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Trial registered on ANZCTR

Registration number
Ethics application status
Not yet submitted
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Detection, quantification and differentiation of upper and lower airway obstruction during mechanical ventilation
Scientific title
Detection of upper and lower airway obstruction in patients with normal lungs and chronic obstructive airways disease and asthma while being mechanically ventilated
Secondary ID [1] 259816 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Lung Disease
265397 0
Condition category
Condition code
Respiratory 265553 265553 0 0
Other respiratory disorders / diseases

Study type
Patient registry
Target follow-up duration
Target follow-up type
Description of intervention(s) / exposure
Observation of airways resistance in patients that are mechanically ventilated.
Two groups of patients will be selected, patients with normal lungs and patients with lower airway obstruction(COAD and asthma)
Each patient will be placed on controlled mechanical ventilation, in SIMV and progressively smaller diameter endotracheal tubes will be inserted into the existing endotracheal tube for a period of less than one minute.
Measurements of flow and volume and determination of resistance will be determined.
The patients will have these measurements done within an hour.
The patients will be recruited when they are in intensive care. The recruitment will therefore not be planned. Only when patients are deemed suitable candidates by their existing ventilation will a relative be contacted for consent purposes.
Intervention code [1] 264257 0
Not applicable
Comparator / control treatment
Patients with normal lungs
Control group

Primary outcome [1] 262359 0
Determination of airway resistances by analysis of the flow and volume pressure curves from a ventilator. These flow and volumes will be measured after insertion of three progressively decreasing sized endotracheal tubes into already existing endotracheal tubes in an unconscious mechanically ventilated patient.
Timepoint [1] 262359 0
Immediately after decreasing airway resistance for less than one minute.
Secondary outcome [1] 273624 0
The above measurements will be analysed to determine the best marker for upper and lower airway resistances.
Timepoint [1] 273624 0
Analysis after ventilatory waveform data has been recorded.

Key inclusion criteria
Unconscious patients intubated and mechanically ventilated in intensive care.
1 group with normal lungs and 1 group with Chronic obstructive airways disease or asthma
Minimum age
18 Years
Maximum age
99 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Patients not under mechanical ventilation in the intensive care environment

Study design
Defined population
Statistical methods / analysis

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)

Funding & Sponsors
Funding source category [1] 264697 0
Name [1] 264697 0
Intensive care department
Address [1] 264697 0
The Alfred Hospital
Commercial Road Prahran Victoria 3181
Country [1] 264697 0
Primary sponsor type
Intensive care department
The Alfred Hospital
Commercial Road Prahran Victoria 3181
Secondary sponsor category [1] 263831 0
Name [1] 263831 0
Address [1] 263831 0
Country [1] 263831 0

Ethics approval
Ethics application status
Not yet submitted
Ethics committee name [1] 266691 0
Research and Ethics Unit
Ethics committee address [1] 266691 0
The Alfred Hospital
Commercial Road Prahran 3181
Ethics committee country [1] 266691 0
Date submitted for ethics approval [1] 266691 0
Approval date [1] 266691 0
Ethics approval number [1] 266691 0

Brief summary
During mechanical ventilation, increased upper airway resistance may be due to a partial obstruction of the
artificial airway or a large airway abnormality. Increased lower airway resistance is usually due to acute or
chronic airways disease. Either of these problems can lead to increased work of breathing, uncoordinated
ventilator support, respiratory distress and difficulty weaning. Recognition of these problems can lead to
important interventions such as bronchoscopy, artificial airway change or reposition, bronchodilator therapy
and change of ventilation strategy that can improve patient distress and safety. Quantification of these
variables can allow assessment of severity and the response to intervention.
Our hypotheses are that
1. the most valuable variable for quantifying reduced expiratory airflow will be the passive expiratory volume
expired during the first second of expiration PEV1 expressed as a percentage of the Vt (PEV1/Vt ratio). This
is similar to the well recognised standard of FEV1/VC ratio from spirometric quantification of (lower) airflow
2. the most valuable variable for quantifying increased inspiratory resistance during VCV with decelerating
inspiratory flow or during PCV will be the difference between the Paw and calculated Palv during early
inspiration divided by the inspiratory flow at that time.
3. Upper airway obstruction will be distinguished from and lower airway obstruction by a higher inspiratory
resistance relative expiratory resistance
We propose to examine these hypotheses in patients with normal lungs with added inspiratory resistances
and in patients with lower airway obstruction (COAD or asthma) to show whether measurements of flow and
volume are independent of or can account for ventilator pattern (flow rate, flow pattern, tidal volume) and can
recognise and quantify both increasing resistances in large (upper) airways and lower airway obstruction to
distinguish between them.
Two patient groups will be selected based on the following lung pathology
1. Normal Lungs: 20 mechanically ventilated patients with no significant underlying lung disease and no
significant lung injury will be selected.
Each will be studied to provide a normal values of the resistance measurements.
Then each will be given a series of 3 upper airway resistances for a period of less than a minute to mimic
large airway obstruction (similar to a partially blocked endo-tracheal or tracheostomy tube). This will be
achieved by placing a 10 cm sterilized flexible tube in the endo-tracheal or tracheostomy tube to simulate a
residual diameter equivalent to an ETT size (internal diameter) 6, 4.5 and 3 mm. This is little different to and
carries no more risk than routine patient suctioning where the artificial airway is partly occluded to a similar
degree for a short time
2. Lower airway obstruction (COPD, Asthma): 20 mechanically ventilated patients with known obstructive
airways disease (lower airway obstruction)
Each patient group will be placed in controlled mechanical ventilation and given the same series of
ventilatory patterns to determine the reliability of the measurements of inspiratory and expiratory resistance
measurements under different ventilatory conditions
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 32360 0
Address 32360 0
Country 32360 0
Phone 32360 0
Fax 32360 0
Email 32360 0
Contact person for public queries
Name 15607 0
David Tuxen
Address 15607 0
Intensive Care , The Alfred, Commercial Rd Prahran,
Country 15607 0
Phone 15607 0
+61 3 90763036
Fax 15607 0
+61 2 90763780
Email 15607 0
Contact person for scientific queries
Name 6535 0
David Tuxen
Address 6535 0
Intensive Care , The Alfred, Commercial Rd Prahran, Victoria
Country 6535 0
Phone 6535 0
+61 3 90763036
Fax 6535 0
+61 3 90763780
Email 6535 0

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