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Ventilator Review

Ventilator Review. Indications. Prophylactically (neuromuscular, impending failure, pre-op, post op) Airway protection (sedated, stroke, trauma, drug OD) Ventilatory failure (pH less than 7.25, CO2>50) Shunts/oxygenation failure. Impending Ventilatory Failure.

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Ventilator Review

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  1. Ventilator Review

  2. Indications • Prophylactically (neuromuscular, impending failure, pre-op, post op) • Airway protection (sedated, stroke, trauma, drug OD) • Ventilatory failure (pH less than 7.25, CO2>50) • Shunts/oxygenation failure Kishore P. Critical Care Conference

  3. Impending Ventilatory Failure • Pt maintains marginally acceptable blood gas values at the expense of significant increased WOB. • Progressive acidosis and hypoventilation ensue.

  4. Severe Hypoxemia • Pa02 < 60 mm Hg on Fi02 of 50% or greater.

  5. Prophylactic Ventilatory Support • Risk of pulmonary complications • Reduce hypoxia of major body organs • Reduce cardiopulmonary stress

  6. Initial Settings • Generic startup: • AC or SIMV modes • PC, VC or PRVC • FIO2 40-60% • Rate 8-12 • VT 8-10 ml/kg or PC 15-25 cmH2O • Flow 40-60L, I-time 0.8-1.25 • Sensitivity 1-3 flow or pressure • PEEP 0-5 • Rise time 50%, 0.2-0.4 seconds Kishore P. Critical Care Conference

  7. Combinations • AC-PC • AC-VC • AC-PRVC • SIMV-VC (PS, TC, VS) • SIMV-PC (PS, TC, VS) • SIMV-PRVC (PS, TC, VS) • Spontaneous (PS, TC, VS, PAV) • APRV • HFOV • HFPV • HFJV Kishore P. Critical Care Conference

  8. Settings/Monitored Data • PEEP • FIO2 • I-time • Flow • Sensitivity • Rate • Mode • Breath Type • VT • Pressure limit • Rise time • Pressure Support • Volume Support • Tubing Compensation • MAP • PIP • Total rate • Minute Ventilation • Plateau pressure • Dynamic/static compliance • WOB, Time constant • Spontaneous/mech Volume Kishore P. Critical Care Conference

  9. Initial Setup • Acute air trapping (Asthma/COPD exacerbation) Restrictive disease (ARDS, PN, Pulmonary fibrosis) • AC or SIMV • VC with lower VT 5-7 ml/kg with rate 14-20 OR PC 15-25 with rate 14-20 OR PRVC low VT range • FIO2 depending on previous ABG/FIO2 setting • IT 0.7-0.9, Flow 60L, achieve appropriate I:E ratio

  10. Initial Setup • If you have a ABG prior to startup, adapt initial settings per blood gas and prior device • Ex: if patient has extreme respiratory/met acidosis: hyperventilate patient if patient was actively breathing prior to being on vent, if patient apneic, then use normal vent settings • Use PEEP for patients with shunts, pulmonary edema • Suggest sedation for initial ventilator stabilization (Versed, Ativan, Deprivan, Fentanyl, Morphine, Precedex…) Kishore P. Critical Care Conference

  11. Alarms • High PIP: 10-15 above • Low PIP: 5 below • High rate: 10-15 above total rate • Ve: 2-3 L above/below • VT: 200-300 above/below • Apnea alarms 20 seconds • ALWAYS READJUST ALARMS PER PT CHANGES OR VENT CHANGES Kishore P. Critical Care Conference

  12. MODES • AC, SIMV, CPAP/Spontaneous • AC all breaths are mechanical, patient can trigger a breath only, but machine will complete the breath for the patient • SIMV both mechanical and spontaneous breaths, must calculate spontaneous VT, support Spont breath with PSV, VS or TC • CPAP all breaths are spontaneous Kishore P. Critical Care Conference

  13. Settings Review • Trigger: What begins inspiration, either time, flow or pressure; or via NAVA. The time applies to non patient triggered breaths. Control trigger by setting sensitivity • Set sensitivity 1-3. If the sensitivity is set >3 may lead to difficulty triggering breath on and induce WOB, if set to low may cause auto-triggering • Set in all modes (including CPAP, PSV still needs a trigger!) • Assess triggering by looking at pressure-time graph or pressure-volume loop

  14. Work to Trigger Adjust sensitivity per patients ability, missed triggers will lead to asynchrony 30 Paw cmH2O Sec 1 2 3 4 5 6 -10

  15. Assisted Breath VT Clockwise to Counterclockwise LITERS 0.6 Expiration 0.4 Assisted Breath 0.2 Inspiration Paw cmH2O -60 40 20 0 20 40 60

  16. Settings Review • Cycle: This is what cycles the breath off. Either flow, pressure or volume. Pressure and volume limits are the most common • Volume: Set appropriate per patients size. If patient has restrictive lungs or is air trapping severely, use 5-7 ml/kg range otherwise 8-10 • Set in VC and PRVC. Too much volume can cause volutrauma/barotrauma • Assess with Volume-time or Pressure-volume graphic Kishore P. Critical Care Conference

  17. Setting Review • Volume control used to set a consistent minute ventilation. • In VC you set the VT, flow and flow pattern. The pressure and I-time are variable • On PRVC the volume is only targeted not guaranteed, will fluctuate with changing breathing patterns. You set target VT, I-time, pressure limit and rise time. Kishore P. Critical Care Conference

  18. PV loop • Note over distention • Patient triggers • Asynchrony • RAW

  19. Pressure-Volume Loop Changes The pressure-volume loop changes, flattening out and moving to the right. What could cause this to happen? VT LITERS 0.6 0.4 0.2 Paw 60 40 -60 -20 20 0 -40 cmH2O

  20. Changes in Compliances Did anybody say decrease in compliance? The difference between the white arrow and the red arrow represents a change in compliance as indicated by an increase in pressure without a corresponding increase in tidal volume. Indicates a drop in compliance (higher pressure for the same volume) VT LITERS 0.6 0.4 0.2 Paw 60 40 -60 20 20 0 40 cmH2O

  21. Setting Review • Pressure Limit: Set 15-25, increase to increase VT, decrease to lower VT • Set in PRVC and Pressure control but… • All breath types have pressure limits set in the alarms, in the alarm setting, the high pressure alarm becomes the pop-off, patient will not be able to exceed this level. This is why it is important to set alarms appropiately. Kishore P. Critical Care Conference

  22. Flow Acceleration PercentAKA: Rise Time Minimal Pressure Overshoot P Slow rise Moderate rise Fast rise . V Pressure Relief Time

  23. Pressure time graph • Used to assess patient triggering • Used to assess inadequate flow rate/double breaths • Assess level of PEEP • Assess rise time • Assess Plat time

  24. Setting Review • Generally Pressure control is used for patients with restrictive disease, but can be used with any patient • Helps with patients asynchrony because patient dictates their own flow pattern. • In PC, you set Pressure limit, I-time and rise time. Volume and flow are variable • Pressure limited, time cycled Kishore P. Critical Care Conference

  25. Ventilator Review • MODES: • AC: start with this mode if patient is apneic or if patient’s spontaneous breaths are inadequate or erratic. Patient can trigger breaths but machine will complete the breath at preset limits • SIMV: May start with this mode on any patient who is apneic if you suspect he/she will regain spontaneous breathing. Otherwise, use only if spontaneous breaths are adequate. Must set a PSV in this mode or VS or TC Kishore P. Critical Care Conference

  26. Ventilator Review • CPAP/Spontaneous: May start for Type I failure, patient must have ability to breathe spontaneously without much need for ventilatory support. Must have a PSV or ATC or VS • PRVC: duel mode, set in either AC or SIMV mode. Set pressure limit, target VT…Does not work well with erratic breathing patterns Kishore P. Critical Care Conference

  27. PSV • PSV only applies to spontaneous inspiratory breaths, used to augment spontaneous VT, set to achieve spontaneous VT of 5-7ml/KG, set above measured RAW • Start with a PSV of about 10, titrate or increase as needed. PSV max = 20-25 • Pressure limited, patient cycled, set sensitivity and rise time, e-sens

  28. Pressure Support Ventilation - PSV • Applies a preset pressure plateau to the patient’s airway for the duration of spontaneous breathing. • Used only in ventilator modes that allow for spontaneous breathing

  29. Pressure Support Ventilation - PSV • Patient has control over • Tidal Volume • Inspiratory Time • RR • What is the cycling mechanism for Pressure supported breaths?

  30. Ventilator Review • APRV: for restrictive lungs only, spontaneously breathing • HFOV: for restrictive lungs only, sedate/paralyze. • ASV: used as a single mode, from start to finish, not for ARDS or neurological breathing patterns Kishore P. Critical Care Conference

  31. Ventilator Review • Flow: Set only in Volume control. When set use either constant or decelerating patterns. Increased flow= decreased I-time. Give patients with COPD increased flows to meet demands and give long E-time. Increase when you increase VT, or change flow pattern • I-time: Set in PRVC, PCV. Increase or decrease to achieve appropriate I:E, increased rates=decreased I-time. Inverse used for restrictive diseases to increase oxygenation Kishore P. Critical Care Conference

  32. Setting Flow • The easiest rule of thumb to follow is that a patient requires a peak flow roughly four times that of the minute ventilation (if the MV is 15 liters, the patient requires a PF of >60 liters). However if the patient is breathing spontaneously, then bedside adjustment is required to ensure that flow matches patient efforts. The peak flow should be set slightly higher if a decelerating waveform pattern is being used, and, in particular, those with airflow obstruction

  33. A higher expiratory flow rate and a decreased expiratory time denote a lower expiratory resistance. A decrease in expiratory resistance may also be observed after the patient receives a bronchodilator (e.g. MDI or aerosolized neb tx). Monitoring the duration of the therapy’s effect can help determine the indicated frequency of therapy. 120 . SEC V LPM 1 3 4 5 6 2 120

  34. Flow Patterns • Constant/Square: • Causes lower I-time, less MAP, higher PIP • Only set in VC • Can increase oxygenation • Generally uncomfortable for your patients

  35. Flow Patterns • Ramp • Can be set in volume, automatic pattern in PC • Will increase MAP, and prolong I-time • When switching from constant to ramp, you may have to increase flow to maintain same I-time, I:E ratio

  36. Pressure time graph • Used to assess patient triggering • Used to assess inadequate flow rate/double breaths • Assess level of PEEP • Assess rise time • Assess Plat time

  37. Flow vs.Time Curve Constant Flow Descending Ramp 120 INSP Inspiration . V SEC LPM 1 2 3 4 5 6 EXH 120

  38. Flow-Time Curve 120 INSP . Insp. Pause V SEC LPM 1 2 3 4 5 6 Expiration EXH 120

  39. Patient / Ventilator SynchronyVolume Ventilation Delivering a Preset Flow and Volume 30 Adequate Flow Paw Sec cmH2O 1 2 3 4 5 6 -20

  40. Patient / Ventilator SynchronyThe Patient Is Out breathing the Set Flow 30 Air Starvation Paw Sec cmH2O 1 2 3 4 5 6 What we see here is a patient’s inspiratory flow demand greater than the peak flow set on the ventilator, which can lead to patient/ventilator dysynchrony. What are we going to do to amend this situation? -20 What options do we have?

  41. Humidification • The gas delivered to patient during mechanical ventilation should be filtered, humidified, and heated • Heated humidifier (requires heated circuit, delivers 100% RH) or HME • HME only supplies about 50% humidity • Contraindicated with • Dehydration • Thick secretions • Hypoventilation • Prolonged use >72 hours • Patients who are hyperventilating

  42. PEEP • Increases the baseline airway pressure. • Optimal PEEP: • Increase PaO2 (above 60 at minimum not over 100, with least amount of hemodynamic effects) • Assess intrinsic PEEP with flow-time and expiratory pause • Two major indications • Shunt and refractory hypoxemia • Decreased FRC and lung compliance • Atelectasis, pulmonary edema, air trapping

  43. Complications of PEEP • Decrease venous return (decreases CO, decreases blood to kidney, GI tract, liver…) Causes ADH release and fluid accumulation • Barotrauma • Increased ICP • Alterations in renal function and H20 balance • Alterations in liver function. • ASSESS hemodynamics (CVP, PAP, PCWP, Blood Pressure/MAP, urine output, lab values…)

  44. Effects on Intrapleural Pressure • PEEP increases intrapleural pressure • The extent of the increase is determined by: 1. The amount of PEEP applied 2 The stiffness of the individual’s lung

  45. Effects on Intrapleural Pressure • The > the pulmonary compliance, the > the transmission of PEEP to the intrapleural space and the greater the increase in intrapleural pressure.

  46. Effects on FRC • Regardless of the condition of the lung at the time of application, PEEP increases FRC • FRC is increased by these primary mechanisms: 1. Lungs are elastic. Any increase in end expiratory pressure increases over all lung volume.

  47. Effects on FRC • FRC is increased by these primary mechanisms: • The diameter of conducting airway can increase 1 to 2 mm as PEEP is applied. • In pts with a decrease FRC as a result of alveolar collapse caused by surfactant instability, PEEP maintains alveoli inflated after they are recruited by the peak airway pressure.

  48. Effect on Pulmonary Compliance • Because PEEP increases FRC, it alters pulmonary compliance.

  49. Effect on Pulmonary Compliance • Monitoring of effective static compliance can be used to help to determine the “optimal” or most appropriate PEEP level - Best compliance changes in VT will change the PEEP considered optimal Vt should always be constant during PEEP titration

  50. Effect of PEEP on Deadspace • Because PEEP increases FRC by distending alveoli, deadspace is usually increased in: - Patients with normal lungs - Patients with COPD - Pts with non-homogeneously distributed disease process

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