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Trial registered on ANZCTR

Registration number

ACTRN12617000562370

Ethics application status

Approved

Date submitted

19/04/2017

Date registered

21/04/2017

Date last updated

11/03/2020

Date data sharing statement initially provided

11/03/2020

Type of registration

Prospectively registered

Titles & IDs

Public title

A comparison of arterial and blood gas analyses in sleep studies

Scientific title

GAS (Gas Analysis in Sleep) study: a comparison of arterial and venous blood gas analyses in sleep study participants
CapGAS substudy: a comparison of arterial and capillary blood gas analyses in sleep study participants

Secondary ID [1]

Nil known

Universal Trial Number (UTN)

U1111-1195-2949

Trial acronym

GAS Study

Linked study record

None

Health condition

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

Hypoventilation

Condition category

Condition code

Respiratory

Other respiratory disorders / diseases

Respiratory

Sleep apnoea

Intervention/exposure

Study type

Interventional

Description of intervention(s) / exposure

A venous blood gas will be taken as paired with each arterial blood gas (generally two per patient in a one night sleep study at the commencement and end of the study). Transcutaneous measurements of CO2, if taken as part of the sleep study, will also be recorded, along with the time between blood samples and relevant personal information.

In the ethics-approved substudy, on completion of enrolment for venous and arterial blood gas comparisons, further participants will be recruited to compare capillary and arterial blood gases. Information on patient preference on sampling technique is recorded.

Intervention code [1]

Diagnosis / Prognosis

Comparator / control treatment

The study compares the values obtained from venous and arterial blood gas measurements and non-invasive percutaneous measurements. Each patient provides both "treatment" and "control" data.

Control group

Active

Outcomes

Primary outcome [1]

Relationship between arterial and venous blood gas carbon dioxide tensions in terms of absolute and relative bias (a composite outcome). This is assessed statistically by comparing the values from arterial and venous blood gases. In the independently-analysed CapGAS substudy the comparison will be between capillary and arterial blood gases.

Timepoint [1]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Primary outcome [2]

Relationship between arterial and venous blood gas carbon dioxide tensions in terms of a Bland-Altman plot and 95% limits of agreement. This is assessed statistically by comparing the values from arterial and venous blood gases. In the independently-analysed CapGAS substudy the comparison will be between capillary and venous blood gases.

Timepoint [2]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [1]

Comparison of the difference of (percutaneous carbon dioxide vs venous carbon dioxide measurements) and (percutaneous carbon dioxide vs arterial carbon dioxide measurements) as a single endpoint. This is assessed statistically by comparing the values from arterial and venous blood gases and the percutaneous carbon dioxide measurement recorded at the time of taking the blood gases. In the CapGAS substudy, capillary samples replace venous samples.

Timepoint [1]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [2]

Data modelling to illustrate any evident consistent relationships between venous and ABG pCO2 when measured twice in the same patient over the course of the sleep study.

Timepoint [2]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [3]

Data modelling to illustrate how the pvCO2-paCO2 relationship is affected by pH, haemoglobin, oxygen saturation, bicarbonate or a combination of these.

Timepoint [3]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [4]

Relationship between arterial and venous blood gas pH in terms of a Bland-Altman plot and 95% limits of agreement. This is assessed statistically by comparing the values from arterial and venous blood gases.

Timepoint [4]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [5]

Relationship between arterial and venous blood gas pH in terms of absolute and relative bias (a composite outcome). This is assessed statistically by comparing the values from arterial and venous blood gases.

Timepoint [5]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [6]

To determine if capillary blood gas samples can be obtained more consistently than ABG samples and the time required to obtain a successful CAPgas or ABG.

Timepoint [6]

At the time blood gases would otherwise be taken for the sleep study, which is generally at the start of the study (before sleep) and the end of the study (upon waking in the morning).

Secondary outcome [7]

To compare patient pain with arterial and capillary blood gas sampling using a rating scale.

Timepoint [7]

To compare operator preference between arterial and capillary blood gas sampling.

Eligibility

Key inclusion criteria

Patients having a diagnostic, continuous positive airway pressure (CPAP) or ventilation sleep study which includes arterial blood gas analysis.

Minimum age

18 Years

Maximum age

No limit

Sex

Both males and females

Can healthy volunteers participate?

No

Key exclusion criteria

Pregnancy, inability to consent, outside age group

Study design

Purpose of the study

Diagnosis

Allocation to intervention

Randomised controlled trial

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

The trial is randomised only as to the order of ABG and VBG collection, but participants are not randomised to a control group [there was no option above]. Patients will be allocated by sealed-envelope selection. Envelopes will be opaque and shuffled as well as is practicable.

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

Envelopes will be opaque and shuffled as well as is practicable.

Masking / blinding

Open (masking not used)

Who is / are masked / blinded?

Intervention assignment

Crossover

Other design features

Blinding will not be practicible.

Phase

Not Applicable

Type of endpoint/s

Statistical methods / analysis

Paired analysis of arterial and venous/capillary samples is to be made for carbon dioxide tension, pH, oxygen tension, oxygen saturation and total haemoglobin (as a marker of variability) by methods for testing measures. Correlation coefficients will be examined.

Recruitment

Recruitment status

Completed

Date of first participant enrolment

Anticipated

1/05/2017

Actual

28/06/2017

Date of last participant enrolment

Anticipated

7/07/2017

Actual

30/04/2019

Date of last data collection

Anticipated

8/07/2017

Actual

1/05/2019

Sample size

Target

141

Accrual to date

Final

142

Recruitment in Australia

Recruitment state(s)

VIC

Recruitment hospital [1]

Austin Health - Austin Hospital - Heidelberg

Recruitment postcode(s) [1]

3084 - Heidelberg

Funding & Sponsors

Funding source category [1]

Hospital

Name [1]

Austin Hospital

Address [1]

145 Studley Rd, Heidelberg VIC 3084

Country [1]

Australia

Funding source category [2]

Other Collaborative groups

Name [2]

Institute for Breathing and Sleep

Address [2]

145 Studley Rd, Heidelberg VIC 3084

Country [2]

Australia

Primary sponsor type

Hospital

Name

Austin Hospital

Address

145 Studley Rd, Heidelberg VIC 3084

Country

Australia

Secondary sponsor category [1]

Other Collaborative groups

Name [1]

Institute for Breathing and Sleep

Address [1]

145 Studley Rd, Heidelberg VIC 3084

Country [1]

Australia

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

Austin Health Human Research Ethics Committee

Ethics committee address [1]

145 Studley Rd, Heidelberg VIC 3084

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

16/10/2016

Approval date [1]

31/03/2017

Ethics approval number [1]

HREC/16/Austin/441

Summary

Brief summary

Patients having sleep/CPAP/ventilation (SCV) studies for chronic respiratory failure often require arterial blood to be taken for measurement of blood oxygen, pH and carbon dioxide measurement - so called arterial blood gases (ABGs). These measurements are used to assist in 
1.	identifying inadequate breathing
2.	determining need for assisted ventilation in patients with known or possible ventilatory disorders (eg chronic respiratory or neuromuscular disease or reduced ventilatory capacity associated with obesity ( “obesity hypoventilation syndrome”) .
3.	providing information to assist in modification of ventilator settings in such patients. 
An arterial blood sample is somewhat more difficult to obtain and generally believed to be more painful than a venous sample (venous blood gases (VBGs)), but there is currently no evidence that VBGs can adequately replace the role of ABGs in this setting.
The project will involve taking a venous blood sample for VBGs at the same time as the standard arterial blood sample (for ABGs) from patients already having SCV studies already including ABGs. The results from the arterial and venous samples will be compared. The study will involve an additional paired blood test for each ABG (estimated two per patient), during the same visit and should take minimal extra time (estimated 10 minutes total). At the end of the study we will compare the ABG and VBG measurements to see if we can use venous gases as a reliable alternative to ABGs in future. The data may also be used to see if we can use an equation to better approximate the arterial values from VBGs and if there is a consistent relationship between VBGs and transcutaneous measurements (across skin) of carbon dioxide, which are already being measured.

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Prof Christine McDonald

Address

Austin Health
145 Studley Rd, Heidelberg VIC 3084

Country

Australia

Phone

+61394965000

Fax

Email

christine.mcdonald@austin.org.au

Contact person for public queries

Name

Christine McDonald

Address

Austin Health
145 Studley Rd, Heidelberg VIC 3084

Country

Australia

Phone

+61394965000

Fax

Email

christine.mcdonald@austin.org.au

Contact person for scientific queries

Name

Steven Lindstrom

Address

Austin Health
145 Studley Rd, Heidelberg VIC 3084

Country

Australia

Phone

+61394965000

Fax

Email

drsjlindstrom@gmail.com

Data sharing statement

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

No

No/undecided IPD sharing reason/comment

Some data collected prior to 25th October 2018.

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

No additional documents have been identified.