Volume Targeted Ventilation in the Neonate
Volume Targeted Ventilation in the Neonate
Volume Targeted Ventilation in the Neonate
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<strong>Volume</strong> <strong>Targeted</strong> <strong>Ventilation</strong> <strong>in</strong> <strong>the</strong><br />
Nabeel Ali, MD, FRCPC<br />
Nabeel.ali@mcgill.ca<br />
<strong>Neonate</strong><br />
June 11 th 2011
Conflict of Interest<br />
No conflicts to disclose
Objectives<br />
Review <strong>the</strong> basics of volume ventilation <strong>in</strong><br />
<strong>the</strong> neonate<br />
Discuss <strong>the</strong> particularities of some<br />
common methods of provid<strong>in</strong>g volume<br />
target ventilation<br />
Brief overview of <strong>the</strong> practical applications<br />
of volume guarantee <strong>in</strong> <strong>the</strong> neonate
What’s wrong with pressure<br />
ventilation?<br />
Pressure limited ventilation:<br />
– Ma<strong>in</strong>stay of neonatology s<strong>in</strong>ce <strong>the</strong> 1970s<br />
– Certa<strong>in</strong>ty of deliver<strong>in</strong>g constant pressure<br />
– Don’t have to worry about leaks<br />
– “simple” <strong>in</strong> application
.<br />
T-piece<br />
Patient Patient
What’s wrong with pressure<br />
ventilation?<br />
Rationale:<br />
– Volutrauma maybe more <strong>in</strong>jurious than high<br />
pressures<br />
– Animal studies suggest that as few as six volume<br />
<strong>in</strong>flations reduce effect of surfactant, and causes<br />
<strong>in</strong>flammatory edema <strong>in</strong> <strong>the</strong> lungs<br />
– Avoid<strong>in</strong>g low lung volumes may also be important<br />
(derecruitment, atelectrauma, etc…)<br />
– Adults evidence from ARDS trials<br />
– Ultimate goal is to reduce VILI (pneumothorax, BPD,<br />
etc…)
What are <strong>the</strong> approaches to<br />
volume ventilation <strong>in</strong> <strong>the</strong> neonate?<br />
<strong>Volume</strong> cycled ventilation (VCV)<br />
– Set volume delivered by <strong>the</strong> ventilator<br />
– Ventilator breath cycles off when set volume<br />
is delivered<br />
– Similar to pediatric and adult ventilators<br />
– Available s<strong>in</strong>ce 1981 (Bourns LS)
What are <strong>the</strong> approaches to<br />
volume ventilation <strong>in</strong> <strong>the</strong> neonate?<br />
Characteristics of VCV:<br />
– <strong>Volume</strong> is constant, pressure is variable<br />
– Square flow waveform: peak volume and<br />
pressure are delivered at <strong>the</strong> end <strong>the</strong> breath<br />
– TCPL: decelerat<strong>in</strong>g flow pattern, early peak<br />
than trails off<br />
– More efficient distribution of gas <strong>in</strong> 2<br />
compartment lung model with different time<br />
constant
.<br />
<strong>Volume</strong> vs Pressure Controlled Breath<br />
Pressure<br />
Flow<br />
<strong>Volume</strong> Control Pressure Control<br />
time<br />
Pressure<br />
Flow<br />
time
What are <strong>the</strong> approaches to<br />
volume ventilation <strong>in</strong> <strong>the</strong> neonate?<br />
<strong>Volume</strong> targeted ventilation<br />
– <strong>Volume</strong> limit, or hybrid modes<br />
– Modified pressure ventilation with target volumes<br />
– More modern ventilators with computer controlled<br />
circuitry<br />
– More accurate measurements of tidal volume at <strong>the</strong><br />
wye<br />
– Algorithms for leak compensation, circuit compliance<br />
compensation, etc…<br />
– PIP is adjusted to try to achieve a desired V T
<strong>Volume</strong> targeted ventilation
Understand<strong>in</strong>g volume target<br />
ventilation<br />
Where is <strong>the</strong> reference tidal volume measured?<br />
– At <strong>the</strong> wye? (Babylog 8000, Leoni +)<br />
– In <strong>the</strong> mach<strong>in</strong>e? (Servo i)<br />
What is <strong>the</strong> reference volume?<br />
– Exhaled tidal volume: PIP will fluctuate more<br />
– Inhaled tidal volume: <strong>in</strong>spiratory leaks will result <strong>in</strong><br />
overestimation<br />
What is <strong>the</strong> accuracy of <strong>the</strong> volume<br />
measurement (important <strong>in</strong>
<strong>Volume</strong> ventilation<br />
Are <strong>the</strong> measurements accurate?<br />
<strong>Volume</strong>-limit<strong>in</strong>g on <strong>the</strong> Avea was activated and set at 6 mL. Each ventilator was set up with a conventional dual heated wire<br />
circuit to give VT = 5 mL <strong>in</strong> <strong>the</strong>ir respective modes for VT-targeted ventilation, with decelerat<strong>in</strong>g flow. Mean differences with<br />
tested with ANOVA with significance established as P < 0.05.<br />
John Salyer, RRT, Cary Jackson RRT. Respiratory Care Service, Children's Hospital and Regional Medical<br />
Center, Seattle Wash<strong>in</strong>gton.
Wheeler et al. The Cochrane Library. 2010
Wheeler et al. The Cochrane Library. 2010
Wheeler et al. The Cochrane Library. 2010
Some examples…<br />
<strong>Volume</strong> guarantee (VG)<br />
– Draeger Babylog 8000, VN500<br />
– Leoni Plus<br />
– Operator sets a VG and PIP max<br />
– Computer compares V Te of previous breath to VG and<br />
adjusts PIP up or down (max 3 cmH 2O)<br />
– Triggered and untriggered breaths are controlled<br />
separately<br />
– Max <strong>in</strong>spired V Ti is 130% of previous breath<br />
– Unreliable with leaks above 40% (or less…)
Some examples…<br />
Pressure regulated volume control (PRVC)<br />
– Siemens Servo-I (Servo 300)<br />
– Flow cycled mode<br />
– Cl<strong>in</strong>ician sets V T and PIP max<br />
– Test breath at 10cmH 2O above PEEP, calculates<br />
needed pressure to achieve volume pressure for<br />
subsequent breaths<br />
– Next 3 breaths with<strong>in</strong> 75% of calculated value<br />
– Increments of 3 cmH 2O<br />
– Max PIP is 5cmH 2O of set PIP max<br />
– Adjusted to 4 breath average
Some examples…<br />
O<strong>the</strong>r examples:<br />
– VAPS (volume assured pressure support)<br />
– VSV (volume support ventilation)
Practical applications
Cl<strong>in</strong>ical cases: case #1<br />
25 week <strong>in</strong>fant born by C/S for maternal<br />
bleed<strong>in</strong>g<br />
Mo<strong>the</strong>r did not receive antenatal steroids<br />
BW: 790g, Apgar 3-5-7<br />
Required bagg<strong>in</strong>g at birth, <strong>the</strong>n <strong>in</strong>tubated<br />
for poor respiratory effort<br />
Received surfactant, 1 st dose <strong>in</strong> DR<br />
Admitted to NICU
Case #1<br />
On admission you choose to go with<br />
volume target ventilation. Your ventilator is<br />
a Babylog 8000 Plus<br />
Suggested start<strong>in</strong>g parameters?
Mode: A/C<br />
– PEEP 6cmH 2O<br />
– PIP (max) 20cmH 2O<br />
– Rate 40<br />
– Ti: 0.3 secs<br />
Case #1<br />
– VG: 3.5mL (4-5 mL/kg)<br />
FiO2 drops to 35%
Case #1<br />
After sett<strong>in</strong>g <strong>the</strong> <strong>in</strong>itial parameters <strong>in</strong>fant<br />
rema<strong>in</strong>s stable for 4 hours<br />
Around 6 hours after birth <strong>the</strong> nurses<br />
compla<strong>in</strong> because <strong>the</strong> ventilator starts to<br />
r<strong>in</strong>g: V T not reached<br />
What is <strong>the</strong> problem?<br />
What are your options?
Case #1<br />
Review of <strong>the</strong> <strong>in</strong>fant reveals:<br />
– poor air entry,<br />
– poor chest expansion,<br />
– FiO 2 at 55%<br />
– Chest X-Ray shows bilateral haz<strong>in</strong>ess, ETT well<br />
positioned<br />
– Effective tidal volume is 3.5mL/kg with PIP 18-20<br />
What is your cl<strong>in</strong>ical impression?<br />
What are your <strong>the</strong>rapeutic options?
Case #1<br />
What are your options?<br />
– Repeat surfactant<br />
– Increase PEEP (may actually reduce effective<br />
PIP!)<br />
– Increase PIP max<br />
– Turn off VG!
Case #1<br />
You raise <strong>the</strong> PIP to 25cmH 2O (+5 above<br />
estimated needed PIP, or 20% above<br />
needed PIP) and <strong>the</strong> tidal volume slowly<br />
rises and <strong>the</strong> alarms go away<br />
You repeat treatment with surfactant and<br />
<strong>the</strong> FiO 2 starts to drop to 30%, <strong>the</strong><br />
effective PIP starts to drop below<br />
20cmH 2O
Case #1<br />
A blood gas comes back at 6 hours of life:<br />
– pH=7.19, pCO 2=71, HCO 3=23<br />
What is your impression?<br />
What are your <strong>the</strong>rapeutic options?
Case #1<br />
pCO 2 is proportional to m<strong>in</strong>ute ventilation<br />
(V E)<br />
VE = V T x RR<br />
Your options: <strong>in</strong>crease <strong>the</strong> VG or <strong>in</strong>crease<br />
rate (if possible)
Case #1<br />
On review<strong>in</strong>g <strong>the</strong> patient:<br />
– Mode is AC, backup rate is 40/m<strong>in</strong>, <strong>in</strong>fant is breath<strong>in</strong>g<br />
at 50-60<br />
– VG is set at 3.5mL (4.5mL/kg)<br />
– Effective PIP is around 16-18, PIP max is set at<br />
25cmH 2O<br />
Options:<br />
– Increase VG: smaller babies may need higher VG (5-<br />
6mL/kg) due to <strong>the</strong> more pronounced effect of dead<br />
space<br />
– Increase rate above spontaneous rate
Case #1<br />
You are at <strong>the</strong> end of your shift and you<br />
sign out to your colleague that he should<br />
<strong>in</strong>crease <strong>the</strong> VG to 4.0mL (5mL/kg)<br />
Instead he turns off <strong>the</strong> VG function, and<br />
sets <strong>the</strong> PIP to 18<br />
One hour later <strong>the</strong> repeat blood gas<br />
shows: pH=7.27, pCO 2=55, HCO 3=27<br />
What happened?
Case #1<br />
TCPL ventilation: tidal volume is variable<br />
Effective average V T must have <strong>in</strong>creased<br />
Increas<strong>in</strong>g VG to 6 or 7mL/kg would have<br />
accomplished <strong>the</strong> same th<strong>in</strong>g
Case #1<br />
You return <strong>the</strong> next morn<strong>in</strong>g to f<strong>in</strong>d that <strong>the</strong><br />
<strong>in</strong>fant is on <strong>the</strong> same sett<strong>in</strong>gs, but now with an<br />
FiO 2 of 21%<br />
You are dismayed that your chosen method<br />
ventilation (VG) was changed<br />
Your colleague doesn’t understand <strong>the</strong> benefits<br />
of volume target ventilation<br />
Be<strong>in</strong>g cognizant of all <strong>the</strong> latest literature on <strong>the</strong><br />
subject, you feel obligated to enlighten him
<strong>Volume</strong> ventilation: VG
Cheema IU, S<strong>in</strong>ha AK, Kempley ST, Ahluwalia JS. Impact of volume guarantee ventilation on<br />
arterial carbon dioxide tension <strong>in</strong> newborn <strong>in</strong>fants: A randomised controlled trial. Early Hum<br />
Dev. 2006 Jun 30
Evidence?<br />
Wheeler et al. Cochrane Review, update 2010<br />
12 randomized trials of 629 <strong>in</strong>fants<br />
– Reduction <strong>in</strong> death or BPD at 36 weeks: RR 0.73<br />
(0.57-0.93), NNT=8<br />
– Reduction <strong>in</strong> pneumothorax: RR 0.43, (0.25-0.85),<br />
NNT=17<br />
– Days of ventilation: -2.36 days (-3.9 to -0.8)<br />
– PVL/Gr 3-4 IVH: RR 0.48 (0.28-0.84), NNT=11
Cl<strong>in</strong>ical cases: case #2<br />
The same <strong>in</strong>fant is now at 29 weeks CGA (4<br />
weeks chronological), and now on CPAP.<br />
Current weight 1.03kg<br />
Overnight he deteriorates, developp<strong>in</strong>g<br />
<strong>in</strong>creased apnea and bradycardia, requir<strong>in</strong>g re<strong>in</strong>tubation.<br />
You suspect sepsis.<br />
You choose <strong>the</strong> follow<strong>in</strong>g sett<strong>in</strong>gs:<br />
– Mode: AC + VG<br />
– PEEP = 5, PIP =25, VG=5mL (6mL/kg)<br />
– Rate 50/m<strong>in</strong>
Case #2<br />
The <strong>in</strong>fant stabilizes with an FiO 2 of 27% on <strong>the</strong>se<br />
sett<strong>in</strong>gs, and acceptable blood gases<br />
The nurses call you because <strong>the</strong> ventilator r<strong>in</strong>gs all <strong>the</strong><br />
time<br />
On exam<strong>in</strong>ation you note an episode where <strong>the</strong> <strong>in</strong>fant’s<br />
chest is not mov<strong>in</strong>g, although he doesn’t appear apneic<br />
The ventilator shows no exhaled VT, and a very low<br />
m<strong>in</strong>ute ventilation<br />
The <strong>in</strong>fant desaturates to 50% requir<strong>in</strong>g more O2, <strong>the</strong>n<br />
recovers after 2 m<strong>in</strong>utes<br />
These episodes seem to recur a few times per hour
What is happen<strong>in</strong>g?<br />
Case #2<br />
How should you respond
Bolivar et al 2007
Esquer et al. Neonatology 2007<br />
Active exhalation
Possible <strong>the</strong>rapies?<br />
– Sedatives…<br />
– Noth<strong>in</strong>g!<br />
– Extubation<br />
– Role of VG?<br />
Case #2
Case #2<br />
The <strong>in</strong>fant has now been <strong>in</strong>tubated for<br />
three days.<br />
Current sett<strong>in</strong>gs:<br />
– SIMV, rate 30<br />
– PIP 20, PEEP 5, VG= 6mL (6mL/kg)<br />
– FiO2= 25%<br />
The nurse calls you because <strong>the</strong> ventilator<br />
is r<strong>in</strong>g<strong>in</strong>g low V T all <strong>the</strong> time
Case #2<br />
Upon exam<strong>in</strong>ation you note that <strong>the</strong> PIP is<br />
always hitt<strong>in</strong>g <strong>the</strong> maximum of 20cmH 2O<br />
The effective V T is around 2.5mL/kg<br />
You note a variable leak that is around 40-<br />
50%<br />
The <strong>in</strong>fant has a size 2.5 ETT<br />
What are your options?
Case #2<br />
Re-<strong>in</strong>tubate with a larger tube<br />
Turn off VG function: will get rid of alarm,<br />
but will not correct <strong>the</strong> problem<br />
Trial of extubation<br />
Us<strong>in</strong>g VG <strong>in</strong> <strong>the</strong> sett<strong>in</strong>g of large leaks is<br />
not recommended
Case #3<br />
34 week <strong>in</strong>fant admitted with RDS. BW 2.0kg.<br />
Intubated at 8 hours of life <strong>in</strong>creas<strong>in</strong>g distress<br />
and oxygen need. Received surfactant.<br />
Initial parameters: AC+VG, 25/6, rate 40,<br />
VG=10mL<br />
FiO 2 drops to 21% 6 hours after surfactant dose.<br />
How should this <strong>in</strong>fant be weaned towards<br />
extubation?
Turn off VG?<br />
Switch to SIMV?<br />
PSV?<br />
Wean<strong>in</strong>g <strong>in</strong> VG:<br />
Case #3<br />
– Lower VG to <strong>the</strong> lower end of <strong>the</strong> range<br />
– Ma<strong>in</strong>ta<strong>in</strong> adequate PEEP to avoid atelectasis<br />
– Effective PIP should start to fall (12-14 cmH 2O)<br />
– Lower backup rate if us<strong>in</strong>g AC/PSV to well below<br />
<strong>in</strong>fant’s spontaneous rate (i.e. 20/m<strong>in</strong>)
Case #3<br />
You switch your <strong>in</strong>fant to PSV +VG with a<br />
backup rate of 20, and he cont<strong>in</strong>ues to<br />
brea<strong>the</strong> at 40 m<strong>in</strong>ute with no signs of<br />
distress or apnea<br />
You lower <strong>the</strong> VG to 8mL (4mL/kg) and<br />
<strong>the</strong> effective PIP drops to 9-11 cmH 2O<br />
You consider <strong>the</strong> <strong>in</strong>fant is ready for<br />
extubation
Summary<br />
<strong>Volume</strong> target ventilation is available<br />
cl<strong>in</strong>ically on several mach<strong>in</strong>es, but <strong>the</strong><br />
actual mode and application may vary<br />
from maker to maker<br />
VTV reduces several morbidities such as<br />
oxygen dependance at 36 weeks,<br />
pneumothorax and IVH
<strong>Volume</strong> guarantee: practical tips<br />
Initial VG 4-5mL/kg <strong>in</strong> most <strong>in</strong>fants, 5-6mL/kg<br />
may be necessary <strong>in</strong> smaller <strong>in</strong>fants (
References<br />
Goldsmith & Karotk<strong>in</strong>. Assisted <strong>Ventilation</strong><br />
of <strong>the</strong> <strong>Neonate</strong>. 5 th edition. 2011. Elsevier-<br />
Saunders<br />
<strong>Volume</strong> Guarantee <strong>Ventilation</strong>. Keszler M,<br />
Abubakar KM. Cl<strong>in</strong>ics <strong>in</strong> Per<strong>in</strong>atology.<br />
34:107-116. 2007