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Airway Pressure Release Ventilation
APRV review and indications in paediatrics
APRV
Terminology How it works Indications Advantages/disadvantages Review of paediatric studies Set-up (paed specific) Weaning Discussion
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
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
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
How does it work?
APRV waveform
Indications
Recruitable low compliance lung disorders Lung dysfunction secondary to thoracic restriction
i.e.. obesity, acites Inadequate oxygenation with FiO2 > .60 PIP> 35 cmH2O and /or PEEP>10 cmH2O Lung protective strategies (high PEEP, low Vt) are
failing Can be used with other interventions i.e.. INO
therapy, prone positioning
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
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
Disadvantages
Volumes affected by changes in compliance and resistance and therefore close monitoring required
Integrating new technology Limited research and clinical experience
Paediatric Studies
Studies in the paediatric population are few and small
Several are ongoing 3 published Most evidence is extrapolated from the adult
studies
Airway pressure release ventilation in paediatricsSchultz T, et al. Pediatric Crit Care Med. 2001 jul;2(3):24 3-6
a prospective, randomized, cross-over trial of 15 PICU pt. >8kg
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
Airway pressure release ventilation in paediatricsSchultz T, et al. Pediatric Crit Care Med. 2001 jul;2(3):24 3-6
Airway Pressure Release in a Paediatric PopulationJones R, Roberts T, Christensen D. St.Luke’s 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
Airway Pressure Release Ventilation: A Pediatric Case SeriesKrishnan,J. ,Morrison, M.: University of Maryland, Pediatric Pulmonology 42:83-88. 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
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
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
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
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
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
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.
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
Set-up
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
Lets talk!
Any questions?