High%20Frequency%20Ventilation

1
High Frequency Ventilation

• Level 1
• Mark Willing, RRT-NPS

2
Indications for High Frequency Ventilation

• Failure of conventional mechanical ventilation to
  relieve respiratory acidosis
• Those patients at risk for or have developed a
  pneumothorax, pulmonary interstitial emphysema,
  pneumomediastinum, or other air-leak syndrome
• A general lung protective ventilator strategy

3
General Concepts

• Low tidal volumes (less than 2ml/kg)
• Rapid rates (up to 900 breaths/min)
• May be lung protective due to decreased
  volutrauma
• May be more efficient at ventilation than
  conventional ventilation methods

4
Enhanced Efficiency of Ventilation

• Ventilation during high frequency ventilation is
  achieved by a combination of factors contributing
  to enhanced removal of CO2
• Simultaneous inspiration and expiration due to
  unique gas flow pattern
• Dependent upon maintaining as many open alveoli
  as possible
• Enhanced mixing of gases in the airways and
  between alveoli

5
Gas entering the lungs travels centrally, while
gas leaving the lungs swirls around it
6
Minute Ventilation

• The amount of gas that is exchanged within the
  lung in one minute is called minute ventilation
• As minute ventilation is increased, the amount of
  CO2 in the blood may decrease
• Minute ventilation during conventional
  ventilation and spontaneous breathing is
  calculated as
• Respiratory Rate X Tidal Volume
• Minute ventilation during high frequency
  ventilation is calculated as
• (Respiratory Rate)0.5 X (Tidal Volume)2
• Therefore, tidal volume is the primary
  determinant of minute ventilation during high
  frequency ventilation

7
High Frequency Jet Ventilation
8
High Frequency Jet Ventilation Concepts

• The inhalation valve is placed as close to the
  patient as possible to deliver a crisp jet
  stream of fresh gas deep into the lungs.
• A conventional ventilator is used in tandem to
  assist in oxygenation. Through manipulation of
  inspiratory time, PEEP, PIP, and rate, the mean
  airway pressure can be adjusted for optimal
  oxygenation and alveolar recruitment.
• Passive exhalation requires a lower set rate
  (320-480 breaths/minute)

9
High Frequency Jet Ventilator Adjustments

• Increasing the PIP setting may increase the
  delivered tidal volume, therefore lowering the
  CO2 in the bloodand vice-versa
• Oxygenation is primarily influenced by the
  conventional ventilator through manipulation of
  the PEEP, PIP, inspiratory time, and rate

10
Servo Pressure

• Respiratory therapists and nurses, alike, will be
  charting the servo pressure
• Servo pressure is an indirect measurement of the
  delivered tidal volume
• Changes in servo pressure give the bedside
  practitioner information regarding changes in
  compliance and resistance
• As the servo pressure increases, it may be
  indicative of improving compliance and
  resistanceand vice-versa.

11
Common Alarms

• Cannot meet PIP and/or Loss of PIP
• Leaks in the circuit (associated with an acute
  increase in servo pressure and high servo alarm).
  Little or no chest wiggle and breath sounds.
• Excessive respiratory effort by the patient
  (associated with repeated high/low servo and mean
  airway pressure alarms).
• Recent disconnect for suctioning or repositioning
  (associated with a high/low servo and mean airway
  pressure alarm).
• Near or complete extubation (associated with a
  high servo pressure and alarm). Loud upper
  airway noises, little to no chest wiggle, air
  escaping out the mouth.

12
What To Do

• These two alarms are commonly associated with
  circuit disconnects and suctioning, which may be
  associated with severe, and perhaps
  life-threatening, alveolar collapse and oxygen
  desaturation.
• The RN must notify the RRT and have this person
  available at the bedside prior to position
  changes, suctioning, and surfactant
  administration.
• In the event that the RRT is currently
  unavailable, it is best to leave such elective
  procedures until such time an RRT can assist with
  or perform the procedure without the RN.
• If at any other time, if the ventilator fails to
  establish the set PIP, immediately notify the
  respiratory therapist.
• Hand-bagging a patient with a manual resuscitator
  bag may be very dangerous to certain premature
  infants, therefore immediate response from a
  respiratory therapist is critical.

13
Positioning the Circuit

• The small bore, clear tubing coming off the jet
  adapter must not be in a dependent position. Any
  secretions or water obstructing the tube will
  result in inaccurate pressure readings, damage
  the pressure transducer in the patient box,
  and/or will cause inaccurate pressure delivery to
  the patient.
• The elbow on the in-line suction catheter should
  be positioned in such a manner that water
  condensation is not injected or lavaged down the
  airway.
• The green jet tubing should be as straight as
  possible to reduce any dampening of the jet
  stream into the airway.

14
High Frequency Oscillatory Ventilation
15
High Frequency Oscillatory Ventilation Concepts

• Open as many alveoli as possible without over
  distending the lung
• May create blood pressure problems due to high
  lung volume, therefore volume expanders and/or
  vasoactive drugs may be needed
• Active exhalationpulls the gas out of the lungs
  on the expiratory cycle
• Active exhalation allows for higher set
  ventilatory rates (up to 900 breaths/min)

16
The SensorMedics high frequency oscillator pushes
and pulls gas above and below a set mean airway
pressure
17
Settings

• Frequency (Hertz, Hz)
• Mean Airway Pressure (MAP)
• Amplitude (Delta P, change in pressure)

18
Hertz (Hz)

• 60 cycles in a minute 1 Hertz
• 120 breaths/min 2 Hz, and so on
• 15Hz on an oscillator is 900 breaths/min
• The smaller the patient, the higher the Hz
  setting,and vice-versa
• Less than 2kg patient 12-15Hz
• Children in the PICU may be on 6-10Hz

19
Mean Airway Pressure (MAP)

• Primary determinant of alveolar lung volume and
  critical to the efficiency of ventilation and
  oxygenation
• Use chest X-rays to determine over/under-inflation
  of lung and then adjust MAP accordingly

20
Amplitude

• Amplitude Delta P Change in pressure
• As the change in pressure increases, it may
  increase the tidal volume, therefore decrease the
  CO2 in the bloodand vice-versa
• For example, on conventional ventilation, a PIP
  of 24 and a PEEP of 4 results in a change in
  pressure of 20, and corresponds to a certain
  tidal volumeno different with high frequency
  ventilation

21
Circuit Positioning

• The circuit should be tilted upward a few degrees
  to allow for water condensation to drain backward
  towards the ventilator.
• The endotracheal tube should be kept as straight
  as possible to reduce any dampening of the
  pressure.

22
What do I do if the ventilator turns off?

• The ventilator will automatically stop if there
  is a disconnect in the circuit, and may create
  profound, and perhaps life-threatening, alveolar
  collapse and oxygen desaturation.
• Notify the RRT immediately.
• Gently hand-bag the patient using appropriate
  inspiratory pressures (manometer), rate, and PEEP
  (PEEP valve) until the respiratory therapist
  arrives.
• As with all patients receiving high frequency
  ventilation, any elective procedures such as
  suctioning, surfactant administration, and
  position changes require the presence of an RRT.

23
Whats that chirping noise?

• Chirping or an intermittent alarm from the
  ventilator commonly occurs when the mean airway
  pressure has come close to the upper and lower
  alarm limits.
• This is as a result of
• An improper alarm setting
• Water spitting out of the control valve
• Excessive respiratory effort from the patient
• The MAP setting has been allowed to wander
• Inadequate flow to meet the inspiratory demands
  of the patient.

24
Summary

• High frequency ventilation can provide enhanced
  gas exchange beyond what is capable with
  conventional ventilation.
• The open-lung or high-volume lung strategies have
  recently proven to be most successful with and
  without the presence of active air-leaks.
• High frequency ventilation may provide a means of
  a lung protective strategy for ventilating
  patients with poor lung compliance at risk for
  developing air-leak syndromes.
• High lung volume strategy coupled with the
  relatively stable intrathoracic volume may reduce
  venous return to the heart and decrease blood
  pressure. Some patients may benefit from an
  increase in intravascular volume and/or
  administration of medications that increase blood
  pressure.
• Procedures such as suctioning, position changes,
  and surfactant administration are to be left for
  some time at which an RRT can be present, even if
  it means before or after the designated stim
  time.