Physiological Response to Heliox21 and Air O2
Recruitment status was: Not yet recruiting
|Study Design:||Allocation: Randomized
Endpoint Classification: Pharmacodynamics Study
Intervention Model: Crossover Assignment
Masking: Single Blind (Subject)
Primary Purpose: Basic Science
|Official Title:||Phase 4, Single Centre, Single Blinded,Prospective Randomised Cross Over Comparison on the Physiological Response of Post Extubation Intensive Care Patients to Non-invasive Ventilation Using Either Air O2 or Heliox21|
- The difference between the f/VT ratio* [ Time Frame: After four hours of Heliox21 and after four hours of Air O2. ] [ Designated as safety issue: No ]*f/VT is the measurement of breathing rate to tidal volume (f/VT) ratio
|Study Start Date:||January 2012|
|Estimated Study Completion Date:||April 2013|
|Estimated Primary Completion Date:||January 2013 (Final data collection date for primary outcome measure)|
For Heliox21 the percentage of O2 will match the percentage of O2 prior to extubation, and Helium will make up the remainder (e.g. Helium 65% + O2 35%), and the O2 concentration will be titrated as their clinical condition indicates (as O2 increases Helium will decrease and vice versa).
|Active Comparator: Air O2||
Drug: Air O2
For Air-O2 the percentage of O2 delivered will match the patient's percentage of O2 prior to extubation, and will be titrated as their clinical condition indicates.
Failure to wean from mechanical ventilatory support occurs when the magnitude of respiratory system loading exceeds its capacity to respond. Extubation success depends on the condition being resolved or improved. Gas exchange capacity, respiratory muscle strength, laryngeal function and cough strength, nutritional status and psychological state can all lead to extubation failure. However, efforts to reduce the work of breathing might offer an alternative strategy.
Studies recently carried out in both paediatric and adult populations disclose the serious consequences of failed extubation, namely prolonged intensive care and hospital stays, greater mortality rates and increased care costs.
Gas flow in an airway can be either laminar or turbulent. There needs to be a greater pressure differential to drive a turbulent flow than a laminar one. Helium is an inert gas with no systemic biological effects (at standard temperature and pressure).
The low density and viscosity of Helium means that its substitution for nitrogen in air allows laminar flow to be maintained at much higher flow rates, and flow rates to be maintained at much lower working pressures (5). As a result, the use of helium-oxygen mixtures (Heliox21) has potential to reduce work of breathing, and also to limit dynamic gas trapping through increased cavity emptying, and altered lung mechanics/ forced expiratory pressures. As a result, Heliox21 has been used as a respiratory therapeutic bridge for over 30 years, with demonstrable advantage in the management of conditions including tracheal obstruction and chronic obstructive pulmonary disease (COPD).
In theory, the use of Heliox21 should reduce work of breathing by improving the balance between work demand and capacity during the process of weaning patients from mechanical ventilation. In general studies of the use of Heliox21 after extubation have been limited. Thus, we aim to extend our knowledge of the potential role for Heliox21 in the post-extubation environment of the Intensive Care Unit. Whilst Heliox21 has generally been administered through a simple face-mask (+/- rebreathing bag), the development of the HAMILTON G5 AVEA ventilator now allows the accurate administration of Heliox21 (21% helium/79% oxygen) with defined inspired fractional oxygen concentrations. This advent offers the means to safely administer helium as an adjunct to non-invasive ventilatory support.
Main inclusion criteria:
All patients with a predicted requirement for post extubation non-invasive ventilatory support continuous positive airway pressure/bilevel positive airway pressure/noninvasive ventilation(CPAP/BiPAP/NIV) will be eligible.
The primary outcome measure:
The difference between the frequency to tidal volume (f/VT) ratio* after four hours of Heliox21 and the f/VT ratio after four hours of Air O2.
Please refer to this study by its ClinicalTrials.gov identifier: NCT01498432
|Whittington Hospital NHS Trust|
|London, United Kingdom, N19 5NF|
|Study Director:||Chris Hargreaves||Whittington Hospital NHS Trust|
|Principal Investigator:||Daniel S Martin||University College, London|