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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
21/04/2017
Type of registration
Prospectively registered

Titles & IDs
Public title
A comparison of arterial and blood gas analyses in sleep studies
Scientific title
Gas Analysis in Sleep study: a comparison of arterial and blood gas analyses in sleep study participants
Secondary ID [1] 291655 0
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 302810 0
Condition category
Condition code
Respiratory 302304 302304 0 0
Other respiratory disorders / diseases
Respiratory 302305 302305 0 0
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.
The venous and arterial blood tests will be taken by nursing staff, sleep scientists and occasionally doctors where appropriate.
Intervention code [1] 297741 0
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] 301713 0
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.
Timepoint [1] 301713 0
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] 301833 0
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.
Timepoint [2] 301833 0
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] 333656 0
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.
Timepoint [1] 333656 0
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] 333959 0
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] 333959 0
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] 333978 0
Data modelling to illustrate how the pvCO2-paCO2 relationship is affected by pH, haemoglobin, oxygen saturation, bicarbonate or a combination of these.
Timepoint [3] 333978 0
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] 333979 0
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] 333979 0
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] 333980 0
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] 333980 0
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).

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
Gender
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
Mean age and the percentage of tests from males will be reported.
Tests will be done for normality of data distribution. (eg. “gladder” in Stata)
Repeated-measures ANCOVA will be used for the primary analysis of pvCO2-paCO2 controlling for within-subject correlation against the hypothesized 0mmHg and forms the basis for the sample size calculation above.
Linear regression will provide the absolute and relative bias of pvCO2 vs paCO2, reporting the constant and gradient of the derived equation and the r2 value. Similar statistics can be performed for the relationship between (paCO2 vs ptCO2) and (pvCO2 vs ptCO2).
Collected data is to be used to test equation/s for estimating paCO2 from pvCO2 and other data collected in this study (in particular the pulse oximetry reading). Multivariate linear regressions with co-variates be used to explore the hypothesis of the impact of variables [saO2 – svO2] and [saO2 – svO2]*Hb on the degree of difference in paCO2 and estimated values.
A Bland-Altman bias plot, linear regression/ MANCOVA, 95% limits of agreement, F-tests of co-variates and a comparison of correlation coefficients (using Fisher’s z transformation and its variants such as corcor in Stata) will be used to test differences between true and estimated values of paCO2.
Similar statistics will be performed for pH, bicarbonate and base-excess where appropriate.
A pre-specified subgroup of patients with a pCO2 >60mmHg may be expanded upon.

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
VIC
Recruitment hospital [1] 7816 0
Austin Health - Austin Hospital - Heidelberg
Recruitment postcode(s) [1] 15749 0
3084 - Heidelberg

Funding & Sponsors
Funding source category [1] 296155 0
Hospital
Name [1] 296155 0
Austin Hospital
Address [1] 296155 0
145 Studley Rd, Heidelberg VIC 3084
Country [1] 296155 0
Australia
Funding source category [2] 296156 0
Other Collaborative groups
Name [2] 296156 0
Institute for Breathing and Sleep
Address [2] 296156 0
145 Studley Rd, Heidelberg VIC 3084
Country [2] 296156 0
Australia
Primary sponsor type
Hospital
Name
Austin Hospital
Address
145 Studley Rd, Heidelberg VIC 3084
Country
Australia
Secondary sponsor category [1] 295056 0
Other Collaborative groups
Name [1] 295056 0
Institute for Breathing and Sleep
Address [1] 295056 0
145 Studley Rd, Heidelberg VIC 3084
Country [1] 295056 0
Australia

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 297402 0
Austin Health Human Research Ethics Committee
Ethics committee address [1] 297402 0
145 Studley Rd, Heidelberg VIC 3084
Ethics committee country [1] 297402 0
Australia
Date submitted for ethics approval [1] 297402 0
16/10/2016
Approval date [1] 297402 0
31/03/2017
Ethics approval number [1] 297402 0
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 73926 0
Prof Christine McDonald
Address 73926 0
Austin Health
145 Studley Rd, Heidelberg VIC 3084
Country 73926 0
Australia
Phone 73926 0
+61394965000
Fax 73926 0
Email 73926 0
christine.mcdonald@austin.org.au
Contact person for public queries
Name 73927 0
Prof Christine McDonald
Address 73927 0
Austin Health
145 Studley Rd, Heidelberg VIC 3084
Country 73927 0
Australia
Phone 73927 0
+61394965000
Fax 73927 0
Email 73927 0
christine.mcdonald@austin.org.au
Contact person for scientific queries
Name 73928 0
Dr Steven Lindstrom
Address 73928 0
Austin Health
145 Studley Rd, Heidelberg VIC 3084
Country 73928 0
Australia
Phone 73928 0
+61394965000
Fax 73928 0
Email 73928 0
drsjlindstrom@gmail.com

No data has been provided for results reporting
Summary results
Not applicable