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High Frequency Oscillatory Ventilation
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High Frequency Oscillatory Ventilation Presentation Transcript

  • 1. High Frequency Oscillatory Ventilation
    PeteyLaohaburanakit, MD, FCCP
    Critical Care Services
    Rogue Valley Medical Center
  • 2. Outline
    What is HFOV?
    Ventilator-induced lung injury (VILI)
    How does HFOV work?
    Basic concept and gas exchange
    Oxygenation and ventilation in HFOV
    Clinical studies
    Initiation and adjustment
    Care for patients on HFOV
    Potential complications
  • 3. What is HFOV?
    Not to be confused with high frequency jet ventilation (HFJV), which is rarely used
    First established use in neonatal ARDS
    HFOV’s claim to fame is reduction of ventilator-induced lung injury (VILI)
  • 4.
  • 5. What is VILI?
    Two major causes
    Alveolar distension
    High plateau pressure
    Cyclical opening and closing of atelectatic lung
    Large pressure swing at the alveolar level from large tidal volumes
  • 6.  V
     P
     V
     P
     V
     P
  • 7. Zoneof
    Overdistension
    Injury
    “Safe”
    Window
    Volume
    Zone of
    Derecruitment
    and Atelectasis
    Injury
    Pressure
  • 8. Injury
    Injury
  • 9.
  • 10. How does HFOV work?
    The piston oscillates the lung around a constant mean airway pressure with high frequency
    The mean airway pressure (Pmaw) is almost always higher than conventional ventilation
    Small tidal volume with less pressure swing reduces VILI
    One way to look at it – CPAP with rapid oscillation
  • 11. CDP
    “Continuous
    Distending
    Pressure”
    Adjust Valve
    ET Tube
    Oscillator
    Patient
    BIAS Flow
  • 12. Pressures at alveolar level
  • 13.
  • 14. Gas exchange in HFOV
    Direct bulk flow
    Longitudinal (Taylor) dispersion
    Pendeluft
    Asymmetric velocity profiles
    Cardiogenic mixing
    Molecular diffusion
  • 15. HFOV and CMV
  • 16. Decoupling of Ventilation and Oxygenation
    Controls for oxygenation
    Pmaw
    FiO2
    Alveolar recruitment maneuver
    Controls for ventilation
    Amplitude (DP)
    Hertz
    Inspiratory time
    Cuff deflation
    Permissive hypercapnia
  • 17.
  • 18. Oxygenation
    Primarily controlled by mean airway pressure (Pmaw)
    Pmaw is a constant pressure used to inflate the lung and hold the alveoli open
    Since the Pmaw is constant, it reduces the injury that results from cycling the lung open for each breath
  • 19. x
    Bias Flow
    CDP Control Balloon
  • 20. Ventilation
    Controlled by the movement of pump/piston mechanism
    Alveolar ventilation during CMV is defined as f x Vt
    Alveolar ventilation during HFOV is defined as f x Vt2
    Changes in volume delivery have the most significant effect on ventilation
  • 21.
  • 22.
  • 23. Regulation of stroke volume
    The stroke volume will increase if
    The amplitude increases (higher DP)
    The frequency decreased (longer cycle time)
    There is an increase in inspiratory time
  • 24. Amplitude (DP)
    The force created by piston movement
    Dependent on the power setting
    Results in chest wiggle
  • 25.
  • 26. Inspiratory time
    Controls the time for movement of the piston
    Increases inspiratory time increases CO2 elimination
    Increases inspiratory time increases delivered Pmaw
  • 27.
  • 28. PaO2
    PaCO2
  • 29. Clinical Data
    Pilot studies
    Mehta S et al. Crit Care Med 2001
    Derdak S et al. Am J RespirCrit Care Med 2002
    Multicenter oscillatory ventilation for ARDS trial (MOAT)
    OSCILLATE – Canadian clinical trials group
  • 30. Pilot Studies
    HFOV was as effective as CMV for ARDS
    HFOV patients reached oxygenation goals earlier
    Early implementation was associated with better outcomes
    CMV groups were not ventilated with ARDS Network protocol*
  • 31. MOAT Study - Design
    13 university-affiliated medical centers, recruitment 1997-2000
    Eligibility:
    age >= 16 on mechanical ventilation
    PaO2/FiO2 < 200 while on PEEP >= 10
    Bilateral pulmonary infiltrates on CXR
    No evidence of left atrialhypertension
  • 32. MOAT Study - Design
    Exclusion:
    Weight < 35 Kg
    Severe COPD or asthma
    Intractable shock
    Severe airleak
    Nonpulmonary terminal diagnosis
    FiO2 > 0.80 for more than 2 days
  • 33. MOAT Study - Results
    N=148
    Mean age 50
    APACHE II score 22
    PaO2/FiO2 ratio 112
    Oxygenation index (OI) 25
    Mean duration on mechanical ventilation prior to HFOV 2.8 days
  • 34. MOAT Study -Results
    A : Mean airway
    pressure
    B : P/F ratio
    C : Oxygenation
    Index
    D : PaCO2
  • 35. MOAT Study - Results
  • 36. MOAT Study – OI for prognosis
  • 37. MOAT Study - Criticisms
    Not powered to evaluate mortality (would need n=199)
    Control group did not comply with ARDS Network standards
    Higher Vt (8 ml/kg measured wt, 10.6 ml/kg ideal wt)
    Peak Paw 38 cm H2O at 48 hours
  • 38. OSCILLATE Study
    Canadian Clinical Trials Group
    The OSCILLation in ARDS Treated Early
    Goal N = 94
    Completed in December 2008
  • 39. HFOV for ARDS
    When to consider?
    The earlier the better
    FiO2 >= 0.60, PEEP >= 10 with P/F ratio < 200
    Plateau pressure > 30
    Oxygenation index (OI) > 24
    OI = (FiO2 x 100) x Pmaw / PaO2
    Failed ARDS Net protocol
  • 40. Key to success
    Patient selection
    Timing of initiation
    Early application provides protection and reduces risks of further lung damage
    Rescue with HFOV may or may not improve mortality
    The later HFOV is started the less chance of survival
  • 41. Initial settings
    Recruitment maneuver
    Pmaw 5 cmH2O above CMV Pmaw
    FiO2 1.0
    Frequency 5-6 Hertz
    Power 40, adjust for good chest wiggle
    Inspiratory time at 33%
    Set bias flow at > 25 lpm, go higher if needed
  • 42. Ventilator Strategies - Goals
    Normalize lung volume
    Minimize pressure change at alveolar level
    Wean FiO2 to a safe level first
    Physiological targets
    SaO2 between 88% and 93%
    Delay weaning Pmaw until FiO2 < 0.5
    pH > 7.25
    PaCO2 in the range of 45-70 mmHg
  • 43. Oxygenation Strategies
    Initial Pmaw 5 cm > CMV Pmaw
    Increase Pmaw until you are able to decrease FiO2 to 60% with SaO2 of 90%
    Avoid hyperinflation – CXR
    Optimize preload, myocardial function
    Mean arterial pressure > 75 mmHg
  • 44. Adjusting the settings
    Hypercapnia
    Increase DP
    Decrease frequency
    Increase inspiratory time
    Deflate the cuff
    Hypocapnia
    Increase frequency
    Decrease DP
  • 45. Bedside Monitoring
    Chest wiggle factor
    Chest X-ray
    Arterial blood gas
  • 46. Chest wiggle factor (CWF)
    Wiggling from clavicles to mid-thighs
    Monitor at initiation and closely thereafter
    Reassess after any position change
    Absent or diminished CWF
    Airway or ET tube obstruction
    Asymmetrical CWF
    One-lung intubation
    Pneumothorax
    Unilateral mucous plug
  • 47. Chest X-ray
    First CXR at 1 hour, no later than 4 hours
    Chest inflation to 10-12th ribs
    Get CXR if unsure whether is patient is hyperinflated or derecruited
    Do not stop the piston or disconnect the patient from HFOV for CXR
    The purpose of CXR is to assess lung inflation while the patient is on HFOV
  • 48. Physical Exam
    Heart sounds
    Stop the piston, listen to the heart sound quickly, re-start the piston
    Breath sounds
    Cannot be heard with HFOV
    Intensity of sound produced by the piston should be equal throughout
    If not, get CXR
  • 49. Patient care
    Suctioning
    Indicated by decreased or absent CWF, decrease in SaO2 or increase in PaCO2
    Every time the patient is disconnected from HFOV, the lung is de-recruited
    Closed suction catheter may mitigate de-recruitment, DP may need adjustment to compensate for attenuation of DP due to right angle adapter
    May require temporary increase in Pmaw
  • 50. Patient Care
    Bronchodilator therapy
    Rarely needed because HFOV is relatively contraindicated in active airflow obstruction
    Only few ones with active bronchospasm
    Administered via bagging
    IV Terbutaline for patients who do not tolerate disconnections
  • 51. Patient Care
    Humidification
    Traditional heated humidifier
    Heated wire humidifier
    Circuit
    Longer, flexible circuit allows patient positioning to prevent skin breakdown
  • 52. Patient Care
    Positioning
    Avoid disconnection
    After change of position, observe chest wiggle, SpO2 and PtcCO2
    Check ET tube position
    Readjust HFOV parameters as needed
  • 53. Patient Care
    Sedation
    Patient often needs to be heavily sedated to avoid spontaneous breathing
    Spontaneous breathing leads to unstable, fluctatingPmaw
    Paralytics have become less popular
  • 54. Weaning from HFOV
    Wean FiO2 for SaO2 > 90%
    Once FiO2 is < 0.60, recheck CXR
    If CXR shows appropriate inflation, begin decreasing Pmaw in 2-3 cmH2O increments
    Wean DP in 5 cmH2O increments for PaCO2
    Once the optimal frequency is found, leave it alone
  • 55. Transition to CMV
    Stable Pmaw
    Tolerates positioning and nursing care
    Stable blood gases
    Resolution of original lung pathology
    Switch to PCV
    Vt6 ml/kg
    PEEP, PC and i-time adjusted to Pmaw comparable to the HFOV-generated Pmaw
  • 56. HFOV Failure
    Failure criteria
    Inability to decrease FiO2 by 10% within 24 hours
    Inability to improve ventilation or maintain ventilation with (PaCO2 < 80 or pH > 7.25)
  • 57. Potential Complications
    Hypotension
    IV fluid boluses until CVP or PCWP increased by 5-10 mmHg
    Vasopressors in refractory cases
    Pneumothorax
    Progressive hypotension and desaturation
    Diminished or absent CWF
    Diminished chest auscultation
  • 58. Potential Complications
    Endotracheal tube obstruction
    Rise in PaCO2 in otherwise stable patient
    Inability to pass suction catheter