PHYSICS ALERT! – how gases are exchanged in HFOV HFOV relies on fancier mechanisms of gas exchange such as (take a deep breath, it’s a long list…) molecular diffusion, dispersion, turbulence, Pendelluft, cardiogenic mixing and collateral ventilation. This creates small tidal volumes (less than the dead space of the lung and the circuit). HFOV uses a constant distending pressure (mean airway pressure ) with pressure variations oscillating around the MAP at very high rates – up to 900 cycles per minute. In conventional ventilation, large pressure changes (the difference between PEEP and PIP) recreate ‘physiological’ tidal volumes, while gas exchange depends on bulk convection (expired gas exchanged for inspired gas). HFOV is a way to reduce maximum pressure, reduce tidal volume and reopen those alveoli, improving oxygenation. We still don’t know to what extent the different factors damage the lungs, but high pressures (barotrauma), shear stress (large tidal volumes) and high inspired oxygen levels are all culprits. In severe lung disease invasive, high pressure ventilation can be very damaging, and actually end up worsening the lung condition. In short: when a child or infant can no longer move enough air in and out of their lungs to maintain gas homeostasis, for whatever reason, this is our cue to step in with some form of mechanical ventilation (see this earlier post for the basics).Īll forms of mechanical ventilation are of course unphysiological, uncomfortable and potentially damaging to the lungs themselves.
High frequency oscillatory ventilation (HFOV) is an alternative method of mechanical ventilation which can help a patient out in specific circumstances, and can be used as a ‘lung protective strategy’ in the management of some severe lung conditions.
Osculator medical how to#
Does the thought of high frequency ventilation make you shake with fear? In this article, Shri Alurkar, one of the Nottingham PICU Consultants explains when to use it, what it does and how to turn the knobs.
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