High Frequency Ventilation
OVERVIEW
High Frequency Ventilation ventilation with small tidal volumes at high frequencies
TYPES
- high-frequency positive-pressure ventilation
- high-frequency percussive ventilation
- high-frequency jet ventilation
- high-frequency oscillatory ventilation
HIGH FREQUENCY POSITIVE-PRESSURE VENTILATION
- TV 3-4mL/kg at 60-100/min
- conventional mechanical ventilator
- often used with high PEEP
- expiration is passive and relies on elastic recoil
- -> risks: gas trapping, hyperinflation and overdistension injury
HIGH-FREQUENCY PERCUSSIVE VENTILATION
- aims to combine high frequency and conventional ventilation
- conventional ventilator used + a gas driven piston at the end of the ETT
- piston generates oscillation at 3-15Hz with short expiratory times which are superimposed on conventional inspiratory-expiratory pressure waves.
- high frequency bursts generate auto-PEEP through breath stacking -> then are stopped and allow alveolar pressure to fall back to baseline.
- improves alveolar recruitment with exposing them to high peak airway pressures
HIGH FREQUENCY JET VENTILATION
- jet drive pressure augments TV
- expiration is passive and gas trapping with intrinsic PEEP can develop
- risks: trauma to upper airway, humidification and warming a problems, lung injury through shear forces
HIGH-FREQUENCY OSCILLATORY VENTILATION
- oscillating diaphragm creates pressure waves in the ventilator circuit.
- diaphragm is active in both directions -> creates inspiratory and expiratory pressure waves -> expiration is active.
- clinicians set: flow rate, mean airway pressure, frequency, inspiratory-expiratory ratio, energy applied to the oscillating diaphragm.
- see HFOV page for more details
Advantages
- decreased risk of overdistention injury
- increases mean airway pressure -> improved oxygenation and prevention of atelectrauma
- good evidence base in paediatrics and neonates
References and Links
Journal articles
- Evans E, Biro P, and Bedforth N. Jet ventilation. Contin Educ Anaesth Crit Care Pain (2007) 7 (1): 2-5 doi:10.1093/bjaceaccp/mkl061 [Cited 21 Dec 2014] Available at URL: http://ceaccp.oxfordjournals.org/content/7/1/2.full
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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