THEORY OF OPERATION
4-4 SERHT50NA A0808
When PEEP/CPAP is set above 0, the ventilator mode is CPAP
(without Psupport) or Bi-level Positive Airway Pressure (with
Psupport). Ensure that Ptrig is set so the HT50 detects all
spontaneous patient efforts.
Entries for tidal volume, pressure control,
ƒ, t
I
and Low Paw alarm
limit are all inactive in SPONT mode. However, users can preset
these parameters for future A/CMV or SIMV operation.
As with all HT50 operating modes, Back-up Ventilation is activated
if the Low ▼V
•
I
alarm limit is violated.
PSUPPORT
(Pressure Support)
Psupport only functions during patient triggered spontaneous
breaths in SIMV and SPONT modes. During each spontaneous
breath, the ventilator supports the patient by elevating the airway
pressure to the Psupport + PEEP level. Breaths are terminated
when (1) flow to the patient drops to 25% of that breath’s peak flow
rate, or (2) the target airway pressure is exceeded by 3 cmH
2
O
(mbar), or (3) after 3 seconds of inspiration.
PRESSURE CONTROL
(Pressure Control Ventilation)
The HT50 targets and maintains patient airway pressure at the
set pressure control level throughout inspiration. Breath
termination occurs when (1) the set t
I
elapses, or (2) Paw
exceeds the Pressure Control setting by 8 cmH
2
O (mbar).
NOTE: The target airwa
y pressure for pressure controlled
mandatory breaths in A/CMV and SIMV is the display setting
above ambient pressure, not above PEEP.
Both time and patient triggered mandatory breaths can be
delivered in A/CMV and SIMV Pressure Control operation. During
SIMV Pressure Control operation, patients can breathe
spontaneously between mandatory breaths with or without
pressure support.
NOTE: When disconnecting the patient circuit during PCV/PSV
ventilation, i.e
. for suctioning, the flow may increase in order to
compensate for the low pressure. After reconnecting the patient
circuit, the flow will automatically readjust to meet the patient’s
demand.
To Next Page
Loading...
