ResMed Elisee 150 Clinical Manual page 59

PS.VT
Principle of pressure support with minimum tidal volume
Inspiratory phase
The start of each cycle is triggered by the patient. However, the Elisée 150 has a backup rate
setting (Fmini): if the number of cycles triggered by the patient is less than the backup rate,
support cycles will be triggered by the device.
PS.VT mode also allows an apnea time to be set, at the end of which the ventilator commences
apnea ventilation if the patient does not trigger a cycle (see "Principle of Apnea ventilation" on
page 62). The patient can still trigger a cycle after the device has commenced apnea ventilation.
If the patient triggers three consecutive cycles, ventilation switches back to pressure support.
Apnea ventilation is available only when "Fmini = No".
The delivered cycle begins with pressure support ventilation. The Elisée 150 constantly
calculates, from the V
minimum tidal volume (V
If it calculates that the target minimum V
pressure support mode (see "Figure 4.26: PS.VT curve - Minimum tidal volume (Vt) delivered
without switching to volumetric mode." on page 59). However, if it calculates that the V
be reached by staying in pressure support mode, the ventilator will switch to volumetric mode.
The Elisée 150 then delivers the remaining part of the minimum tidal volume while maintaining a
constant flow at an appropriate level until the target minimum tidal volume is reached (see "Figure
4.27: PS.VT curve - Minimum tidal volume delivered with switch to volumetric mode." on page
60). Switching to volumetric mode means that the set pressure will be exceeded during that cycle
in order for the minimum tidal volume to be delivered. Setting a Pmax alarm value limits the
extent to which the set pressure will be exceeded.
Note: To ensure optimum comfort, the minimum V
established in pressure support mode. If it is set too close to the established V
mode will be triggered too often. This note is only an indication; the minimum V
based on a balance between benefit and comfort.
P
V
V
Figure 4.26: PS.VT curve - Minimum tidal volume (V
mode.
The target minimum tidal volume is delivered through pressure support alone. The ventilator
doesn't switch to volumetric mode while in PS.VT mode. The inspiratory flow progressively
reduces until the expiratory trigger threshold is reached.
NOT013189-6
already delivered and the inspiratory time remaining, whether the target
T
) will be able to be delivered.
T
will be reached, the Elisée 150 continues the cycle in
T
should be set to a lower value than the V
T
t
t
t
) delivered without switching to volumetric
T
will not
T
TE
, a volumetric
TE
should be set
T
Ventilation 59/170