Hamilton G5 - Principles of Operation

B-14 624074/07
B Modes of ventilation
B.5.1.2 Principles of operation
The APV modes operate in this order:
1. Assessing the breathing pattern. The APV modes start
by determining the patient’s volume/pressure response
(V/P). This is achieved based on the previous ventilation or
on a sequence of three (3) test breaths. V/P is defined as:
Vt / (Ppeak – PEEP/CPAP)
2. Achieving the target volume. The device uses V/P to cal-
culate the lowest inspiratory pressure applied to achieve the
VTarget. The minimal pressure delivered is 3 cmH
2
O above
PEEP.
The operator sets the VTarget, rate, PEEP/CPAP, and the
high Pressure alarm limit. The adaptive controller compares
the monitored Vt to the VTarget. If the patient’s actual tidal
volume is equal to the VTarget, APV maintains the inspira-
tory pressure. If the monitored tidal volume is higher or
lower than the target volume, the inspiratory pressure is
gradually adjusted by up to 2 cmH2O per breath to attain
the target level.
The inspiratory pressure is adjusted within this range: (PEEP
+ 3 cmH2O) to (high Pressure alarm limit – 10 cmH2O).
In this case, HAMILTON MEDICAL recommends a high
Pressure alarm limit setting at least 10 cmH2O above peak
pressure. On its pressure curve display, the device displays
a blue band 10 cmH2O below the set high Pressure alarm
limit.
3. Maintaining the target volume with the lowest
inspiratory pressure. The parameters needed for APV are
measured breath by breath. When required, the operator
recalculates the minimal inspiratory pressure to achieve the
target volume based on the current lung characteristics.
The minimal inspiratory pressure is limited to minimum
3 cmH2O above PEEP.
The continuous reassessment of the patient’s dynamic lung
status is designed to guarantee the required ventilation
while preventing hypoventilation or barotrauma.