1. HFOV Presented by SAYU ABRAHAM
SLE5000
HFOV
Presented by
SAYU ABRAHAM

2. High Frequency Ventilation
Defined by FDA as a ventilator that delivers more than 150 breaths/min.
Delivers a small tidal volume, usually less than or equal to anatomical dead space volume.
While HFV’s are frequently described by their delivery method, they are usually classified by their exhalation mechanism (active or passive).

3. Differences between HFOV and CMV
CMV HFOV
Rates
Tidal Volume ml/kg ml/kg
Alv Press 0 - > 50 cmH2O cmH2O
End Exp Vol Low Normalized

4. HFV Gas Exchange
Henderson first published his findings in 1915, assessing dead space relationship in ventilation.
He stated, “there may easily be a gaseous exchange sufficient to support life even when Vt is considerably less than dead space.”

5. High Frequency Ventilation
Types of HFV’s Approved for use in both Neonates and Pediatrics
SLE HFOV
SensorMedics 3100A HFOV
Bird Volumetric Diffusive HFPPV
Types of HFV’s Approved for use in Neonates Only
Bunnell Life Pulse HFJV
Infrasonics Infant Star (discontinued) HFFI

6. SLE5000 Electrically powered, electronically controlled
Conventional and HFOV ventilator
Paw of mbar
Delta P from 4 – 180 mbar
Frequency of Hz
I:E Ratio 1:1
Active exhalation

7. “HFOV”: SLE 2000 Insp. Line Resistor (Trigger sensibility)
Bias flow 5l/min
Peep adjustment
Rotating jet
Exp. Valve Block

8. Indications of HFOV Neonatal RDS/HMD Air leak syndromes MAS PPHN CDH

9. Ventilator Induced Lung Injury
Barotrauma
Volutrauma
Stretch Injury
Biochemical Injury

10. Pulmonary Injury Sequence of the neonatal patient:
Absence of Surfactant
Atelactasis
Tidal Breathing
High Distending Pressures
Airway Stretch / Distortion
Cellular Membrane Disruption
Edema / Hyaline Membrane Formation
Higher FIO2 , Volumes, Pressures
Volutrauma, Barotrauma, Biotrauma
PIE, BPD

11. Pulmonary Injury Sequence
If we cannot prevent the injury sequence , then the target goal is to interrupt the sequence of events.
High Frequency Oscillation does not reverse injury, but will interrupt the progression of injury.

12. Ventilator Induced Lung Injury
Barotrauma
Air leaking into pleural space
Air leaking into interstitial space (PIE)
Tearing at Bronchio-Alveolar Junction as lung is recruited and allowed to collapse
Most occurs in dependent lung zones (transition zone)

13. Effect of 45 cmH2O PIP
Control min min

14. Ventilator Induced Lung Injury
Stretch Injury
Alters capillary transmural pressures
Changes in transmural pressure causes breaks in capillary endo and epithelium
Increases leak of proteinacious material
Promotes Atelectasis

15. Ventilator Induced Lung Injury
Volutrauma
Caused by cycling of the lung (change in surface area), independent of pressure required
Alters Surfactant function
Promotes Atelectasis
Increases capillary leak of proteinacious material
Dreyfuss,D ARRD 1988;137:1159

16. Ventilator Induced Lung Injury
Premature baboon model
Coalson J. Univ Texas San Antonio

17. Ventilator Induced Lung Injury
Premature baboon model
Coalson J. Univ Texas San Antonio

18. Pulmonary Injury Sequence
There are two injury zones during mechanical ventilation
Low Lung Volume Ventilation tears adhesive surfaces
High Lung Volume Ventilation over-distends, resulting in “Volutrauma”
The difficulty is finding the “Sweet Spot”
Froese AB, Crit Care Med 1997; 25:906

19. Ventilator Induced Lung Injury
HFOV with Surfactant as Compared to CMV with Surfactant in the Premature Primate
HFOV resulted in
Less Radiographic Injury
Less Oxygenation Injury
Less Alveolar Proteinaceous Debris
Jackson C AJRCCM 1994; 150:534

20. HFOV

21. Theory of Operation
Oxygenation is primarily controlled by the Mean Airway Pressure (Paw) and the FiO2
Ventilation is primarily determined by the stroke volume (Delta-P) and the frequency of the ventilator.

22. HFOV effectively decouples: Oxygenation & Ventilation

23. HFOV Principle: Pressure curves CMV / HFOV
Injury
Injury

24. Principles of the SLE5000 HFOV
“Super-CPAP” system
to maintain lung volume

25. Optimized Lung Volume Strategy:
Increase Lung Volume above critical opening pressure to the Optimum and keep it there in Inspiration and Expiration.
Benefits: - homogenous gas distribution
- reduced regional atelectasis
- maximized gas exchange area and pulmonary blood flow
- better matching of ventilation/perfusion
- reduction of intrapulmonary shunting
- reduced Oxygen exposure

26. Optimized Lung Volume Strategy:
Decrease Tidal Volumes to less or equal to dead space and increase frequency.
Benefits: - enhanced gas exchange due to combined gas transport mechanisms
- no excessive volume swings
- reduced regional over-inflation and stretching
- reduced Volutrauma

27. Oxygenation
The Paw is used to inflate the lung and optimize the alveolar surface area for gas exchange.
Paw = Lung Volume

28. Paw = CDP CDP = Lung Volume CT 2 CT 1 CT 3 Continuous Distending
Pressure

29. “Open up the lung up and keep it open!”
Burkhard Lachmann, 1992

30. Primary control of CO2 is by the stroke volume produced by the Delta P Setting.

31. Regulation of stroke volume
The stroke volume will increase if
The amplitude increases (higher delta P)
Stroke volume

32. Secondary control of PaCO2 is the stroke volume produced by the set Frequency.

33. Regulation of stroke volume
The stroke volume will increase if
The amplitude increases (higher delta P)
The frequency decreases (longer cycle time)
Stroke volume

34. HFOV Principle: I + + + + + Amplitude Delta P = Tv = Ventilation
CDP=FRC=
Oxygenation E - - - - -
HFOV = CPAP with a wiggle !

35. Pressure transmission
Gerstmann D.

36. Airway Pressure Transmission HFOV :
Amlitude
Delta P =
TV =
Ventilation I E + _
CDP / MAP
= Lungvolume
= Oxygenation
ET Tube
Trachea
Alveolus
Transmission

37. HFOV Mechanisms of Gas Transport

38. Mechanisms of HFOV Gas Exchange
There are six mechanisms of gas exchange during HFOV
Convective Ventilation
Asymmetrical Velocity Profiles
Taylor Dispersion
Pendeluft
Molecular Diffusion
Cardiogenic Mixing

39. Practical preparation
Avoid leak around the E.T tube
Tc PO2,CO2,Pulse oxymeter and invasive blood pressure monitoring
Baseline CXR
Optimize blood pressure and perfusion(volume replacement and inotropes)
Muscle relaxant/sedation
Reusable low compliance circuits must be used

40. NURSING CARE
Perform through suction before connecting to the oscillator.
Assess patient upon commencement of HFOV.Monitor vital signs, chest wiggle must be evaluated upon initiation and followed closely thereafter. If chest wiggle diminishes it may be ETtube moved or obstructed. Chest wiggle on one side indicates patient developed pneumothorax,thus chest wiggle assessment should be performed after repositioning.
Auscultation the chest by putting in standby mode.
A closed suction should be used. It is not necessary to disconnect the patient to suction as this will potentially derecruit lung volumes.
The point at which the ET tube is cut and secured at lips should be initially noted this measurement is reference.

41. Continued……… Evaluation of lung expansion on CXR
Check capillary refill, skin color and temperature
Comparing central and peripheral pulses
Monitoring of ECG Tracing
Frequent CXR’s blood gases in initial stabilization period
Optimal lung volume for oxygenation is 8-9 rib inflation
Blood pressure and perfusion should be optimized prior to HFOV,any volume replacement should be completed and inotropes commenced if necessary

42. Continued………
Muscle relaxants are not indicated since spontaneous respiratory effort will be a clinical indicator of adequacy of ventilation
Sedation with opiates is often indicated
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