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Advanced modes of Mechanical Ventilation-Do we need them?
- 1. Advanced Modes of Mechanical Ventilation Dr. T.R. Chandrashekar Intensivist K.R.Hospital Bangalore
- 5. Synchronised Intermittent Mandatory Ventilation Pressure Controlled Ventilation/Assist Volume controlled ventilation/Assist Basic Modes? Pressure Support Ventilation PS BASIC Modes SIMV VC AVC PC
- 7. Smartcare ASV NAVA PAV PPS Advanced/ Closed loop ventilation APRV/BIPAP DUOPAP Advanced Modes that are going to stay in practice …..
- 8. 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
- 9. 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, (%)
- 12. Goals of ventilation Setting the Ventilator Ventilator-Induced Lung Injury Lung protective ventilation Gas Exchange PaO2/PaCo2 Accepting hypoxia and hypercarbia Due to low volume ventilation Patient Comfort Synchrony sedation /paralysis Early weaning Hemodynamics
- 13. Patient effort Ventilator assistance . Kondili et al, Br J Anesthesia 2003;91:106 Resistive load Elastic load . Pmus Paw Resistance x flow Compliance x volume + + = Equation of motion for Mechanical Ventilation Controlled ventilation Pt/vent work shared-interaction
- 15. Conventional Modes( Open loop) Basic modes-CMV/SIMV/PS Clinician Ventilator Patient Once parameters are set there is no sharing of information between the ventilator and the patient same settings are delivered each breath unless the clinician wants to change the settings Patient has to adapt to the ventilator
- 16. Advanced modes- Closed Loop Ventilation Closed Ventilation-ASV/PAV+/NAVA Clinician Ventilator Patient % of support/ parameters are set- there is sharing of information between the ventilator and the patient which leads to change in every delivered breath appropriate to patients lung characteristics –Resistance / compliance /Edi Ventilator Adapts to the patient Information is feed back from pt to vent
- 17. Advanced Closed Loop Ventilation Advanced Closed Ventilation- Smartcare/NeoGanesh Clinician Ventilator Patient Intensivists brain What SmartCare/PS does Monitor the patient for at least 15 min Classify situation into one of 8 diagnoses A clinical protocol is stored in the knowledge base Adjust Pressure Support. Step width varies based on actual pressure, humidification etc. Monitor ≥ 15 min Select therapeutic measure Classify every 5min Adjust Pressure Support < 4 cmH2O
- 18. Anything close to normal physiology is Advanced What is close to physiology in positive pressure ventilation? Ventilation starts /ends / and is as much as the brain wants
- 20. NAVA PAV+/ASV Respiratory center output Peripheral nerve transmission Muscle Electrical activation Contraction Lung distension Respiratory compliance Airway resistance Airway opening pressure Flow/volume Alveolar ventilation Gas exchange Blood gases Proportionality of support means Support stats and ends and is as much as the Brain wants Chemo receptors Lung and airway reflexes Respiratory muscle afferents If ventilator uses any of These parameter to alter Breath pattern then ventilation will Be more synchronized and Proportional to what brain wants
- 21. Proportional Assist Airway assistance
- 22. 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
- 23. What are the problems with conventional modes ? Trigger delay/Synchrony issues
- 24. Phases of ventilatory cycle Delay, Missed breaths Flow not proportionate to patients effort -dyssynchrony/overassist VIDD/ Runway Asynchrony can occur at the start of a breath (trigger asynchrony Asynchrony can occur during the breath (flow asynchrony Asynchrony can occur at the end of a breath (cycle or termination asynchrony).
- 25. Old modes trigger delay
- 26. Trigger in conventional modes Time delay We are targeting the last part of the cycle and Also add the delay from the Y piece to the machine end Trigger delay is inbuilt in the old modes
- 27. Ventilator TE Neural TI Neural TE Trigger delay Ventilator TI Asynchrony Synchrony BRAIN Ventilator Missed breaths/flow asynchrony Runways INS/Exp Cycling asynchrony
- 29. NAVA Neurally adjusted ventilatory assist Recorded electrical activity of the diaphragm % of support is based upon a gain factor, set by the clinician, which translates a given electrical activity of the diaphragm into pressure assist Translates into a positive relationship between ventilator assistance and patient effort Esophagus
- 30. NAVA
- 31. NAVA-what the brain wants? Output is after analysing many inputs
- 32. 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
- 33. Better synchrony Studies prove Better quality of sleep and less arousals- PAV+/NAVA Patient may do more work (WOB) on ventilator if there is dys-synchrony between the ventilator and the patient
- 35. Proportional support is vital No Diaphragm activity Missed breaths Over assist leads to increased Tidal volume Auto PEEP –missed breaths and also decreased diaphragm activity Possibly to much pressure support which had suppressed the diaphragmatic activity Increase the PS
- 39. Short of staff Closed loop = Less work in ICU Quick weaning = Short stay in ICU Easy to use = Less need for specialists Low costs High patient safety Advantages:
- 40. The Future of Mechanical Ventilation Automated mechanical ventilation is the future
- 46. DUAL MODES VAPS
- 47. 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
- 49. 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
- 52. 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
- 54. PAV+/PPS
- 56. 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+
- 57. 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
- 58. PAV+ Start patients at 70% and wean back to stabilize When disease process has sufficiently reversed, decrease %Support over 2 hr intervals
- 59. + 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
- 64. Spontaneous ventilation in assisted breaths Diaphragm with sedation P abdominal Area of increased ventilation Area of increased perfusion Risk of over distention Risk of atelectasis Good ventilated area Area with good perfusion R ! R ! R ! Spontaneous breathing Diaphragm with low sedation1 Spontaneous ventilation in assisted breaths Controlled ventilation Better V/Q Less VILI R ! R ! R !
- 65. 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 or more) Inverse ratio ventilation
- 67. 5 possible breath types in BIPAP High incidence of asynchrony issues
- 69. Pplat = Palv; Pplat = Transpulmonary Pressure? transpulmonary pressure = 45 cm H 2 O 0 5 10 15 20 25 30 -5 -10 -15 45 cms of H2O PCV 20 cm H 2 O, PEEP 10 cm H 2 O; Pplat 30 cm H 2 O -15 cm H 2 O Active inspiratory effort
- 75. Smartcare These therapeutic measures are based on a clinical protocol that has been tested and verified during several years of development ..
- 79. Thank you Innovation and Automation is the future
Notas do Editor
- 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.
- 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
- So: There is less work to do in the ICU Patients have shorter stays in the ICU And there is less need for specialists in the ICU All this means: Low costs: you need fewer resources to do the same job. High patient safety: the closed loop and the quick weaning always enhance safety. [Click: Next slide.]
- 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.
- We’ve used a variety of mechanical ventilation strategies for low lung volume disorders. Ventilation with normal tidal volumes but low PEEP level requires high pressures, and the shear forces created during the inflation- derecruitment- reinflation sequence can cause severe lung injury. Using normal tidal volumes with high PEEP means even higher pressure, and can overdistend relatively healthy lung tissue. In an effort to protect the ARDS lung from further, ventilator- induced injury, some clinicians advocate a so- called “open lung approach” of high PEEP and tidal volumes of 6 mL/ kg of body weight, or less. This may result in high arterial CO2, referred to as “permissive hypercapnia”. Dr. John Luce from UCSF points out, however, that hypercapnia may be unavoidable with this strategy in patients with severe Acute Lung Injury. Really, the only permission given is to ourselves as clinicians, making high CO2 “O.K.”, which makes us feel better. But not the patient. Hypercapnia is uncomfortable, and patients usually require heavy sedation to control their ventilation. A large, prospective, multicenter trial of high versus low tidal volume use in ARDS is currently underway in the U.S.
- Peak and Mean airway pressures are reduced Less invasive, less mechanical Weaning is smooth and effortless Less sedation and muscle relaxants Spontaneous breathing contributes to better gas exchange and secretion clearance. Greater comfort and less stress for patients
- 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.
- The previous case was a best case example. During weaning, patients often show signs of ventilatory instabilities such as Hyper or Hypoventilation, tachypnea, or are simply not adequately ventilated. SmartCare classifies these situations into 8 different diagnoses, and adapts the pressure support accordingly to bring the patient back-on-track. For every diagnosis a different set of therapeutic measures is incorporated into the protocol.