1. HFOV high frequency Oscillatory Ventilation
Becky Varela & Jamie Wood

2. Overview High Frequency Ventilation (HFV)
High Frequency Oscillatory Ventilation (HFOV) and how it works
When do we use HFOV
Basic Parameters for HFOV
How HFOV prevents Ventilator Induced Lung Injury (VILI)

3. High Frequency Ventilation
Provides augmented gas distribution
By means of numerous gas transport mechanisms.
Convection, transit time, direct ventilation
Pendalluft effect
Taylor dispersion
Asymmetric velocity
Cardiogenic Mixing
Molecular diffusion
Collateral Ventilation

4. Convection, Transit Time and Direct Ventilation
is the transport of air flow at a constant equal velocity that is parabolic in shape.
Transit Time:
Airflow to the alveoli will vary in proportion to the length of the Bronchial airways.
Direct Ventilation:
Results from bulk air flow to alveoli that have a much shorter transit time.

5. Asynchronous Filling Taylor Dispersion Pendalluft Effect
At the end of expiration:
Alveoli with short time constants (fast alveoli units) are empty.
Alveoli with longer time constants (slow alveoli units) are still emptying
Asynchronous filling:
Gases will move from slow units to fast units because of pressure gradients between the alveoli.
The relationship between:
Axial velocity profile (Turbulence)
the diffusion of gases in motion
and the branching network of the lungs.

6. Asymmetry
Cardiogenic Mixing
Airflow moving through the airways moves in a u-shape formation. At the center of the lumen air will move at a faster velocity, than air that is closest to the wall.
Asymmetry
Occurs with rapid respiratory cycles. Gases (O2) at the center of the lumen will advance further into the lungs as gases (CO2) along the wall of the airway moves out towards the mouth.
As the heart beats the heart provides additional peripheral mixing by exerting pressure against the lungs during contraction of the heart.
This pressure promotes the movement of gas flow through the neighboring parenchymal regions.

7. Collateral Ventilation
Molecular Diffusion
Collateral Ventilation
Maintaining a constant distending pressure with HFV within the lungs along with movement of gas molecules promotes gas diffusion across the alveolar membrane, at a faster rate.
Collateral ventilation increases with HFV due to connections between the alveoli
(Pores of Kohn)

9. Oscillation/Frequency Hz
How does it work?
Small tidal volumes at high frequency are generated by low amplitude pressure oscillations. These tidal volumes that are approximately equal to dead space.
High mean airway pressures (PEEP) provides distending pressure.
HFOV can provide 5-15 Hz equal to (900 breaths/min.
What is HFOV
HFOV has all of the elements of high frequency ventilation discussed previously.
Also provides a bias oscillatory gas flow used to generates positive and negative pressure fluctuations referred to as amplitudes or (Delta-P)
Oscillation/Frequency Hz
Amplitude
MAP/PEEP

12. HFOV: 3100A Oscillator Subsystem Uses an
External Air/O2 Blender
1. Provides blended air/O2 and cooling to the oscillator
Oscillator Subsystem
Uses an
1.electronic control circuit called the square wave form driver
2. Forward and backward linear motion provides inspiratory and expiratory gas flow.
3. Provides frequent small VT in HZ
External Humidifier
1. Attaches and functions with the patient’s circuit
2. Capable of flows up to 40 LPM
Pneumatic Logic and Control System
Comprised of 4 pneumonic controls
1. Bias flow
2. Mean Pressure adjustments
3. Mean pressure limit control
4. Patient circuit calibration adjustment
Pressure Monitoring System
1. Safety and alarms rely on this system
2. The PMS senses pressures within the patient’s circuit through the tubing that runs from the y-coupler
Electronic Power Supply
Monitors:
1. Alarms
2. Pressures
3. Function of the oscillator
Patient Circuit
Provides:
1. Bias flow/pressure
2. Pressurized oscillations
3. Pressure limiting

13. 3100 A 18 3100A Interface: Bias flow knob Mean Pressure adjustment
Mean Pressure Limit
Power
% Inspiratory Time
Frequency
Start/Stop
Mean Airway Pressure
Set Max Paw
Set Min Paw
Paw >50 cm H2O
Paw <20 cm H2O
Power failure Button
Reset
15a Battery Low
15b Source Gas Low
16. Oscillator Overheated
17. Oscillator stopped
second Silence
13-14 4 8 3 11 5 9 7 2 6 10 12 1
15b 16
15a 17

14. Adjustable Parameters
Amplitude:
Determines the volume of gas generated by each frequency wave
Oscillation/ Frequency (Hz)
Frequency = The Rate
15 Hz =900 BPM for neonates
12-14 Hz =600 BPM for termed infants
8 Hz =480 BPM for children 6-10 kg
6 Hz =360 BPM for children above 10 kg
IT%
Inspiratory Time Percentage
33% IT = 22 milliseconds a 15 Hz
I:E: For HFOV
I:E also determines the time for movement of the piston to generate another oscillatory breath.
Initial I:E of 1:2 for 3-15 Hz at 33% IT
MAP/PEEP:
Maintains constant distending pressure in the airway
15-18 cmH2O
Amplitudes
2.5 for
3.0 for
4.0 for
5.0 for
6.0 for
7.0 for
Weight: kg/mg
<2.0 kg.
<3.0 kg
< kg kg
< 10 kg
>20 kg

15. Pulmonary Diseases and Disorders treated with HFOV

16. Pneumopertioneum
Sub cu-emphysema
Pneumopercardium
Pneumomediastinum
Pneumothorax
ARDS

17. Potential Advantages of HFOV are 1
Potential Advantages of HFOV are  1. Uniform inflation of the lung fields 2. Improves gas exchange  3. Improves lung mechanics  4. Enables stable lung inflation o Allows recruitment of alveolar space o Reduces the risk of volutrauma  o Reduces risk of high peak airway pressure (PIP) o Reduces the risk of airway stretching o Improves V/Q matching 5. Reduces air leak  6. Decreases the amount of inflammatory mediators and alveolar edema 7. Prevents the development of hyaline membrane disease (HMD)

18. CMV VS HFOV
During CMV, there are swings between the zones of injury from inspiration to expiration.
During HFOV, the entire cycle operates in the “safe window” and avoids the injury zones.
INJURY
HFOV
CMV
INJURY

19. HFOV is used to prevent Ventilator Induced Lung Injury
Volume
Pressure
Zone of Overdistention
Safe window
Zone of Derecruitment and atelectasis
Goal is to avoid injury zones
and operate in the safe window

20. Indications:
When traditional ventilation fails
Airleak syndromes
For patients with severely low lung compliance
Refractory hypoxemia
Contraindications:
ICP
obstructive lung disease
increased airway resistance (small endotracheal tube)
asthma
secretions
increased physiological dead space

21. Work Citations Page:
Alves, Amanda. “High Frequency Oscillatory Ventilation HFOV; a new strategy in the
Treatment of patients with Acute Respiratory Distress Syndrome and low lung compliance.” CIMC Web 13 August 2014.
Birch, Pita. “Newborn Services Clinical Guideline High Frequency Oscillatory Ventilation.”
Web. 14 August
CareFusion; “3100A High frequency oscillatory ventilation; Operator’s manual.” CareFusion
Corporation Savi Ranch Parkway Yorba Linda, CA Web 18 August 2014
Haines, Mike. “Mechanical Ventilation: High Frequency Ventilation.” Respiratory Therapy
Files. Web. 8 August 2014.
Jeng, Mei-Jy. Lee, Chen, Soong. “Neonatal air leak syndrome and the role of high-frequency
ventilation.” Sci Verse Science Direct Journal of the Chinese Medical Association 75 (2012) 551e559 Web. 8 August
Prost, Allen. “High Frequency Oscillation Ventillation.avi.” Youtube.com
Web 24 Aug
Slee-Wijffels1, Fieke YAM. RM van der Vaart, Twisk, Markhorst, Plötz5 “High-frequency
oscillatory ventilation in children: a single-center experience of 53 cases, pp. R274” Open Access. 16 Web August