1. Newer modes of Mechanical Ventilation Dr. T.R. Chandrashekar Director Critical Care K.R.Hospital Bangalore
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3. SIMV PCV ACV CMV Basic Modes? PS Newer [Alternative] Modes ? Volume support (VS) Volume Assured Pressure Support (VAPS) Pressure regulated volume control ventilation (PRVC) Mandatory minute ventilation (MMV) PROPORTIONAL ASSIST VENTILATION(PAV) ADAPTIVE SUPPORT VENTILATION(ASV) Smartcare/Automatic tube Compensation BIPAP/DUOPAP Airway pressure release ventilation (APRV ) High Frequency Ventilation/oscillation Partial Liquid Ventilation (Perflurocarbon) Neurally Adjusted Ventilatory Assist (NAVA) Fractal ventilation
4. What are Physicians Doing? 1,638 patients in 412 ICUs 47% Assist-Control Ventilation 46% Pressure Support and/or SIMV 7% Other Variability in modes across nations No variability in settings Esteban et al, AJRCCM 2000; 161:1450-8
5. Modes of Ventilation during Weaning Esteban et al, AJRCCM 2000;161:1450 PS SIMV + PS Intermittent SB trials Others SIMV Daily SB trials Number of ventilated patients, (%)
11. Trigger in conventional modes We are targeting the last part of the cycle and Also add the delay from the Y piece or the machine end Trigger delay is inbuilt in the old modes
13. Sinderby et al, Nature Med 1999;5:1433 Time (s) 0 1 4 3 2 0 1 4 3 2 Airway Pressure Trigger Onset of diaphragmatic electrical activity Onset of ventilator flow Neural Trigger 0 20 -5.0 0.0 0.0 0.5 -1 0 1 Flow (l/s) Volume (l) P es (cm H 2 O) P aw (cm H 2 O ) Missed breaths
14. PAV+ vs. PCV /PSV example PCV 15 cmH2O PAV+ at 75% Compared to PCV, the PAV+ mode better matches patient’s effort to ventilator output. PAV+ P T P T P T P T P T P T Proportional support has synchronised inspiration to expiration cycling
15. These can lead to disuse atrophy of the respiratory muscles (VIDD) or lowering of the CO 2 set point. Either case can delay weaning and result in more ventilator days! or M Younes. Proportional Assist Ventilation, A New Approach to Ventilatory Support. Theory. Am Rev Respir Dis 1992;145:114-120. The practitioner’s typical response to an increase in demand is what? we need to select a level of pressure support that is “ not too low, not too high, but just right”. Proportional support to patients effort which can change from breath to breath is ideal Increase support Sedate
16. Proportional support is vital No Diaphragm activity Missed breaths Possibly to much pressure support which had suppressed the diaphragmatic activity Increase the PS
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20. Closed Loop Ventilation Ventilator Patient Clinician Open Loop Ventilation Basic modes- PS/SIMV/CMV Set volume/presuure/flow Patient has to adapt to the ventilator Gets feedback on lung resistance/compliance Adapts to the patient- ASV/PAV+/NAVA Smartcare Intensivists brain
26. Lung Compliance Changes and the P-V Loop Volume (mL) PIP levels Preset V T P aw (cm H 2 O) Volume Targeted Ventilation COMPLIANCE Increased Normal Decreased
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28. Lung Compliance Changes and the P-V Loop Volume (mL) Preset PIP V T levels P aw (cm H 2 O) COMPLIANCE Increased Normal Decreased Pressure Targeted Ventilation
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31. 60 -20 60 Flow L/min Volume Switch from Pressure control to Volume control L 0 0.6 40 VAPS-Volume assured Pressure Support Normal PS If Compliance decreases P aw cmH 2 0 Set tidal volume cycle threshold Set pressure limit Tidal volume met Tidal volume not met Flow cycle
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34. PAV+ uses the compliance and resistance information collected every 4-10 breaths to know what it’s fighting against . PAV+ uses the flow and volume information collected every 5 milliseconds to know what the patient wants. PAV+ combines this data with the %Supp information input by the clinician to determine how much pressure to supply to the system. PAV+
35. The clinician will NOT set a rate, tidal volume, flow or target pressure. Instead, the clinician will simply set the percentage of work that the ventilator should do. f %Supp x x x x PAV+ V . V t P i
36. PAV+ Start patients at 70% and wean back to stabilize When disease process has sufficiently reversed, decrease %Support over 2 hr intervals
37. + PAV+ Potential Benefits 1. Comfort. 2. Lower peak airway pressure. 3. Less need for paralysis and/or sedation. 4. Less likelihood for over ventilation. 5. Preservation and enhancement of patient’s own control mechanisms such as metabolic ABG control and Hering-Breuer reflex. Some patients have a high rate normally, so a high rate on PAV + may or may not reflect distress; check other signs; Try increasing assist to see if rate goes down Don’t be surprised if RR climbs when switching from other modes
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40. APRV settings P aw T high (4-5) Sec T low P high P low ( 1 sec) Time-triggered, Time-cycled, Pressure-limited, Spontaneous breathing is allowed at any point during the ventilatory cycle FLOW P high -This parameter is set with the goal of improving oxygenation. P low -The setting of this parameter has the goal of facilitating ventilation or CO2 clearance. It is this inverse inspiratory:expiratory (I:E) ratio that distinguishes APRV from bi-level positive airway pressure (BiPAP=1:1)
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44. Smartcare These therapeutic measures are based on a clinical protocol that has been tested and verified during several years of development ..
NAVA Training Presentation 2007 NAVA Training Presentation.ppt The electrical discharge of the diaphragm is captured through the introduction of an Edi Catheter fitted with an electrode array. Since NAVA uses the Edi to control the ventilator, it is important to understand what the signal represents. All muscles (including the diaphragm and other respiratory muscles) generate electrical activity to excite muscle contraction. This electrical excitation is controlled by nerve stimulus and controlled in magnitude by adjusting the stimulation frequency (rate coding) or by adjusting the numbers of nerves that are sending the stimulus (nerve fiber recruitment). Both, the rate coding and nerve fiber recruitment will be transmitted into muscle fiber motor unit action potentials which will be summed both in time and space producing the intensity of the electrical activity measured on the muscle. To reduce the influence of external noise, the measurement of the muscle electrical activity is performed by bipolar differential recordings, where the signal difference between two single electrodes is measured. For example the resting Edi measured with electrodes in the esophagus in a healthy subject typically ranges between a few and 10 μ V. Patients with chronic respiratory insufficiency may demonstrate signals 5-7 times stronger. Due to the differential recording and low signal amplitude, measurement of Edi is sensitive to electrode filtering, external noise, and cross-talk from other muscles e.g. the heart which produces electrical amplitudes of about 10-100 times that of the diaphragm. Since, the Edi must always be present to initiate a contraction of the diaphragm it should always be possible to record the signal in healthy subjects
LRF -This slide shows how PAV+ software may improve ventilator synchrony. -The top three boxes represent pressure vs. time for PCV while the bottom three boxes represent the same thing for PAV+ software. -The green line represents the effort input from the patient’s diaphragm and the red line represents the pressure output from the ventilator. -In PCV the ventilator’s output is the same despite changes in the diaphragm’s input. -In PAV+ mode, the machine’s output mirrors the input of the diaphragm. -If the patient pulls a little bit, the vent pushes a little bit. If the patient pulls a lot then the vent pushes a lot.
LRF M Younes. Proportional Assist Ventilation, A New Approach to Ventilatory Support. Theory. Am Rev Respir Dis 1992;145:114-120.
LRF -Potential benefits as listed by Dr Younes in one of his early papers. M Younes. Proportional Assist Ventilation, A New Approach to Ventilatory Support. Theory. Am Rev Respir Dis 1992;145:114-120.
So, there are only four settings for APRV as seen on this graph of airway pressure and flow : • the high pressure, P- high, the CPAP level to keep the lungs open, • the duration, or time, that the CPAP pressure is held at the airway, called T- high, • the release pressure, P- low, that allows additional CO2 removal, • and the duration, or time, that pressure is released, called T- low. We see flow in and out of the lungs with spontaneous breathing during the time that the higher pressure is applied to the airway. And here we see the larger flow, or exhaled volume, from the lungs during the release. Again, it’s very important that the release time be short so that lung volume is maintained. How can we assess that? Well, I’d love to be able to actually measure FRC at the bedside in the ICU, but that really isn’t practical today. Notice that the expiratory flow tracing during the release doesn’t reach the zero line before the high pressure is re- applied. Because flow is still coming from the lungs, we know that volume remains in the lungs. In other words, we are intentionally trapping gas in the lung by limiting the release time. When we set T- high, we are really setting the frequency of releases, which is like setting the ventilator rate.
It was decided that the third knob would be Minute Volume: the volume of gas delivered to the patient every minute. So there we have it: One mode. And three controls. Three knob ventilation. The first design goal. [Click: Next slide.]
Then, just once, and never again for this patient , you enter an indication of the patient’s body size. And the body size indicator that ASV uses is Ideal Body Weight . That’s a reference point for ASV to use. If you are not sure where to get this information, you will find it on a chart hanging on the ventilator. You look up the patient’s height. And the table gives you his ideal body weight. [Pause.] And that’s it! That’s what you have to do. From this point on, ASV does everything else automatically. Pretty simple... You set up the minute volume. ASV does everything else. You can see why we say that ASV is suitable for non-specialist operators! So! What exactly does ASV do? [Click: Next slide.]
[Point out to the audience that the operator is doing nothing!] This is what happens – and happens completely automatically: ASV starts by giving the patient three test breaths to determine – amongst other things – the compliance, or pressure/volume ratio of the lung. Remember: ASV only delivers these three test breaths once. [Click: Next slide.]
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