lung size, the existent pressure gradient at the beginning of inspiration between the
upper airway and the alveoli, the respiratory system compliance and the available
inspiratory time.
The pressure waveform developed during inspiration is rectangular, being the flow of
the descending ramp type (decelerating flow). The typical pressure plotting shows a
rapid lineal increase until the set pressure limit is reached. Pressure is maintained
constant during the set inspiratory time. It cannot be changed.
This mode works with the Assist/Control characteristic, changing from a manner to
other according to the patient's demand (inspiratory effort).
If the patient’s inspiratory effort is reduced or an apnea episode is present, then, the
inspiration will be triggered by time (set machine frequency).
On the other hand, the patient's inspiratory effort could be enough to trigger the
ventilator and begin the inspiratory phase with he/she own breathing frequency and
according with the set trigger sensitivity.
In PCV it is possible to regulate the pressurization, that is to say, the rising speed of
the pressure until reaching the selected pressure limit. The pressurization is regulated
by means of the Rise Time keys, one to increase and another to diminish the speed.
Specific Controls for the PCV mode:
PCV: It regulates the pressure level.
Rise Time: Two keys to increase or to lower the pressurization time.
Pressure Support
Definition and Operative Proceeding: Pressure support ventilation is a
spontaneous ventilation mode where the patient begins and ends the inspiratory
phase; this means that he keeps control of the frequency, the duration of the
inspiration and of the tidal volume. As in all modes limited by pressure, the tidal
volume (VT) is variable, depending on the regulated pressure in relation to the
respiratory system impedance, as well as to the patient’s demand.
In this ventilator, the pressure support is programmed directly, alone or in
combination with other modes.
The patient begins the inspiratory phase according to him/her inspiratory effort and set
Inspiratory Sensitivity (pressure or flow). The inspiration end depends on the set Expiratory
Sensitivity (40. 33, 25, 15, 10 or 5% of the initial peak flow). As a safety measure, the end of
inspiration can be for pressure (3 cm H
2
O above the adjusted one) or time (3 seconds
maximum).
Specific Controls for the PSV mode:
PSV: It regulates the pressure level.
Rise Time: Two keys to increase or to lower the pressurization time.
Continuous Positive pressure (CPAP)
Definition and Operative Proceeding: In this mode the ventilator should generate,
by means of a partial closing of the expiratory valve, a continuous positive pressure in
the breathing circuit. When the patient inspires, the proportional solenoid valves will
open providing a flow according to the patient's demand. In this mode, the flow varies
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