Potentially harmful effects of inspiratory synchronization during pressure preset
ventilation
ELECTRONIC SUPPLEMENTARY MATERIAL
Richard JCM1,2,5, Lyazidi A1,2, Akoumianaki E1, Mortaza S3, Cordioli RL1,4,Lefebvre JC1, Rey N1,
Piquilloud L3, Sferrazza-Papa GF1, Mercat A3, Brochard L1,2,6
1 University
Hospital of Geneva, Intensive Care Unit, Geneva, Switzerland
2
University of Geneva, School of Medicine, Geneva, Switzerland
3
University Hospital of Angers, Intensive Care Unit, France
4 Hospital
5
Israelita Albert Einstein, São Paulo, Brazil
UPRESS EA 38 30 , Hôpital Universitaire de Rouen, Rouen, France
6 INSERM
Unit 955, Team 13, University Paris-Est, Créteil, France.
Dr. JCM Richard and A. Lyazidi contributed equally to this work.
Contact information:
Jean-Christophe Richard
Service des soins intensifs – Hôpitaux Universitaires de Genève
4 Rue Gabrielle Perret-Gentil
1211 Genève 14
Email: jcmb.richard@gmail.com
Detailed description of the ventilator mode categories.
We tested all the Pressure Preset Ventilatory (PPV) modes which were available in the
following five ICU ventilators: Engström (General Electric, Fairfield, CT), Evita XL
(Dräger, Lübeck, Germany), G5 (Hamilton Medical, Rhäzuns, Switzerland), PB 840
(Covidien, Carlsbad, CA) and Servo-i (Maquet, Solna, Sweden). Differences and
1
similarities concerning the function of PPV modes in each ventilator tested are
presented in Table 1S.
In the presence of spontaneous inspiratory efforts the PPV modes differ with regard to
the presence of an inspiratory synchronization window i.e. a time period during which
the ventilator can be triggered by the patient. We called this attempt of the ventilator to
provide pressure delivery in response to patient’s effort ‘inspiratory synchronization’ (isynchronization). We subsequently defined three PPV mode categories based on their
different levels of i-synchronization:
(1) Non i-synchronized modes are those, in which the ventilator is never triggered by
the patient, i.e., the ventilator does not attempt to synchronize the transition between
the two pressure levels with patient’s effort. The mode that falls into this category is
‘Airway Pressure Release Ventilation’ (APRV) in Evita XL and G5 and Pressure Assist
Control (PAC) with the inspiratory triggering inhibited in the Engström ventilator.
Despite different names it functions identically in all three ventilators: it is a timetriggered and time-cycled PPV mode allowing, though, unrestricted spontaneous
breathing due to a constantly open expiratory valve. Non i-synchronized PPV mode is
not available in PB 840 and Servo-i ventilator.
(2) In partially i-synchronized modes there is an i-synchronization window. Provided
that spontaneous efforts appear during this window the ventilator will be triggered.
Hence, whether an effort manages to trigger the ventilator depends not only on the
phase of the cycle in which it occurs (inspiratory, expiratory) but also on the duration of
the synchronization window: the longer the window the more likely for an effort to
trigger the ventilator. The latter differs from one ventilator to another (Table 1S).
Partially i-synchronized modes are available in all ventilators tested. However, they are
named differently: Biphasic positive airway pressure (BIPAP), BiLevel, Bivent, DuoPaP.
In all but one (Engström) ventilators tested, partially i-synchronized modes allows the
addition of pressure support (PS) either for any spontaneous effort (Servo-i) or, more
commonly, for efforts occurring during PEEP level (PB 840, G5, and Evita XL).
(3) In fully i-synchronized modes any effort occurring at PEEP level will trigger the
ventilator. This category corresponds to pressure assist control (PAC) in Engström, G5,
PB 840 and Servo-i and to BIPAP assist in Evita XL.
Detailed description of sedation protocol during the observational study.
2
Nurses adapted sedation three times per day according to the algorithm that proposed
four distinct rules according percentage (%) of spontaneous ventilation (SV), pH and
Richmond Agitation Sedation Scale (RASS) score. The RASS target was -2 to -3. The
percentage of SV during APRV should be kept between 10 to 50% of total mechanical
ventilation and it can be easily assessed at the bedside by means of the trends displayed
on the screen of Dräger ventilator (figure 2S) and pH should stay between 7.30 to 7.45.
1. SV < 10% and RASS < - 2: consider sedation decrease (too much sedation)
2. SV < 10% and RASS OK (pH>7.45): consider reduction in RR of APRV (too much
ventilation)
3. SV > 50% and RASS OK (pH<7.30): consider increase of RR of APRV (ventilation
insufficient)
4. SV > 50% and RASS > -2: consider increase sedation (not enough sedation)
3
Ventilator
EvitaXL
G5
Modes
I synchronization
APRV
Non
BIPAP
Partially
BIPAPassist
Fully
APRV
Cycle
Time-trig only
Time-trig or Patient-trig (variable
synch. window)
Time-trig or Patient-trig
(Any effort at PEEP)
Time-cycled only
Time-cycled or Patient-cycled
(variable synch. window)
Rate
Unrestricted
Rate
Unrestricted
Time-cycled only
THIGH
Unrestricted
NA
Non
Time-trig only
Time-cycled only
Rate
Unrestricted
Relative to
PEEP level
Partially
Time-trig orPatient-trig
(Synch. window for the last 25% of
TLOW, max 1.5 s)
Time-cycled or Patient-cycled
(Synch. window for the last 25% of
THIGH, max 1 s)
Rate
Unrestricted
Relative to
PEEP level
Fully
Time-trig or Patient-trig
(Any effort at PEEP )
Time-cycled only
THIGH
Insp:
Unrestricted
Exp: Not possible
NA
Partially
Time-trig or Patient-trig
(Synch. window for the last 25% of
PEEP )
Time-cycled or Patient-cycled
(Synch. window for the last 25% of
THIGH)
Rate
Unrestricted
Relative to
PEEP & to
PHIGH level
PAC
Fully
Time-trig or Patient-trig
(Any effort at PEEP )
Time-cycled only
THIGH
Insp:Unrestricted
Exp: Possible
(Paw > 3 cmH2O)
NA
BiLevel
Partially
Time-cycled or Patient-cycled
(Synch. window for the last 30% of
THIGH, max 3 s)
Rate
Unrestricted
Relative to
PEEP level
PAC
Fully
Time-cycled only
THIGH
Unrestricted
NA
Bilevel
Partially
Time-trig or Patient-trig
Time-cycled or Patient-cycled
(variable synch. window)
Rate
Unrestricted
Relative to
PEEP level
PAC
Fully
Time-trig or Patient-trig
(Any effort at PEEP )
Time-cycled only
Rate
Unrestricted
NA
Non
Time-trig only
Time-cycled only
Rate
Unrestricted
NA
DuoPAP
Bi-vent
Servo-i
Engstrom
Parameter
constant
SPONTANEOUS CYCLES
Additional
During PHIGH
PS
Trigger
PAC
PB 840
MANDATORY CYCLES
trigger ON
PAC (APRV)
trigger OFF
Time-trig or Patient-trig
(Synch. window for the last 40% of
PEEP , max 4 s)
Time-trig or Patient-trig
(Any effort at PEEP )
NA
Relative to
PEEP level
4
Table 1S: Description of the different names of pressure preset modes and their
characteristics in the five ICU ventilators tested. Hence PEEPhigh or Phigh correspond to
high airway pressure; TPEEP or TPEEPlow is the time spent at PEEP (or low airway
pressure) and THIGH or TPEEPhigh or TINSP the time at high airway pressure. NA: not
applicable
5
Figure 1S: The percentage of spontaneous ventilation during APRV displayed on the
screen of Dräger ventilator indicating total minute ventilation and spontaneous
ventilation (black and gray on the ventilator screen, respectively).
6
I-synchronized cycles
Non i-synchronized mode
(ml/kg)
10
VT (ml)
Mandatory cycles
6
Spontaneous cycles in PEEP
4
0
(ml/kg)
10
Partially i-synchronized mode
VT (ml)
6
4
0
(ml/kg)
10
Fully i-synchronized mode
VT (ml)
6
4
0
Without inspiratory effort
With inspiratory effort
Time (sec)
Figure 2S: Volume-time curves of the 3 different PPV modes, before and after the
initiation of spontaneous efforts. The inspiratory to expiratory ratio was 1:3. The dotted
horizontal lines below and above 6ml/kg/ ideal body weight (IBW) correspond to 4 and
10 ml/kg IBW, respectively. The VT values are expressed in ml/kg IBW for a male subject
of 182 cm height and IBW of 75 kg. As the level of synchronization increases, the
occurrence of cycles with high VT increases (i-synchronized cycles).
7
Figure 3AS: The i-synchronization effect of spontaneous breathing during pressure
preset ventilation modes. Tidal volume and its variability at a spontaneous respiratory
rate of 30 cycles/min and an I:E ratio of 1:3. Partially i-synchronized modes were tested
with and without pressure support (PS) for efforts occuring at PEEP level.
8
I/E 3:1 RR 30
1000
70
60
Tidal volume (ml)
50
600
40
30
400
20
200
10
0
Non
i-synchronized
modes
Partially
i-synchronized
modes
PS 0
Partially
i-synchronized
mode
PS 15
Fully
i-synchronized
modes
Coefficient of variation (%)
800
0
Figure 3BS: Tidal volume and its variability at a spontaneous respiratory rate of 30
cycles/min and an I:E ratio of 3:1. Partially i-synchronized modes were tested with and
without pressure support (PS) for efforts occuring at PEEP level. *p<0.05 vs non isynchronized modes, † p<0.05 vs partially i-synchronized modes (PS 0)
9
Figure 4S: Tidal volume and its variability at a spontaneous respiratory rate of 20
cycles/min and an inspiratory to expiratory ratio of 3:1. Partially i-synchronized modes
were tested with and without pressure support (PS) of inspiratory efforts at PEEP level.
10
Table 2S: Tidal volume measured at each ventilator during spontaneous breathing. The
inspiratory to expiratory ratio was 1:3 and the respiratory rates tested were 20 and 30
cycles/min. Partially i-synchronized modes were tested with and without pressure
support (PS) of inspiratory efforts at PEEP level.
*p<0.05 vs non i-synchronized modes, † p<0.05 vs partially i-synchronized modes (PS 0), ‡
p<0.05 vs partially i-synchronized modes (PS 15).
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Comparative
study
Study
Observationnel
study
Patient Sexe
Age
Weight
(years)
(kg)
Size
(cm)
IGS2
PaO2/FiO2
Crs
Ventilation ICU stay
(mmHg) (ml/cmH2O) (days)
(days)
Recording
duration
(days)
ARDS etiology
P01
M
47
73
172
44
147
22
7
10
1
Pneumonia
P02
M
83
112
165
36
100
29
15
16
6
Pneumonia
P03
M
63
76
158
52
77
36
50
60
14
Pneumonia
P04
M
66
79
162
30
108
18
8
8
2
Pneumonia
P05
F
77
67
164
50
96
21
32
32
7
Pneumonia
P06
F
36
68
165
30
74
18
6
8
3
Pneumonia
P07
F
64
101
156
71
86
27
7
7
5
CPR
P08
F
41
64
159
35
118
24
5
9
2
Malaria
Mean
60
80
163
44
101
24
16
19
5
(SD)
(16)
(17)
(5)
(14)
(24)
(6)
(16)
(18)
(4)
P01
M
44
57
163
36
180
35
16
35
NA
Pneumonia
P02
F
66
65
169
89
169
71
10
15
NA
Pneumonia
P03
F
80
62
160
79
236
22
5
7
NA
Pneumonia
P04
M
83
74
167
59
233
44
12
15
NA
Pneumonia
68
(18)
65
(4)
165
(4)
66
(23)
205
(35)
43
(21)
11
(5)
18
(12)
NA
Mean
(SD)
Table 3S: General clinical characteristics
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Figure 5S: Individual averaged VT according to the PPV modes tested during the clinical
comparative study. Patient number 02 ventilated with I:E ratio of 1:3.2 exhibited larger
VT during PAC compared to the 3 others patients ventilated with a I:E around 1:2.
13