Hfov

High Frequency Oscillatory Ventilation SensorMedics High Frequency Oscillator 3100a SensorMedics Front Panel Diagram displaying set up of SensorMedics circuit Start-up and Initiating HFOV SensorMedics Oscillator Initiating HFOV is the responsibility of the medical staff. Always ensure that the Sensormedics Oscillator is plugged into the red uninterrupted power supply (UPS). An oxygen analyzer is required in circuit and placed accordingly (see diagram). Perform circuit calibration: 15 Ensure stopper is inserted in patient Y connection (a lung is not used). 16 Turn Bias gas flow to 20 LPM. Switch machine on. 17 Turn Mean Pressure Limit to max 18 Turn Mean Pressure Adjust to max 19 Depress and hold reset. Observe PAW display for a reading of 39-43cm H2O. Adjust bias gas flow slightly to achieve this if necessary. 20 An inability to achieve this PAW means a leak in the circuit. 21 (Refer to troubleshooting 22 Initiating treatment 23 Turn Bias gas flow back to 15 LPM 24 Set frequency (Hz) to 10-15 as per medical order 25 Our default setting is 10Hz 26 Check Inspiratory-time is 33% 27 Set power on 2. 28 Determine treatment MAP. Rotate the mean pressure limit anti-clockwise to set PAW (MAP) to limit 5cm above treatment setting. Be aware if the infant later requires higher MAP levels, the limit may have to be increased. 29 Rotate Mean Pressure Adjust control anti-clockwise to set treatment MAP. 30 Note: These dials are sensitive to major adjustments. 31 If a very high MAP is required, the Bias gas flow may have to be increased to 20 LPM. 32 Set pressure alarms 2cm above and 3cm below set PAW. 33 Check inspired O2 level on O2 blender to the side of oscillator. 34 Press ‘start’ to commence HFOV on infant. Medical staff to adjust amplitude while observing chest movement. 35 Adjust Piston Control to keep the piston in a central position. 36 Turn humidifier on and set at 39°- 2. 37 Nitric oxide may be administered in this circuit (see Nitric Oxide Protocol). 38 Troubleshooting: SensorMedics Oscillator Ventilator. Follow the steps below if the SensorMedics Oscillator fails to calibrate to 39-43cm H2O, or for other technical difficulties. 39 Check the water trap is closed. 40 Check Bias Gas Flow is on 20 LPM. Increase Bias Flow slightly 41 Remove and check the limit, control and dump cap/diaphragm valves (see diagram). Replace valves if circuit still fails to calibrate. 42 If circuit cannot be calibrated to 39-43cm H2O, replace with a new circuit. 43 If there has been a disconnection, push reset/power and hold till oscillations are recommenced. 44 Battery low: has no audible alarm, means there is no electrical power to battery that supplies amplitude/power dial. The HFOV will still work. 45 If you cannot see an index above, please press the "Refresh" button of your browser. High frequency ventilation (HFV) is defined by the ‘high frequency’ (2.5-15 Hz) and low tidal volume (0.5-5 mL/kg). The tidal volume is barely greater than the dead space hence alternative mechanisms of gas transport are required to explain the effect of HFV 1. Indications for high frequency ventilation include 1. Rescue following failure of conventional ventilation (PPHN, Meconium).2,3 2. Air leak syndromes (pneumothorax, pulmonary interstitial emphysema) 4 3. To reduce barotraumas when conventional ventilator settings are high. Terminology Frequency: High frequency ventilation rate (Hz, cycles per second) MAP: Mean airway pressure (cmH2O) Amplitude: delta P or power is the variation around the MAP Oxygenation is dependent on MAP and FiO2: MAP provides a constant distending pressure equivalent to CPAP. This inflates the lung to a constant and optimal lung volume maximizing the area for gas exchange and preventing alveolar collapse in the expiratory phase.  Ventilation is dependent on amplitude and to lesser degree frequency. Thus when using HFV CO2 elimination and oxygenation are independent. Initial settings on HFV Optimal lung volume strategy (aim to maximize recruitment of alveoli). • Set MAP 2-3 cmH2O above the MAP on conventional ventilation • MAP in 1-2 cmH2O steps until oxygenation improves Set frequency to 10 Hz Low volume strategy (aim to minimize lung trauma) • Set MAP equal to the MAP on conventional ventilation • Set frequency to 10 Hz Adjust amplitude to get an adequate chest wall vibration. • Obtain an early blood gas and adjust settings as appropriate. • Changes in frequency should only be made in discussion with attending Neonatologist. Making adjustments once established on HFV Poor Oxygenation Increase FiO2 Increase MAP (1-2cmH2O) Over Oxygenation, Decrease FiO2Decrease MAP (1-2cmH2O) Under Ventilation, Increase Amplitude, Decrease Frequency (1-2Hz) if Amplitude Maximal Over Ventilation, Decrease Amplitude, Increase Frequency (1-2Hz) if Amplitude Minimal Chest Radiograph • Initial x-ray at 1-2 hrs to determine the baseline lung volume on HFV (aim for 7-8 ribs). • A follow-up chest x-ray in 4-6 hours is recommended to assess the expansion. • Thereafter repeat chest x-ray with acute changes in patient condition. Weaning • Reduce FiO2 to 9 ribs). • Reduce MAP in 1-2cm increments to 8-9. • In air leak syndromes (low volume strategy), reducing MAP takes priority over weaning the FiO2. • Wean the amplitude in 4cm H2O increments. • Do not wean the frequency • Consider switching to conventional ventilation when MAP