Proportional Assist Ventilation (PAV+) and Neurally Adjusted Ventilatory

Assist (NAVA)

L. Brochard

Laurent Brochard Toronto

Laurent Brochard Toronto

PAV et NAVA

Conflicts of interest

• Our clinical research laboratory has received research grants for clinical trials from the following companies – Covidien (PAV+)

– Dräger (SmartCare)

– General Electric (FRC)

– Maquet (NAVA)

– Fisher Paykel (Optiflow)

– Vygon (CPAP)

Proportional Assist Ventilation (PAV+) and Neurally Adjusted

Ventilatory Assist (NAVA)

• Two (Canadian) proportional modes

Proportional Modes: what for?

• Better Patient-Ventilator Synchrony

• Better adaptation to changes in demand

• Optimal tidal volume (and frequency) for lung protection

ABC of ventilation PSV, PAV, NAVA

Trigger Control Cycling end

expiration

PSV Flow or

Pressure

Constant

Pressure

% Peak-

Flow

PEEP

NAVA patient

EMG

Pressure

proportion-

nal to

EMGdi

End of

EMGdi

PEEP and

EMGdi

PAV Flow or

Pressure

Pressure

proportion-

nal to flow

and volume

End of

Patient

Flow

PEEP

RESPIRATORY SYSTEM MODEL

Compliance and Resistance = CONSTANT

Pressure, Volume, Flow= VARIABLES

Equation of Motion

muscle + ventilator

G: gains for volume (VA) and flow (FA) VA is a fraction (percentage) of Ers, and FA is a fraction of Rrs

Equation of motion

Pappl = (VxE) + (V'xR)

Pappl = Paw + Pmus

Pappl = (VxE) + (V'xR) = Pel + Pres

Gain

huge

Paw proportional

Gianouli et al AJRCCM 1999

Estimation of Elastance

300 ms end inspiratory pause manoeuvre at a random intervals of 4 to 10 breaths : PplatPAV

EPAV = (PplatPAV - PEEPtot) / Vt

Younes M, et al. AJRCCM 2001;164:50-60

FLOW

Pes

Paw

GAIN = 40%

Settings in PAV+

FiO2 PEEP Gain

How to adjust it?

understand « Gain »

K = 1

1 - Gain

(P0 = 0) Ptot = K . |Pmus| For a Gain of 75% support

K = 1

0.25

K = 1

1 - 0.75

K = 4

Paw

25% 75%

100%

Ptot

Pmus

Carteaux et al CCM 2013

Adaptation of the Gain every 8h if needed

Clinical data collected daily

A computer was connected to the

ventilator for continuous recording

of ventilator’s data (sampling frequency =

1 min)

19 switch to ACV

52 PAV+

33 until Extubation

27 settings according to

protocol (82%)

4 needed additional

settings 2 out of the

rules

1 Intolerance 18 Aggravation

Carteaux et al CCM 2013

Each box-plot represents a patient

PTPmus median values all over PAV+ ventilation per patient P

TP

mu

s (c

mH

20.s

.min

-1)

Carteaux et al CCM 2013

Conclusions

• Many patients tolerate PAV+ ventilation over several days

• Setting PAV+ to target a « normal » level of effort seems feasible

• The target is reached in 85% of the cases

• Refinement of the Paw criteria may be necessary

Elec

tro

des

+ -

+ -

+ -

+ -

+ -

+ -

+ -

+ -

+ -

Filtrage

Ventilateur

Amplification

Catheter Edi

J. Appl.Physiol. 1998, 85: 2146–2158,

NAVA catheter: position

NA

VA

NA

VA

NAVA uses Eadi for…

Triggering

Cycle

Deliver proportional assist

NA

VA

Courtesy of H Roze

Courtesy of H Roze

Courtesy of H Roze

Double – trigg NAVA

Paw = Edi x Gain de NAVA

Titration?

Brander L, et al. Chest 2009; 135:695-703

NA

VA

14 patients

Intensive care Med 2012; 38(2):230-9

NA

VA

15 patients

NA

VA

Patient 1

Patient 2

G Carteaux 2010

% of total pressure supported by NAVA

% P

tot

NAVA G Carteaux 2010

Colombo et al. ICM 2008

Physiologic response to varying levels of pressure support and neurally

adjusted ventilatory assist in patients with acute respiratory failure

Control?

Neurally adjusted ventilatory assist decreases ventilator-induced lung injury

and non –pulmonary organ dysfunction in rabbits with acute lung injury

Brander et al. ICM 2008

Control?

Pmus,Peak = (Paw,Peak – PEEP) . 1 – Gain

Gain

Delta Paw (cm H20) = Paw,Peak - PEEP

1 2 3 4 5 6 7 8 9 10 12 15 17 20 25 30 35 40

% assist

20 4 8 12 16 20 24 28 32 36 40 48 60 68 80 100 120 140 160

25 3 6 9 12 15 18 21 24 27 30 36 45 51 60 75 90 105 120

30 2 5 7 9 12 14 16 19 21 23 28 35 40 47 58 70 82 93

35 2 4 6 7 9 11 13 15 17 19 22 28 32 37 46 56 65 74

40 2 3 5 6 8 9 11 12 14 15 18 23 26 30 38 45 53 60

45 1 2 4 5 6 7 9 10 11 12 15 18 21 24 31 37 43 49

50 1 2 3 4 5 6 7 8 9 10 12 15 17 20 25 30 35 40

55 1 2 2 3 4 5 6 7 7 8 10 12 14 16 20 25 29 33

60 1 1 2 3 3 4 5 5 6 7 8 10 11 13 17 20 23 27

65 1 1 2 2 3 3 4 4 5 5 6 8 9 11 13 16 19 22

70 0 1 1 2 2 3 3 3 4 4 5 6 7 9 11 13 15 17

75 0 1 1 1 2 2 2 3 3 3 4 5 6 7 8 10 12 13

80 0 1 1 1 1 2 2 2 2 3 3 4 4 5 6 8 9 10

85 0 0 1 1 1 1 1 1 2 2 2 3 3 4 4 5 6 7

90 0 0 0 0 1 1 1 1 1 1 1 2 2 2 3 3 4 4

Pmus,Peak

Gain

( )

Carteaux et al CCM 2013

Pmus

RR

Ti Te

Pmus,Peak

PTPmus

Pmus,Peak x Ti

2 PTPmus = x RR

CRITERIA FOR WEANING TRIAL -Resolution of the pathologie requiring intubation -No sign of ARD -Fi02 50% -SaO2 ≥ 90% -Conscious patient -No vasopressor, haemodynamic stability

Adjust FiO2 and PEEP

According to: -Oxygenation (SpO2, PaO2) - Underlying respiratory disease

How to adjust the Gain 1

Standard settings

Assess Pmus

Pmus < 5 cmH2O 5 Pmus 10 cmH2O Pmus > 10 cmH2O

Decrease Gain in steps of 10%

Optimal WOB area. Decrease Gain in steps of 5% while Pmus remains in this area.

Increase Gain in steps of 10%

Initiating PAV+

INITIAL SETTINGS -Gain: 50% -Inspiratory trigger: 1 l/min -Expiratory trigger: 1% -FiO2 et PEEP: no specific rule

ALARMS -Paw max: 40 cmH2O -RR: 40/min -Vte max: 10 ml/kg -Vte min: 0 ml

If appears, while Pmus is in the optimal area

-Signs of ARD -Vte < 5 ml/kg -Respiratory acidosis

Increase Gain in steps of 10%

-Vte > 10 ml/kg -Respiratory alcalosis

Decrease Gain in steps of 10%

FiO2 & PEEP optimisation

2 Aditional settings

Search another hypertotilation’s cause

Persistance Lack

Regardless of the Gain