HIGH FREQUENCY VENTILATION (HFV) Neonatal & Pediatric

HFV 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 VENTILATION (HFV) A form of “pressure” ventilation No volumes set, measured, or controlled The only real control is time

Traditional Teaching of Gas Exchange: CMV or Spontaneous Breathing 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 HFV Mechanical ventilation using tidal volume less than or equal to dead space volume and delivered at supra physiologic rates! FDA defines as rates > 150 breaths/min

Tidal Volumes < Anatomical Deadspace It is possible to adequately ventilate the lungs with tidal volumes equivalent to deadspace using much higher frequencies than normal

Dogs Regulate their temperatures by panting Very shallow, very fast breaths Breaths are smaller than anatomic deadspace Yet dogs do just fine

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

Why HFV? Can ventilate the lungs at very small tidal volumes and very high respiratory rates Why do we wish to do this?

HFV 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 Air leak syndromes: PIE, pneumomediastinum, pneumothorax, pneumopericardium, pneumoperitoneum, and sub Q emphysema

INDICATIONS FOR HFV 1.BAROTRAUMA - pulmonary airleaks.  PNEUMOTHORAX PULMONARY INTERSTITIAL EMPHYSEMA (PIE)  2. Respiratory failure unresponsive to conventional ventilation   PIE – gas leaking into the interstitium that usually presents with 72 hours of initiation of MV. Tiny air leaks usually caused by overdistension. “Salt and pepper” like appearance on CXR due to linear lucencies that are present. Respiratory failure unresponsive to conventional ventilation = rescue treatment (when all else fails).

PIE

HIGH FREQUENCY 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). #4 used in conjuction with CV.

HIGH FREQUENCY VENTILATION (HFV) The FDA defines HFV as a rate >150/min Clinicians: 40-150

HFV Terminology Hertz Amplitude Power Inspiratory Time Mean Airway Pressure FIO2 Bias flow

Hertz Another name for frequency Cycles per second 1 Hertz = 60 cycles per minute Range 2-28 <4 or >15 rarely used Ex: 2Hz = 120 breaths/min.

AMPLITUDE 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 Amplitude = delta P Directly proportional – increase Amp, increased Vt.

AMPLITUDE Adjust the amplitude until you achieve vigorous chest wall vibrations Setting responsible for chest wiggle.

HFJV-High Frequency Jet Ventilation The Bunnell Life Pulse High Frequency "Jet" Ventilator

HFJV-High Frequency Jet Ventilation: Circuit The patient box

High 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 This method required reintubation with the jet ET tube.

HFJV-High Frequency Jet Ventilation 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 The lifeport adapter does not require reintubation. Pressure monitoring tube CV connection Jet injection port Jet port cap Inserts into ET tube Monitor port connection – connects to patient box.

Jets are used in conjunction with a conventional ventilator.

Jets are used in conjunction with a conventional ventilator.

HFJV-High Frequency Jet Ventilation 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 Ventilation 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. Rate = 420 Larger pt’s and pt’s prone to gas trapping need a lower rate (240-360bpm) to increase expiratory time. CV breaths assist with recruitment and stabilizing the alveoli (rarely > 10 bpm) too few sigh breaths with lower PEEP levels = atelectasis too many = barotrauma

HFJV: 3 concepts I-Time Jet nozzle Passive exhalation (Refer to handout) I time = 0.02; fixed; rate adjust changes E time only. Jet nozzle – built into the ET tube adapter; squirts gas into the ETT at high velocities allowing the gas to penetrate deeper into the lungs with each breath, penetrating through deadspace instead of pushing it ahead of the fresh gas. Also facilitates airway clearance Passive exhalation Can run at lower MAP’s compared to HFOV.

Inspiratory 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 Higher PEEP can be used in order to keep the lungs open with sufficient mean airway pressures to oxygenate. Tidal volume does not change with changes in HFJV frequency, only the E-time changes. Adjust rate to give longer E time for patients with hyperinflation.

HFV verses CMV Servo P (alarm) = amt of gas flow or Vt delivered by the vent to achieve PIP ordered. Max=22psi.

Passive Exhaltion Operates at lower Mean Airway Pressure than Oscillator

Primary 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 PIP is set 2 cmH2O below setting on CV. PEEP is set by vent. Amp = primary determinant of PaCO2; rate is secondary.

HFJV PIP Drops dramatically as approaches alveoli VIDEO Increased PIP increased delta P to improve ventilation. Decreased PIP decreased delta P to decrease ventilation. PaCO2 regulated by changes in PIP or delta P NOT rate or frequency. (Pull up practice jet from website and play around with settings. http://www.bunl.com/product-tabs2.html then click on interactive life pulse)

High Frequency Oscillation 3100A – infants 3100B – adults, children >35kg

SensorMedics Front Panel

High 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 Ventilation 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 Can do higher rates than the jet.

HFV Terminology Hertz Amplitude (Power) Inspiratory Time Mean Airway Pressure FIO2 Bias flow Hertz – usually around 10 on osc. Bias flow: Premature – 10-15 lpm Near term – 10-20 lpm Small child – 15-25 lpm Large child – 20-30 lpm Adults – 20-40 lpm

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

Amplitude (Power) Alveolar ventilation is directly proportional to POWER, so the level of PaCO2 is inversely proportional to the power Increase power (amp) decreases PaCO2 Decrease power (amp) increases PaCO2

Amplitude (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% 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 Pressure Average positive pressure in the lung Mean Airway Pressure correlates with oxygenation MAP is equivalent to CPAP. Set 1-2 cmH2O above MAP on CV. Increase in small increments until improvement in oxygenation (SpO2, transcutaneous) or until proper extension on CXR (8-10 ribs) Overinflation = decreased venous return, CO Decrease MAP if overinflated.

Mean 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.  Wean MAP 0.5 -1 Q2-3 hrs.

COMPLICATIONS ASSOCIATED 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.). During suctioning – temporarily increase MAP to decrease lung derecruitment.

Contraindications Obstructive airway disease Non-homogeneous lung disease due to risk of hyperinflation

2 Strategies High Mean Airway Pressure Low 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 Pressure Jets can operate at lower mean airway pressures than Oscillators

HFV Jets = Passive Exhalation Oscillators = Active 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 Oscillator is good at preventing airleaks but the jet is better when airleaks are present.

NBRC 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 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 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 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 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? Increase the amplitude Decrease the amplitude Increase the PEEP level Increase the inspiratory time

NBRC 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? Increase the amplitude Decrease the amplitude Increase the PEEP level Increase the inspiratory time

NBRC 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: Initiating conventional ventilation Increasing the amplitude Decreasing the MAP Changing the FiO2

NBRC 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: Initiating conventional ventilation Increasing the amplitude Decreasing the MAP Changing the FiO2