Triggering Rise Time E Sens

1. Mechanical Ventilation
“ Rise Time, E sens, Triggering”

2. A - work to trigger
B - rate of rise to pressure adjustment
C - preventing pressure overshoot and sustaining the breath
D - transition into expiration
Smarter Breath Delivery
Pressure
A
C
(PCV Only)
D
(PS Only)B

3. Improving Patient-Ventilator Synchrony
“Smart” Rise Time
1. ¯ WOB, specifically insp. muscle effort ,
associated with inappropriate flow rate
during PSV or PCV.
2. less problems associated with flow and
achievement of set pressure in response to
changes in lung condition as SRT is self-
adjusting due to a Pressure Memory
Algorithm

4. •Usually applicable in all pressure breaths if available
•Tailors inspiratory rise in pressure ventilation to match
patient demand or reach MAP goals
•Should allow rise to be tailored from slow to fast
1. Rise to Pressure Adjustment
40P
CIRC
cmH
2
O
INSP
L
min
EXP
PLOT SETUP
30
20
10
0
10
-20
80
60
40
20
0
20
-80
40
60
V
.
0 4 8 12s2 6 10
UNFREEZE
Slow rise Moderate rise Fast rise

5. A - work to trigger
B - rate of rise to pressure adjustment
C - preventing pressure overshoot
and sustaining the breath
D - transition into expiration
Smarter Breath Delivery
Pressure
A
C
(PCV Only)
D
(PS Only)B

6. Patient with ­ Airway Resistance
Gas flow is greatest
where resistance is
low, hence
overinflation of
normal lung units.
¯ V/Q
PvCO2 =
46
mmHg
PvO2 =
40 mmHg
PaO2 =
70 mmHg
PaCO2 =
45 mmHg
PaCO2 =
43 mmHg
PaO2 =
60 mmHg

7. 40P
CIRC
cmH
2
O
INSP
L
min
EXP
PLOT SETUP
30
20
10
0
10
-20
80
60
40
20
0
20
-80
40
60
V
.
0 4 8 12s2 6 10
UNFREEZE
RES = 5 RES = 20 RES = 50
cmH
20/L/SEC cmH
20/L/SEC cmH
20/L/SEC
Without Adjustment of Pressure Rise
•Most ventilators are sensitive to changes in impedance
–increasing resistance causes pressure to rise more
quickly

8. •Not all clinicians want to adjust rate of rise (time, interest)
•Smarter rise settings should automatically adjusts flow
output as resistance or compliance varies
–maintains similar shape of curve through any patient
size or impedance change which reduces the need for
intervention
40P
CIRC
cmH
2
O
INSP
L
min
EXP
PLOT SETUP
30
20
10
0
10
-20
80
60
40
20
0
20
-80
40
60
V
.
0 4 8 12s2 6 10
UNFREEZE
RES = 5 RES = 20 RES = 50
cmH
20/L/SEC cmH
20/L/SEC cmH
20/L/SEC

9. A - work to trigger
B - rate of rise to pressure adjustment
C - preventing pressure overshoot and
sustaining the breath
D - transition into exhalation

Smarter Breath Delivery
Pressure
A
C
(PCV Only)
D
(PS Only)
B

10. Expiratory W.O.B. and auto-PEEP
in the COPD Patient
MJ Tobin. NEJM 2001; 344: 1986-96.

11. PS and WOB during Expiration
P
R
E
S
S
U
R
E
Esens allows the clinician to adjust the ventilator’s onset of
expiration to match the patient’s breathing pattern.
F
L
O
W
PS overshoots
target
Esens
fixed
25%
Esens
adjusted
to 50%
Normal
Problem
resolved
0
100
0
15

12. Expiratory Sensitivity
PS Termination Criteria
Pressure support breaths terminate
when patient flow decelerates to a
percentage of peak flow
Flow

13. Expiratory Sensitivity
20% (Set)
35% (Leak Rate)
•Leaks can cause inability to terminate
pressure supports breaths causing profound
asynchrony
Flow

14. Expiratory Sensitivity
20% (Set)
40% (Set)
35% (Leak Rate)
•E
SENS
allows adjustment of the termination criteria for
pressure supported breaths
–sets the percent of peak flow that cycles the pressure
support breath into exhalation
–helpful in compensating for prolonged inspiratory times
when leaks are present or titrating insp times in PS
–can improve synchrony between patient and ventilator
Flow

15. How FlowHow Flow--Triggering Works!Triggering Works!
Base Flow 5
Sens1lpm
5lpm
1lpm
4lpm
Patient
removes
Base Flow 14
Sens7lpm
14lpm
Chest tube leak
removes 6lpm
Patient must
remove only
1lpm
7lpm
Without a Leak With a Leak

16. How Much Does It Take To
Trigger A Breath?
Imagine setting the Flow
Sensitivity at 1 LPM:
1 LPM = 16.6ml/100msec
or
.83 ml/5msecs

17. Pressure vs Flow Triggering
•Pressure Triggering
–No gas flow
–Longer delay time
–Poor approach with
leaks
–Higher WOB
–Not a mode of
ventilation
•Flow Triggering
–Flow at the wye
–Decreased delay
–Electronic signal
–Less WOB
–Not a mode of
Ventilation

18. Flow Triggering Articles
•Sassoon - flow-by causes lower WOB at 10
cm H2O during CPAP breathing than
pressure
Crit care med 1989
•Saito - Inspiratory WOB is lower with
flow-by and similar to PS of 5 cm H2O
Crit care med 1990