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Basic modes of mv

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Modes of ventilatory Support

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Basic modes of mv

  1. 1. Basic Modes of MV Mostafa Elshazly Professor Of Pulmonary Medicine Chairman Of Pulmonary Critical Care Unit (PCCU) Kasr Alainy School Of Medicine Cairo University elshazly66@Hotmail.com
  2. 2. Invasive Mechanical Ventilation Workshop
  3. 3. • Normal breathing is composed of an infinite range of breaths that vary in depth and timing to suit any and every circumstance from sleeping, yawning or coughing to singing or running.
  4. 4. • Mechanical substitution of the natural act of breathing could never hope to match what nature has achieved, but within the ICU ventilator we do have at our disposal a range of breath types that are characterized by properties that fall into two principle domains, those of cycling and inspiratory motive force.
  5. 5. • The cycling properties of a breath describe what makes the breath start, what makes the breath end and describes the relationship the breath has with other breaths. an active ‘flow’ (TI flow ) an end-inspiratory pause (TIpause )
  6. 6. • The cycling properties of a breath describe what makes the breath start, what makes the breath end and describes the relationship the breath has with other breaths.
  7. 7. • The inspiratory motive force simply refers to the mechanism the ventilator uses to drive gas into the lungs.
  8. 8. Ventilatory Support FULL PARTIAL All energy provided by ventilator e.g. ACV / full support SIMV ( RR = 12-26 & TV = 8-10 ml/kg) Pt provides a portion of energy needed for effective ventilation e.g. SIMV (RR < 10) Used for weaning WOB total = WOB ventilator (forces gas into lungs)+ WOB patient (msls draw gas into lungs)
  9. 9. What Is A ‘ Mode Of Ventilation’ ? • A ventilator mode is delivery a sequence of breath types & timing of breath
  10. 10. Inspiratory Cycling Triggering • Inspiratory cycling that is determined by the ventilator usually occurs because a certain amount of time has elapsed since the last breath. • Alternatively inspiratory cycling can be at the patient’s instigation
  11. 11. Inspiratory Cycling Triggering ( manual)
  12. 12. Inspiratory Cycling Triggering ( machine)
  13. 13. Inspiratory Cycling Triggering (Patient) • They are pressure trigger sensitivity and flow trigger sensitivity .
  14. 14. Inspiratory Cycling Triggering (Patient)
  15. 15. Inspiratory Cycling Triggering (Patient)
  16. 16. Inspiratory Cycling Triggering (Patient)
  17. 17. Expiratory Cycling • Expiratory cycling can be based on either time or flow.
  18. 18. Expiratory Cycling • Ventilator allows exhalation to begin when a preset inspiratory time has ended and a preset tidal volume or a preset inspiratory pressure has been reached. 1. Time Cycled
  19. 19. Expiratory Cycling • Ventilator allows exhalation to begin when a preset inspiratory time has ended and a preset tidal volume or a preset inspiratory pressure has been reached. 1. Time Cycled
  20. 20. Expiratory Cycling • Ventilator allows exhalation to begin when inspiratory flow decreases to a preset expiratory trigger. • Flow-dependent expiratory cycling can only operate when inspiration is PSV. • IFR rises rapidly to a peak and then falls exponentially. • When the IFR falls below a specific threshold, measured as a percentage of the PIF , the ventilator cycles into expiration 2. Flow Cycled
  21. 21. Expiratory Cycling • Ventilator allows exhalation to begin when inspiratory flow decreases to a preset expiratory trigger. 2. Flow Cycled
  22. 22. Inspiratory Motive Force • During inflation, a MV causes gas to flow into a patient’s lungs and it can only do so by creating a pressure gradient between the upper airway and the alveoli.
  23. 23. Inspiratory Motive Force
  24. 24. Inspiratory Motive Force
  25. 25. Inspiratory Motive Force • In each case, one variable is the primary, independent variable whose change in value is predetermined, and the other is the secondary, dependent variable whose change in value can only be measured. • In other words, to effect PPV, we can either choose to deliver a predetermined volume and accept the pressure change that this causes, or effect a predetermined pressure change and accept the volume that this delivers.
  26. 26. Inspiratory Motive Force • In each case, one variable is the primary, independent variable whose change in value is predetermined, and the other is the secondary, dependent variable whose change in value can only be measured. • In other words, to effect PPV, we can either choose to deliver a predetermined volume and accept the pressure change that this causes, or effect a predetermined pressure change and accept the volume that this delivers.
  27. 27. Inspiratory Motive Force • Pressure • Volume • Dual control • Occurs in situations where inspiration starts out as volume control and then switches to pressure control before the end of the breath (or vice versa).
  28. 28. Inspiratory Motive Force • Volume as the drive to inspiration • With VCV, the Vt is preset and the ventilator generates the flow required to deliver this volume in the available Ti , with the airway pressure being entirely dependent on the Raw & C of the respiratory system.
  29. 29. Inspiratory Motive Force • Volume as the drive to inspiration
  30. 30. Inspiratory Motive Force • Volume as the drive to inspiration
  31. 31. Inspiratory Motive Force • Pressure as the drive to inspiration • In PCV, the airway pressure generated during inspiration is set with the resulting Vt depending upon the respiratory system compliance and resistance.
  32. 32. Inspiratory Motive Force • Pressure as the drive to inspiration • In PCV, the airway pressure generated during inspiration is set with the resulting Vt depending upon the respiratory system compliance and resistance.
  33. 33. Inspiratory Motive Force • Pressure as the drive to inspiration • In PCV, the airway pressure generated during inspiration is set with the resulting Vt depending upon the respiratory system compliance and resistance.
  34. 34. Inspiratory Motive Force
  35. 35. Inspiratory Motive Force • Multi-parameter breaths • Most intensive care ventilators now offer dual parameter modes that combine the volume guarantees of VCV with the pressure and flow characteristics of PCV.
  36. 36. Classification of modes  Broadly speaking, modes fall into four categories, as described above:  Mandatory,  Triggered,  Spontaneous and  Hybrid modes Within these categories the wide and often confusing range of PPV modes offered by the modern intensive care ventilator can be understood by considering the following key elements:
  37. 37. Classification of modes  Broadly speaking, modes fall into four categories, as described above:  Mandatory,  Triggered,  Spontaneous and  Hybrid modes ➢ What determines Trigger? ➢ What drives control parameter ➢ Is feedback intra-breath or inter-breath? ➢ What determines cycling?
  38. 38. Classification of mode • Mandatory Modes • Continuous Mandatory Ventilation (CMV) is the simplest mode of ventilatory support. • Vt & RR are fixed and there is no synchronization with the patient’s respiratory efforts.
  39. 39. Classification of mode • Mandatory Modes • Continuous Mandatory Ventilation (CMV) is the simplest mode of ventilatory support. • PIP &Ti are fixed and there is no synchronization with the patient’s respiratory efforts.
  40. 40. Classification of mode • Mandatory Modes
  41. 41. Classification of mode • Mandatory Modes
  42. 42. Classification of mode • Mandatory Modes • Volume-targeted pressure control combines the benefits of volume and pressure control • The volume is set, but rather than being delivered as a constant flow rate for a set period of time, it is delivered as a pressure-controlled breath with a square wave of pressure and a decelerating flow rate.
  43. 43. Classification of mode • Mandatory Modes
  44. 44. Classification of mode • Triggered Modes • Pressure Support
  45. 45. Classification of mode • Triggered Modes • Pressure Support • Spontaneous breathing is assisted with an increase in airway pressure following each inspiratory effort . • The ventilator continues to deliver the breath until the inspiratory flow has decreased to a specific level (e.g., at 25% of the peak inspiratory flow) (flow cycle-off).
  46. 46. Classification of mode • Triggered Modes • Pressure Support • Spontaneous breathing is assisted with an increase in airway pressure following each inspiratory effort . • The ventilator continues to deliver the breath until the inspiratory flow has decreased to a specific level (e.g., at 25% of the peak inspiratory flow) (flow cycle-off).
  47. 47. Classification of mode • Triggered Modes • Volume-targeted pressure support (VS ) • Is a modification of pressure support and can be considered a dual parameter mode applied to a support mode.
  48. 48. Classification of mode • Triggered Modes • Proportional assist ventilation(PAV ) • Is a modification of pressure support and can be considered a dual parameter mode applied to a support mode. • The degree of support varies according to patient effort such that with increasing patient effort more support is provided. It has been described as the ventilator equivalent of power steering.
  49. 49. Classification of mode • Triggered Modes
  50. 50. Classification of mode • Assist control • In AC the patient is able to trigger ventilator breaths • Vt & RR are set as in CMV. However, the set frequency should be considered as the minimum or back-up rate that the ventilator will deliver if the patient makes no respiratory efforts when the mode is effectively identical to CMV. • However, if the patient makes an inspiratory effort, the ventilator delivers a breath of the set tidal volume. Hybrid Modes
  51. 51. Classification of mode • Assist control • In AC the patient is able to trigger ventilator breaths • Vt & RR are set as in CMV. However, the set frequency should be considered as the minimum or back-up rate that the ventilator will deliver if the patient makes no respiratory efforts when the mode is effectively identical to CMV. • However, if the patient makes an inspiratory effort, the ventilator delivers a breath of the set tidal volume. Hybrid Modes
  52. 52. Classification of mode • Synchronized intermittent mandatory ventilation • This ventilation mode is a transition from assist-controlled (A/C) ventilation mode to pressure support ventilation (PSV) mode. • So, the type of breath that is delivered is a combination of mandatory breath, assisted breath, and pressure support. Hybrid Modes
  53. 53. Classification of mode • Synchronized intermittent mandatory ventilation • Cycle of SIMV is divided into two parts: • SIMV period • Spontaneous period Hybrid Modes
  54. 54. Classification of mode • Synchronized intermittent mandatory ventilation • Cycle of SIMV is divided into two parts: • SIMV period • Patient trigger in AC trigger window will deliver assisted breath while in inspiratory time Ti. • If there is no patient trigger until assist control trigger window has elapsed, the mandatory breath will be delivered while in inspiratory time Ti. Hybrid Modes
  55. 55. Classification of mode • Synchronized intermittent mandatory ventilation • Cycle of SIMV is divided into two parts: • SIMV period • Spontaneous period • Every patient trigger of spontaneous breath while in spontaneous period will be given and supported by pressure support. Spontaneous period ends when the SIMV cycle ends. Hybrid Modes
  56. 56. Classification of mode • Synchronized intermittent mandatory ventilation • Cycle of SIMV is divided into two parts: • SIMV period • Spontaneous period • Every patient trigger of spontaneous breath while in spontaneous period will be given and supported by pressure support. Spontaneous period ends when the SIMV cycle ends. Hybrid Modes
  57. 57. Classification of mode • Synchronized intermittent mandatory ventilation Hybrid Modes
  58. 58. Classification of mode • Synchronized intermittent mandatory ventilation Hybrid Modes
  59. 59. Classification of mode • Synchronized intermittent mandatory ventilation Hybrid Modes
  60. 60. Classification of mode • Synchronized intermittent mandatory ventilation Hybrid Modes
  61. 61. Classification of mode • bi-level ventilation • In its simplest form, bi-level ventilation can be likened to a form of CPAP in which the level of CPAP cycles between two different pressures with the phase transitions synchronized to the patient’s inspiration and expiration Hybrid Modes
  62. 62. Classification of mode • bi-level ventilation • The patient’s spontaneous breathing activity is unsupported and the user simply sets the duration (Thigh) and pressure (Phigh) for the high-pressure phase as well as the duration (Tlow) and pressure (PEEP) for the low- pressure phase. Hybrid Modes
  63. 63. Classification of mode • bi-level ventilation • More recent implementations of the bi-level concept have added pressure support to breaths triggered during the low-pressure phase or during both low and high phases . • The ability to maintain spontaneous ventilation throughout all phases of ventilation is claimed to improve comfort as it prevents the patient ‘fighting the ventilator’. Hybrid Modes
  64. 64. Classification of mode • bi-level ventilation • More recent implementations of the bi-level concept have added pressure support to breaths triggered during the low-pressure phase or during both low and high phases . • The ability to maintain spontaneous ventilation throughout all phases of ventilation is claimed to improve comfort as it prevents the patient ‘fighting the ventilator’. Hybrid Modes
  65. 65. Classification of mode • Airway pressure release ventilation • APRV is a variant of bi-level ventilation where a relatively high airway pressure is maintained for a prolonged period with brief episodes when the airway pressure falls to a lower value . • Spontaneous ventilation is maintained throughout. APRV maintains a high mean airway pressure promoting lung recruitment and is an effective method of improving oxygenation in patients with severe ARDS . Hybrid Modes
  66. 66. Classification of mode • Airway pressure release ventilation • APRV is a variant of bi-level ventilation where a relatively high airway pressure is maintained for a prolonged period with brief episodes when the airway pressure falls to a lower value . • Spontaneous ventilation is maintained throughout. APRV maintains a high mean airway pressure promoting lung recruitment and is an effective method of improving oxygenation in patients with severe ARDS . Hybrid Modes

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