1. HEATHER, FITSUM, AND LISAMARIE

2.  APRV was described initially by Stock and Downs in 1987 as a continuous positive airway pressure (CPAP) with an intermittent release phase. APRV applies CPAP (P high) for a prolonged time (T high) to maintain adequate lung volume and alveolar recruitment, with a time-cycled release phase to a lower set of pressure (P low) for a short period of time (T low) or (release time) where most of ventilation and CO 2 removal occurs.

3. APRV-Drager BiVent- Servo I BiLevel-Puritan Bennett 840 DuoPAP-C1 by Hamilton

4.  Airway Pressure Release Ventilation provides two levels of Continuous Positive Airway Pressure while allowing the patient to breathe spontaneously at any time.  Increases MAP by increasing Inspiratory Time  Both pressures are time triggered and time cycled.

5.  ‘P high’ should be below the high inflection point (HIP) on the static volume-pressure curve, while ‘P low’ should be above the low inflection point (LIP) on the same curve  T high’ should allow complete inflation of the lungs, as indicated by an end-respiratory phase of no flow when spontaneous breathing is absent, and ‘T low’ should allow for complete exhalation with no gas flow at its end to assure absence of intrinsic or auto PEEP

6.  For the initial set up, an optimum high CPAP level is determined much as the optimum PEPP,  The high CPAP level is interrupted intermittently to allow pressures to drop very briefly (for about 1 second or less) to a lower CPAP level.  Reducing the CPAP reduces the patient’s FRC and allows patient exhalation and ventilation.

7.  It is also recommended setting ATC to 100% and trying to avoid over-sedation.  Initial setup and transition from conventional ventilation  P high is usually set at a level between 20 and 30 cm H 2 O.  P low is set between 0 and 5 cm H 2 O initially.  T high: 4–6 s  T low: 0.2-0.8 seconds

8.  p-High is the upper CPAP or pressure setting when utilizing APRV.  p-High regulates end-inspiratory lung volume & is analogous with mean airway pressure  P-high generally establishes an Paw intended to maintain oxygenation by restoring FRC.  Overdistention of the lung must be avoided, so a P-high of 35 cmH2O is probably the maximum accepted level.

9.  Some practitioners have noted the use of Phigh up to 45 cmH2O, but this level may be damaging to the lungs unless the chest-wall compliance is reduced form abdominal distention or prone positioning.  The use of P-high may help in the recruitment of collapsed alveoli and the maintenance of these recruited units.  It can take as long as 8 hours or longer for recruitment to occur, this is reflected in a progressive improvement in oxygenation and lung compliance.

10.  PEEP is the lower pressure setting  P Low is the airway pressure level resulting from the pressure release. Other authors may refer to P Low as the PEEP level, the release pressure, or the P2 pressure.  A Plow of 0 cmH2O allows an unimpeded expiratory gas flow and a rapid drop in pressure.

11.  T High- is the inspiratory time IT phase for the high CPAP level (P High).  T High corresponds with the length of time for which P High is maintained  Allows for sustained recruitment allowing for improved gas exchange by increasing alveolar surface area.

12.  Thigh is set at a a minimum of 4.0 seconds.  Values less that 4 seconds can affect the Paw in a negative way, losing the benefits of the APRV mode.  Thigh can then be progressively increased to 12 to 15 seconds in 0.5 to 2.0 second intervals until the target is achieved.  Slow progression is better than the increase of the I:E ratio in large increments, such as 2:1 or 3:1.

13.  T Low is the length of time for which the P Low is held  T High + T Low will give you the total time of one cycle.  The t-Low sets the time interval for the low pressure/CPAP phase (p- Low).  Allows for intermittent release in airway pressure, providing paCO2 removal.

14.  Increase FiO2  ↑P High(1-2cmH2O), T High(0.5 sec), or both.  Increasing P High=increased MAP, increased alveolar recruitment, should result in increased oxygenation.

15.  ↑P High and ↓ T High simultaneously= Increased Ve.  Possibly ↑ T Low

16.  Increase T High(0.5 to 2.0 sec)  ↓ P High(1-2 cmH 2 O but avoid de-recruitment and monitor O2

17. https://youtu.be/jy1PpCJATUQ

18.  Preserves Spontaneous Breathing  During spontaneous negative pressure inspirations, pleural pressure becomes more negative, which reduces the intra-thoracic pressure and right arterial pressure= increase in venous return, and improves preload which results in increased cardiac output.

19.  Improves oxygenation to poorly aerated areas of the lungs by using the open lung approach.  Uses Lower Peak Inspiratory Pressures  Prevents De-recruitment and alveolar damage.  Maintains Diaphragmatic muscle  Less Sedation, Less time in ICU.  Higher MAP achieved.  Better V/Q match and reduced dead space.  Increased Comfort for patient.

20.  A study conducted by Kaplan LJ, Bailey H, Formosa V compared hemodynamic effects in ALI/ARDS patients using APRV and IRPCV and they found patients using APRV showed:  Higher Cardiac Index  Higher DO2  Higher SVO2  Higher Urine Output  Lower Inotropes and Vasopressors used  Lower Lactate concentrations

21.  Because Pressure is targeted, volume depends on compliance, Raw and the patient’s spontaneous efforts.  No complete support of CO2 removal but relies on patient’s ability to eliminate it.

22.  Keep plateau pressures < 30 cm H 2 O  Use low tidal volume ventilation (4-5 mL/kg IBW)  Use PEEP to restore the functional residual capacity (FRC)  It is ideal for Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS)

23.  Consider APRV if the following are present…  Bilateral Infiltrates  PaO 2 /F I O 2 ratio < 300 and falling  Plateau pressures greater than 30 cm H 2 O  No evidence of left heart failure (e.g. PAOP of 18 mm Hg or greater)

24.  Expiratory flow generally is not permitted to return to baseline; therefore auto-PEEP is intentionally present, which helps maintain an open lung and prevents repeated collapse and reexpansion of alveoli.  As soon as the release period is complete, the higher level of CPAP is restored.  The optimum duration of the release time is a function of the time constant of the respiratory system.

25.  The clinician sets a high pressure (Phigh) slightly greater than the measured mean airway pressure, inspiratory pressure, or plateau pressure during conventional ventilation  The low pressure (Plow) is set between 0 and 5 cmH2O  The frequency controls the rate of the rapid pressure release from the Phigh and Plow which, in combination with spontaneous ventilation, aids in alveolar ventilation and breathing at Phigh allows recruitment of air spaces.

26.  Spontaneous breathing at a higher pressure not only aids in alveolar recruitment but, through the application of pleural pressure change, improvements in the distribution of lung volume to diseased lung units may improve FRC and pulmonary compliance.

27.  Patients who require heavy sedation.  COPD Patients with extreme air trapping  Neuromuscular patients

28.  Avoiding extension of lung injury  Minimal oxygen toxicity with high mean airway pressure  Recruiting alveoli & preventing de-recruitment  Minimizing peak airway pressure  Preventing atelectasis  Using sedation and paralysis conservatively

29.  In acute respiratory distress syndrome (ARDS), the functional residual capacity (FRC) and lung compliance are reduced, and thus the elastic work of breathing (WOB) is elevated.  By applying CPAP, the FRC is restored and inspiration starts from a more favorable pressure-volume relationship, facilitating spontaneous ventilation, and improves oxygenation.  Applying ‘P high’ for a ‘T high’ (80–95% of the cycle time), the mean airway pressure is increased insuring almost constant lung recruitment (open-lung approach), in contrast to the repetitive inflation and deflation of the lung using conventional ventilatory methods, which could result in ventilator-induced lung injury (VILI);or the recruitment maneuvers, which have to be done frequently to avoid derecruitment.

30. https://youtu.be/j3dcf1WHxyo

31.  Wean FiO 2 First  “Drop and Stretch”  Reduce the P High 2 to 3 cm H2O at a time and lengthen T High 0.5 to 2 seconds at a time, or as the patient tolerates. T low can be reduced or maintained.  P High should be reduced until it meets P Low.

32.  Pressure Support may be added to support spontaneous breathing and decrease WOB as P High is reduced.  Wean until patient is in Cpap.  Add Pressure Support judiciously.  Add Pressure Support to P High in order to decrease WOB while avoiding over-distention, P High + PS < 30 cmH 2 O.

34.  http://rc.rcjournal.com/content/57/2/282.full.pdf http://rc.rcjournal.com/content/57/2/282.full.pdf  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC273 2103/#CIT15 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC273 2103/#CIT15  http://www.americannursetoday.com/airway- pressure-release-ventilation-a-boost-for-spontaneous- breathing/ http://www.americannursetoday.com/airway- pressure-release-ventilation-a-boost-for-spontaneous- breathing/  http://www.atsjournals.org/doi/full/10.1164/ajrccm. 164.1.2001078#.VgNFnt9Viko http://www.atsjournals.org/doi/full/10.1164/ajrccm. 164.1.2001078#.VgNFnt9Viko  http://adc.bmj.com/content/80/5/475.full http://adc.bmj.com/content/80/5/475.full  http://www.draeger.com/sites/assets/PublishingIma ges/Generic/UK/Booklets/rsp_new_nomenclature_ve ntilation_modes_ICU_booklet_9066477_en.pdf http://www.draeger.com/sites/assets/PublishingIma ges/Generic/UK/Booklets/rsp_new_nomenclature_ve ntilation_modes_ICU_booklet_9066477_en.pdf

35.  http://www.ncbi.nlm.nih.gov/pmc/articles/P MC2732103/ http://www.ncbi.nlm.nih.gov/pmc/articles/P MC2732103/  Cairo, J., & Pilbeam, S. (2012). Pilbeam's mechanical ventilation: Physiological and clinical applications (5th ed.). St. Louis, Mo.: Elsevier Mosby.