Dräger Babylog 8000 plus Operating Instructions Manual page 133

Pattern 2, no plateau
Without inspiratory pressure plateau, P
influence on V . A portion of *
T
with each mandatory breath, only the remaining portion
actually flows into the lungs. The patient circuit is thus
ventilated alongside the patient. Tidal volume may be
calculated approximately as
. * . C
V = T /(C + C
T in insp rs rs
with C as the circuit compliance. Especially for very
c
small patients, the influence of the circuit system can be
quite considerable, because C
order of magnitude.
Only half of the set continuous flow, e.g., goes into the
patient's lungs with values of C
This effect of "co-ventilating" a patient circuit is shared
by all ventilators. Babylog 8000 plus therefore features a
flow sensor at the wye to measure true inspiratory and
expiratory tidal volumes.
Assist Control Ventilation
(A/C)
Ventilator breaths are synchronized with a patient's own
spontaneous breathing. A breath starts with a spon-
taneous breathing effort and ends at inspiratory time T
The mandatory breath is shaped by the same settings as
in CMV. Babylog 8000 plus detects spontaneous
breathing via its flow measuring system. A ventilator
breath is triggered if
– inspiratory flow is measured following an expiration,
and
– the continuously inspired volume during the spon-
taneous inspiration (trigger volume V
set trigger threshold, and
– V has been inspired before the end of T
trig
In addition, a ventilator breath may only be started when
0.2 s have elapsed after the end of the previous breath in
order to provide sufficient time for expiration.
The patient will control the ventilator rate.
It can rise to a maximum of
f = 1/(T + 0.2 s + T )
max in RT
with T as trigger response time, which is the time from
RT
the begin of a spontaneous inspiration until the begin of
the triggered ventilator breath.
If the patient fails to trigger breaths, ventilation is
performed as in CMV.
A/C is suitable for patients with sufficient spontaneous
respiration and respiratory control. Weaning may be
performed by successively decreasing inspiratory
pressure.
has no
insp
fills the patient circuit
insp
)
c
and C are of the same
c rs
= C .
rs c
.
in
) reaches the
trig
.
ex
Theory of Operation
Ventilation Modes
133