Mallinckrodt
Puritan Bennett 840 Ventilator

The PB 840 ventilator is designed for critical care ventilation of adult and pediatric patients. Initial setting of Ideal Body Weight (IBW - lowest setting 10 lbs) automatically sets ventilator controls for a tidal volume of 6 ml/kg. The display features 2 screens. The top allows continuous viewing of waveforms or a log of alarm history. The bottom screen provides easy access of control settings, apnea ventilation, and alarm settings.

Modes include volume controlled, pressure controlled, or volume-targeted-pressure controlled (VC+) breaths in Assist/Control and for the mandatory breaths in SIMV modes. Spontaneous ventilation includes pressure support, volume support and CPAP. BiLevel ventilation is another option capable of providing two level-CPAP. The rate (breaths/min) is set along with pressure levels for the high and low PEEP and the time at high PEEP. The patient can breathe spontaneously at the high and low levels of pressure and pressure support can be added to all spontaneous breaths. BiLevel may be set as high as a 10:1 I:E ratio.

The trigger mechanism may be set as a pressure or flow trigger. Baseline flow is automatically 1.5 LPM above the flow trigger setting which is adjustable from 1 - 20 LPM. The 840 also has automatic tube compensation (TC) to provide an adjustable level of pressure support to overcome the resistance of breathing through the endotracheal tube.

After connecting circuit and mains, leave patient wye open and power ON. If patient wye is blocked during power ON, ventilator will alarm and switch to safety ventilation. After the 840 does a power on self test, the bottom screen will appear as seen on the left. Same patient, new patient, or short self-test (SST) may be selected by touching screen and highlighting item.
If SST is selected, operator has 4 seconds to press Test button on left side of ventilation to activate SST. The 840 SST only requires the operator to 1) block patient wye, 2) disconnect inspiratory limb of circuit and 3) disconnect expiratory limb of circuit. During SST, the type of humidifier may be selected.
   

After touching New Patient, the screen goes to IBW. Touch IBW and adjust body weight with knob, then press "Accept" located above knob and to the right of CLEAR. IBW is given in pounds and kilograms. The 840 will automatically set tidal volume to equal 7.25 ml/kg. All parameters can be adjusted.

After accepting body weight, touch CONTINUE to go to ventilator settings.

 Touch MODE and adjust knob to select A/C, SIMV, Spontaneous, or BiLevel. Then touch Mandatory Type to select VC, PC, or VC+ ventilator breaths. Touch Trigger Type to select Pressure, Flow, or TC Trigger. Press Accept, then touch CONTINUE.

Note: if SIMV, Spontaneous, or BiLevel mode is selected by turning the knob, an icon for selecting Pressure Support appears. It is recommended that pressure support be set, even if a PS of 0 is desired, rather than selecting 'none'.

Had SIMV-PC been selected, the screen goes to default settings as shown on left. Touch CONTINUE to adjust ventilator settings. Note that Vent Setup is active along the bottom of the screen. All of the ventilator settings can now be adjusted by touching frequency (for SIMV rate) and adjusting knob. Accept is pressed after all settings have been adjusted. A bar displaying the effect of frequency and inspiratory time settings (1 and 2) on I:E ratio would be visible as shown below. 3 indicates the Flow Acceleration % setting on the default value of 50%.

 Flow Acceleration % or rise time % alters the initial flow allowed during pressure control or pressure supported breaths. 100% provides the maximum or unlimited initial flow and an immediate increase in pressure. Values less than 50% reduce the initial blast effect of flow and may increase patient comfort. The I:E Ratio bar is also shown at left. The orange arrow indicates which of the three values may be locked or fixed during pressure control ventilation: inspiratory time (locked), I:E ratio, or expiratory time.

After adjusting the ventilator settings, touch Apnea Vent along bottom of screen to set apnea ventilation and apnea interval. The Apnea Ventilation controls are light blue indicating that these settings are available for adjustment.

Touch Alarms (next to Apnea Vent) to set
  • High inspiratory pressure (P circ)
  • High frequency (f tot)
  • High and Low Minute Ventilation (VE tot) volume
  • High and Low Mandatory Tidal Volume
  • High and Low Spontaneous Tidal Volume
Alarm limits are set by touching alarm box and adjusting knob. After all alarms are adjusted, press Accept. Actual patient values are indicated by flags on the left of the bar.

This whole time the NPB 840 has been waiting for you to set everything and connect to the patient. No alarms have been going off. It hasn't even tried to give a breath. "Vent Startup in Progress" has been displayed above the top screen. Ventilation will start when you connect to the patient.

Touching the file icon next to Alarms will bring up the view shown here. Touch 'More Settings' to adjust the Expiratory Sensitivity % and Disconnect % in spontaneous modes. The Expiratory Sensitivity % adjusts the flow cycle level of pressure supported breaths. In the event of a leak, the ES % can be adjusted so that pressure supported breaths will end. Maximum setting is 45% which will be
effective for all but large leaks. There is also a Disconnect % which adjusts the % loss of the returned flow signaling a disconnect alarm. A setting of 50% will mean the expiratory tidal volume must fall to half of the inspiratory volume before an alarm is activated.

The top screen allows continuous viewing of waveforms. Waveforms may be pressure/time, flow/time, volume/time, and pressure/volume. Up, lateral, and down arrows on the right side of the screen adjusts the scale. To change waveforms, touch 'Plot' and adjust knob. The waveforms are color coded. Green indicates a mandatory inspiration and red indicates a spontaneous breath. The patient's parameters are displayed along the top of the screen.

Touching the clipboard icon will display a record of the last 86 alarm conditions and what happened to them.