Neonatal Ventilation:
“The Bivent”
Paul Kingma, MD PhD
Ventilation Basics: Goals
• Oxygenation
– FiO2
– Mean airway pressure
• Ventilation
– Respiratory rate
– Tidal volume
Conventional Pressure Ventilation
Itime
Pressure
PIP
PS
PEEP
Time
Conventional Pressure Ventilation
How do you improve oxygenation?
Itime
Pressure
PIP
PS
PEEP
Time
Conventional Pressure Ventilation
How do you improve oxygenation?
Itime
Pressure
PIP
PEEP
PS
Time
Conventional Pressure Ventilation
How do you improve ventilation?
Itime
Pressure
PIP
PS
PEEP
Time
What do you do?
• If a 2700g intubated baby has oxygen sats
70% and pCO2 80 and…
• 30%FiO2 and ventilator settings of 16/5
and rate of 20?
• 100%FiO2 and ventilator settings of 28/7
and rate of 60?
Risk of Lung Injury
Conventional Pressure Ventilation
How do you improve oxygenation?
Itime
Pressure
PIP
PEEP
PS
Time
Conventional Pressure Ventilation
How do you improve oxygenation? LONG I time
Itime
Pressure
PIP
PS
PEEP
Etime
Time
Reynolds and Strang: 1970’s
• Inverse I:E ratio
– Improve oxygenation in neonates
Inverse I:E in infants = Air Leak
• Factors associated with pulmonary air leak
in premature infants receiving mechanical
ventilation. Jpeds 1983 R.A. Primhak
– Compare infants with pneumothorax vs
ventilated controls
– “No significant difference was found between
the groups in any clinical factor, nor in any
maximum ventilator setting other than a
longer maximum inspiratory time in the study
group.”
Conventional Pressure Ventilation
How do you improve oxygenation? LONG I time
Problem: Inverse I:E…Breath Stacking…Pneumothorax
PIP
Pressure
PS
PEEP
Time
Is there a better way to increase
Itime?
Another Option: Airway Pressure
Release Ventilation (APRV)
• Think of it as sustained high CPAP with timed
“releases” to encourage ventilation
• High and low CPAP settings: P high and P low
• Baseline is at P high with pressure released
periodically to allow ventilation
• Release time is short to prevent collapse
• Spontaneous exhalation allowed during ALL
phases of respiratory cycle.
– Therefore no breath stacking and no pneumothorax
Potential Advantages: Adults
• Uses lower PIP to maintain oxygenation and ventilation without
compromising the patient’s hemodynamics (Syndow AJRCCM 1994, Kaplan, CC,
2001)
– Longer I-time means higher mean airway pressure with lower peak
pressures
• Shown to improved V/Q matching (Putensen, AJRCCM, 159, 1999)
• Decreases dead space ventilation
– Longer I-time allows diffusion of gases
• Spontaneous respiration may
– reduce need for sedation and avoid large changes in CO2 (Ratheberger, 1997;
Putensen 2001)
– improved ventilation in dependent lung regions
• Better cardiac filling when compared to HFOV
• Reduces time at extremes of pressure volume curve
– decreased atelectasis
– decreased barotrauma
What about Pediatrics?
• Very little data
What about Pediatrics?
• Schultz, et al Crit Care Med 2001
• Cross over study from SIMV to APRV or
reverse in 15 patients with mild to
moderate lung disease
• Findings
– Comparable oxygenation and ventilation with
significantly lower peak pressures (33 vs 19
cm H2O)
– No change in hemodynamic variables
What about Pediatrics?
• Krishnan, et al Ped Pulmonol, 2007
• Case series of 7 pts (age 1 – 16 years)
• Findings
– Oxygenation (decrease in OI) improved with
APRV over time
– No problems with ventilation
– No change in sedation requirements but No
patients required neuromuscular blockade
– No change in hemodynamic stability
– Easier pt care than with HFOV
What about Pediatrics?
• Dermirkol, et al Indian J Pediatr 2010
– Case series of 3 patients (3.5-11 mo old)
changed from PC to APRV
– Findings
• FiO2 decreased from 0.97 to 0.68
• Mean Airway pressure increased from 17.9 to 27
cm H2O
• Tidal volume increased from 8.3 ml/kg to 13.2
ml/kg
What about Pediatrics?
• Kamath et al. Ped Pulmonol 2010
• Retrospective study of 11 pts on APRV for
12 hours due to failed conventional vent.
• Findings after 10 hrs on APRV
– FiO2 decreased from 0.83 to 0.67
– Mean airway pressure increased from 16.1 to
21.1 cm H2O
– No change in HR, CVP, BP, UOP, IVF
What about Neonates?
• No Data
• Neonatal Sheep. Martin et al, 1991 Crit
Care Med
– Compared with PPV, APRV provided similar
ventilation and oxygenation with lower peak
pressures and without compromising
cardiovascular performance.
APRV in Neonates
When we know NOTHING
it is easy to be an expert!
This is where I come in 
APRV Terminology
• AKA: Bivent (Servo), APRV (Drager and
Hamilton), Bilevel (Puritan-Bennett)
• P High - the upper CPAP level.
• P Low - the lower CPAP setting.
• T High - is the inspiratory time phase for
the P High.
• T Low - is the release time allowing gas
exchange and CO2 elimination
Bi-Vent Ventilation
P High
T low
T High
How do you pick the settings?
Two Approaches
• Similar to Pressure Targeted Ventilation
– Select Phigh and Plow based on expected
upper and lower inflection points of pressure
volume curve
– 1-3:1 inverse Thigh to Tlow ratio
– Tlow long enough to allow minimal trapping of
exhaled gas
Two Approaches
• “Habashi method”
– Phigh set to plateau pressure in conv vent
– Plow set to zero!
– Thigh adjusted to determine desired “release
rate”
– Tlow adjusted to stop exhalation at 50-70% of
peak-expiratory flow
What do we do in NICU?
Initial Settings
• Newly intubated
– P high—set at desired plateau pressure (typically 13–24 cm H2O
in NICU) to achieve oxygenation and chest rise
• Absolute value (NOT relative to P Low)
• Bivent requires lower peak pressures than SIMV because of longer
I-time
– P low—0-5 cm H2O (mostly 3 cm H2O)
• “Set” value but often actual PEEP is higher because of limited
exhalation time
– T high—1–3 secs (1/0.2 = release rate of 50, 3/0.2 = release
rate of 19)
• Used to control release rate
• Time in Bivent is an absolute value not a relative value
– T low—0.2–0.4
• Used to control alveolar recruiting, “actual” PEEP, and tidal volumes
• More on this in a bit
In the NICU: Initial Settings
• Transition from conventional ventilation
– Phigh—peak airway pressure in pressure-cycled
mode minus 2-4
– PEEP—0-5 cm H2O
– T high—1–3 secs (usually target similar rate)
– T PEEP—0.2–0.4 sec
• Transition from HFOV
– Phigh—target mPaw equal to HFOV plus 0–2 cm
H2O
– PEEP—0-5 cm H2O
– T high—1–3 secs (use judgment to determine rate)
– T PEEP—0.2–0.4
Adjusting Settings: Increase
Oxygenation
• Increase FiO2
• MAP
– Increase P high (1-2 cm per change)
– Increase T high (will impact rate also)
– Increase Pressure support
• Unlike SIMV or AC
– Plow in Bivent has minimal impact on oxygenation
– Tlow does not impact oxygenation directly (may
impact recruitment)
Adjusting Settings: Oxygenation
• T high
– Increasing T high will improve
oxygenation by increasing time at P High
and subsequently increasing mean airway
pressure
– Increasing T high will also worsen
ventilation by decreasing the number of
releases per minute
– Therefore, when adjusting T high, make
small changes ~10% to avoid dramatic
shifts in both oxygenation and ventilation
Adjusting Settings: Increasing
Ventilation
• Increase P high to raise the tidal volume
• Decrease T high to raise the number of
releases per minute (may need to increase
Phigh to produce same mean airway
pressure
• Increase PS
• Decrease Plow – more later
• Increase Tlow – more later
Plow
• Recommend set Plow at 0 cm H2O.
• This provides a rapid drop in pressure,
and a maximum pressure gradient for
unimpeded expiratory gas flow during
pressure release.
• However, may lead to lung collapse if left
unchecked….
Plow Reality Check
• Adult literature (Habashi) recommends setting Plow at 0 cm H2O,
but to avoid potential risk of severe collapse if Tlow is too long, I
usually set Plow no lower than 2-3 cm in neonates.
• This provides a rapid drop in pressure and a maximum pressure
gradient for unimpeded expiratory gas flow during pressure release.
• BUT if you are brave and need absolute maximum exhalation rate,
then set Plow to 0 cm H20 but monitor very closely for changes in
lung compliance and quickly make appropriate changes in Tlow
• HOW do you adjust Tlow?
RT Comfort Zone
Tlow
Expiratory Flow
Goal: Maximum ventilation without risk of atelectasis
De-recruitment
Recruitment
From Habashi, et al 2005
Tlow
• To avoid collapse
– Set Tlow so that expiratory flow from patient ends at about 50 to 75% of
peak expiratory flow
• In practice, this is difficult with neonates
– Can also look at “actual” PEEP on vent to determine how low of
pressure patients lungs are actually seeing
• Target “normal” actual PEEPS of 5 cm H2O
• Tlow
– Too little results in not enough tidal volume
– Too much results in atelectasis
– Will change as compliance changes
Bivent Weaning
• With SIMV we wean by lowering PIP and increase time during
expiratory phase of cycle.
– If you do this in BIVENT, patient will develop collapse from too long of
Tlow.
– Therefore DO NOT WEAN RATE IN BIVENT BY INCREASING Tlow
• With BIVENT you lower pressure and increase time during
inspiratory phase of cycle.
– Gradually lower Phigh to decrease mean airway pressure
– Gradually increase T High to lower number of releases per minute (this
will increase your mean airway pressure so you may need to decrease
Phigh even more)
• Eventually patient will wean to equivalent of CPAP PS
• As settings decrease remember may need to adjust PS to help with
increased respiratory work load
Bivent Weaning: Drop and Stretch
Weaning- Habashi method: Drop-and-Stretch
Things to keep in mind
• Bivent is a pressure mode of ventilation and will not
change in response to changes in lung compliance
• Tlow must be monitored frequently for changes in
expiratory flow
• Airway plugging can significantly impact expiratory flow
• Technically, without spontaneous breaths, Bivent is the
same as AC with a long I time BUT…
• Since patient initiated inhalation/exhalation can occur at
P High, “breath stacking” should not occur and the risk of
pneumothorax should be minimal
• Limited data in pediatrics and no data in neonates
What is our experience so far?
The End
Questions?