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The “How To” of BiVent
Created by: David Pitts II, RRT
Clinical Applications Specialist, Maquet
Birmingham, Alabama
Sponsored by Maquet, Inc – Servo Ventilators

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  • Maintaining spontaneous ventilation tends to improve ventilation-perfusion matching by preferentially providing ventilation to dependent lung regions that receive the best blood flow.
  • APRV

    1. 1. The “How To” of BiVent (APRV) Created by: David Pitts II, RRT Clinical Applications Specialist, Maquet Birmingham, Alabama Sponsored by Maquet, Inc – Servo Ventilators
    2. 2. Objectives <ul><li>Provide the definition and names for APRV </li></ul><ul><li>Explain the four set parameters. </li></ul><ul><li>Identify recruitment in APRV using exhaled CO 2 . </li></ul><ul><li>Recommend appropriate initial settings for APRV </li></ul><ul><li>Make adjustments based on arterial blood gas results </li></ul><ul><li>Discontinue ventilation with APRV </li></ul>
    3. 3. Lung Protective Strategies <ul><li>Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) </li></ul><ul><li>Keep plateau pressures < 30 cm H 2 O </li></ul><ul><li>Use low tidal volume ventilation (4-6 mL/kg IBW) </li></ul><ul><li>Use PEEP to restore the functional residual capacity (FRC) </li></ul>
    4. 4. Keeping Plateau Pressure < 30 cm H 2 0 <ul><li>What do you do if CO 2 is rising and the plateau pressure is at 30 cm H 2 O? </li></ul>
    5. 5. Alternative Techniques <ul><li>Increase the ventilator rate </li></ul><ul><li>Permissive Hypercapnia </li></ul><ul><li>Airway Pressure Release Ventilation </li></ul><ul><li>High Frequency Ventilation </li></ul><ul><li>Extracorporeal Life Support </li></ul>
    6. 6. Indications <ul><li>Primarily used as an alternative ventilation technique in patients with ARDS. </li></ul><ul><li>Used to help protect against ventilator induced lung injury. </li></ul>
    7. 7. Goal <ul><li>To provide the lung protective ventilation supported by the ARDSnet research. </li></ul><ul><li>Use an “Open lung” approach. </li></ul><ul><li>Minimize alveolar overdistension. </li></ul><ul><li>Avoid repeated alveolar collapse and reexpansion. </li></ul><ul><li>Restore FRC through recruitment and, </li></ul><ul><li>Maintain FRC by creating intrinsic PEEP. </li></ul>
    8. 8. APRV Description <ul><li>A mode of ventilation along with spontaneous ventilation to promote lung recruitment of collapsed and poorly ventilated alveoli. </li></ul><ul><li>The CPAP is released periodically for a brief period. </li></ul><ul><li>The short release along with spontaneous breathing promote CO 2 elimination. </li></ul><ul><li>Release time is short to prevent the peak expiratory flow from returning to a zero baseline. </li></ul>
    9. 9. Ventilation With APRV <ul><li>The short release along with spontaneous breathing promote CO 2 elimination. </li></ul><ul><li>Release time is short to prevent the peak expiratory flow from returning to a zero baseline. </li></ul>
    10. 10. APRV
    11. 11. AKA <ul><li>BiVent – Servo </li></ul><ul><li>APRV – Drager </li></ul><ul><li>BiLevel – Puritan Bennett </li></ul><ul><li>APRV – Hamilton </li></ul><ul><li>Etc. </li></ul>
    12. 12. Consider APRV when the Patient Has -- <ul><li>Bilateral Infiltrates </li></ul><ul><li>PaO 2 /F I O 2 ratio < 300 and falling </li></ul><ul><li>Plateau pressures greater than 30 cm H 2 O </li></ul><ul><li>No evidence of left heart failure (e.g. PAOP of 18 mm Hg or greater) </li></ul><ul><li>In other words, persistent ARDS </li></ul>
    13. 13. Possible Contraindications <ul><li>Unmanaged increases in intracraneal pressure. </li></ul><ul><li>Large bronchopleural fistulas. </li></ul><ul><li>Possibly obstructive lung disease. </li></ul><ul><li>Technically, it may be possible to ventilate nearly any disorder. </li></ul>
    14. 14. Terminology <ul><li>P High – the upper CPAP level. Analogous to MAP (mean airway pressure) and thus affects oxygenation </li></ul><ul><li>PEEP (Also called Plow) is the lower pressure setting. </li></ul><ul><li>T High - is the inspiratory time IT(s) phase for the high CPAP level (P High). </li></ul><ul><li>T PEEP or T low - is the release time allowing CO 2 elimination </li></ul>
    15. 15. Terminology <ul><li>T High plus T PEEP (T low) is the total time of one cycle. </li></ul><ul><li>I:E ratio becomes irrelevant because APRV is really best thought of as CPAP </li></ul><ul><li>With occasional releases </li></ul>
    16. 16. Bi-Vent Set-up Screen
    17. 17. Advantages of APRV <ul><li>Uses lower PIP to maintain oxygenation and ventilation without compromising the patient’s hemodynamics (Syndow AJRCCM 1994, Kaplan, CC, 2001) </li></ul><ul><li>Shown to improved V/Q matching (Putensen, AJRCCM, 159, 1999) </li></ul><ul><li>Required a lower V E suggesting reduced V D /V T (Varpula, Acta Anaesthesiol Scand 2001) </li></ul>
    18. 18. Compared to PCIRV – Advantages of APRV <ul><li>APRV uses lower peak and mean airway pressures, </li></ul><ul><li>Increases cardiac index, </li></ul><ul><li>Decreases central venous pressure, </li></ul>
    19. 19. Additional Advantages - Compared to PCIRV <ul><li>APRV increases oxygen delivery and </li></ul><ul><li>Reduces the need for sedation and paralysis </li></ul><ul><li>APRV also improves renal perfusion and urine output when spontaneous breathing is maintained. (Kaplan, Crit Care, 2001; Hering, Crit Care Med 2002) </li></ul>
    20. 20. New Water Coolers are Being Installed in the ICU Waiting Rooms
    21. 21. Advantages of Spontaneous Breathing <ul><li>The benefits of APRV may be related to the preservation of spontaneous breathing. </li></ul><ul><li>Maintaining the normal cyclic decrease in pleural pressure, augmenting venous return and improving cardiac output. (Putensen, AJRCCM, 1999) </li></ul><ul><li>The need for sedation is decreased. </li></ul>
    22. 22. Preserve Spontaneous Breathing <ul><li>The dashed line in each figure represents the normal position of the diaphragm. </li></ul><ul><li>The shaded area represents the movement of the diaphragm. (Froese, 1974) </li></ul>
    23. 23. Spontaneous v.s. Paralyzed <ul><li>Spontaneous breathing provides ventilation to dependent lung regions which get the best blood flow, as opposed to PPV with paralyzed patients. ((Frawley, AACN Clinical 2001. Froese, Anesth, 1974). </li></ul>
    24. 24. Spontaneous v.s. Paralyzed <ul><li>During PPV (paralyzed patient), the anterior diaphragm is displaced towards the abdomen with the non-dependent regions of the lung receiving the most ventilation where perfusion is the least. </li></ul>
    25. 25. Try as we might. We can’t get away from it?
    26. 26. Other Advantages of Spontaneous Breathing <ul><li>Reduces atrophy of the muscles of ventilation associated with the use of PPV and paralytic agents. (Neuman, ICM,2002) </li></ul>
    27. 27. Another Advantage <ul><li>During PPV atelectasis formation can occur near the diaphragm, when activity of this muscle is absent. (paralysis) </li></ul><ul><li>However, if spontaneous breathing is preserved, the formation of atelectasis is offset by the activity of the diaphragm. (Hedenstierna, Anesth, 1994) </li></ul>
    28. 28. Initial Settings – P High <ul><li>P High – Set a plateau pressure (adult) or mean airway pressure (pediatric) </li></ul><ul><li>Typically about 20-25 cm H 2 O. </li></ul><ul><li>In patients with Pplateau at or above 30 cm H 2 O, set at 30 cm H 2 O </li></ul>
    29. 29. Setting P high <ul><li>Over-distention of the lung must be avoided. Maximum P high of 35 cm H 2 O. (controversial) </li></ul><ul><li>Exceptions for higher settings – morbid obesity, decreased thoracic or abdominal compliance (ascites). </li></ul>
    30. 30. Setting T high <ul><li>The inspiratory time (T high ) is set at a minimum of about 4.0 seconds </li></ul><ul><li>In children, others use lower settings (Children’s Med Ctr. Uses 2 sec.) </li></ul><ul><li>T high is progressively increased (10 to 15 seconds (Habashi, et al) </li></ul><ul><li>Target is oxygenation. </li></ul>
    31. 31. Setting T high <ul><li>Progress slowly. For example, 5 sec T high to 0.5 sec T low , a 10:1 ratio. </li></ul><ul><li>Increasing to 5.5 sec to 0.5 sec is an 11:1 ratio; not a big change. </li></ul><ul><li>Old patients may be fragile. </li></ul>
    32. 32. APRV
    33. 33. Release Time - T PEEP <ul><li>Currently, with ARDS thinking is not to let exhalation go to complete emptying, i.e. do not let expiratory flow returning to zero. ( McCunn, Crit Care 2002) </li></ul><ul><li>Thus, regional auto-PEEP a desirable outcome with APRV </li></ul>FLOW
    34. 34. Setting PEEP or P low in APRV <ul><li>Set PEEP at zero cm H 2 O. </li></ul><ul><li>This provides a rapid drop in pressure, and a maximum  P for unimpeded expiratory gas flow. (Frawley, AACN Clin Issues 2001) </li></ul><ul><li>Avoid lung collapse during T low . </li></ul>
    35. 35. Establishing T PEEP (Time at low pressure) <ul><li>Set T PEEP (T low) so that expiratory flow from patient ends at about 50 to 75% of peak expiratory flow. </li></ul><ul><li>This can be determine saving a screen and calculating peak expiratory flow. </li></ul><ul><li>Or, it can be estimated </li></ul>
    36. 36. Expiratory Flow
    37. 37. T PEEP – Setting The Time <ul><li>Adults 0.5 to 0.8 seconds </li></ul><ul><li>Pediatric/neonatal settings 0.2 to 0.6 seconds. </li></ul><ul><li>Or one time constant. (TC = C x R) </li></ul>
    38. 38. T PEEP – Using the Tc
    39. 39. Release Time in ARDS <ul><li>Atelectasis can develop in seconds when Paw drops below a critical value in the injured lung. (Neumann P, JAP 1998, Newmann P, AJRCCM 1998, Frawley, 2001; McCunn, Internat’l Anesth Clinics 2002). </li></ul><ul><li>Too long a release time would interfere with oxygenation and allow lung units to collapse. </li></ul>
    40. 40. Rat Lung Model – Dr. Slutsky
    41. 41. Initial Settings <ul><li>P high 20-30 cm H 2 O, according to the following chart. </li></ul>T High/T low - 12-16 releases T low = 0.5 sec and P low = 0 P/F MAP <250 15-20 <200 20-25 <150 25-28 T High (s) T low (s) Freq. 3.0 0.5 17 4.0 0.5 13 5.0 0.5 11 6.0 0.5 9 T high range 4-6 sec. PS- as indicated with special attention given to PIP.
    42. 42. Bi-Vent Settings Set Releases and I:E Create releases and I:E
    43. 43. Bi-Vent Ventilation P High T High T PEEP
    44. 44. Spontaneous Breathing Spontaneous Breaths Patient Trigger (On P High) (On P High)
    45. 45. Spontaneous Breathing w/PS Spontaneous Breaths w/PS
    46. 46. Identifying Lung Recruitment – CO 2 Monitoring
    47. 47. Making Changes in APRV Settings Based on ABGs
    48. 48. Control Settings for CO 2 <ul><li> P (P high – P low ) determines flow out of the lungs and volume exchange (V T and PaCO 2 ). </li></ul><ul><li>Some clinicians suggest a target minute ventilation of 2 to 3 L/min. (Frawley, 2001). </li></ul><ul><li>Optimize spontaneous ventilation. </li></ul>
    49. 49. CO 2 Elimination To Decrease PaCO 2 : <ul><li>Decrease T High. </li></ul><ul><ul><li>Shorter T High means more release/min. </li></ul></ul><ul><ul><li>No shorter than 3 seconds </li></ul></ul><ul><ul><li>Example: T High 5 sec. = 12 releases/min </li></ul></ul><ul><ul><li>T High 4 sec = 15 releases/min </li></ul></ul><ul><li>Increase P High to increase  P and volume exchange. (2-3 cm H 2 O/change) </li></ul><ul><ul><li>Monitor Vt </li></ul></ul><ul><ul><li>PIP (best below 30 cm H 2 O) </li></ul></ul><ul><li>Check T low. If possible increase T low to allow more time for “exhalation.” </li></ul>
    50. 50. To Increase PaCO 2 <ul><li>Increase T high. (fewer releases/min) </li></ul><ul><li>Slowly! In increments of 0.5 to 2.0 sec. </li></ul><ul><li>Decrease P High to lower  P. </li></ul><ul><ul><li>Monitor oxygenation and </li></ul></ul><ul><ul><li>Avoid derecruitment. </li></ul></ul><ul><li>It may be better to accept hypercapnia than to reduce P high so much that oxygenation decreases. </li></ul>
    51. 51. Management of PaO 2 <ul><li>To Increase PaO 2 </li></ul><ul><li>Increase F I O 2 </li></ul><ul><li>Increase MAP by increasing P High in 2 cm H 2 O increments. </li></ul><ul><li>Increase T high slowly (0.5 sec/change) </li></ul><ul><li>Recruitment Maneuvers </li></ul><ul><li>Maybe shorten T PEEP (T low) to increase PEEPi in 0.1 sec. increments (This may reduce V T and affect PaCO 2 ) </li></ul>
    52. 52. Going Too Fast
    53. 53. Weaning From APRV <ul><li>FiO 2 SHOULD BE WEANED FIRST. (Target < 50% with SpO 2 appropriate.) </li></ul><ul><li>Reducing P High, by 2 cmH 2 0 increments until the P High is below 20 cmH 2 O. </li></ul><ul><li>Increasing T High to change vent set rate by 5 releases/minute </li></ul>
    54. 54. Weaning From APRV <ul><li>The patient essentially transitions to CPAP with very few releases. </li></ul><ul><li>Patients should be increasing their spontaneous rate to compensate. </li></ul>
    55. 55. During Weaning <ul><li>Add Pressure Support judiciously. </li></ul><ul><li>Add Pressure Support to P High in order to decrease WOB while avoiding over-distention, </li></ul><ul><li>P High + PS < 30 cmH 2 O. </li></ul>
    56. 56. Pressure Support with APRV
    57. 57. Weaning Bi-Vent Lower Rate Longer T High Lower P High Add PS
    58. 58. Weaning Bi-Vent Lower Rate Longer T High Lower P High Add PS
    59. 61. Perceived Disadvantages of APRV <ul><li>APRV is a pressure-targeted mode of ventilation. </li></ul><ul><li>Volume delivery depends on lung compliance, airway resistance and the patient’s spontaneous effort. </li></ul><ul><li>APRV does not completely support CO 2 elimination, but relies on spontaneous breathing </li></ul>
    60. 62. Disadvantages of APRV <ul><li>With increased Raw (e.g.COPD) </li></ul><ul><ul><li>the ability to eliminate CO 2 may be more difficult </li></ul></ul><ul><ul><li>Due to limited emptying of the lung and short release periods. </li></ul></ul><ul><li>If spontaneous efforts are not matched during the transition from P high to P low and P low to P high , may lead to increased work load and discomfort for the patient. </li></ul><ul><li>Limited staff experience with this mode may make implementation of its use difficult. </li></ul>
    61. 63. The End Thank You!