Airway Pressure Measurement - Dräger Babylog VN500 Instructions For Use Manual

Airway pressure measurement

Babylog VN500 measures the airway pressure in-
directly by means of two internal pressure sensors.
The sensors are installed in the inspiratory and ex-
piratory lines, thereby eliminating the need for an
external pressure measuring line between the
Y-piece and the device. As long as one side is with-
out flow, the measured value of the flowless pres-
sure sensor corresponds to the airway pressure at
the Y-piece.
During ventilation, there is a constant basic flow.
However, due to this constant basic flow, the zero-
flow condition is never attained either on the in-
spiratory or expiratory side. The pressure mea-
sured by the inspiratory pressure sensor varies with
the variations in airway pressure but is increased
by the pressure drop in the inspiratory line of the
breathing circuit. The pressure measured by the
expiratory pressure sensor is reduced by the pres-
sure drop in the expiratory line of the breathing cir-
cuit. These pressure differences are caused by the
flow resistance of the breathing circuit.
During expiration, the value measured at the in-
spiratory pressure sensor (Pinsp) is reduced by the
pressure drop caused by the basic flow (Flow
the inspiratory line of the breathing circuit (R
Paw = P – R x Flow
insp insp
Paw: Airway pressure at the Y-piece
Pinsp: Airway pressure at the inspiratory pres-
sure sensor
R : Flow resistance of the inspiratory breath-
insp
ing hose
Flow : Basic flow
bf
Instructions for Use Infinity Acute Care System – Babylog VN500 SW 2.n
) in
bf
):
insp
bf
During inspiration, the value measured by the expi-
ratory pressure sensor (P
the airway pressure by the amount of the pressure
drop caused by the flow (normally
≤ Flow
(Flow ) through the expiratory line of the
out bf
breathing circuit (R ):
exp
Paw = P + R x Flow
exp exp
Paw: Airway pressure at the Y-piece
P : Airway pressure in expiratory breathing
exp
hose
R : Flow resistance of the expiratory breath-
exp
ing hose
Flow Flow through the expiratory valve during
out:
inspiration
The hose resistances are determined by
Babylog VN500 during the device check.
The user can configure whether the setting occurs
via the pressure ramp Slope with a basic flow of
6 L/min or with an adjustable inspiratory flow
Insp. flow and an expiratory basic flow of 6 L/min.
Description
) is raised relative to
exp
out
267