High Frequency Ventilation ventilation with small tidal volumes at high frequencies
- 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
- 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
- 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