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Ventilation Modes and Current Trends

Ventilation Modes and Current Trends. Denny Gish, BSRT, RRT Clinical Specialist, Adult Respiratory Care Legacy Emanuel Hospital and Health Center. Objectives. Review current ventilator modes Mode descriptions Review trends in Respiratory Care ARDS Network recommendations Best PEEP

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Ventilation Modes and Current Trends

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  1. Ventilation Modes and Current Trends Denny Gish, BSRT, RRT Clinical Specialist, Adult Respiratory Care Legacy Emanuel Hospital and Health Center

  2. Objectives • Review current ventilator modes • Mode descriptions • Review trends in Respiratory Care • ARDS Network recommendations • Best PEEP • Recruitment Maneuvers • Identify various methods of High Frequency Ventilation

  3. Modes of Ventilation The Critical Question... How do you choose ?

  4. What Starts the Breath ? • Controlled or timed breaths • Controller is really an interval timer • Assisted breaths are triggered by patient inspiratory effort in addition to Controlled breaths • Spontaneous breaths allowed in some modes

  5. What Ends the Breath ? • Preset pressure reached • Preset volume is delivered • Preset time has elapsed

  6. Ventilator Settings • Mode: Volume control, Pressure control, Spontaneous, etc(how the breath goes in) • Vt:Tidal Volume(size of breath 8-10 cc/kg, 4-6cc/kg for ARDS) • “Volutrauma” can be as damaging as “Barotrauma” • f : Frequency(rate # breaths per minute 10-15 bpm) • PEEP:Positive End Expiratory Pressure(>/= 5 cmH20) • IP:Inspiratory Pressure(ideally < 30 cmH20) • FIO2: Fraction of Inspired Oxygen All ordered by MD or by unit protocol • Ti or V: Inspiratory time or Flowrate (how long it takes the breath to go in - generally per RT discretion based on pt comfort & condition)

  7. Ventilator Measurements • Vt = tidal volume - cc’s or ml’s • f= frequency, # breaths per minute - bpm • Ve = minute ventilation ( Vt* f) liters per minute • I:E Ratio= insp time to exp time (norm is 1:2) • PIP (or PAP) = Peak Inspiratory Pressure – cmH20 • MAP = Mean Airway Pressure – cmH20 • PEEP = Positive End Expiratory Pressure – cmH20 • Pplat = Plateau or Static Pressure (true lung inflation pressure (eliminates airway & tubing resistance) – cmH20 • Cstatic = Static Compliance (normal 40-60 ml/cmH2O) Learn to read measurements off vent screen

  8. Some Basic Modes • Volume Control: set Vt & f, pt may assist • Pressure Control: set IP & f, pt may assist • Synchronized Intermittent Mandatory Ventilation: set Vt & f, pt may take unassisted spontaneous breaths as well • Mandatory Minute Volume Ventilation – MMV: mandatory breaths are only provided if spontaneous breathing is not sufficient and below the prescribed minimum ventilation. • Pressure Support: pt’s own Vt & f, supported by insp boost to augment pt’s insp efforts. Pt may breathe deep or shallow, fast or slow w/o intervention from vent.

  9. Name that Mode of Ventilation Evita XL – Ventilation Modes • CMV– Continuous Mandatory Ventilation *AKA- Assist/Control • MMV– Mandatory Minute Ventilation *AKA-Smart SIMV • PCV–Pressure Controlled Ventilation *used when PIP is >35 • APRV– Airway Pressure Release Ventilation *Low compliance disorders • CPAP-Continuous Positive Airway Pressure – with or without PS

  10. Draeger V 500 Ventilation mode VC-CMV- Draeger XL has CMV, but it is NOT the same! VC-AC–Works like CMV on the Draeger XL VC-MMV-Draeger XL has MMV and it performs exactly like the VC-MMV on the V500 PC-AC – Draeger XL has PCV PC-APRVwith AutoRelease - Draeger XL does not have an autorelease function SPN-CPAP/PS/VS-Draeger XL has CPAP mode that has Pressure Support capabilities, but no Volume Support

  11. Now…Puritan Bennet 840

  12. Viasys Avea

  13. Servo I buy

  14. More Advanced Modes • Volume Support: pt’s own f w/PS for goal Vt. Vent guarantees Vt by adjusting the PS based on lung compliance and/or resistance to ensure a preset tidal volume. • Pressure Regulated Volume Support:set f and goal Vt, pt may assist. Ventilator automatically adjusts pressure up or down, from breath to breath, as patient's airway resistance and lung compliance changes, in order to deliver the goal tidal volume. • Volume Control Plus: same as PRVC • Airway Pressure Release Ventilation: High and low pressures set w/minimal timed releases to facilitate gas exchange, high MAP w/very Inverse I:E ratio. Pt may breathe spontaneously during high pressure holds.

  15. ARDS Current Definition The 1994 North American-European Consensus Conference (NAECC) Criteria: • Onset - Acute and persistent • Radiographic - Bilateral pulmonary infiltrates • Oxygenation - regardless of the PEEP, with a Pao2/Fio2 ratio  300 for ALI and  200 for ARDS • Exclusion criteria - Clinical evidence of Left Atrial Hypertension or a PAOP of  18 mmHg. Bernard GR et al., Am J Respir Crit Care Med 1994

  16. Traditional Approach High priority to traditional goals of acid-base balance and patient comfort Lower priority to lung protection Low Stretch Approach High priority to lung protection Lower priority to traditional goals of acid-base balance and comfort Tidal Volume Strategies in ARDS

  17. Physiologic Benefits vs Patient-Important Outcomes PaO2 improvement vs Survival Benefit • For ARDS, inhaled nitric oxide improves PaO2, but not mortality (Taylor et al, JAMA 2004;291:1603) • High tidal volumes in patients with ARDS improves PaO2, but mortality is lower for small tidal volumes (ARDSnet, N Engl J Med 2000; 342:1301) • For ARDS, prone position improves PaO2, but not mortality (Gattinoni, N Engl J Med 2001;345:568)

  18. ARDS Network Low VT Trial • Patients with ALI/ARDS of < 36 hours • Ventilator procedures • Volume-assist-control mode • 6 vs. 12 ml/kg of predicted body weight Vt (PBW/Measured body weight = 0.83) • Plateau pressure  30 vs.  50 cmH2O • Ventilator rate 6-35 to achieve a pH goal of 7.3 to 7.45 • Oxygenation goal: PaO2 55 - 80 mmHg, SpO2 88 - 95% ) ARDS Network. N Engl J Med. 2000.

  19. Lung Recruitment • First and foremost performed toprovide an arterial oxygen saturation of 90% or greater at an FiO2 of less than 60% • Recruitment of nonaerated lung units (open-lung concept) but risk of regional lung overinflation : a highly controversial issue!

  20. Recruitment Maneuvers (RMs) • Effective in improving arterial oxygenation at low PEEP and small tidal volumes. • Recruitment maneuvers may be poorly effective or deleterious, inducing overinflation of the most compliant regions, hemodynamic instability, and an increase in pulmonary shunt resulting from the redistribution of pulmonary blood flow toward nonaerated lung regions. • The effect of recruitment may not be sustained unless adequate PEEP is applied to prevent derecruitment. • Many questions still need to be answered

  21. PEEP in ARDS:How much is enough ? • PEEP, by avoiding repetitive opening and collapse of atelectatic lung units, could be protective against VILI • PEEP, has been shown to prevent surfactantloss in the airways and avoid surface film collapse. • The lung is kept open by using PEEP to avoid end-expiratory collapse. • High PEEP should make the mechanical ventilation less dangerous than low PEEP. Levy MM. N Engl J Med. 2004. Rouby JJ, et al. Am J Respir Crit Care Med. 2002. Gattinoni L, et al. Curr Opin Crit Care. 2005.

  22. Optimizing PEEP • Optimizing PEEP. • PEEP level is at low lung volume and below critical opening pressure. • PEEP increased to optimize compliance.

  23. larson

  24. ARDS Network Low VT Trial Allowable combination of FiO2 and PEEP: FiO20.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 1.0 1.0 1.0 PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18 20 22 24

  25. APRV Mode • First described 1987 • Baseline airway pressure is the upper CPAP level, and the pressure is intermittently “released” to a lower level, thus eliminating waste gas • Time spent at low pressure (short expiratory time): prevents complete exhalation; maintains alveolar distension

  26. APRV Evidence • Prospective, randomized intervention study (N=45); PC/PS vs. APRV; patients with ALI • Oxygenation was significantly better in APRV group • Sedation use and hemodynamics were similar Puntsen, Am J Respir Crit Care Med,2001

  27. Thigh Tlow Phigh Paw Plow insp Flow exp APRV settings

  28. “If this... why not this?” - John B. Downs, MD

  29. High Frequency VentilationHFOVOscillatoryHFJVJETHFPVPercussive

  30. High Frequency Percussive VentilationHFPV • -High Frequency Percussive Ventilation (HFPV) is a hybrid form of high frequency ventilation. • -This concept of pneumatic diffusive / convective protocols is not related to high frequency vibration, jet insufflation or electronically controlled crank or magnetically servoed dynamic oscillators.

  31. Rationale for HFV-Based Lung Protective Strategies • HFV uses very small tidal volumes • Avoids excessive end-inspiratory lung volumes • Allows for higher end-expiratory lung volumes to achieve better recruitment • HFV uses much higher respiratory rates • Allows for maintenance of normal PaCO2 even with very small tidal volumes

  32. High-frequency Ventilation • HFOV may improve oxygenation when used as a rescue modality in adult patients with severe ARDS failing CV. • HFOV may be considered for patients with severe ARDS: • FiO2 > 0.60 and/or SpO2 < 88% on CV with PEEP > 15 cm H2O, or • Plateau pressures (Pplat) > 30 cmH2O, or • Mean airway pressure  24 cm H2O, or • Airway pressure release ventilation Phigh 35 cm H2O • HFOV for adults with ARDS is still in its infancy and requires further evaluations. Higgins J et al., Crit Care Med 2005

  33. High Frequency Percussive VentilationHFPV • -High Frequency Percussive Ventilation (HFPV) is a hybrid form of high frequency ventilation. • It is a combination of convective style ventilation and percussive high frequency linked together.

  34. Inverse Ratio Ventilation • Technique used prior to latest generation of vents • Used in refractory hypoxemia • Another way to increase FRC • Expiratory time is longer than inspiratory time. • Heavy sedation/paralytics required • Fluids, pressors usually needed as well due to decrease in venous return to thorax Sometimes occurs inadvertently by erroneous vent changes or pt agitation & high RR. Must be corrected!

  35. Other Advanced Interventions Require separate or additional machines • Inhaled Nitric Oxide selective pulmonary artery vasodilator. Used for pulm htn, lg saddle PE’s, to reduce intrapulmonary shunting & improve V/Q matching. Prohibitively expensive, may cause methemoglobin buildup • High Frequency Ventilation high frequency (>200 breathes per min) • HFOV, HFJV, HFPV • Extracorporeal Membrane Oxygenation (ECMO)similar to bypass pump used in cardiac surgery

  36. Adjuncts • Recruitment Maneuver • PEEP - does not recruit alveoli, but can help maintain alveolar stability • Prone positioning – has not changed morbidity or mortality outcomes in ARDS, but has been shown to help improve oxygenation

  37. A man suffered from insomnia and dyslexia. He was also an agnostic. What did he do? He stayed up all night wondering if there was a DOG.

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