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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