14/04/15  

1  

‘From Art to Science’

What is an optimal Paw strategy? A physiological rationale Anastasia Pellicano Monitoring and Volume Guarantee David Tingay Pulmonary circulation and lung recruitment – experimental evidence

Graeme Polglase

Endotracheal tube suction Andreas Schibler

Day 2 Session 1: Optimising the application of HFOV

Old and new concepts in the application of high frequency oscillatory ventilation

HIGH-FREQUENCY VENTILATION: VOLUME GUARANTEE AND OTHER NEW CONCEPTS  

David Tingay

Neonatal Research, Murdoch Childrens Research Institute Neonatology, Royal Children’s Hospital Dept of Paediatrics, University of Melbourne, Melbourne, Australia

14/04/15  

2  

Op#mising  care  of  the  neonate  with  lung  disease  Sailing  Between  Scylla  and  Charybdis  

Ate

lect

asis

S

heer

For

ce In

jury

Volutraum

a B

arotrauma

Biotrauma Oxidative Injury

NAVIGATION TOOLS

Determinants  of  Gas  Exchange  

OXYGENATION

VENTILATION

Lung Volume Volume State FiO2

V/Q mismatch

Minute Ventilation Freq

VT (ΔP)

Volume State (CRS)

Paw

Paw

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Monitoring  Ven#la#on  during  HFOV  

VENTILATION Minute Ventilation

Freq

VT (ΔP)

Volume State (CRS) Paw

SM3100 •  No active

physiological feedback

•  (Florian Monitor – Scalfaro 2001)

•  Indirect monitoring of CO2

Modern HFV •  Realtime AO

feedback •  Flow, VT, ‘DCO’

CRS  –  NO  (prac3cally)  due  to  the  complexity  of  the  pressure  –  flow  waves  

Monitoring  during  HFOV  TcCO2  

•  TcCO2  is  reliable  during  HFOV  in  infants  Zimova-­‐Herknerova  2006,  Walsh  &  Carlo  1988,  Yamada  et  al  1986,  Chan  &  Greenough  1994,  Tingay  et  al  2013  

•  Posi3on  is  important  –  Well  perfused  site  (chest/shoulder)  –  Visible  (burns)  

•  Know  your  device  –  Calibra3on  –  Opera3ng  temperatures  effects  reliability  –  Risks  include  burns  

•  TcCO2  mandated  at  RCH  during  HFOV  

Deflation series

VT (mL/kg)

0 1 2 3 4 5

TcC

O2 (

mm

Hg)

0

20

40

60

80

100

120

140

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Monitoring  during  HFOV  Ven#la#on  

•  VT/VT2  

–  NOT  a  direct  measure  of  Alveolar  CO2  

–  Reliable  proxy  or  trend  (usually)  –  Numbers  meaningless  

Scalfaro  2001,  Hager  2006,  Zimova-­‐Herknerova  2006  

•  DCO/MVHF  –  As  per  VT

2  Tingay  et  al  CCM  2013  

•  EtCO2  –  Not  enough  3me  for  Alveolar  Plateau  –  Tidal   volumes   too   small   (even   for  

mainstream  devices)  –  Large  deadspace  at  airway  opening  

Deflation series

VT (mL/kg)

0 1 2 3 4 5

VTRIP

(% o

f max

imum

VTRIP

)

0

20

40

60

80

100

Monitoring  during  HFOV  DCO  

•  DCO  =  Diffusion  coefficient  of  CO2  at  an  Alveolar  Level  •  A  mathema3cal  measure  of  Alveolar  Minute  Ven3la3on  =  f  x  VT

2  

•  Displayed  value  meaningless   and  DCO  will   vary   for   every  baby  according   to  lung  size,  disease  and  frequency  

•  Prac3cally   an   easier   value   to   interpret   than   VTHF   at   the   bedside   but   if  Frequency  constant  both  are  the  same  

Tingay et al CCM 2013

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PV relationship influences lung mechanics

& Tingay CCM 2013

Distinct relationship between Paw & VL and TcCO2, VT & MV Each optimised on the deflation limb 2 – 4 cmH2O before Pclose Popt could be predicted [y = a + bx + cx2 (+dx3)]

The  use  of  modern  monitoring  allows  refinement  of  the  op#mal  region  of  ven#la#on  

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

The reverse is true – the state of the lung may alter mechanics and thus Amplitude needed to optimise CO2 clearance

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•  Con3nuous   regula3on   of   oscillatory  amplitude   to   compensate   for   dynamic  changes  in  the  respiratory  system  

•  P o t e n 3 a l l y   f e w e r   p e r i o d s   o f  hyperven3la3on  and  faster  weaning  

•  What  is  the  right  VG  se0ng  in  HFOV?  •  We   don’t   know   but   it   wont   be   a   single  

value!  

Data courtesy Jane Pillow

HFV  +  Volume  Guarantee  

Wt (kg)

5 Hz 2.83 mL/kg

10 Hz 2.0

mL/kg

15 Hz 1.63 mL/kg

0.5 10 10 10 1 40 40 40 2 160 160 159 3 360 360 359

Targe#ng  VT  is  more  complicated  than  on  CMV  Tidal  volume,  Fr  and  Compliance  

Tidal   volume   increases  with:  •  Increasing  compliance  (esp  at  

low  Hz)  •  Increasing  ETT  ID  

No   single   VT   (range)   can   be  considered  op>mal  during  HFV  

Pillow et al AJRCCM 2001

14/04/15  

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•  Changes in VThf setting caused appropriate changes in PaCO2 •  Preterm infants in progress:

1.  HFOV vs HFOV+VG crossover: No difference in PCO2, FiO2, DP, VThf, DCO but hypocarbia 36% (VG) vs 23%. ?n, PAW, strategy. ADC 2014; 99:A497-498

2.  PAS 2014: 2 mL/kg VThf a reasonable starting setting (VN500)

A  non-­‐evidence  based  prac#cal  approach  to  HFO+VG  

•  Start  HFOV  without  VG  but  with  monitoring  •  Set  Freq  for  disease,  size  and  device  

•  When  TcCO2  stable   (ideally  with  abg)  set  VG  to  deliver  current  VT  at  that  ΔP  (limit  +5  cmH2O)  

•  Note  ‘DCO’  values  

Low VT alarm Check Patient +/- need to increase ΔP

If Freq changed alter set VT to maintain stable DCO

Adjust ΔP for chest wiggle and TcCO2

Adapted from Jane Pillow

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8  

Babylog VN 500

5 10 150

2

4

6

8

Frequency (Hz)

V T (m

l)

Fabian HFO

5 10 150

2

4

6

8

Frequency (Hz)

V T (m

l)

Leoni plus

5 10 150

2

4

6

8

Obstructive (C4R200)

Normal (C4R70) Restrictive (C2R70)

Mixte (C2R200)

Frequency (Hz)

V T (m

l)

5 10 150

1

2

3

4

5

Babylog VN 500

Frequency (Hz)

V T (m

l)

Leoni plus

5 10 150

1

2

3

4

5 Normal (C2R100)Restrictive (C1R100)Obstructive (C2R200)Mixte (C1R200)

Frequency (Hz)

V T (m

l)

Fabian HFO

5 10 150

1

2

3

4

5

Frequency (Hz)

V T (m

l)

a

b

FIGURE 3

Monitoring  Oxygena#on  during  HFOV  

OXYGENATION

Lung Volume Volume State FiO2

V/Q mismatch

Paw

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Lung

Vol

ume

Pressure

Oxygenation

Optimising lung volume during HFOV optimises alveolar surface available for gas exchange PAW = Lung Volume = PaO2

Van Kaam et al Ped Res 2000

Relationship between PAW, Lung Volume and SpO2

•  SpO2 reliably identified TLC (overdistension) and CCP (collapse)

& Miedema J Peds 2011

& Tingay AJRCCM 2006

14/04/15  

10  

Lung – Ventilator Interaction

• Oxygenation is a summary of the overall volume state of the lung (and perfusion)

• Assuming that the response to ventilation is uniform within the lung overly-simplifies reality

•  Imbalances in the volumetric behaviour of lung regions results in Ventilator-Induced Lung Injury

•  Cross-sectional ‘single slice’ recording

•  16 AgCl electrodes around the chest

•  Software can generate a 32x32 matr ix of ΔZ at d i f ferent f r equenc ies f o r r eg i ona l comparisons

•  Allows real-time radiation-free visualisation of relative EEV, VT, Lung Mechanics and perfusions

Figure adapted from Pillow et al Ped Pul 2008

Electrical Impedance Tomography

14/04/15  

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Using EIT in the ICU Short-term monitoring of high risk interventions

R L

Correct ETT

Left MB

Oesphagus

Schmolzer et al Ped Pul 2012

Endotracheal Tube (ETT) Intubation •  ETT malposition is frequent •  Incorrectly placed ETT is a dangerous complication •  Chest Xray (Gold Standard) is not ideal •  Most bedside tools aim to identify Oesphageal ETT

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EIT  to  guide  PAW  seNngs  during  HFOV  

Miedema et al J PEds

The  new  EIT  –  anatomically  correct  imaging  

R L

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Summary  •  Monitoring   of   parameters   that   approximate   lung   mechanics  

are   now   rou3nely   available   but   not   infallible   and   how   to  interpret  is  unknown  

•  Targe3ng   of   VT   theore3cally   provides   a   mechanisms   of  stabilising  PaCO2  but  the  guidelines  need  valida3ng  

•  New   methods   of   real-­‐3me   volume   monitoring   are   on   the  horizon  and  in  animal  studies  hold  promise  

14/04/15  

14  

‘From Art to Science’

What is an optimal Paw strategy? A physiological rationale Anastasia Pellicano Monitoring and Volume Guarantee David Tingay Pulmonary circulation and lung recruitment – experimental evidence

Graeme Polglase

Endotracheal tube suction Andreas Schibler

Day 2 Session 1: Optimising the application of HFOV

Old and new concepts in the application of high frequency oscillatory ventilation