1) High frequency ventilation (HFV) uses small tidal volumes and high respiratory rates to improve gas exchange through mechanisms like molecular diffusion and pendulum flow rather than conventional alveolar ventilation. 2) HFV can be delivered through high frequency positive pressure ventilation (HFPPV), high frequency jet ventilation (HFJV), or high frequency oscillatory ventilation (HFOV). 3) Evidence does not clearly support using HFV over conventional ventilation as a primary therapy for preterm infants with respiratory distress, though it may be considered as a rescue therapy when conventional ventilation fails.

1. HIGH FREQUENCY
VENTILATION
Dr. ADHI ARYA
SENIOR RESIDENT –GMCH -32 CHANDIGARH

2. • INTRODUCTION
• MECHANISM OF VENTILATION
• WHY HFV
• TYPES OF HFV
• USES
• TERMINOLOGY AND SETTINGS( INITIATION AND WEANING OFF)
• MONITORING/ROUTINE CARE ON HFV
• COMPLICATIONS
• EVIDENCE

3. INTRODUCTION
HFV is a type of mechanical ventilation that uses a constant distending
pressure (mean airway pressure [MAP]) with pressure variations
oscillating around the MAP at very high rates
This creates small tidal volumes, often less than the dead space. HFOV
relies on alternative mechanisms of gas exchange such as molecular
diffusion, Taylor dispersion, turbulence, asymmetric velocity profiles,
Pendelluft, cardiogenic mixing and collateral ventilation

4. NATURAL HIGH FREQUENCY VENTILATION
• HUMMINGBIRD
• DOG’S PANTING

5. MECHANISM OF ACTION
•ALVEOLAR VENTILATION = (Vt-Vd) * RATE
• IN HFV Vt< Vd, so actualluy no ventilation
should occur

6. HFV Provides augmented gas distribution by means of numerous
gas transport mechanisms.
 Convection ventilation( bulk flow)
 Pendalluft effect
 Taylor dispersion
 Asymmetric velocity profiles
 Cardiogenic Mixing
 Molecular diffusion
 Collateral Ventilation

7. Convection, Transit Time and Direct
Ventilation
Convection
 is the transport of air flow at a
constant equal velocity that is
parabolic in shape.
TO SHORT PATH LENGTH UNITS
THAT BRANCH OFF FROM
PROXIMAL AIRWAYS

8. 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.
Asynchronous Filling

9. Taylor Dispersion
The relationship between:
 Axial velocity profile (Turbulence)
 the diffusion of gases in motion
 and the branching network of the lungs.

10. Asymmetry
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.

11. • Asymmetrical Velocity Profiles
• Inspiration
• The high frequency bulk flow creates a “bullet” shaped flow profile, with the central molecules
moving further down the airway than those molecules found on the periphery of the airway.
• Expiration
• The velocity profile is blunted so that at the completion of each return, the central molecules
remain further down the airway and the peripheral molecules move towards the mouth of the
airway

12. Cardiogenic Mixing
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.

13. Collateral VentilationMolecular Diffusion
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)

15. WHY HFV
THEORITICAL ADVANTAGES
• SMALL TIDAL VOLUMES
limits alveolar over distension
• HIGHER MAP
Better alveolar recruitment
• CONSTANT mPaw during inp and exp
preventing end alveolar collapse

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

17. Pressure and Volume Swings
INJURY
INJURY
CMV
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.

20. TYPES OF HFV
Based on characteristic of exhalation (Active /Passive/ Hybrid )and
source of generation
– 3 types
1. HFPPV
2. HFJV
3. HFOV

22. USES
1. failure of conventional ventilation in the term infant (Persistent
Pulmonary Hypertension of the Newborn [PPHN], Meconium
Aspiration Syndrome [MAS]).4,5
2. Air leak syndromes (pneumothorax, pulmonary interstitial
emphysema [PIE])7
3. Failure of conventional ventilation in the preterm infant (severe
RDS, PIE, pulmonary hypoplasia) or to reduce barotrauma when
conventional ventilator settings are high.
4. Lung hypoplasia syndromes

23. TERMINOLOGY

24. Oxygenation
Depends on
1) MAP
2) Fio2

25. Ventilation
Depends on
1. amplitude( depth of oscillations around MAP)
2. Frequency
3. Ti

26. • CMV
ALVEOLAR VENT = FREQ * TV
•HFV
ALV VENT= F*TV2

27. More TV in 6 Hz Cycle as compared to 8 Hz

28. INITIAL SETTINGS
DEPENDS ON PATHOLOGY
• OPTIMAL LUNG VOLUME STRATEGY
• LOW VOLUME STRATEGY

29. • SEVERE RESPIRATORY FAILURE
One-study sites that 50% of infants studied who met the criteria for
ECMO were successfully managed with HFV alone.
• Initially, start with a MAP 2 cm higher than with conventional
ventilation and incrementally increase it. Very high MAPs may be
needed to achieve adequate oxygenation.

30. • PERSISTENT PULMONARY HYPERTENSION
• Hyperventilate to achieve a PaCO2 of 25-35 Torr with a pH of 7.45-7.55. Some
literature suggests a pH of 7.55-7.65.
• Hyperoxygenate generally by maintaining the FIO2 at 1.0. Increase the MAP to
maintain adequate oxygenation

31. LUNG HYPOPLASIA SYNDROMES
• Initially use the same MAP as on conventional ventilation then
aggressively increase in 1cm increments to optimum lung volume.
• Adjust the amplitude to give a PaCO2 of 45-50.

32. • AIR LEAK SYNDROMES
• • Initially set the MAP 1-2 cm H2O below the MAP on conventional
mechanical ventilation.

34. WEANING

35. COMPLICATIONS
• HYPOTENSION ( Increased intrathoracic pressure -- decreased VR)
• AIRLEAKS
• IVH/PVL
• NECROTISING TRACHEOBROCHITIS

36. MONITORING
1. SEDATION
2. AUSCULTATION
3. CXR (1hr after initiation or any change in settings/deterioration)
4. SUCTIONING
5. BP MONITORONG

37. SUSTAINED INFLATION
lung recruitment maneuver.
• There are several ways in which to perform a SI maneuver.
• In our institution, the piston is paused (thus leaving the patient in CPAP) and the Paw
is increased by 8-10 cm H2O for 30-60 seconds.
• Once the SI maneuver is completed, the piston is restarted.
• Potential complications:
• Pneumothorax
• CV compromise / altered hemodynamics

38. When To Utilize A SI Maneuver
• When initiating HFOV to recruit lung
• After a disconnect or loss of FRC/Paw
• After suctioning (even with a closed suction system)
• Inability to wean FiO2
• When considering increasing Paw
• A recruitment maneuver may recruit lung allowing you to
maintain the baseline Paw and, thus, not increase support.

39. EVIDENCE ( should answer these three
questions)

40. EVIDENCE

43. PULMONARY OUTCOMES OF CONTROLLED TRIALS OF HFV
DURING SURFACTANT ERA AND SYNCHRONOSED VENTILATION

45. AS PRIMARY MODE
• AS A PRIMARY MODE
Elective high frequency ventilation compared to conventional
mechanical ventilation in the early stabilization of infants with
respiratory distress - Cochrane-March 2015
Insufficient evidence exists to support the routine use of high
frequency oscillatory ventilation instead of conventional ventilation for
preterm infants

46. AS RESCUE THERAPY
• Preterm
Rescue high-frequency jet ventilation versus conventional ventilation
for severe pulmonary dysfunction in preterm infants
Cochrane oct 2015
• Existing evidence does not support the use of rescue high-frequency
jet ventilation compared with conventional mechanical ventilation for
treatment of preterm infants with severe pulmonary problems

47. AS RESCUE THERAPY
Term
• High frequency oscillatory ventilation versus conventional
ventilation for infants with severe pulmonary dysfunction born at or
near term
cochrane may 2009
There are no data from randomized controlled trials supporting the use
of rescue HFOV in term or near term infants with severe pulmonary
dysfunction.

48. HFJV VS HFOV
• High frequency jet ventilation versus high frequency oscillatory
ventilation for pulmonary dysfunction in preterm infants
Cochrane database May 2016
• no evidence to support the superiority of HFJV or HFOV as elective or
rescue therapy