The use of small, high frequency pressure oscillations allowing the application of high mean airway pressures to optimize lung volume recruitment and prevent end-expiratory collapse, without exposure to injurious peak airway pressures during inflation
In addition, the circuit allows optimal gas conditioning, reducing the likelihood of airway trauma and thickening of secretions. HFOV improves outcome by decreasing shear forces associated with the cyclic opening of collapsed alveoli
Weight guidelines
3100B is placed on pt weighing greater than 35kg
HFOV Calibrations
Prior to patient use both calibrations should be performed
Patient calibration – top of machine
Circuit calibration – side of machine
Inspiration and expiration phases are both active
The advantages of active exhalation are
Controlling lung volumes
Preventing hyperinflation
Power determines the amount of power that is driving the oscillator piston forward and backward resulting in an air volume
When auscultating you listen for presence and symmetry of piston sounds, bright or dull. Asymmetry might represent
Improper ETT placement
Pneumothorax
Heterogeneous lung disease
Mucus plugging
The MAP upper and lower alarms should be set at 3 cmH2O above and below the MAP setting
HFOV patients should have increased sedation and possibly neuromuscular blockade.
Typical starting settings
MAP set 2-5 cm H2O above the map on current conventional ventilation
Initial delta P is titrated upward until a visible “wiggle” from shoulders down through the hips
Inspiratory time set to 33%
Bias Flow
3100A may be set between 10-30 LPM
3100B may be set between 20-40 LPM
Attempt to use the lowest Bias Flow possible to meet patient’s demand and deliver a stable MAP (minimum 10 Lpm)
The use of a lower Bias Flow setting will decrease the turbulence in the circuit that results from excessive flow
The MAP and delta P settings should not be at a ratio greater 1:3
This creates an excessive amount of negative pressure on the patient airways that can lead to air trapping
To Improve Ventilation
Increase the delta P improves ventilation
Reducing the frequency (Hz
Lower frequencies have a larger volume displacement and improved CO2 elimination
To Improve Oxygenation
Increase FiO2
Increase MAP
Trouble Shooting
Leaks, check the:
Humidifier
Leak around ETT
Mushroom valves
Tubing Connections
Leak Diaphragm
Open stop-cock on drain syringe
HFOV will not reset
Increase bias flow due to inadequate bias flow set
MAP Limit is set too high. Needs a minimum of 20% of the set MAP Limit to start
Look for a large leak
Unable to further increase MAP
Check to see if MAP Limit setting is too low
Increase bias flow, if maxed on MAP and MAP limit knobs
Chest oscillation is diminished or absent, Consider:
Decreased pulmonary compliance
ETT disconnect
ETT obstruction
Severe bronchospasm
Chest oscillation is unilateral, Consider:
ETT displacement (right mainstem)
Pneumothorax
MAP is fluctuating
Check the high-pressure setting
Check for spontaneous breathing (bias flow is too low)
Amplitude changed over the past couple of hours while the Power setting remained unchanged:
Amplitude increased:airway resistance increased, and/or total lung compliance decreased
Amplitude decreased:airway resistance decreased, and/or total lung compliance increased
Consider weaning when:
Pneumothoracies and/or pulmonary interstitial emphysema have resolved, if present
Mean airway pressure has been weaned to the 10-12 cm H2O range
The delta P has been weaned to less than 30 cm H2O
Blood gases have been stabilized within the following ranges