PB 840 Mechanical Ventilator

Readings Pages 580 - 599 in Mosby’s Do review questions on pages 597 - 598 in the same text

The Basics Microprocessor-controlled Electrically and pneumatically driven Pressure, flow, time, manual trigger Time, flow cycled Pressure-cycled only if upper alarm reached Pressure-limited Active exhalation valve decreases work of breathing Priority based alarms Touch screen user interface Explain the meaning of active exhalation valve, contrast with 900c, what happens when your patient coughs.

The Not-So-Basics Available modes A/C SIMV Volume Pressure VC+ With spontaneous breath types PS or TC Split out into 2 slides.

The Not-So-Basics Available modes Spontaneous Bilevel PS or CPAP TC (Automatic tube compensation) VS ( Volume support) PA (PAV+) Bilevel Split out into 2 slides.

Flow/Pressure Trigger Pressure monitored at two points in circuit Insp manifold and just after exp check valve 0.1 - 20 cmH20 below PEEP “New patient” default value – 2.0 cmH20 Flow trigger Base flow is 1.5 L/min > the operator-selected value for flow sensitivity Backup pressure sensitivity 2.0 cmH20 preset in case flow sensors do not detect flow 0.5 to 20 L/min Do I want to go this specific?

Ventilator Guts Hot wire anemometer Built-in heated viral/bacteria filter Filters 99.97% of 0.3 micron particle size at 100 L/min when new Do I need these specs!

840 Modular Design Touch Screen Display Breath Delivery Unit Can be mounted separately Breath Delivery Unit San be mounted separately from cart 2 2 6 9 9 6

Making Simple Changes Turn Accept Touch OK? 6 11 11 11

Software-Controlled Screens Only current modes and settings are displayed (less confusing) Information can appear as needed to help make decisions easier and safer

Software-Controlled Screens

Breath Delivery Unit 14 11 12 12 15 15

Breathing During PCV Patient efforts during the inspiratory phase of PCV can result in fighting and pressure spikes 40 PCIRC cmH2O INSP L min EXP 30 20 10 -20 80 60 -80 V . 4 8 12s 2 6 Spontaneous Efforts PCV W/O Active Valve PCV with Active Valve C B D Alright, shows what active exhalation devices actually do, move to earlier? A

Active Exhalation Valve During inspiration, the valve is closed with the force of the insp pressure setting Allows coughing or spont breathing at upper pressure level by venting excess pressure and flow (PCV or BiLevel) 40 PCIRC cmH2O INSP L min EXP 30 20 10 -20 80 60 -80 V . 4 8 12s 2 6 Spontaneous Efforts PCV W/O Active Valve PCV with Active Valve Better than previous slide.

Esens Exp sens% Peak insp flow @ which ventilator cycles from insp to exp Only active in spont modes PS, VS, TC Explain Esens on all vents here.

Dsens Setting specifies allowable % of volume loss, which causes ventilator to declare a disconnect Doesn’t explain anything! Meant for leaks in system, or patient, adapts to that – i.e. BP vistula

Rise Time % Allows RT to adjust how quickly ventilator generates insp press for pressure-based breaths Larger % = reaches P faster ex. 90% Smaller % = reaches P slower ex. 10% Active in P breaths only VC+, PC, PS, TC, VS, PAV+ Compare to Servo 300

What About New Modes? AutoFlow VAPS CPAP PAV SIMV ILV BIPAP Auto Mode APRV ASB SPONT VS What about new modes? There are so many modes of ventilation out there that it can get a bit confusing. The same mode can even have a different name depending on which manufacture your talking about. Shouldn’t we be talking about TC and PAV? Hate this slide! Are we explaining all of these here? I think just dump it! MMV PLV PRVC PS CMV PPS PCV VCV IPPV 11 12 5 5 5 5 5

BiLevel Ventilation Similar to 840 PCV with active exhalation valve Substantial improvements for spontaneous breathing Better synchronization, more options for supporting spontaneous breathing Spontaneous Breaths Synchronized Transitions This may just confuse our students since we never use bilevel this way. Should they know that in theory you can set it up this way and then move on to APRV? This slide illustrates spontaneous breathing at PEEPH and PEEPL. It is possible to synchronize the transition from PH to PL with the patient’s respiratory cycle (i.e. the fall to PL synchronized with the patient’s expiratory phase. Also, notice at PEEPH that there is a spontaneous breath that is pressure-supported). Also notice at PEEPL that the spontaneous breath is pressure-supported. Spontaneous Breaths P T

BiLevel Settings Mandatory breath-type PC only Spont. breaths PS or TC RR, PEEP high, Time @ PEEP high, PEEP low (RR changes time @ PEEP low) Spont. breaths only during PEEP low time unless higher than PEEP high settings Confusing!

Then What Is APRV? APRV is similar but utilizes a very short expiratory time for pressure release This short time at low pressure allows for ventilation APRV always implies an inverse I:E ratio All spontaneous breathing is done at upper pressure level Spontaneous Breaths P “Release” T 65 65 17 17 17 17 17

Clinical Advantages To APRV ‘Biologically variable tidal volume’ helps to minimize atelectrauma while ventilating using the “open lung” strategy P Spontaneous Breath PEEPH WTF? PEEPL Synchronized Transitions T

Volume Support Spont mode, no set RR Set – Vt, esens, rise time % Similar to Servo 300 As pt does more work, pressure level decreases to target chosen Vt As pt does less work, pressure levels increase to target chosen Vt Slope is rise time %

VC + Dual mode, similar to PRVC Set Target Vt, PEEP, Ti, RR, slope, FiO2, RR 1st breath del a volume-targeted, decelerating flow waveform breath Measures Raw and Cl Delivers next breath P req to get target Vt Pressure limited to 5 cmH20 below upper pressure limit Why? The primary difference from the PRVC on the 300 is the active exhalation valve and the way the start-up works. Start-up breath is a traditional VC breath; it measures the pressures and then moves into PC-type breaths. If you read the manual, it says that it is basically PC targeted to a VT. Check on the vol targeted breath part.

TC Automatic tube compensation Spont. breath type that attempts to overcome the imposed WOB from an artificial airway How? Set % support Tube type ID tube Slope and esens What is th WOB from an ETT? The resistance to flow – No compliance issues, just the higher the flow, the higher the resistive pressure, meaning the more pressure needed to overcome it. Resistance from the 2 factors – Length and radius/diameter, radius having a much larger impact, so must know sise/diameter, but length can just use ETT vs. trach. There are major problems with this mode as it is not an adjunct, so does not support the above WOB induced by ETT. So it’s useful in spont. breathing during APRV, but of no use to us outside of that as our patients are ventilated because they need more help than to just overcome ETT. If all they need is help overcoming WOB imposed by ETT, why do they need an ETT? If it was added to PSV then it might be beneficial. There would be problems with doing this (other vents do it), in that it is very difficult to compare across patients i.e. one RT places pt on PSV of 5 and TC of 50%, another sets up with PSV of 3 and TC of 70%. Which is getting more support, when can we extubate pt? It’s probably best to leave at a fixed number such as 100% and then wean PSV down to 0

PS Spont. breath type Same as other ventilators discussed

Standard Backup Power Source Battery is spec’d for a minimum of 30 minutes Actual life exceeds 1 hour So what? Check specs 24 20 27 30 30 27

Oxygen Analyzer Auto cal Auto alarms Only seen if FIO2 is out of range Easily replaced Can be disabled MUST hit 100%/O2Cal button after changing to recalibrate 18 18 21 21

840 Respiratory Mechanics Automated Manoeuvres Static mechanics and auto-PEEP manoeuvres Messages appear if measured values are suspect Corrective action suggestions also appear

Respiratory Mechanics Measurements Static Mechanics and Auto-PEEP Plateau Pressure 15 cm PEEP 5 cm VTE 500 cc Peak Flow = 60 L/min

Respiratory Mechanics The gold standard for measuring compliance and resistance utilizes a volume breath delivered with a square wave flow and adequate plateau 40 PCIRC cmH2O INSP L min EXP PLOT SETUP 30 20 10 -20 80 60 -80 V . 4 8 12s 2 6 UNFREEZE Flow and Stiffness Stiffness Alone Resistance is completely bogus because so much is based on flow. At low flows, it is unimportant, at high flows very relevant. But no one really measures it. Really, it would help you in trending asthmatics, but you don’t want to put a plateau on an asthmatic and blow a pneumo. No Flow

Respiratory Mechanics: Requirements For Accuracy No significant leaks Patient should be at rest Should account for circuit compliance, especially in pediatrics With leak cannot hold a plateau, so will either get a false number or an error code. Patient can’t be making spont. effort, either insp or exp, or actually any muscle tightness. The question is, is this a false condition? Really, is a patient completely at rest? As soon as they start triggering or spontaneously breathing it becomes challenging to get accurate results, and results are likely to include some error. Don’t create autopeep, or restrict exhalation, but you may temporarily do so by performing test. Allow this to return to baseline prior to performing next test.

Inaccuracies in Calculating Respiratory Mechanics Inaccurate peak pressure, plateau pressure, or PEEP pressure will make results unreliable Many times these inaccuracies go unnoticed, resulting in clinicians using poor values or losing trust in measurements First statement ok, second one brutal.

Patient Effort During Inspiratory Plateau Patient Inspiratory Efforts Plateau Pressure = ??

Plateau Time Too Short P T Results in falsely low compliance value Displayed Plateau Pressure 20 cm PEEP 5 cm Actual Plateau Pressure 15 cm VTE 500 cc P T ?????????????????????????? 500 20-5 = 33 ml / cmH20 500 15 - 5 = 50 ml / cmH20 Results in falsely low compliance value

Static Compliance and Leaks Displayed Plateau Pressure 10 cm PEEP 5 cm Actual Plateau Pressure 15 cm VTE 500 cc P T My question is, which tidal volume are you using here? Are you using set, or exhaled? If using displayed, it will be much lower as it will have lost more volume from the leak. The point is that you as a clinician need to recognize these problems when doing your test and understand that your result is inaccurate and why. 500 15-5 = 50 ml / cmH20 500 10 - 5 = 100 ml / cmH20 Results in falsely high compliance value

Inspiratory Pause Pressing Inspiratory Pause once Schedules an automatic inspiratory pause manoeuvre During next scheduled inspiration, the inspiratory and expiratory valves will close and pressure will equilibrate in the circuit

Inspiratory Pause Pause continues until stability has been reached or 2 seconds has elapsed, whichever is first Waveforms trace will freeze, and the values for compliance and resistance will be displayed To extend pause beyond 2 seconds, hold down the Insp Pause key throughout the manoeuvre

840 Static Mechanics Compliance can be calculated for all mandatory breaths Resistance can only be calculated for volume-based, square wave mandatory breaths Why? Because resistive pressure is changing throughout the breath on a PC or VC+ type of breath, making a calculation is impossible.

840 Auto-PEEP Manoeuvre Press Exp Pause key once to schedule automatic expiratory pause manoeuvre During the next exhalation, the inspiratory and expiratory valves will close and pressure will equilibrate between the circuit and the patient Explain what is happening. What is Autopeep? Peep in the chest that is not measured or picked up at the sensor. Sensor is just before the exhalation valve. What we are looking for is the actual peep, or the total peep in the patient! But look at your flow graphics; you must have exp flow to have a measureable autopeep. This doesn’t mean that there can’t be more pressure loculated in the chest – think ball valve effect at the end of the ETT. Again, why do we measure autopeep? So we can match to help pt trigger. But we can only measure if patient is not making any efforts. Any effort will nullify the test. So if they are in PSV, how do we get a result? You could switch them to a control mode and ask them to not take any breaths. Pt may or may not be able to do this for you; it’s questionable how accurate the test would be. But for sure it is of minimal help because as soon as you change them to a spont. mode, their Ti and Te are going to change which means their autopeep is going to change. Remember, peep is at the end of exhalation: if the length of exhalation changes, the autopeep will change. P Exhalation valve closes T

840 Auto-PEEP Manoeuvre Pause continues until stability has been reached or 2 seconds has elapsed, whichever is first Graphics screen will be automatically called up if not active Trace freezes, and the values for Total PEEP and Intrinsic PEEP are displayed Pause can be extended beyond 2 seconds by holding down the Exp Pause key throughout pause It may take much longer than 2 seconds on a COPD patient to get an autopeep.

Proportional Assist Ventilation Spontaneous breathing mode No user or preset target pressure PAV is an amplifier of patient effort Patient controls breath pattern and target Vt Supports a percentage of WOB from 5 - 95%, with the patient taking on the rest of the work An update over PSV, PSV being around since the 70s. The only updates since then are improved sensitivity, ability to monitor, and Esens. PAV tries to take advantage of the improvement in technology since then. Think of how phones have changed (maybe add in some pictures of technology from the 70’s). Most of our students weren’t even born at that time. Vent randomly estimates resistance and compliance every 4 - 10 breaths, re-evaluates flow every 5 milliseconds.

PAV+ WOB is from patient compliance, airway resistance, and artificial airway resistance Ventilator regularly assesses patient compliance and resistance Requires a/w type and size to calculate resistance Estimates WOB in Joules/L Only other WOB is to overcome autopeep to try. Measures flow generated by the patient and augments their effort based on the % support that you have entered. Basically, the more work they do, the more support they will receive, so support varies on a breath-by-breath basis. The harder they start to work, the more you support them. ETT vs. trach and tube diameter to account for WOB from airway. WOB total and what portion patient is doing are shown graphically.

More PAV+ % support, sensitivity, PEEP, O2, tube ID, tube type Set Not used commonly clinically… yet ETT vs. trach and tube diameter to account for WOB from airway. Why isn’t it being used? Clinician comfort and staff/unit biases. Makes more sense than PSV, but people are much more comfortable using PSV and know what to look at and what they are seeing. It might be up to newer employees to change the culture, bringing in newer thoughts and modes.

Please don’t forget to access Web CT and click on the PB840 icon to view the introduction video to this ventilator

References Nellcor Puritan Bennett, tyco Healthcare. Cairo, J.M.; Pilbeam, S. Respiratory Care Equipment, 8th Edition. Mosby’s.