High frequency ventilation

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High frequency ventilation

• R2 ???

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• Content
• High frequency ventilation
• HPPV
• HFJV
• Characteristics of JV
• Analogy
• HFOV
• Monitoring of HFV

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• High frequency ventilation
• Produce TV at or below dead space
• High frequency positive pressure ventilation
  (HFPPV)
• High frequency jet ventilation (HFJV)
• High frequency oscillation (HFO)

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• Use in major conducting airway surgery
• Use in bronchopleural fistula
• Minimizing air leaks
• PaCO2
• Use in minimizing movement of the operative field
• Minimizing the tidal movement
• Nondependent lung? quiet operative field
• Dependent lung? minimally moving mediastinum
• Gas exchange improved?

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• High frequency positive pressure ventilation
  (HFPPV)
• Conventional
• TV 3-4ml/Kg
• Rate60-120/min
• Inspiration/expiration ratiolt0.3

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• High frequency jet ventilation (HFJV)
• Small cannula or airway
• less interference the surgical field
• Compared with the HFOV?
• Deliver through a standard single-lumen tube
• Pulsed jet, TVlt2ml/Kg
• Rate120-600/min
• Widest use in OR
• Laryngeal, tracheal, bronchial procedures,
  emergency management of the airway
• Bronchopleural, tracheoesophageal fistula

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Characteristics of JV
Characteristics of JV
JV
CV
artificial breathing by insufflation of gas
with high velocity via a narrow nozzle
into the open airway
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Characteristics of JV
JV
CV
Va (Vt - Vd) f
Gas flow is fast, coaxial,partially
simultaneous, inward only Tidal volume ? dead
space
Gas flow slow, bidirectional,
sequential, bulk flow Tidal volume gt dead space
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• Mechanism

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Analogy with Railway
O2
CO2
Conventional ventilation
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Analogy with Railway
Jet ventilation
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• Disadvantage of HFJV
• Unfamiliarity
• Inability monitor end-tidal CO2
• Inability to use potent inhalation agents without
  pollute the OR
• Complication
• Barotrauma
• Mucosal damage
• Tracheobronchitis
• Adequate warming humidification

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• High frequency oscillation (HFO)
• Piston providing positive and negative
  pressure
• The oscillator provide the fresh gas and wash out
  the CO2
• Rate180-3000/min
• Use in patient with ARDS

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Monitoring of HFV
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• Monitoring of HFV
• Peak airway pressure
• CO2 measurement
• Pulse oximetry

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• Monitoring of HFV
• pressure
• Drive pressure15-30 psi
• Mean airway pressure measured in trachea at
  least 5-10cm below the injector
• Air pressure correlate gas exchange
• Peak air pressure ?? PaCO2 ?
• But no unique relationship
• Intrinsic PEEP effect
• High drive pressure
• Inspiratory times

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• Monitoring of HFV
• CO2 measurement
• The system is open
• Capnography is difficult to apply
• ?artificially low
• Method of measurement
• Capnograph placing in the expired circuit
• Interject a conventional breath periodically to
  measure ETCO2
• Compared with the PaCO2 periodically

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• Multiple reports of the successful application of
  HFJV in patients with BPF, it has not proved
  universally advantageous in terms of gas exchange
• In summary, in view of the limitation of HFV, its
  use as a routine procedure for any of the three
  possible thoracic surgery situations cannot be
  recommended.

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Thanks for your attention