 388089 0
Oxygen saturation (SpO2) at time zero; and at the completion of surgery will be recorded. The times at which SpO2 falls to 95% and 92% will also be recorded, should these events occur.
Secondary outcome [2] 388090 0
Surgical conditions - this will seek the opinion of the surgical conditions from our otolaryngologist performing the microlaryngoscopy. This will be recorded immediately after surgery on a proforma describing quality surgical field as poor, adequate or excellent, with a free text comments section.
Timepoint [2] 388090 0
To be documented by consultant surgeon immediately after procedure
Secondary outcome [3] 388091 0
Oral, nose or throat discomfort as reported by patient
Timepoint [3] 388091 0
Discomfort defined by patient complaining of mucosal dryness or pain immediately post operatively and at day 3 -5 post operatively by telephone will be recorded on a scale of none, mild, moderate or severe.

Key inclusion criteria
All patients over the age of 18 years undergoing microlaryngoscopy procedure
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
BMI > 40
Expected > 30 minutes procedure time
Resting saturations on air < 92%

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
central randomisation by computer
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
simple randomisation using computer software
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Our aim is to show that our Lo-Flo catheter technique is non-inferior to THRIVE with regard to CO2 rise, with a non-inferiority margin of 15%. We have chosen 15% because a difference less than this would be insignificant in clinical practice. In a study similar to the one we are proposing, arterial CO2 rose by 0.24kPa/min with THRIVE; with a standard deviation (0.05). The rate of rise was close to linear over a period of up to 30 minutes.

We are assuming the numbers will be similar with the Lo-Flo catheter technique. We then assume that the average gradient is normally distributed and that it is valid to construct a 95% confidence interval for the mean gradient in each group. For a margin of 15% greater rate of rise of CO2 with cannula cf THRIVE, we then have (delta equal to 0.24 multiplied by 0.15, equals 0.036kPa/min)

Under these assumptions, we would need 41 per group to show non-inferiority with 90% power and alpha equal to 2.5%. We have therefore chosen to enrol 45 per group to allow for some failure dropouts.

Note that if it turns out that the cannula technique is better, we will know because the 95% CI for the difference between groups will exclude zero.

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] 17856 0
Monash Medical Centre - Moorabbin campus - East Bentleigh
Recruitment postcode(s) [1] 31714 0
3165 - East Bentleigh

Funding & Sponsors
Funding source category [1] 307025 0
Name [1] 307025 0
Monash Health
Address [1] 307025 0
823-865 Centre Road, Bentleigh East, VIC 3165
Country [1] 307025 0
Primary sponsor type
Monash Health Anaesthetic Department
823-865 Centre Road, Bentleigh East, VIC 3165
Secondary sponsor category [1] 307594 0
Name [1] 307594 0
Monash Health ENT Department
Address [1] 307594 0
823-865 Centre Road, Bentleigh East, VIC 3165
Country [1] 307594 0

Ethics approval
Ethics application status
Ethics committee name [1] 307156 0
Monash Health Human Research Ethics Committee
Ethics committee address [1] 307156 0
Monash Health, 246 Clayton Road
Clayton Vic 3168
Ethics committee country [1] 307156 0
Date submitted for ethics approval [1] 307156 0
Approval date [1] 307156 0
Ethics approval number [1] 307156 0

Brief summary
Trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE) has been widely taken up by anaesthetic and ear, nose and throat (ENT) departments worldwide for airway management. THRIVE is a technique that uses rapidly insufflated, heated and humidified oxygen administered via nasal cannula to maintain oxygenation during periods of apnoea.

It is regularly used for ENT procedures, in particular microlaryngoscopy. It allows for maintenance of oxygenation and unobscured surgical field by anaesthetic endotracheal tubes.

The mechanism by which THRIVE and other apnoeic techniques (such as low flow intra-tracheal oxygen insufflation) maintain oxygenation is well understood, i.e. bulk flow of oxygen from the upper airway to replace the volume of oxygen taken up from the alveoli. However, a concern with all apnoeic techniques is the rise of blood and tissue carbon dioxide (CO2) levels in the absence of ventilation. Much of the support for THRIVE has centred on claims that unlike other apnoeic techniques, it is effective at eliminating CO2..

Recently, however, a study (1) of THRIVE in ENT microlaryngoscopy patients has suggested that when arterial CO2 levels are measured, the rate of rise of CO2 is actually as much as would be expected with other apnoeic techniques.

In our anaesthetic department, we have considerable experience of apneoic oxygenation by low flow intra-tracheal oxygen insufflation (Lo-Flo). An oxygen catheter is directly passed under vision using a laryngoscope through the glottic opening to sit at mid tracheal level. This is then attached to oxygen supply at 0.5-1L/min.

Transcutaenous carbon dioxide (TcCO2) can be easily measured with a transcutaneous probe that attaches to the patient’s skin in a non painful, non invasive manner. It is applied a few minutes prior to the start of the procedure.

This study would build on the previous departmental experience with apnoeic oxygenation research. We plan to compare the two techniques of apnoeic oxygenation for ENT microlaryngoscopy, focusing particularly on the rate of rise of TcCO2. We believe it is likely that we will disprove the now widely held belief that CO2 rises less quickly with THRIVE than with other apnoeic techniques.

(1) Gustafsson IM, Lodenius A, Tunelli J, Ullman J, Jonsson-Fagerlund M. Apnoeic oxygenation in adults under general anaesthesia using transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) – a physiological study. British Journal of Anaesthesia 2017; 118: 610–7
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 106226 0
Dr Richard Barnes
Address 106226 0
Monash Health Anaesthetic Department, 246 Clayton Road, Clayton, Victoria, 3168
Country 106226 0
Phone 106226 0
+61 0395946666
Fax 106226 0
Email 106226 0
Contact person for public queries
Name 106227 0
Dr Katie Fitzsimons
Address 106227 0
Monash Health Anaesthetic Department, 246 Clayton Road, Clayton, Victoria, 3168
Country 106227 0
Phone 106227 0
+61 0395946666
Fax 106227 0
Email 106227 0
Contact person for scientific queries
Name 106228 0
Dr Richard Barnes
Address 106228 0
Monash Health Anaesthetic Department, 246 Clayton Road, Clayton, Victoria, 3168
Country 106228 0
Phone 106228 0
+61 0395946666
Fax 106228 0
Email 106228 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
Individual participant data will not be available during the trial.
What supporting documents are/will be available?
No other documents available
Summary results
No Results