Volume Targeted Ventilation in the Neonate

Volume Targeted Ventilation in the
Nabeel Ali, MD, FRCPC
Nabeel.ali@mcgill.ca
Neonate
June 11 th 2011

Conflict of Interest
No conflicts to disclose

Objectives
Review the basics of volume ventilation in
the neonate
Discuss the particularities of some
common methods of providing volume
target ventilation
Brief overview of the practical applications
of volume guarantee in the neonate

What’s wrong with pressure
ventilation?
Pressure limited ventilation:
– Mainstay of neonatology since the 1970s
– Certainty of delivering constant pressure
– Don’t have to worry about leaks
– “simple” in application

.
T-piece
Patient Patient

What’s wrong with pressure
ventilation?
Rationale:
– Volutrauma maybe more injurious than high
pressures
– Animal studies suggest that as few as six volume
inflations reduce effect of surfactant, and causes
inflammatory edema in the lungs
– Avoiding low lung volumes may also be important
(derecruitment, atelectrauma, etc…)
– Adults evidence from ARDS trials
– Ultimate goal is to reduce VILI (pneumothorax, BPD,
etc…)

What are the approaches to
volume ventilation in the neonate?
Volume cycled ventilation (VCV)
– Set volume delivered by the ventilator
– Ventilator breath cycles off when set volume
is delivered
– Similar to pediatric and adult ventilators
– Available since 1981 (Bourns LS)

What are the approaches to
volume ventilation in the neonate?
Characteristics of VCV:
– Volume is constant, pressure is variable
– Square flow waveform: peak volume and
pressure are delivered at the end the breath
– TCPL: decelerating flow pattern, early peak
than trails off
– More efficient distribution of gas in 2
compartment lung model with different time
constant

.
Volume vs Pressure Controlled Breath
Pressure
Flow
Volume Control Pressure Control
time
Pressure
Flow
time

What are the approaches to
volume ventilation in the neonate?
Volume targeted ventilation
– Volume limit, or hybrid modes
– Modified pressure ventilation with target volumes
– More modern ventilators with computer controlled
circuitry
– More accurate measurements of tidal volume at the
wye
– Algorithms for leak compensation, circuit compliance
compensation, etc…
– PIP is adjusted to try to achieve a desired V T

Volume targeted ventilation

Understanding volume target
ventilation
Where is the reference tidal volume measured?
– At the wye? (Babylog 8000, Leoni +)
– In the machine? (Servo i)
What is the reference volume?
– Exhaled tidal volume: PIP will fluctuate more
– Inhaled tidal volume: inspiratory leaks will result in
overestimation
What is the accuracy of the volume
measurement (important in

Volume ventilation
Are the measurements accurate?
Volume-limiting on the Avea was activated and set at 6 mL. Each ventilator was set up with a conventional dual heated wire
circuit to give VT = 5 mL in their respective modes for VT-targeted ventilation, with decelerating flow. Mean differences with
tested with ANOVA with significance established as P < 0.05.
John Salyer, RRT, Cary Jackson RRT. Respiratory Care Service, Children's Hospital and Regional Medical
Center, Seattle Washington.

Wheeler et al. The Cochrane Library. 2010

Wheeler et al. The Cochrane Library. 2010

Wheeler et al. The Cochrane Library. 2010

Some examples…
Volume guarantee (VG)
– Draeger Babylog 8000, VN500
– Leoni Plus
– Operator sets a VG and PIP max
– Computer compares V Te of previous breath to VG and
adjusts PIP up or down (max 3 cmH 2O)
– Triggered and untriggered breaths are controlled
separately
– Max inspired V Ti is 130% of previous breath
– Unreliable with leaks above 40% (or less…)

Some examples…
Pressure regulated volume control (PRVC)
– Siemens Servo-I (Servo 300)
– Flow cycled mode
– Clinician sets V T and PIP max
– Test breath at 10cmH 2O above PEEP, calculates
needed pressure to achieve volume pressure for
subsequent breaths
– Next 3 breaths within 75% of calculated value
– Increments of 3 cmH 2O
– Max PIP is 5cmH 2O of set PIP max
– Adjusted to 4 breath average

Some examples…
Other examples:
– VAPS (volume assured pressure support)
– VSV (volume support ventilation)

Practical applications

Clinical cases: case #1
25 week infant born by C/S for maternal
bleeding
Mother did not receive antenatal steroids
BW: 790g, Apgar 3-5-7
Required bagging at birth, then intubated
for poor respiratory effort
Received surfactant, 1 st dose in DR
Admitted to NICU

Case #1
On admission you choose to go with
volume target ventilation. Your ventilator is
a Babylog 8000 Plus
Suggested starting parameters?

Mode: A/C
– PEEP 6cmH 2O
– PIP (max) 20cmH 2O
– Rate 40
– Ti: 0.3 secs
Case #1
– VG: 3.5mL (4-5 mL/kg)
FiO2 drops to 35%

Case #1
After setting the initial parameters infant
remains stable for 4 hours
Around 6 hours after birth the nurses
complain because the ventilator starts to
ring: V T not reached
What is the problem?
What are your options?

Case #1
Review of the infant reveals:
– poor air entry,
– poor chest expansion,
– FiO 2 at 55%
– Chest X-Ray shows bilateral haziness, ETT well
positioned
– Effective tidal volume is 3.5mL/kg with PIP 18-20
What is your clinical impression?
What are your therapeutic options?

Case #1
What are your options?
– Repeat surfactant
– Increase PEEP (may actually reduce effective
PIP!)
– Increase PIP max
– Turn off VG!

Case #1
You raise the PIP to 25cmH 2O (+5 above
estimated needed PIP, or 20% above
needed PIP) and the tidal volume slowly
rises and the alarms go away
You repeat treatment with surfactant and
the FiO 2 starts to drop to 30%, the
effective PIP starts to drop below
20cmH 2O

Case #1
A blood gas comes back at 6 hours of life:
– pH=7.19, pCO 2=71, HCO 3=23
What is your impression?
What are your therapeutic options?

Case #1
pCO 2 is proportional to minute ventilation
(V E)
VE = V T x RR
Your options: increase the VG or increase
rate (if possible)

Case #1
On reviewing the patient:
– Mode is AC, backup rate is 40/min, infant is breathing
at 50-60
– VG is set at 3.5mL (4.5mL/kg)
– Effective PIP is around 16-18, PIP max is set at
25cmH 2O
Options:
– Increase VG: smaller babies may need higher VG (5-
6mL/kg) due to the more pronounced effect of dead
space
– Increase rate above spontaneous rate

Case #1
You are at the end of your shift and you
sign out to your colleague that he should
increase the VG to 4.0mL (5mL/kg)
Instead he turns off the VG function, and
sets the PIP to 18
One hour later the repeat blood gas
shows: pH=7.27, pCO 2=55, HCO 3=27
What happened?

Case #1
TCPL ventilation: tidal volume is variable
Effective average V T must have increased
Increasing VG to 6 or 7mL/kg would have
accomplished the same thing

Case #1
You return the next morning to find that the
infant is on the same settings, but now with an
FiO 2 of 21%
You are dismayed that your chosen method
ventilation (VG) was changed
Your colleague doesn’t understand the benefits
of volume target ventilation
Being cognizant of all the latest literature on the
subject, you feel obligated to enlighten him

Volume ventilation: VG

Cheema IU, Sinha AK, Kempley ST, Ahluwalia JS. Impact of volume guarantee ventilation on
arterial carbon dioxide tension in newborn infants: A randomised controlled trial. Early Hum
Dev. 2006 Jun 30

Evidence?
Wheeler et al. Cochrane Review, update 2010
12 randomized trials of 629 infants
– Reduction in death or BPD at 36 weeks: RR 0.73
(0.57-0.93), NNT=8
– Reduction in pneumothorax: RR 0.43, (0.25-0.85),
NNT=17
– Days of ventilation: -2.36 days (-3.9 to -0.8)
– PVL/Gr 3-4 IVH: RR 0.48 (0.28-0.84), NNT=11

Clinical cases: case #2
The same infant is now at 29 weeks CGA (4
weeks chronological), and now on CPAP.
Current weight 1.03kg
Overnight he deteriorates, developping
increased apnea and bradycardia, requiring reintubation.
You suspect sepsis.
You choose the following settings:
– Mode: AC + VG
– PEEP = 5, PIP =25, VG=5mL (6mL/kg)
– Rate 50/min

Case #2
The infant stabilizes with an FiO 2 of 27% on these
settings, and acceptable blood gases
The nurses call you because the ventilator rings all the
time
On examination you note an episode where the infant’s
chest is not moving, although he doesn’t appear apneic
The ventilator shows no exhaled VT, and a very low
minute ventilation
The infant desaturates to 50% requiring more O2, then
recovers after 2 minutes
These episodes seem to recur a few times per hour

What is happening?
Case #2
How should you respond

Bolivar et al 2007

Esquer et al. Neonatology 2007
Active exhalation

Possible therapies?
– Sedatives…
– Nothing!
– Extubation
– Role of VG?
Case #2

Case #2
The infant has now been intubated for
three days.
Current settings:
– SIMV, rate 30
– PIP 20, PEEP 5, VG= 6mL (6mL/kg)
– FiO2= 25%
The nurse calls you because the ventilator
is ringing low V T all the time

Case #2
Upon examination you note that the PIP is
always hitting the maximum of 20cmH 2O
The effective V T is around 2.5mL/kg
You note a variable leak that is around 40-
50%
The infant has a size 2.5 ETT
What are your options?

Case #2
Re-intubate with a larger tube
Turn off VG function: will get rid of alarm,
but will not correct the problem
Trial of extubation
Using VG in the setting of large leaks is
not recommended

Case #3
34 week infant admitted with RDS. BW 2.0kg.
Intubated at 8 hours of life increasing distress
and oxygen need. Received surfactant.
Initial parameters: AC+VG, 25/6, rate 40,
VG=10mL
FiO 2 drops to 21% 6 hours after surfactant dose.
How should this infant be weaned towards
extubation?

Turn off VG?
Switch to SIMV?
PSV?
Weaning in VG:
Case #3
– Lower VG to the lower end of the range
– Maintain adequate PEEP to avoid atelectasis
– Effective PIP should start to fall (12-14 cmH 2O)
– Lower backup rate if using AC/PSV to well below
infant’s spontaneous rate (i.e. 20/min)

Case #3
You switch your infant to PSV +VG with a
backup rate of 20, and he continues to
breathe at 40 minute with no signs of
distress or apnea
You lower the VG to 8mL (4mL/kg) and
the effective PIP drops to 9-11 cmH 2O
You consider the infant is ready for
extubation

Summary
Volume target ventilation is available
clinically on several machines, but the
actual mode and application may vary
from maker to maker
VTV reduces several morbidities such as
oxygen dependance at 36 weeks,
pneumothorax and IVH

Volume guarantee: practical tips
Initial VG 4-5mL/kg in most infants, 5-6mL/kg
may be necessary in smaller infants (

References
Goldsmith & Karotkin. Assisted Ventilation
of the Neonate. 5 th edition. 2011. Elsevier-
Saunders
Volume Guarantee Ventilation. Keszler M,
Abubakar KM. Clinics in Perinatology.
34:107-116. 2007