HIGH FREQUENCY VENTILATION (HFV) Neonatal & Pediatric.

HIGH FREQUENCY HIGH FREQUENCY VENTILATION (HFV)VENTILATION (HFV)

Neonatal & Pediatric

HFV ObjectivesHFV Objectives

• List 4 types of HFV and differentiate how each one operates

• Know the terminology of HFV

• Explain ventilator management of HFV

• List each ventilation strategy

HIGH FREQUENCY HIGH FREQUENCY VENTILATION (HFV)VENTILATION (HFV)

• A form of “pressure” ventilation

• No volumes set, measured, or controlled

• The only real control is time

Traditional Teaching of Gas Traditional Teaching of Gas Exchange: CMV or Spontaneous Exchange: CMV or Spontaneous

BreathingBreathing• Gas exchange occurs because of bulk

transport (convective flow) of the O2 and CO2 molecules from the conducting airways to the peripheral airways.

• Volume of inhaled gas must exceed the volume of dead space. 

High Frequency Ventilation HFVHigh Frequency Ventilation HFV

• Mechanical ventilation using tidal volume less than or equal to dead space volume and delivered at supra physiologic rates!

Tidal Volumes < Anatomical Tidal Volumes < Anatomical DeadspaceDeadspace

• It is possible to adequately ventilate the lungs with tidal volumes equivalent to deadspace using much higher frequencies than normal

DogsDogs

• Regulate their temperatures by panting

• Very shallow, very fast breaths

• Breaths are smaller than anatomic deadspace

• Yet dogs do just fine

HummingbirdHummingbird

• A hummingbird in flight ventilates through the extremely rapid bi-directional movement of its wings

Why HFV?Why HFV?

• Can ventilate the lungs at very small tidal volumes and very high respiratory rates

• Why do we wish to do this?

HFVHFV

• Lungs that leak air:• Very low tidal volumes

put less stress on the lungs that may not be able to withstand the stretch of a normal tidal volume

INDICATIONS FOR HFVINDICATIONS FOR HFV

1.BAROTRAUMA - pulmonary airleaks. 

a. PNEUMOTHORAX

b. PULMONARY INTERSTITIAL EMPHYSEMA (PIE) 

2. Respiratory failure unresponsive to conventional ventilation  

PIEPIE

HIGH FREQUENCY HIGH FREQUENCY VENTILATION (HFV)VENTILATION (HFV)

• Ventilation that uses respiratory rates > the rate of normal breathing. 4 types of HFV: • 1. High frequency jet ventilation

• (HFJV, rate 100-600); 

• 2. High frequency oscillatory ventilation• (HFOV, rate 300-3000/minute). 

• 3. High frequency conventional and positive pressure ventilation (HFCPPV, rate up to 150/minute).

• 4.High frequency flow Interruption (HFFI, rate up to 150/minute).

HIGH FREQUENCY HIGH FREQUENCY VENTILATION (HFV)VENTILATION (HFV)

• The FDA defines HFV as a rate >150/min

• Clinicians: 40-150

HFV TerminologyHFV Terminology

• Hertz

• Amplitude

• Power

• Inspiratory Time

• Mean Airway Pressure

• FIO2

• Bias flow

HertzHertz

• Another name for frequency

• Cycles per second

• 1 Hertz = 60 cycles per minute

AMPLITUDEAMPLITUDE

• A representation of the volume of gas flow in each high frequency pulse or "breath.“

• It “results” in a tidal volume

• Cannot “call” it a tidal volume because you cannot measure the volume with current machines

AMPLITUDEAMPLITUDE

• Adjust the amplitude until you achieve vigorous chest wall vibrations

HFJV-High Frequency Jet HFJV-High Frequency Jet VentilationVentilation

• The Bunnell Life Pulse High

Frequency "Jet" Ventilator

HFJV-High Frequency Jet HFJV-High Frequency Jet Ventilation: CircuitVentilation: Circuit

High Frequency Jet VentilationHigh Frequency Jet Ventilation

 — Uses a jet of gas by inserting a small (14 to 16 gauge) cannula into the lumen of the endotracheal tube and then connecting a specialized ventilator to the cannula.

---A pressure of approximately 35 pounds per square inch (psi) drives the jet of gas from the cannula with an initial respiratory rate of 100 to 150 breaths

HFJV-High Frequency Jet HFJV-High Frequency Jet VentilationVentilation

• The LifePort™ endotracheal tube adapter has eliminated the need to reintubate with a special ET tube. The Life Pulse is easier than ever to implement

Jets are used in conjunction with a Jets are used in conjunction with a conventional ventilator.conventional ventilator.

Jets are used in conjunction with Jets are used in conjunction with a conventional ventilator.a conventional ventilator.

HFJV-High Frequency Jet HFJV-High Frequency Jet VentilationVentilation

• For early intervention and treatment of pulmonary interstitial emphysema and other volutrauma induced lung injury

• Small, high velocity breaths and fast rates coupled with passive exhalation are the key to achieving the lowest therapeutic pressures possible.

HFJV-High Frequency Jet HFJV-High Frequency Jet VentilationVentilation

• 3 control settings: PIP, Rate and I-Time

• Other functions are automatically controlled and manually adjustable

• PEEP and "sigh" breaths are supplied by a conventional ventilator operated in tandem with the Life Pulse.

HFJV: 3 concepts HFJV: 3 concepts

• I-Time

• Jet nozzle

• Passive exhalation

Inspiratory TimeInspiratory Time

• 0.02 seconds• 25 times shorter than 0.5 sec of CMV• Very short I-Time results in tidal volumes that are`10

times smaller than CMV, so higher PEEP can be used• Fixed I. Time• Tidal Volume does not change with changes in HFJV

frequency• I:E Ratio

• 1:3.5 at 660 bpm• 1:12 at 240 bpm

HFV verses CMVHFV verses CMV

Passive ExhaltionPassive Exhaltion

• Operates at lower Mean Airway Pressure than Oscillator

Primary Control VariablesPrimary Control Variables

• Mean Airway Pressure• Determines mean lung volume• Oxygenation

• PEEP• controls Mean Airway Pressure

• Pressure Amplitude (PIP-PEEP)• Delta P• Ventilation (VT)

• No exact levels for size

HFJV PIPHFJV PIP

• Drops dramatically as approaches alveoli

• VIDEO

High Frequency OscillationHigh Frequency Oscillation

SensorMedics Front Panel

High Frequency OscillationHigh Frequency Oscillation• The mechanical oscillator uses a diaphragm, piston, or plate

contained in a chamber• Bi-directional gas flow• Machine pushes gas in on inhalation and pulls gas out on

exhalation

High Frequency Oscillatory High Frequency Oscillatory VentilationVentilation

• Tidal volume typically delivered ≈ 1.5-3.0 cc/kg (< dead space).

• Efficient ventilator secondary to an active expiratory phase

• Piston pushes volume in then pulls the volume out

• Can do higher rates

HFV TerminologyHFV Terminology

• Hertz

• Amplitude (Power)

• Inspiratory Time

• Mean Airway Pressure

• FIO2

• Bias flow

AmplitudeAmplitude (Power) (Power)

A rough representation of the volume of gas generated by each high frequency wave. Range (1.0 - 10.0).

AmplitudeAmplitude (Power) (Power)

• Alveolar ventilation is directly proportional to POWER, so the level of PaCO2 is inversely proportional to the power

AmplitudeAmplitude (Power) (Power)

• 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.

Inspiratory Time: 33%Inspiratory Time: 33%

• Warning – If the I.T. is increased it may lead to air trapping and 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.

Mean Airway PressureMean Airway Pressure

• Average positive pressure in the lung

• Mean Airway Pressure correlates with oxygenation

Mean Airway PressureMean Airway Pressure

• IT IS VERY IMPORTANT TO KEEP MAP CONSTANT DURING THE CONVERSION TO HFV TO PREVENT EXCESSIVE ATELECTASIS AND LOSS OF OXYGENATION. The goal being a MAP equal to or slightly (1-3 cm) below the previous MAP. 

COMPLICATIONS COMPLICATIONS ASSOCIATED WITH HFVASSOCIATED WITH HFV

• A. Hyperinflation or Barotrauma: Decrease MAP

• B. Secretions: Increase frequency of suctioning

• C.  Hypotension: Decrease MAP, and rule out other causes (e.g., pneumothorax, sepsis, dehydration, etc.).

ContraindicationsContraindications

• Obstructive airway disease

• Non-homogeneous lung disease due to risk of hyperinflation

2 Strategies2 Strategies

• High Mean Airway Pressure• RDS

• Open lung• High PEEP/Low tidal volume

• Low Mean Airway Pressure• Air Leaks

• High FIO2

• Low stretch• Allow lung to heal

Mean Airway PressureMean Airway Pressure

• Jets can operate at lower mean airway pressures than Oscillators

HFVHFV

• Jets = Passive Exhalation• Lower Mean Airway Pressures

• Operate at lower rates

• Operates with a conventional ventilator

• Oscillators = Active Exhalation• Higher rates

• Need higher Mean Airway Pressures

• Stand alone

• Cannot do CMV

NBRC Exam ReviewNBRC Exam Review• A 1,500 gram neonate is being ventilated with a high-

frequency oscillatory ventilator at a rate of 10 Hz with a size 2.0 endotracheal tube. Despite an amplitude setting to produce chest wiggle, the patient’s PaCO2 remains high. The therapist should recommend:

a. changing to a size 2.5 endotracheal tube

b. lower the amplitude by 3 cmH2O

c. replacing the endotracheal tube with a cuffed tube

d. changing the frequency to 12 Hz

NBRC Exam ReviewNBRC Exam Review• A 1,500 gram neonate is being ventilated with a high-

frequency oscillatory ventilator at a rate of 10 Hz with a size 2.0 endotracheal tube. Despite an amplitude setting to produce chest wiggle, the patient’s PaCO2 remains high. The therapist should recommend:

a. changing to a size 2.5 endotracheal tube

b. lower the amplitude by 3 cmH2O

c. replacing the endotracheal tube with a cuffed tube

d. changing the frequency to 12 Hz

NBRC Exam ReviewNBRC Exam Review

• When using a high-frequency oscillatory ventilator to manage hypoventilation, the:

a. frequency should be increased

b. amplitude should be increased

c. mean airway pressure should be decreased

d. FiO2 should be decreased

NBRC Exam ReviewNBRC Exam Review

• When using a high-frequency oscillatory ventilator to manage hypoventilation, the:

a. frequency should be increased

b. amplitude should be increased

c. mean airway pressure should be decreased

d. FiO2 should be decreased

NBRC Exam ReviewNBRC Exam Review

• High-frequency oscillatory ventilation is being used with a neonate with RDS. The following settings are in use: 50% oxygen, rate 700/min, amplitude 10 cmH2O, and 4 cmH2O PEEP. The patient’s PaCO2 is 52 torr. What should be recommended to correct the CO2 level?

a. Increase the amplitude

b. Decrease the amplitude

c. Increase the PEEP level

d. Increase the inspiratory time

NBRC Exam ReviewNBRC Exam Review

• High-frequency oscillatory ventilation is being used with a neonate with RDS. The following settings are in use: 50% oxygen, rate 700/min, amplitude 10 cmH2O, and 4 cmH2O PEEP. The patient’s PaCO2 is 52 torr. What should be recommended to correct the CO2 level?

a. Increase the amplitude

b. Decrease the amplitude

c. Increase the PEEP level

d. Increase the inspiratory time

NBRC Exam ReviewNBRC Exam Review• High frequency oscillatory ventilation (HFOV) is initiated for a 25-week premature

neonate with severe RDS. The neonate has a heart rate of 160/min and a blood pressure of 64/40 mmHg. An arterial blood gas analysis obtained 20 minutes after intubation shows:

• pH: 7.26

• PaCO2: 64 torr

• PaO2: 60 torr

• HCO3-: 28 mEq/L

The RT should recommend:

a. Initiating conventional ventilation

b. Increasing the amplitude

c. Decreasing the MAP

d. Changing the FiO2

NBRC Exam ReviewNBRC Exam Review• High frequency oscillatory ventilation (HFOV) is initiated for a 25-week premature

neonate with severe RDS. The neonate has a heart rate of 160/min and a blood pressure of 64/40 mmHg. An arterial blood gas analysis obtained 20 minutes after intubation shows:

• pH: 7.26

• PaCO2: 64 torr

• PaO2: 60 torr

• HCO3-: 28 mEq/L

The RT should recommend:

a. Initiating conventional ventilation

b. Increasing the amplitude

c. Decreasing the MAP

d. Changing the FiO2