Newer modes of mechanical ventilation

Newer modes of mechanical ventilation

1. NEWER MODES OF MECHANICAL VENTILATION Presenter: Dr. Suresh Pradhan Moderator: Prof. UC Sharma

2. ultimate goal of mechanical ventilation is to sustain life and do no harm provide adequate ventilation and oxygenation avoid ventilator-induced lung injury provide patient-ventilator synchrony and allow successful weaning from mechanical ventilation

3. with each generation of ventilators, new modes and variations on previous modes become available there now exist numerous ventilator modes from a variety of manufacturers to describe the technical and clinical aspects of advanced modes of ventilation that have recently become available

4. although heavily promoted by their manufacturers, the clinical role of many of these modes remains unproven use of these modes is often based upon their availability and clinicians bias, rather than evidence that they are superior to traditional modes

5. Why New Modes? Address important clinical issues: Poor trigger Proportional assist to match patients effort Improve patient - ventilator synchrony More rapid weaning Less likelihood of VILI Less hemodynamic compromise More effectively ventilate/oxygenate

6. Nearly 50% time is spend on weaning Striving for better outcomes: The three • S pontaneous breathing (Girard 2008; MacIntyre 2000, Levine 2008) • S ynchrony (Chao 1997;Thille 2006; De Wit 2009) • S edation management (Kress 2000, Girard 2008, De Wit 2009) “S”s All reduce time on mechanical ventilation

7. Arguments Against New Modes Lack high-level evidence for better patient outcomes If we try a new mode and the patient has a good outcome, we say it was due to the new mode. But if try a new mode and there is a bad outcome, we say the patient was going to die anyway. Potential for harm (these are often not reported) Improved gas exchange does not necessarily improve outcomes New is not necessarily better Solution to a problem or in search of a problem?

8. J P Mulier New Ventilation modes Wintersymposium Leuven 8 1 2011 8

9. Different Modes Airway Pressure Release Ventilation (APRV) High Frequency Oscillatory Ventilation (HFOV) High Frequency Jet Ventilation (HFJV) Inverse Ratio Ventilation (IRV) Neurally Adjusted Ventilatory Assist (NAVA)

10. Liquid Ventilation Mandatory Minute Ventilation Adaptive Support Ventilation (ASV) Automatic Tube Compensation

11. Extracorporeal Membrane Oxygenation (ECMO) Prone ventilation Intravascular Oxygenation

12. Airway Pressure Release Ventilation (APRV) a mode of ventilation in which the spontaneous breaths are at an elevated baseline (i.e., CPAP) this elevated baseline is periodically “released” to facilitate expiration has two CPAP or pressure levels—high pressure (P high or PINSP) and low pressure (Plow or PEEP), and the patient is allowed to breathe spontaneously without restriction

13. when the high pressure ( Phigh ) level is dropped or “released” to the low pressure (Plow) level, it simulates a mechanical exhalation likewise, when the low pressure (Plow) level is raised to the high pressure ( Phigh ) level, it simulates an inspiratory mechanical breath

14. mandatory inspiration begins with time-triggered closing of the release valve, airway pressure rapidly increases to the baseline CPAP pressure and is maintained for the duration of inspiration inspiration ends with time-triggered opening of the release valve, which allows the circuit pressure to decrease as the patient exhales unique about this mode is that the patient is allowed to breathe spontaneously at the high or low pressure levels

15. Characteristics of APRV

16. Initial settings P high 15 to 30 cm H 2 O overdistension of lungs must be avoided; so max P high of 35 cm H 2 O recruitment of collapsed alveoli and the maintenance of these recruited units can take as long as 8 hours or longer for recruitment to occur

17. P low 0 to 15 cm H 2 O most recommend P low of 0 cm H 2 O that allows unimpeded expiratory gas flow

18. Indications for APRV similar to that of pressure control, as an alternative to conventional volume-controlled ventilation for patients with significantly decreased lung compliance such as patients with ARDS conventional VC ventilation in these patients is associated with excessive peak airway pressures and barotrauma APRV can provide effective partial ventilatory support with lower peak airway pressure than that provided by the PSV and SIMV modes

19. Advantages provide effective partial ventilatory support with lower peak airway pressure better oxygenation less circulatory interference better ventilation – perfusion matching lesser chance of VILI less sedation and analgesia preserving spontaneous ventilation

20. Disadvantages unpredictable volume delivery requires expertise could be harmful to patients with high expiratory resistance (i.e., COPD or asthma) auto-PEEP is usually present caution should be used with hemodynamically unstable patients asynchrony can occur if spontaneous breaths are out of sync with release time requires the presence of an “active exhalation valve”

21. High Frequency Oscillatory Ventilation ( HFOV ) HFOV was presented in 1952 by Emerson developed for clinical application in the early 1970s by Lunkenheimer clinical use in neonates in 1991 children in 1995, and adults in 2001.

22. HFOV uses high-frequency, low volume oscillations these oscillations create a high mean airway pressure, which improves gas exchange in the lungs by opening collapsed alveoli (alveolar recruitment) and preventing further alveolar collapse the small tidal volumes (typically 1–2 mL) limit the risk of alveolar overdistension and volutrauma

23. Ventilator Settings HFOV requires a specialized ventilator (Sensormedics 3100B, Viasys ) that allows the following adjustments: the frequency and amplitude of the oscillations the mean airway pressure the bias flow rate (similar to an inspiratory flow rate) the inspiratory time (time of the bias flow)

24. Oscillations the frequency range for the oscillations is 4 –7 Hz the pulse amplitude (tidal volume) determines CO2 removal, pulse amplitude is inversely related to the frequency of oscillations; i.e., lower oscillation frequencies result in higher tidal volumes and more effective CO 2 removal the initial pulse amplitude is set at 70–90 cm H 2 O

25. Mean airway pressure the end-inspiratory alveolar pressure (e.g., the plateau pressure during volume control ventilation) should be measured just prior to switching from CMV to HFOV this pressure is a reflection of: (a) alveolar volume, and (b) the risk of alveolar overdistension and volutrauma

26. Advantages comparing HFOV with CMV, have shown a 16–24% increase in the PaO 2 /FIO 2 ratio associated with HFOV studies shows a significant survival benefit with HFOV

27. Disadvantages a special ventilator is needed, along with trained personnel to operate the device cardiac output is often decreased during HFOV because of the high mean airway pressures aerosolized bronchodilators are ineffective during HFOV

28. High Frequency Jet Ventilation (HFJV) characterised by delivery of small tidal volumes (1-3mls/kg) from a high pressure jet at supraphysiological frequencies (1-10Hz) followed by passive expiration

29. Approaches can be applied via different approaches: Supraglottic Trans-tracheal Subglottic

30. Subglottic Jet Ventilation

31. Trans-tracheal Jet Ventilation

32. Advantages and Disadvantages of each approaches

33. Complications of HFJV

34. Inverse Ratio Ventilation (IRV) ratio of inspiratory time (I time) to expiratory time (E time) is known as the I:E ratio in conventional mechanical ventilation, the I time is traditionally lower than the E time so that the I:E ratio ranges from about 1:1.5 to 1:3

35. this resembles the normal I:E ratio during spontaneous breathing the inverse I:E ratio in use is between 2:1 and 4:1 and often it is used in conjunction with pressure-controlled ventilation

36. Physiology of IRV Inverse ratio ventilation (IRV) improves oxygenation by reduction of intrapulmonary shunting improvement of V/Q matching decrease of deadspace ventilation

37. to achieve the same degree of ventilation and oxygenation, IRV requires a lower peak airway pressure and PEEP, but a higher mean airway pressure ( mPaw ) than conventional mechanical ventilation

38. the increase in mPaw during IRV helps to reduce shunting and improve oxygenation in ARDS patient IRV provides a longer I time and shorter E time breath stacking with an increase of end-expiratory pressure is likely when there is not enough time for complete expiration; addition of Auto-PEEP

39. Adverse Effects of IRV increase in mPaw and the presence of auto-PEEP both contribute to the increase of mean alveolar pressure and volume, and the incidence of barotrauma may be as high as that obtained by conventional ventilation with high levels of PEEP higher rate of trans-vascular fluid flow or flooding induced by an increased alveolar pressure this condition may induce or worsen preexisting pulmonary edema

40. Neurally Adjusted Ventilatory Assist (NAVA) is a mode of mechanical ventilation in which the patient’s electrical activity of the diaphragm ( EAdi or Edi) is used to guide the optimal functions of the ventilator

41. the neural controls of respiration originated in the patient’s respiratory center are sent to the diaphragm via the phrenic nerves ↓ in turn, bipolar electrodes are used to pick up the electrical activity ↓ electrical activity of the diaphragm (Edi) is captured ↓ fed to the ventilator ↓ assist the patient’s breathing

42. Edi catheter the electrodes are mounted on a disposable Edi catheter and positioned in the esophagus at the level of the diaphragm

43. NAVA is available for adults, children, and neonates has been used successfully in the management and weaning of mechanically ventilated patients with spinal cord injury other uses and potential applications of NAVA include patients with head injury, COPD, and history of ventilator dependency the ability to wean these patients rapidly reduces or eliminates the incidence of disuse atrophy of the diaphragm

44. Advantages of NAVA improved synchrony lung protection patient comfort

45. Liquid Ventilation technique of mechanical ventilation in which the lungs are insufflated with an oxygenated perfluorochemical liquid Used in ARDS

46. Perfluorocarbon Chemically and biologically inert Have low surface tension O 2 carrying capacity- 2 times CO 2 carrying capacity – 4 times More dense than gas Sufficiently volatile to allow elimination through lungs

47. PFC is instilled at a rate of 1 ml/kg/min body weight through side port of ET tube Advantages improvement in oxygenation increased compliance

48. Mandatory Minute Ventilation also called minimum minute ventilation a feature of some ventilators that provides a predetermined minute ventilation when the patient’s spontaneous breathing effort becomes inadequate

49. Operator presets a target minute ventilation ↓ Patient breathes spontaneously ↓ If the patient's spontaneous breaths generate a lower minute ventilation. ↓ Ventilator supplies either volume or pressure-controlled mandatory breaths

50. Limitations Rapid and ineffective breathing Dangerously high VT Development of auto-PEEP

51. Adaptive Support Ventilation (ASV) a mode of ventilation that changes the number of mandatory breaths and pressure support level according to the patient’s breathing pattern the ventilator measures the dynamic compliance and expiratory time constant to adjust the mechanical tidal volume and frequency for a target minute ventilation

52. the optimal tidal volume is calculated by dividing the minute ventilation by the optimal frequency in terms of the lowest work of breathing the therapist inputs the patient’s body weight and the desired percent minute volume and FiO2 and PEEP algorithm determines the optimal RR/VT combination; I:E ratio according to patient’s respiratory mechanics net result – optimal breathing pattern

53. Advantages early liberation from ventilatory support patient comfort useful in post-operative, COPD and ARDS. intensivist can concentrate on other aspects besides ventilatory support

54. Automatic Tube Compensation ATC was designed specifically to reduce the work associated with ETT resistance to set ATC, the operator has to select the ATC function and enter the tube type (ET / Tracheostomy) and the tube size Available in: Drager Evita XL Puritan Bennett 840 VIASYS Avea

55. theoretically ATC delivers exactly the amount of pressure required to overcome the resistance imposed by the ET / Tracheostomy tube based on the calculated tracheal pressures

56. Studies Show: ATC reduces the risk of air trapping due to resistance from ETT Improves patient – ventilator synchrony Enhances patient comfort

57. Extracorporeal Membrane Oxygenation ( ECMO ) is instituted for the management of life threatening pulmonary or cardiac failure , when no other form of treatment has been or is likely to be successful ECMO is essentially a modification of the cardiopulmonary bypass circuit which is used routinely in cardiac surgery

58. Dynamics of ECMO blood is removed from the venous system either peripherally via cannulation of a femoral vein or centrally via cannulation of the right atrium, Oxygenation & CO 2 removal blood is then returned to the body either peripherally via a femoral artery or centrally via the ascending aorta

59. Indications CARDIAC FAILURE post-cardiotomy ,when unable to get patient off cardiopulmonary bypass following cardiac surgery post-heart transplant usually due to primary graft failure severe cardiac failure due to almost any other cause decompensated cardiomyopathy ,Myocarditis ,Acute coronary syndrome with cardiogenic shock profound cardiac depression due to drug overdose or sepsis

60. RESPIRATORY FAILURE ARDS Pneumonia Trauma Primary graft failure following lung transplantation

61. Two most common forms are: Veno -arterial (VA) a venous cannula is usually placed in the right common femoral vein for extraction and an arterial cannula is usually placed into the right femoral artery for infusion Veno -venous (VV) cannula are usually placed in the right common femoral vein for drainage and right internal jugular vein for infusion

62. Complications a common consequence in ECMO-treated adults is neurological injury, which may include  subarachnoid hemorrhage ischemic infarctions in susceptible areas of the brain hypoxic-ischemic encephalopathy unexplained coma brain death bleeding occurs in 30 to 40 percent of those receiving ECMO and can be life-threatening It is due to both the necessary continuous heparin infusion and platelet dysfunction

63. Prone Ventilation prone positioning has been used many years to improve oxygenation in patients who require mechanical ventilatory for-support for management of the acute respiratory distress syndrome (ARDS) randomized, controlled trials have confirmed that oxygenation is significantly better when patients are in the prone position than when they are in the supine position

64. evidence have shown that prone positioning could prevent ventilator-induced lung injury meta-analyses have suggested that survival is significantly improved with prone positioning as compared with supine positioning among patients with severely hypoxemic ARDS

65. an experimental method of raising the oxygen levels of the blood and reducing carbon dioxide levels by means of a device, the intravenous oxygenator (IVOX), introduced into a vein IVOX consists of a bundle of about 100 very fien siloxane-coated polypropylene hollow fibres through which oxygen is passed the bundle is about 50cms long and is inserted into the inferior venecava Intravascular Oxygenation

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