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Non conventional ventilator modes
 

Non conventional ventilator modes

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    Non conventional ventilator modes Non conventional ventilator modes Presentation Transcript

    • Al jadidi Sulaiman Moderator: Dr Mohd Ridhwan 01/03/12
    • History
      • Negative pressure ventilation
      • -From the mid 1800-1900s
      • -applied negative pressure around the body or thoracic cavity
      • -also known as 'iron lungs'.
      • -Patients with chronic paralytic disorders were successfully ventilated on this cuirass ventilators at home for 25-30 years.
      01/03/12
    • Fell O-Dwyer Device 1888 01/03/12
    • Scandinavian Polio epidemic 1952
      • - Between July-December of 1952, in Copenhagen,
      • - 2722 pt with poliomyelitis were treated in which 315 patients required ventilatory support.
      • Towards the end of the epidemic a few positive pressure ventilators were invented  (the Engstrom, Lundi and the Bang)
      01/03/12
    • Era of respiratory intensive care
      • After polio epidemics, the 1960’s became an era of respiratory intensive care.
      • Positive pressure ventilation with use of an artificial airway replaced the negative pressure technology of respiratory support.
      • The first type of ventilator was pressure cycled (PCV).
      • Eg: Bird mark 7 and Bennet PR2
      01/03/12
    • 01/03/12
    • Present day… 01/03/12
    • 01/03/12
    • The Support and Controlled Modes
      • Pressure Support Ventilation (PSV)
      • Continuous Positive Airway Pressure (CPAP)
      • Bilevel Positive Airway Pressure (BiPAP)
      • Positive End Expiratory Pressure (PEEP)
      • Volume Assured Pressure Support (VAPS)
        • Often just Volume Support
      • Proportional Assist Ventilation (PAV)
        • New version of Volume Assured, Volume Support
      • Volume Control (VC)
        • Truly is CMV but used to describe AC in day to day convo
      • Assist Control Mode Ventilation (ACMV)
        • Often shortened to AC
      • Controlled Mode Ventilation (CMV)
        • Same as VC
      • Pressure Control Ventilation (PC)
      • Synchronized Intermittent Mandatory Ventilation (SIMV)
      • Pressure Regulated Volume Control (PRVC)
      • Volume Controlled with (VC+)
        • What PRVC should have been
      • Inverse Ratio Ventilation (IRV)
        • Is either PC or VC
      01/03/12
    • Hybrid modes and Concepts
      • SIMV with Pressure Support (SIMV-PS)
        • Can be volume or pressure contolled
      • Airway Pressure Release Ventilation (APRV)
      • Bilevel Ventilation Mode (BiLevel)
      • Mandatory Minute Ventilation (MMV)
      • High Frequency Ventilation
      • Neurally-adjusted Ventilatory Assist
      • Fractal Ventilation
      • Vent dyssynchrony
      • Partial Liquid Ventilation
      • Cflex
      • Automatic Tube Compensation (ATC)
      01/03/12
    • The ABC’s of breath delivery 01/03/12
    • % Rise Time 01/03/12
    • Setting Rise Time
      • Monitor volume delivery
      • For pts with increased flow demand use higher rise time
      • Obstructive pts may be comfortable with lower rise time
      • Use f/Vt, P0.1 & observe for signs of dysynchrony
      01/03/12
    • Expiratory Sensitivity (Esens) % 01/03/12
    • Selecting termination criteria
      • Improve pt-ventilator interaction
      • -decrease WOB
      • -increase synchrony
      • Adjust insp time
      • -paed pts & restrictive conditions  decrease
      • -obstructive airway disease  increase
      • -use f/Vt & P0.1 and ventilator graphics to monitor dysynchrony
      01/03/12
      • AIRWAY PRESSURE RELEASE VENTILATION
      • ( APRV )
      01/03/12
    • 01/03/12
    • APRV defined
      • Described as continuous +ve airway pressure (CPAP) with
      • Regular, brief, intermittent release in airway pressure
      • Release phase  alveolar ventilation & removal of Co2
      • Capable of augmenting alveolar ventilation in spont breathing pt OR accomplishing complete ventilation in apnoeic pt
      01/03/12
      • Thus CPAP level drives oxygenation, while the time released aid in co2 clearance
      • Is a time triggered, pressure-limited, time-cycled
      • Allows spontaneous breathing thru’out the entire vent cycle
      • Indications: - ALI or low compliance lung ds, other airway disease
      01/03/12
    • 01/03/12
    • Terminology
      • 4 commonly used term:
      • Pressure high – P high / CPAP level / inflating pressure / P1
      • P low – airway P resulting from the pressure release. aka PEEP level / release pressure / P2
      • T high –length of time for which P high is maintained
      • T low – length of time for which P low is held
      01/03/12
    • 01/03/12
    • 01/03/12
    • Advantages
      • Results in lower peak Paw – a/w reduced risk of vent-associated lung injury
      • Requires lower MV – less dead space ventilation
      • Lung protective strategies:
      • - preset P limit/prevent over distension of alveoli & high vol lung injury
      • - APRV affect tidal vent by decreasing rather than increase airway P.
      01/03/12
      • Animal studies indicate that APRV doesn’t compromise circulatory fx & tissue oxygenation
      • Allow spont breathing to occur at any point in the resp cycle
      • Decrease need for sedation or neuromuscular blockade
      01/03/12
    • Disadvantages
      • As with other pressure-targeted mode of vent, APRV is affected by changes in lung compliance &/or resistance
      • Staff stress with the implementation of APRV
      • Dyssynchrony with APRV has not been identified as problem in the majority of the literature
      01/03/12
    • Application of APRV
      • Set P high at the plateu P, with ceiling level normally at 35cmH2o
      • P low is set at 0
      • (a P low of zero produced minimal exp resistance, thus accelerate exp flow rates, facilitating rapid P drop)
      • T high is set at minimum 4.0 sec
      • T low is set between 0.5 to 1.0 sec (often at 0.8sec)
      •  Mean Paw = 29.2cm water pressure
      01/03/12
      • Rarely an elevated P high (40-45 cm of water pressure) may be indicated
      • ie pts with low-compliance resp systems ( morbid obesity, abd distension, chest wall oedema)
      • Why T high 4.0sec? : goal is to create cont airway pressure level  recruit collapsed alveoli & maintain recruitment  optimising oxygenation and compliance
      01/03/12
    • T low..
      • Most closely studied of the 4 parameters
      • Longer T low in animal with ALI was a/w ↓ in arterial oxygenation & accumulation of hgic fluid in the ETT
      • Excessively long  alveolar derecruitment, atelectasis, airway closure during the release phase
      • Insufficient T low  inadequate exhalation, dead space vent, hypercapnia, haemodynamic compromise
      01/03/12
      • Transition to APRV may not result in instant improvement in oxygenation
      • Sydow et al demonstrated that the max beneficial effect of APRV upon oxygenation occurred 8H after implementation, with no further improvement after 16H
      01/03/12
    • Weaning of the APRV
      • Method to reduce support is thru manipulation of P high & T high
      • P high will be lowered 2-3cm of water pressure at a time
      • T high will be lengthened in 0.5-2sec increment
      • The goal is to arrive at straight CPAP; usually at 12cmH20  then wean CPAP @ extubate at 6-12cmH20
      01/03/12
    • 01/03/12
    • 01/03/12
    • 01/03/12
    • Bilevel ventilation methods:
      • Ventilation methods that allow spontaneous breathing at two airway pressures:
        • BiPAP (Drager E-4 & E-2 dura)
        • BiLevel (NPB 840)
        • APRV (NPB 840, Drager E-4 & E-2 dura)
      • Uses two levels of pressure for two time periods
      • Mandatory breaths at the higher pressure are time cycled
      • Spontaneous breaths can be pressure supported
      01/03/12
    • 01/03/12
      • Uses 2 pressure levels for 2 time periods
      • PEEP low & PEEP high , T high and T low
      • Patient triggering & cycling can change phases
      01/03/12 P T Synchronized Transitions PEEP HIGH PEEP LOW T LOW T HIGH Synchronized Transitions
      • Pressure support may be applied at both pressures during a spont. breath
        • If PS is set higher than PEEP H , the PS pressure is applied to a spontaneous effort at upper pressure
      01/03/12 PEEP High + PS P PEEP L PEEP H Pressure Support
        • If PS is set lower than PEEP H , PS is applied to patient efforts at the lower pressure, PEEP L
      01/03/12 Spontaneous Breaths P Pressure Support T
      • PROPORTIONAL ASSIST VENTILATION
      • (PAV)
      01/03/12
    • History
      • The PAV algorithm was invented and patented in 1990 by Dr. Magdy Younes University of Manitoba, Canada.
      • Manual versions of PAV available on Respironics and Dräger ventilators
      • Closed-loop PAV (PAV+) is a software package for the PB 840 ventilator
      01/03/12
      • PAV is a spontaneous breathing mode that offers
      • assistance to the patient in proportion to the patient’s effort
      • The technique uses the equation of motion and provides ventilatory support in proportion to patient effort.
      • Compared with most ventilatory modes, it has no constraints in terms of flow, volume, and timing, which are "automatically" controlled by the patient's breathing effort.
      01/03/12
      • When the patient ends inspiratory muscle effort, the ventilator rapidly decreases support.
      • In contrast to some other modes of ventilation such as pressure support ventilation (PSV). During PSV, the patient's inspiratory effort may stop, but this may not be detected by the ventilator, and the ventilator may continue to deliver pressure and flow to the airway opening, inflating the patient at a time when the patient is trying to exhale.
      • This is a major cause of patient-ventilator asynchrony
      01/03/12
      • There is great variability in flow and tidal volume on a breath-by-breath basis in most patients.
      • The principle underlying PAV allows the ventilator to deliver the flow and pressure required by the patient on a moment-by-moment basis.
      01/03/12
    • 01/03/12
    • Clinical application 01/03/12
    • 01/03/12
    • 01/03/12
    • Indication in ICU
      • Spontaneously breathing patient
      • Intact respiratory drive
      • Intact neuromuscular function
      • Generally, a patient considered suitable for pressure support ventilation could be considered for PAV.
      01/03/12
    • What to aspect..
      • Higher than expected RR
      • - can be as high as 40bpm
      • - assess pt for comfort
      • Lower then expected tidal volumes
      • MV value may be more variable
      01/03/12
    • Advantages..
      • It enhances the patient's control of his/her ventilatory pattern  comfort
      • Patient ‘drives’ the ventilator
      • Avoid ventilator over-assistance
      • # over assistance  resp muscle disuse + central apnoea
      • Less pt-ventilator asynchrony
      • Continuous monitoring of pt’s compliance & resistance
      01/03/12
    • Disadvantages..
      • Changes in respiratory system mechanics occur on an ongoing basis in patients with respiratory failure
      • Effective and accurate algorithms to measure mechanics on an ongoing basis are necessary
      • ie: resistance of the respiratory system with secretions
      • Dev of autoPEEP
      01/03/12
      • PAV is difficult to understand !!
      • In summary,
      • -breath-by-breath variability is physiologic, and has pathophysiologic importance.
      • -It may improve patient comfort during mechanical ventilation, and there is some suggestion that it may improve oxygenation.
      01/03/12
      • Thank you for listening…
      01/03/12
    • References..
      • www.anaesthesiauk.com
      • Transitioning from mechanical ventilation, Terry L. Forette ,2006
      • Airway pressure release ventilation: Theory & Practice, M.Habashi et al 2001
      • New technique in mechanical ventilation help keep the patient more comfortable, Arthur S. Slutsky, 2002
      01/03/12