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VENTILATION STRATEGIES

Alyssa Morris, R4 July 15, 2010 Thanks to Dr J Lord. VENTILATION STRATEGIES. OBJECTIVES. Indications for ventilation Ventilation terminology Ventilation modes NIPPV IPPV* Cases ARDS Metabolic acidosis Asthma SCM order sets . INDICATIONS. Rosen’s Chapter 1

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VENTILATION STRATEGIES

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  1. Alyssa Morris, R4 July 15, 2010 Thanks to Dr J Lord VENTILATION STRATEGIES

  2. OBJECTIVES • Indications for ventilation • Ventilation terminology • Ventilation modes • NIPPV • IPPV* • Cases • ARDS • Metabolic acidosis • Asthma • SCM order sets

  3. INDICATIONS • Rosen’s Chapter 1 • Failure to maintain or protect the airway • Failure of oxygenation or ventilation • Anticipated clinical course and potential for deterioration

  4. TERMINOLOGY • f, RR = breaths per minute • VE= VTxf (minute volume) • Amount of air that moves in and out of lungs/min • 6-10L/min • VT= VA + VD • 4-10cc/Kg IBW • FiO2= fractional concentration of inspired oxygen • 0.3-1.0  decrease to 0.6 or less asap

  5. TERMINOLOGY • PEEP= positive end expiratory pressure • 5-20 cmH20 • Set vs. auto/intrinsic PEEP • Pinsp= set inspiratory pressure • I time= inspiratory time (0.8-1.7s) • E time= expiratory time • I:E Ratio= I time : E time

  6. TERMINOLOGY/PHYSIOLOGY • Peak Inspiratory Pressure (PIP) • Occurs during inspiration • >35cmH20 leads to alveolar over-distension/injury • Plateau Pressure • Measured by occluding vent for 3-5 sec at end of inspiration • Should not exceed 30cmH20 • Paw-mean= mean airway pressure= MAP • Corresponds to area under the curve in P over T curve • Correlates with O2 delivered • Inc I time = inc mean peak pressure= inc O2 delivery per ventilation

  7. IBW PREDICTION RULES

  8. MODES OF VENTILATION • NIPPV • CPAP • Hypoxemic resp failure • Increasing the compliance decreases the WOB • Start at a pressure of 0-15ccH2O and increasing as tolerated to decrease FiO2 • BiPAP • Combo of CPAP and pressure support ventilation • use in fatigued pt b/c >support during inspiration • IPAP/EPAP (ex start at 10/5 or 12/6) • Has to be a pressure gradient of at least 5 • Increase IPAP as tolerated

  9. MODES OF VENTILATION • Indications for NIPPV (2 or more of): • pH<7.35 with PaCO2> 44mmHg • respiratory distress with moderate to severe dyspnea • RR>25

  10. NIPPV • Contraindications • Cardiac or respiratory arrest • Non-respiratory organ failure • Severe encephalopathy (GCS<10) • Severe UGIB • Hemodynamic instability or dysrhythmia • Facial surgery or trauma or deformity • Upper airway obstruction • Inability to cooperate/protect airway • Inability to clear secretions • High risk for aspiration

  11. MODES OF VENTILATION • IPPV • Volume-Cycled • Ventilator seeks to deliver a constant preset VT • Do not take into account lung compliance • Pressure-Cycled • Ventilator alters gas flow to achieve a preset airway pressure over a preset I time • Variable volumes are delivered to not exceed preset airway pressure • Reduces alveolar overdistension • Combination Pressure-Volume cycled

  12. MODES OF VENTILATION Mode Volume-cycled Pressure-cycled CMV Both PSV AC SIMV PCV MMV

  13. CMV • Controlled Mechanical Ventilation • Apneic, paralyzed, anesthetized patients • Vent provides breaths at a set rate regardless of pt effort • Each breath is triggered, limited and cycled by the vent • Rarely used now

  14. AC • Assist Control • Ventilator delivers preset VT at a set minimum rate • If patient attempts breath, vent delivers a full breath at the preset volume/pressure • AC-PC • AC-VC • Common initial setting • Preset RR- patient can breath above or machine will ensure gets preset rate Q: Can you see any problems that could arise with this setting?

  15. AC • AC-VC • Every breath is a controlled volume preset mandatory breath • Need to have normal lung and chest wall compliance • Advantage • When minute volume requirements are high (ie. metabolic acidosis) • Disadvantages • High peak pressures when compliance is low

  16. AC • AC-PC • Every breath is a controlled pressure preset mandatory breath • Indications • High pressures when using AC-VC • Inverse ratio ventilation • ALI/ARDS • Advantage • Airway pressure will not exceed level of set pressure • Disadvantage • When lung/chest compliance falls VT drops and hypercapnia may occur

  17. PSV • Pressure Support Ventilation • Use only in spontaneously breathing pts • Pressure support is given by vent on each patient initiated breaths • More comfortable • Might not get enough volume, reach mean airway pressure (decreased oxygentation) • Use when weaning

  18. SIMV • Synchronized intermittent mandatory ventilation • Pt receives only the set number of volume controlled mandatory breaths which are synchronized with the pt • Additional breaths above set rate are pressure supported • More comfortable way to deliver volume controlled mandatory breats • Can use in inverse ratio ventilation and ALI/ARDS or pts with periodic apnea

  19. SIMV

  20. MMV • Mandatory Minute Ventilation • Pressure support ventilation with a volume-controlled back-up rate: • Set minimum minute ventilation • If patient breathing above this, all PSV breaths • If patient not meeting minimum, volume-controlled breath(s) delivered to ensure MV

  21. MODES OF VENTILATION

  22. SETTINGS • No matter what mode of ventilation you use, certain settings will need to be considered: • Tidal volume • RR • PEEP • FiO2 • I:E

  23. SETTINGS • Tidal Volume • Normal lung- 8-10cc/kg IBW • Diseased lung – 6-8cc/kg IBW • RR • Usually start at 10-12/min • Exceptions: metabolic acidosis, asthma, ARDS • Base on the patient need and PaCO2 on gas • FiO2 • Start at 85-100% and quickly wean to 60% • SaO2 goal usually >92%

  24. SETTINGS • PEEP • “physiologic” PEEP = 5cmH2O • Use 5 as a minimum • More depending on FiO2, intrinsic lung dz, extra-thoracic pressure • PEEP trial at the bedside • Can use more to help wean to Fi02<60% • SE: • Increases intrathoracic pressure  decreased venous return  decreased cardiac output

  25. SETTINGS • I:E • In normal spontaneous breathing it is 1:4 • In intubated pt it is set at 1:2 to 1:4 • Sensitivity • Negative pressure required to trigger delivery • Usually set at 1-2cmH2O • Intrinsic PEEP makes it harder for the vent to sense a pt triggered breath

  26. TROUBLESHOOTING • Adjusting the vent • pCO2 too high • pCO2 too low • PO2 too high • pO2 too low

  27. pCO2 TOO HIGH • Patient’s minute ventilation is too low • Increase rate or VT or both • Improve dead space • Decrease production: decrease temp, stop seizures, decrease feeds • Sometimes you have to live with the high pCO2 (Permissive hypercapnea) • Target pH >7.2 • May need bicarb infusion if pH <7.2

  28. pCO2 TOO LOW • Minute ventilation is too high • Lower either the rate or tidal volume • Consider pain control or treating anxiety

  29. pO2 TOO HIGH • Your settings are working great • Turn down the FiO2

  30. pO2 TOO LOW • Increase the FiO2 or mean airway pressure • Try to avoid FiO2>70% • To increase MAP • Increase PEEP • Change modes and increase inspiratory pressure or I time • Recruitment maneuvers

  31. QUESTIONS?

  32. CASE 1 • 58M with 4d Hx of fever, productive cough and anorexia. • O/E: T= 39.2, P= 111, RR= 32, 02= 91% NRB, BP= 110/75 • He looks very very tired and has decreased AE thru’ out • PMHx: HTN • Meds: HCTZ

  33. CASE 1

  34. CASE 1 QUESTIONS • What is the definition of ALI and ARDS? • What is your mode of airway management? • What are your settings going to be? • VT • PEEP • FiO2 • RR • I:E

  35. Objective • Determine whether ventilation with lower tidal volumes would improve the clinical outcomes in pts with ALI/ARDS

  36. ARDS NET • Inclusion • Intubated and mechanically ventilated • Acute decrease in PaCO2/FiO2 <300 • Bilateral pulmonary infiltrates w presence of edema • No evidence of increased L atrial HTN

  37. ARDS NET • Exclusion • >36hrs since they met the above criteria • <18 • Enrolled in other trials • Pregnant • Increased ICP • Neuromuscular dz • Sickle cell dz • Severe chronic respiratory dz • Burns >30% BSA • Bone marrow or lung transplant • Any condition w 6m survival <50% • Chronic liver dz

  38. ARDS NET • METHOD • RCT • Vent Procedures • AC until weaned or for 28 days minimum • Control: 12cc/kg predicted weight with a plateau pressure of 50cmH20 • They could decrease by 1cc/kg to maintain pressure goal • Treatment: 6cc/kg predicted weight w/I 4 hrs of randomization with a plateau pressure of 30cmH20 • Could only increase to 8cc/kg to maintain pressure goal • Could give HCO3 for acidosis • Monitored for 28d

  39. ARDS NET • Outcomes • Death before pt was d/cd home and was breathing w/o assistance • Number of days w/o ventilator use from D1-28 • # of days w/o organ or system failure and the occurrence of barotrauma • Results • N= 861

  40. ARDS NET

  41. Lung Protective Strategy • Low VT of 6cc/kg IBW in first 4h • Plateau airway pressure of 30cmH20 • Increased RR • Maintains adequate minute ventilation • Permissive hypercapnea • PEEP • Higher than you would think • And decreased I:E ratio • 1:1 to 1:3

  42. CASE 2 • 32F with known asthma comes in in respiratory distress. • O/E: T= 36.6, P= 112, RR= 29, Sa02= 90% • Looks terrible, ++ accessory muscle use • You have tried aggressive bronchodilators, steroids, fluids, Mg but she is failing and needs airway management.

  43. CASE 2 QUESTIONS • Is there a role for NIPPV in asthma? • How will you vent this patient? • VT • PEEP • FiO2 • RR • I:E

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