Clinical Skills: High-frequency oscillatory ventilation (HFOV)

Hello! This video covers how to set up a patient on high frequency oscillatory ventilation. Normally you’d do everything on this list, but to keep things concise, this video will focus on the steps in blue and will also cover frequently asked questions, troubleshooting, tips, and a summary.

As a word of caution, we’re not covering every possible type of equipment on the market. Make sure you understand how your own equipment works and how it may affect your procedure.

Here is all the equipment you will need: a high frequency oscillatory ventilator, humidified oxygen source, an oxygen saturation monitor, a cardiac and end tidal or transcutaneous CO2 monitor, neuromuscular blocker medications, personal protective equipment, suction equipment, and a self-inflating bag. 

High frequency oscillatory ventilation, or HFOV, differs from conventional ventilation in that instead of delivering a set number of breaths at a certain pressure or volume, HFOV provides volumes equal to or less than the anatomical dead space using respiratory rates with a range of 3 to 15 Hertz which is also 3 to 15 cycles per second. For clarity, 3 to 15 cycles per second is equivalent to 180 to 900 breaths per minute! Whoah.

The lungs are partially inflated to maximize surface area for gas exchange, and the fast breaths allow for a large volume of gas exchange to occur. The fast, small breaths also help reverse and prevent atelectasis, improve CO2 elimination, and reduce the risk of barotrauma and volutrauma which may occur in conventional ventilation.

HFOV also can be employed in patients with acute lung injury, which is also called ALI, and acute respiratory distress syndrome, which is also called ARDS, but is not the first choice in these circumstances.

Calibration of the ventilator absolutely MUST be done before attaching the ventilator to a patient. Use a rubber stopper to block the circuit for calibration and performance procedures. The water trap stopcock should also be closed. If you find an issue (software- or hardware-related) with the machine while calibrating it - just don’t use that ventilator. Go find another machine.

First, adjust ‘bias flow’, which is the constant flow of gas to be delivered to provide oxygen and remove carbon dioxide; it is created by the movement of the piston diaphragm in the circuit. An initial bias flow is usually 20L/min, and it can be set to a rate up to 60 L/min. This flow works to generate the mean airway pressure, also called mPaw, or the average pressure in the airway at any given time. The mPaw is adjusted to provide gentle alveolar distension, to maintain a surface area appropriate for gas exchange.