HIGH FREQUENCY OSCILLATION

OSCILLATOR STRATEGIES | GUIDELINES FOR SPECIFIC DISEASES

Candidates for high frequency oscillation:

• Patients who have a CXR consistent with diffuse, homogeneous lung disease (HMD, aspiration, etc. as long as it is not an asymmetric or localized process and does not have a significant component of air trapping) and "fail" conventional ventilation. (BPD or cystic lung changes would not be a primary candidate for oscillation).

Patients who are "failing" Conventional Ventilation

FiO2 > 50% Rate > 30 BPM and

PIP>20 - < 1000g PIP mid20's - 1000-1500g PIP high 20's - >1500g

• All patients requiring hyperventilation, including, but not limited to, potential ECMO candidates and patients with pulmonary hypertension
• All birth weights and gestational ages would be included (although since HMD would be the most common diagnosis, premature infants would be the most likely candidates for oscillation)
• The above patients would be considered as potential candidates for oscillation at the discretion of the attending Neonatologist. Use of other techniques, such as Jet ventilation, would also be a consideration in these same patients.

Ventilator Settings:

In general, for diffuse alveolar disease, the Mean Airway Pressure on the oscillator should be 3-4 cmH2O higher than on the conventional ventilator. For non-homogeneous lung disease or air leak, the Mean Airway Pressure should be equal to or less than on the conventional ventilator (depending on the clinical situation)

Rate:

>1000gm-2000gm	15 Hz
>2000gm	10-15 Hz

Inspiratory to Expiratory Ratio: 1:2 (Inspiration is 33% of the cycle, Expiration is 66%)

"Power" setting determines the tidal volume and is set somewhat empirically - by observing the patient to see how much chest excursion/movement occurs with oscillation

Practical Concerns:

• Uncut endotracheal tubes will be used to allow for the tube to extend 3-4cm past the lips, so that the patient does not spontaneously extubate. (Patients may need to be re-intubated if they have been intubated with a pre-cut tube)
• Careful assessment must be made of all infants on oscillation and will require:

• Continuous pulse-oximetry and, at least initially, frequent Abg's
• TCM PCO2 will be used to rapidly determine effects of ventilator changes
• A CXR within 30 minutes of changing to oscillation, again within 4 hours after the change and daily as long as the patient are on oscillation
• If frequent changes have been made (especially in MAP), a CXR should be obtained within 2 hours of the last change

• There is no alarm that will tell you that the airway is obstructed, so clinical assessment of the patient (observation for good chest wall movement) is critical if there is an unexplained desaturation or other cardiovascular instability
• Suctioning the airway should only be as necessary (if there is decreased chest wall movement, CXR suggests focal atelectasis, there are increased secretions, etc.) not routine
• Patients will not necessarily need to be paralyzed, since spontaneous respiratory effort will be a clinical indicator of adequacy of ventilation
• Artificial surfactant will need to be manually administered while the patient is on HFOV. It should be given in two separate "doses" while the infant is manually ventilated using pressures to achieve good chest wall movement

End point of oscillation (i.e. time to switch back to CMV) would be when:

• the infant has weaned on FiO2 and MAP and is tolerant of a brief trial of CM
• fails oscillation by blood gas or other criteria
• develops air trapping
• when the acute disease begins to evolve into more chronic BPD (X-ray changes or hyperinflation)

Oscillation Routine

1. The oscillator will be used as a "rescue" therapy, therefore all patients will receive at least a brief trial of conventional ventilation. Patients will be intubated, stabilized, have lines placed, have a CXR, and receive an initial dose of artificial surfactant. If the patient is considered a candidate for HFO prior to intubation, an uncut ETT should be used, otherwise the patient may need to be re-intubated.
2. Use of the oscillator will be discussed with the family of the patient prior to switching to HFO (unless there is some urgent extenuating circumstance).
3. If it is determined that the patient is a candidate for HFO, he will be placed on a warming table.
4. If TCPCO2 is available, a transcutaneous electrode will be placed on the patient and needs to be functional prior to switching to HFO.
5. Settings on the oscillator will be determined by the patient's diagnosis and the clinical circumstances. (See the section "Oscillator Strategies" and also the section, "Oscillator Settings").
6. When HFO is started, a Respiratory Therapist and an MD or NNP needs to be immediately available.
7. The attending Neonatologist will be responsible for all changes in oscillator settings, and therefore needs to give the order for changes or needs to approve changes before they are made.

Oscillator Settings

Power

• determines the amplitude of oscillation (and therefore the tidal volume)
• always start on a setting of "2"
• change so that the amplitude changes in increments of 2-4cm H20
• changes in Power will change MAP, requiring readjustment of MAP

Mean Airway Pressure

• the MAP during CMV determines where you set the oscillator MAP (see "Oscillator Strategies")
• changes should be in 1-2cm H20 increments
• changes during weaning should be done only every 6 hours

Frequency

• 10 or 15 Hz, depending on the size of the patient and the disease
• would rarely be changed
• changes dramatically change amplitude and MAP

Inspiratory Time %

• determines the I:E ratio
• set at 33% (33% of cycle is inspiration)
• 33% = I:E ratio of 1:2
• this variable is not routinely changed

Oscillator Strategies | Guidelines for Specific Diagnoses

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