Airway Pressure Release Ventilation

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Airway Pressure Release Ventilation

• APRV review and indications in paediatrics

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APRV

• Terminology
• How it works
• Indications
• Advantages/disadvantages
• Review of paediatric studies
• Set-up (paed specific)
• Weaning
• Discussion

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APRV

• Continuous positive airway pressure with regular,
  brief releases in airway pressure to facilitate
  alveolar ventilation and CO2 removal
• Time triggered, pressure limited, time cycled
  mode
• Allowing unrestricted spon. Breathing throughout
  the ventilatory cycle

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Terminology

• P high the baseline airway pressure level,
• P low airway pressure resulting from airway
  release (PEEP)
• Time high the length of time that P high is
  maintained
• Time PEEP time spent in airway release at P low
  

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How does it work?

• The constant airway pressure at P high
  facilitates alveolar recruitment and therefore
  enhances gas diffusion
• The long time at P high allows alveolar units
  with slow time constants to open
• The timed releases in pressure T PEEP allows
  alveolar gas to be expelled via natural lung
  recoil not with repetitious opening of alveoli

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APRV waveform
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Indications

• Recruitable low compliance lung disorders
• Lung dysfunction secondary to thoracic
  restriction i.e.. obesity, acites
• Inadequate oxygenation with FiO2 gt .60
• PIPgt 35 cmH2O and /or PEEPgt10 cmH2O
• Lung protective strategies (high PEEP, low Vt)
  are failing
• Can be used with other interventions i.e.. INO
  therapy, prone positioning

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Advantages

• Significantly lower peak Paw and improved
  oxygenation when compared to conventional
  ventilation
• Requires lower min. vol. suggesting decreased
  dead space ventilation
• Avoids low volume lung injury by avoiding
  repetitious opening of alveoli

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Advantages

• Allows for spontaneous breathing at all points in
  the respiratory cycle
• Spon. breathing tends to improve V/Q matching
• Decreased need for sedation and near eliminating
  need for neuromuscular blockade

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Disadvantages

• Volumes affected by changes in compliance and
  resistance and therefore close monitoring
  required
• Integrating new technology
• Limited research and clinical experience

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Paediatric Studies

• Studies in the paediatric population are few and
  small
• Several are ongoing
• 3 published
• Most evidence is extrapolated from the adult
  studies

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Airway pressure release ventilation in
paediatricsSchultz T, et al. Pediatric Crit Care
Med. 2001 jul2(3)24 3-6
Airway pressure release ventilation in
paediatricsSchultz T, et al. Pediatric Crit Care
Med. 2001 jul2(3)24 3-6

• a prospective, randomized, cross-over trial of 15
  PICU pt. gt8kg
• Randomized to either VCV (9) or APRV (6)
• APRV had lower PIP and Pplat than VCV in all
  patients
• No sig. differences in physiologic variables
  e.g.. EtCO2

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Airway Pressure Release in a Paediatric
PopulationJones R, Roberts T, Christensen D.
St.Lukes Reginal Medical Center, Boise, ID AARC
open Forum 2004

• A case series of 7 paediatric patients aged 3 to
  13 with ALI
• All failing conventional PPV with severe
  hypoxemia
• 2 failed HFOV with severe hypoxemia
• 6/7 lower PIP, all had higher MAP, all had
  improved oxygenation, all had lower FiO2
  requirements

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Airway Pressure Release Ventilation A Pediatric
Case SeriesKrishnan,J. ,Morrison, M. University
of Maryland, Pediatric Pulmonology 4283-88. 2007

• retrospective review of 7 pediatric cases
• Approved by the University of Maryland
  institutional review board
• All pt.s failed on conventional ventilation
• Implemented similar starting parameters as to be
  described later

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Case 1

• 9 y.o. leukemia with septic shock, ARDS and MSOF
• SIMV PC , FiO2 1.0, PIP/PEEP 38/14 cmH2O,
  PaO2 91 mmHg
• Failed HFOV secondary to hypotension
• APRV Phigh 37 cmH20, Plow 0cmH2O with Pmean of
  32 cmH2O
• PaO2 improved over 84 hrs and required no NMB
• Weaned and d/ced home

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Case 2

• 5 y.o. 60 body area burns with development of
  sepsis and ARDS
• Failed convention ventilation (39/19) and was
  placed on HFOV with intractable hypercarbia
  (PaCO2 121mmHg)
• APRV of 40/0 PaCO2 improved to 78mmHg
• MSOF worsened and pt. made limited resuscitation

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Case 3

• 8 y.o. CF with development of ARDS
• Pt. required heavy sedation with CV with 30/13
  and FiO2 .50
• APRV settings 28/0 and sedation was decreased and
  pt. was extubated to NIV
• No NMB was required

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Case 4

• 4 y.o. with fever, jaundice, hepatomegaly,
  pancytopenia and hypofibrinogenemia
• Requiring CRRT for MSOF and ARDS
• CV with 40/10 cmH20 and FiO2 1.0
• APRV 34/0 and O2 weaned to .6 and NMB was lifted
• Weaned to CPAP and septic shock resolved but pt
  suffered an intracranial haemorrhage which led to
  his death
• Autopsy revealed hemophagocytic
  lymphohistiocytosis

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Case 5

• 1 y.o. leukemia post bone marrow transplant with
  sepsis and neutropenia and graft vs host disease
  and tracheotomy
• Difficult to ventilate with PaCO2 of 64mmHg and
  tachypnea and distress
• APRV 30/0 cmH20 and was rapidly weaned with
  noted increase in comfort
• Weaned to FiO2 to .45 and PaCO2 39mmHg
• Later exacerbation of leukemia resulted in renal
  failure

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Hints for set-up

• P high same as plateau or 125 of mean Paw
• PEEP 0 cmH2O
• T PEEP long enough to get returned Vt but not
  long enough to derecruit titrate to end at 25
  -50 of the PEF
• T high manipulated to achieve RR
• PS set to avoid flow hunger with spon. resps.

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Set-up
Set-up

• Be patient
• The change to APRV may not provide instant
  improvement in oxygenation
• The effects may take hours to be realized
• Has been shown that the maximum benefit occurred
  at approx. 8 hours after implementation

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Weaning

• Decrease FiO2 first and then P high is small
  increments
• As compliance improves the TCs lengthen and T
  PEEP may need adjustment to allow for adequate
  Vt
• When P high is weaned to a low level consider
  extubation
• Lengthen T high and therefore decreasing the of
  pressure releases per minute

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Lets talk!

• Any questions?