Sensor Medics 3100 AHigh Frequency Oscillatory

Ventilation (HFOV)

Allel ieh Javier Capistrano, RTRPPediatric Respiratory TherapistSection of Pulmonary Medicine

Philippine Children’s Medical Center

The Sensormedics 3100A Oscillatory Ventilator is indicated for ventilatory support and treatment of respiratory failure and barotrauma in neonates who weigh between .540 and 4600 kilograms and who are between 24 and 43 weeks gestational age.

Indications

Neonatal Respiratory Distress SyndromePersistent Pulmonary HypertensionMeconium Aspiration SyndromeCongenital Diaphragmatic HerniaNeonatal Lung HypoplasiaNeonatal Air Leak Syndrome

Goals

Improve and maintain oxygenationEliminate CO2 retentionCreate less lung injury

Adverse Effects

The adverse effects associated with high frequency oscillatory ventilation can be divided into three categories:

1. Pulmonary Barotrauma

2. Cardiovascular Effects

3. Removal of natural defense mechanisms with intubation

Equipment

One high-output humidifier with temperature feedback circuit.One disposable breathing circuit with heated wire.One manual water-feed system.One Oxygen/ Air Blender with 50 psi connectionsOne Oxygen line with 50 psi connection (to drive bias gas flow)One Air line with 50 psi connection (to connect to the air cooling inlet)

Procedure

Perform circuit calibration: 1.Insert stopper into the patient Y connection. 2. Turn Bias gas flow to 20 LPM. 3. Turn on the power. 4. Adjust Mean Pressure Limit to max. 5. Turn Mean Pressure Adjust to max. 6. Depress and hold reset. 7. Observe MAP display for a reading of 39-43 cm H2O. 8. Adjust bias gas flow slightly to achieve this pressure if necessary.

Failure to achieve this MAP indicates a leak in thecircuit.

Ventilator performance checkout:

1. Set “Bias Flow” to 20 lpm.

2. Turn power on, oscillator off.

3. Set “Mean Pressure Limit” to maximum.

4. Adjust MAP to 19-21 cmH2O.

5. Set “Frequency” to 15 Hz.

6. Set “I-time” to 33%.

7. Turn oscillator on.

8. Turn “Power” to 6.00.

9. Center the piston.

10. Check the amplitude values against the graph on tip of the ventilator. If the values are in range, the ventilator is ready for placement.

11. Fill out the ventilator log sheet and place in the logbook. Fill out the blue sticker and place on the ventilator

Initiating treatment:

1. Set Frequency (Hz) to desired rate. 2. Check that Inspiratory Time (I.T.) is set at 33%, unless otherwise

directed by physician.3. Adjust the Power knob to desired level.4. Once the physician has determined starting MAP, decrease the Bias

flow rate to ~15L/min 5. Adjust the Mean Pressure Limit knob in a counter-clockwise fashion

to a pressure of 18-22 cmH2O

6. Using the Mean Pressure Adjust knob set the MAP to the desired setting.

7. Set pressure alarms 4 cm H2O above and below the set MAP.8. Check inspired FiO2 levels from the Air/ Oxygen blender on

the side of the oscillator using a calibrated oxygen analyzer.9. Press start to begin HFOV once connected to the patient’s

endotracheal tube.10. Adjust Piston Control to keep piston in a central position 11. Turn humidifier on and set in the invasive humidification

mode.

Troubleshooting during circuit calibration:

1. Check that the water trap is closed.2. Check that Bias Gas Flow is on 20 LPM. Increase Bias

Flow slightly.3. Remove and check the limit, control, and dump

cap/diaphragm valves. Replace valves if circuit still fails to calibrate.

4. Replace circuit if it cannot be calibrated to 39-43 cm H2O.

5. If there has been a disconnection, push reset/power and hold until oscillations resume.

Controls Bias Flow 0–40 liters per minute (LPM) Continuous, 15-turn control.

Mean Pressure Adjust Approximately 3–45 cmH2O minimum range; Bias Flow dependent.

Mean Pressure Limit Approximately 10–45 cmH2O mean proximal airway pressure.

Power At 100% power, ΔP >90 cmH20 max amplitude of proximal airway pressure.

Frequency-Hz 3–15 Hz oscillator frequency.

% Inspiratory Time 30–50% of oscillatory cycle.

Start/Stop Oscillator enable/disable.

Set Max awP Alarm Thumbwheel 0–49 cmH2O mean airway pressure.

45 –Sec Silence Inhibits audible alarm function for 45 seconds (±5 seconds).

Reset Resets awP >50 cmH2O and <20% of “Set Max awP” alarms if condition has been corrected; always resets power failure alarm.

Pressure Measurement Range: –130 to +130 cmH2O airway pressure. Pressure Limit 20 psig.

Alarms

Safety Alarms

Audible and visual indicators, machine intervention.

awP >50 cmH2O

Indicators activated, oscillator stopped, and dump valve opened when limit exceeded.

awP >20% of “Set Max awP”

Indicators activated, oscillator stopped, and dump valve opened

when limit exceeded.

Warning Alarms Audible and visual indicators, operator intervention.

Set Max awP exceeded

Indicators activated when set limit exceeded. Set Max awP

Thumbwheel switch marked in cmH2O. Set Min awP

Thumbwheel switch marked in cmH2O. Alarm (audible)

3khz modulated tone. AC Power Visual indication of AC power applied (I/0).

INITIAL SETTINGS

FREQUENCY term infants10 Hz (600 BPM) premature infants 15 Hz (900 BPM) (< 2.5 kg). children between 6-10 kg, 8 Hz, children > 10 kg, 6 Hz

INITIAL SETTINGINSPIRATORY TIME (I.T.)

Set initially at 33% (e.g. 22 milliseconds at 15 Hz, 41 milliseconds at 8 Hz, 55 milliseconds at 6 Hz).

1) Warning - The percent of I.T. should never be increased because it will lead to air trapping and fulminant barotrauma. Total I.T. should only be increased by decreasing frequency, thus leaving the I:E ratio constant. I.T. can be decreased to 30% to heal air-leaks.

2) I:E ratio: ≈ 1:2 for 3-15 Hz at 33% I.T.

INITIAL SETTINGS

POWER the volume of gas generated by each high frequency

wave. Range (1.0 - 10.0). Maximum true volume of gas generated by the piston is

365 cc. Maximum amplitude or volume delivered is highly

variable and depends on the following factors: circuit tubing (compliance, length and diameter), humidifier (resistance and compliance - water level), ET tube diameter and length (FLOW is directly proportional to r4/l, where r = radius of airway and l = length of airway), the patient's airways and compliance.

1) Set the POWER initially at if weight is:

<2.0 kg 2.5 < 2.5 kg 3.0 2.5 - 4.0 kg 4.0 4.0 - 5.0 kg 5.0 < 10 kg 6.0 > 20 kg 7.0

MAPOxygenation on HFOV is directly proportional to MAP, which is similar to CMV, however with the SensorMedics HFOV the MAP is generated by PEEP. Thus during HFOV: MAP = PEEP.

1. Initial MAP Settings:a) Neonates - Initial MAP should be 2-4 cm above the

MAP on CMV.b) Infants/Children - Initial MAP should be 4-8 cm above

the MAP on CMV.c) If starting immediately on HFOV 15-18 cm in

infants/children.

Patient Management during HFOV

Step Action

1 Positioning:

The Oscillator should be placed at the head of the

patient’s bed.

The brakes should be on at all times.

Patient Repositioning:Patients should be individually assessed for frequency of

repositioning. When patient is stable, patients should be repositioned

every 2-4 hours. Repositioning is to be done only at physician direction.

A respiratory therapist will be present for all major repositioning of the infant

Avoid disconnection during repositioning.Caution: Inadvertent disconnection from HFOV cancause alveolar collapse and loss of lung volume.

Suctioning:

In-line suction catheters will be used on patients during

HFOV in order to maintain MAP.

Suction is done on an as needed basis only, unless

otherwise directed by the physician.

WEANING

OXYGENATIONOnce oxygenation is adequate and the patient is ready

to be weaned follow these steps:1) First only wean FiO2 until < 0.50-0.60 unless hyper-

inflated.2) Once FiO2 < 0.50-0.60 or hyper-inflated, decrease

MAP by 1 cm Q4-8h; if OXYGENATION is lost during weaning then increase MAP by 3-4 cm to restore lung volumes and begin weaning again, but proceed more slowly with decreases in MAP.

3) Minimal MAP ≈ 8-16 cm with FiO2 < 0.40-0.50, at this point one can convert to CMV or remain on HFOV while the patient continues to heal and grow (e.g., 8-12 cm < 2.5 kg, 13-16 cm > 2.5 kg).

References Sensormedic High Frequency Oscillatory Ventilator Operating Manual.

Whitaker, K., Comprehensive Perinatal and Pediatric Respiratory Care,

Delmar, Albany, New York, 2001.