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14/04/15
1
HFOV IN PRACTICE: The recruitable lung
David Tingay
Ini$a$ng HFOV Preterm Infant
• 28/40 GA • BW 1 kg • Intubated at 1 hr • Paw 12 cmH2O • FiO2 1.0 • SpO2 86% • PaO2 45 mmHg • PaCO2 55 mmHg
5
10
15
20
25
P aw (c
m H
2O)
Pinitial Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
HFOV Settings?
Pre-HFOV Questions • Device? • Monitoring • Positioning • Sedation/ Analgesia/
MR • Cardiac Support • PPHN • Biochemical support
14/04/15
2
Favours HFV Favours CMV Cools (PreVILI Group) Lancet
HFOV vs CMV: High Lung Volume Strategy
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3
High lung volume strategy (HLVS) Tradi$onal defini$on Cochrane database defini$on (at least 2 of):
1. Ini-al use of a higher mean airway pressure than on CMV
2. Ini-al weaning of frac-onal inspired oxygen before mean airway pressure
3. Use of alveolar recruitment manoeuvres
Ini$a$ng HFOV Preterm Infant
• 28/40 GA • BW 1 kg • Intubated at 1 hr • Paw 12 cmH2O • FiO2 1.0 • SpO2 86% • PaO2 45 mmHg • PaCO2 55 mmHg
5
10
15
20
25
P aw (c
m H
2O)
Pinitial Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
HFOV Settings?
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4
‘Sta$c’ Paw HLVS How do you know you are in the Safe Window?
& Froese CCM 1997
The Open Lung Concept
Lachmann ICM 1990 ‘open the lung, find the closing pressure, re-‐open it and keep it open!’ • Achieve Lung Recruitment • Iden-fy the lowest pressure that maintains that recruitment
(OPTIMAL PRESSURE; POPT) • Exploit the hysteresis of the lung • Exploit PEEP – an expiratory phenomenon that maintains
recruitment
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5
Rela$onship between PAW and EELV
PV rela-onship can be mapped at the bedside with PAW
& Tingay et al AJRCCM 2006 & Miedema et al J Peds 2011
Term Infants Preterm Infants
Ini$a$ng HFOV Preterm Infant
5
10
15
20
25
P aw (c
m H
2O)
Pinitial Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
Paw 21 FiO2 0.5 SpO2 88% PaO2 60 mmHg PaCO2 70 mmHg
Popen Paw 20 FiO2 0.5 SpO2 93% PaO2 65 mmHg PaCO2 60 mmHg
Paw 16 FiO2 0.7 SpO2 94%
Paw 18 FiO2 0.6 SpO2 95%
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6
Region of Op$mal Ven$la$on?
& Froese AJRCCM 2002
Inflation Limb
Recruitment is ongoing (inhomogeneity)
At no point can all mechanical causes of VILI be minimised & Hickling et al AJRCCM 2001 & Jonson ICM 2005
Deflation Limb
Alveolar stability maintained & Albaiceta CCM 2004
Opening pressure > collapsing forces & Rimensberger ICM 2000
Ini$a$ng HFOV Preterm Infant
5
10
15
20
25
P aw (c
m H
2O)Pinitial
Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
Popen Paw 20 FiO2 0.5 SpO2 93% PaO2 65 mmHg PaCO2 60 mmHg
Pclose Paw 8 FiO2 0.6 SpO2 84% PaO2 32 mmHg PaCO2 49 mmHg
Paw 12 FiO2 0.4 SpO2 95%
Paw 18 FiO2 0.4 SpO2 96%
Paw 14 FiO2 0.4 SpO2 95%
Paw 10 FiO2 0.4 SpO2 90%
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Relationship between PAW, Lung Volume and SpO2
• SpO2 reliably identified TLC (overdistension) and CCP (collapse)
• SpO2 cannot precisely delineate between small volume state changes
& Miedema J Peds 2011
& Tingay AJRCCM 2006
Ini$a$ng HFOV Preterm Infant
5
10
15
20
25
P aw (c
m H
2O)Pinitial
Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
Popen Paw 20 FiO2 0.5 SpO2 93% PaCO2 60 mmHg
Pclose Paw 8 FiO2 0.6 SpO2 84% PaCO2 49 mmHg
Popt Paw 11 FiO2 0.4 SpO2 92% PaCO2 41 mmHg
Paw 20 FiO2 0.4 SpO2 95%
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8
OLV during HFOV in newborn infants Rimensberger et al Pediatrics 1999
– LVO (If FIO2 >0.4): 1-‐2 cm H2O Paw steps every 1-‐2 mins UNTIL FIO2≤0.4 (max Paw 25 cm H2O)
– THEN Paw decreased un-l FIO2 ≤0.4 and PaO2 ≥60 mmHg Less ven-lator days, Lower oxygen dependency, Less CLD Transient high Paw is well tolerated, even in preterm infants
DeJaegre et al AJRCCM 2006 Similar LVO strategy:
– Pmax FIO2 at CDPOPT ≤ 0.25 before surfactant FIO2 at CDPOPT ≤ 0.25 in 75% and ≤ 0.3 in 98% An aggressive recruitment strategy using oxygena?on to guide the recruitment process is feasible and safe during HFV in preterm infants with RDS.
Tingay et al AJRCCM 2006 OLV resulted in op-mal SpO2, TcCO2, VT and Crs Op-mal Paw iden-fied ager aggressive recruitment at CCP+2 – 4 cm H2O
The Amsterdam experience
An open lung ventilation strategy using oxygenation to guide the recruitment process is feasible and safe during HFV in preterm infants with RDS.
n = 103
FIO2 at CDPOPT ≤ 0.25 in 75% and ≤ 0.3 in 98%
TcCO2 was reduced by 9 mmHg after optimal recruitment (pre-surfactant)
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9
Ini$a$ng HFOV Preterm Infant
5
10
15
20
25P a
w (c
m H
2O)Pinitial
Paw 14 FiO2 0.8 SpO2 90% PaO2 52 mmHg PaCO2 53 mmHg
Popen Paw 20 FiO2 0.5 SpO2 93% PaCO2 60 mmHg
Pclose Paw 8 FiO2 0.6 SpO2 84% PaCO2 49 mmHg
Popt Paw 11 FiO2 0.4 SpO2 92% PaCO2 41 mmHg
Paw 20 FiO2 0.4 SpO2 95%
J Clin Invest 1959. 38:2168
PV rela$onship influences lung mechanics
Atelectasis → CRS low = PCO2 high
↑ CRS = PCO2 lower
Overdistension → CRS low + ↑ dead space = PCO2 high
↑ CRS + ↓ deadspace = PCO2 lower
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Is Oxygena$on the best marker of the op$mal EEV?
Paw (cmH2O above Pcl)
PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
Vol
ume
chen
ge (
t0 -
t1)
(%)
-35
-30
-25
-20
-15
-10
-5
0
5
VentralDorsal
*
*
PAW (cmH2O above PCL)
PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
VT
HF (
mL/K
g)
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
XR
S (
cm
H2O
*s/L
)
-90
-80
-70
-60
-50
-40
-30
-20
-10 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
VL (
% V
L a
t P
max)
30
40
50
60
70
80
90
100
110 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
Sp
O2/F
iO2
250
300
350
400
450
500
Pmax
Pstart
Pstart
Pmax
Pmax
Pstart
A
B
C
Pmax
Pstart
D
PAW (cmH2O above PCL)
PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
VT
HF (
mL
/Kg)
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
XR
S (
cm
H2O
*s/L
)
-90
-80
-70
-60
-50
-40
-30
-20
-10 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
VL (
% V
L a
t P
ma
x)
30
40
50
60
70
80
90
100
110 PCL PCL+2 PCL+4 PCL+6 PCL+8 PCL+10
Sp
O2/F
iO2
250
300
350
400
450
500
Pmax
Pstart
Pstart
Pmax
Pmax
Pstart
A
B
C
Pmax
Pstart
D
& Zannin Ped Res 2014
PV rela$onship influences lung mechanics
Tingay et al CCM 2013
6 8 10 12 14 16 18 204.0
4.5
5.0
5.5
6.0
7.0
7.5
8.0
8.5
CDP (cm H2O)
Impe
danc
e Vt TcpC
O2
Miedema et al. ERJ 2012
14/04/15
11
The Op$mal Safe Window The region of the Defla/on Limb >Pclose that balances op/mal oxygena/on and lung mechanics
0 25 50 75 100
0
50
100
Paw (%)
V L (%
)
Pmax
Pfinal
SpO2
Region of optimal volume
TcCO2
MVHF
VTao
VTRIP
Opt
imal
Paw
ra
nge
Pinitial
Safe Zone
Tingay et al CCM 2013
Smolich et al 2014 PSANZ (Preterm Lambs)
14/04/15
12
How long un$l EEV stablises aRer a Paw change? Preterm infants
Miedema et al ICM 2012
Tingay PhD data
How long un$l EEV stablises aRer a Paw change? Term infants
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13
But, I must give surfactant! Op$mum point of ven$la$on may change
• N=15 preterm infants • EIT measurements during OLV before and ager surfactant
administra-on • Surfactant administra-on:
– Increased EELV by 61±39% – Improved distribu-on of ven-la-on:
- V:D ra-o 1.16 vs 0.81 – Lowered the CCP:
- 16.4±3.1 vs 10.4±2.4 cm H2O
& Miedema et al AJRCCM 2011
PEEP PIP
Volu
me Surfactant
Setting the Frequency - Considerations
• Frequency influences the stroke volume • The time constant of the lung determines frequency • Lung disease and size determines time constant • BUT there are risks of going too high and too low in the RDS lung • Compliant lungs - marked damping of HFOV pressure • Potential for barotrauma in the poorly recruited lung at low frequency
Pillow et al AJRCCM 2001
↑Raw
↓C
↑Raw↓C
Frequency (Hz)
Pea
k C
arin
al P
ress
ure
10 20 30
Venegas & Fredberg Crit Care Med 1994
14/04/15
14
SeVng the Frequency – Prac$cal guide Suggested ini/al maximum frequency seVngs
PIE in evolution
}
Established PIE with high FiO2 and CO2 retention
}
} Preterm HMD (Dräger BL+VN)*
Meconium aspiration syndrome } }
Preterm HMD
Term lung disease
}
15
14
13
12
11
10
9
8
7
6
5
Weaning to extuba$on
Options: Preterm Term
Wean to low PAW and extubate directly from HFOV √ √
Wean to low PAW, brief period of low rate SIMV (or ETCPAP), then extubate
√
When lung disease improved transfer to synchronized IMV and extubate when able
√
14/04/15
15
At what HFOV seVngs can we extubate?
FiO2 < 0.3 PAW 6-8 cm H2O ΔP 10-15 cm H2O WOB satisfactory
pH > 7.25
Preterm van Velzen A et al PCCM 2009 • 214 preterm infants (29.5 ± 2.5
wk, BW 1300 ± 480 g)• Early OLV HFOV• E x t u b a t i o n f r o m H F O V
attempted at a median age of 62 hrs
• Successful in 193 (90%) of the infants.
• PAW at the time of extubation 6.8 ± 1.6 cmH2O
At what HFOV seVngs can we extubate?
FiO2 < 0.3 PAW 6-8 cm H2O ΔP 10-15 cm H2O WOB satisfactory
pH > 7.25
FiO2 < 0.3 PAW 6-10 cm H2O ΔP 15-20 cm H2O WOB satisfactory
pH > 7.25
Preterm Term
14/04/15
16
Summary • In the atelecta-c lung, lung recruitment can be individualised
using an open lung strategy • Watch your pa-ent, use the clues available and adapt
EEV
SpO2
Mechanics
‘From Art to Science’
HFOV in practice – the recruitable lung David Tingay/Andreas Schibler HFOV in the non-recruitable lung Peter Dargaville
Day 2 Session 2: Putting HFOV into clinical practice
Old and new concepts in the application of high frequency oscillatory ventilation
14/04/15
17
Pressure cost of ven$la$on Peak alveolar distension
( ) TLCVVD TEEalv /+=Normal RDS
PEEP (cmH2O)
f (Hz) PEEP
(cmH2O)
f (Hz)
Dalv Dalv
Venegas J & Fredberg J, Crit Care Med, 1994
Shaded regions = ‘safe’ Paw & Fr options (Peak Dalv < 90% TLC) RDS = less rood for error in choice of Paw and Fr
Hysteresis For any given Pressure there is a range of volumes that can exist Thus, for any given Volume there is a range of pressures that can achieve it That pressure will always be lower on the defla-on limb, because Pcl < Pop
Crotti et al AJRCCM 2001
Gattinoni et al AJRCCM 2001