Newer modes of ventilation

modes of ventilation and their evolution till date

1. NEWER MODES OF VENTILATION PRESENTER- DR. RICHA KUMAR MODERATOR- DR. AREFA JALIL

2. THE ORIGIN OF MECHANICAL VENTILATION Andreas Vesalius is the first person to describe  mechanical ventilation in 1543 “But the life may…be restored to the animal, an opening must be attempted in the trunk of trachea, in which a tube of reed or cane should be put; you will then blow into this, so that the lung may rise again and the animal take in air.. And as I do this, and take care that the lung is inflated in intervals, the motion of the heart and arteries does not stop….”

3. Mechanical ventilation is administered primarily in patients unable to maintain adequate alveolar ventilation The role is supportive and is used to buy time while addressing the condition that lead to respiratory failure. It should aim at “providing support , doing least harm”

4. The ability of ventilator to initiate , maintain and terminate an assisted breath derives its basis from “ equation of motion” Ventilator pressure to deliver a breath = pressure needed to overcome the airway resistance + pressure needed to inflate the chest wall and the lung

5. Equation of Motion Ventilation Pressure (to deliver tidal volume) = Elastic Pressure (to inflate lungs and chest wall) + Resistive Pressure (to make air flow through the airways) P = Resistance x Flow + Elastance x Volume Pressure = P resistive + P elastance

6. PROBLEMS WITH CONVENTIONAL MODES OF VENTILATION IN critical care setting, all the parameters in equation of motion change with time A ventilator setting appropriate for one point of time may not be optimal with patient deterioration or improvement. Deliver the set parameters and take no feedback from the patient

7. Classical volume or pressure control modes are “OPEN LOOPS” (feed back loop is absent ) Newer modes target to make alterations with changing lung and take feedback from patient parameters and are “closed loop” type

8. Inspiration Expiration 1 20 1 2 3 -3 20 2 1 20 1 2 3 -3 20 2 Inspiration Expiration Volume/Flow Control Pressure Control Time (s) Time (s) Paw Paw Pressure Volume Flow

9. Control Variables

10. NEED OF NEWER MODES Conventional modes are uncomfortable More safely assist patient Less need for heavily sedation & paralysis More effectively ventilate/oxygenate Improve patient – ventilator synchrony Less haemodynamic compromise Lung protective ventilation : less likelihood of Ventilator Induced Lung Injury More rapid weaning

11. EVOLUTION  OF  MECHANICAL  VENTILATORS

12. Modern ventilators now incorporate complex computer based algorithms, and are capable of simultaneously controlling two variables. Intrabreath control (dual control WITHIN a single breath, DCWB) : During a part of an essentially pressure-targeted breath, flow is also controlled Interbreath control (dual control from breath to breath, DCBB): The configuration of a pressure-targeted breath is manipulated n SUBSEQUENT breaths to deliver a targeted tidal volume Dual-Controlled Modes

13. VOLUME ASSURED PRESSURE SUPPORT

14. Dual Control within a Breath volume-assured pressure support (VAPS) This is modification of pressure control mode This mode allows a feedback loop based on the volume It makes ventilator to switch from pressure control to volume control if a minimum set TV is not achieved. Bear 1000 Tbird Bird 8400Sti

15. operator adjustable parameters are same as in conventional PC mode – pressure limit, peak flow rate, ventilator rate, and PEEP Additionally “minimum TV” is also defined This combination provides an optimal inspiratory flow during assisted/controlled cycles, reducing the patient’s work of breathing commonly seen during Ventilator Assisted Ventilation (VAV) and causes lower intrinsic PEEP Unlike typical PSV, VAPS assures stable tidal volume along with pressure support in patients with irregular breathing patterns

16. Benefits of VAPS Lower peak airway pressure Reduced patient work of breathing Improved gas distribution Less need for sedation Improved patient comfort

17. ADEQUATE PATIENT EFFORT If the delivered volume equals the preset volume, the configuration of the breath is similar to that of a pressure supported breath : the flow is decelerating the breath is flow-cycled

18. INADEQUATE PATIENT EFFORT If the flow fall below the set tidal volume within the assigned inspiratory time, the machine delivers a volume controlled breath : flow targeted volume cycled

19. P aw cmH 2 60 -20 60 Flow L/min Volume Set flow limit Set tidal volume cycle threshold Set pressure limit Tidal volume met Tidal volume not met Switch from Pressure control to Volume/flow control Inspiratory flow greater than set flow Flow cycle Inspiratory flow equals set flow Pressure limit overridden L 0.6 40

20. Set pressure limit should not be too high to cause unwanted trauma to lung and generate higher volume than minimal Set flow rates must not be very low as in situations where minimal volume is not met  it would cause a delayed switch from pressure control to volume control and would lead to unwanted prolongation of inspiratory time Patients with airflow obstruction should be monitored closely in order to prevent air trapping DISADVANTAGES/ LIMITATIONS OF VAPS

21. Applications of VAPS A patient who requires a substantial level of ventilatory support and has a vigorous  ventilatory drive to improve gas distribution  and synchrony A patient being weaned from the ventilator  and having an unstable  ventilatory drive who may require backup tidal volume as a safety net in case the patients effort or/and  lung  mechanics change

22. VOLUME SUPPORT

23. Dual control breath-to-breath Pressure-limited flow-cycled ventilation Volume Support Servo 300 Maquet Servo- i

24. VS (Volume Support) Entirely a spontaneous mode Ventilator assesses initial breaths and steps up pressure support in subsequent breaths if TV is low

25. Tidal volume is used as feedback control to adjust the pressure support level Intended to provide a control tidal volume and increased patient comfort Delivers a patient triggered (pressure or flow), pressure targeted, flow cycled breath Can also be timed cycled (if TI is extended for some reason) or pressure cycled (if pressure rises too high). It adjusts pressure (up or down) to achieve the set volume (the maximum pressure change is < 3 cm H 2 O and ranges from 0 cm H 2 O to 5 cm H 2 O below the high pressure alarm setting

26. INDICATIONS Spontaneous breathing patient who require minimum ventilatory effort Patients who have inspiratory effort needing adaptive support Patients who are asynchronous with the ventilator Used for patients ready to be “ weaned ” from the ventilator Used for patients who cannot do all the WOB but who are breathing spontaneously

27. The ventilator delivers a single spontaneous pressure support type of breath and uses variable pressure support levels to provide the target tidal volume During weaning or awakening from anesthesia, the patient assumes a higher spontaneous tidal volume and the ventilator decreases the pressure support level accordingly

28. When the spontaneous tidal volume decreases, the ventilator increases the pressure support level automatically to maintain the target tidal volume. During VS, the ventilator frequency and minute ventilation are determined by the triggering effort of the patient. The inspiratory time is determined by the patient respiratory demand .

29. VS (Volume Support) ( 1 ) , VS test breath (5 cm H2O); ( 2) , pressure is increased slowly until target volume is achieved; ( 3) , maximum available pressure is 5 cm H2O below upper pressure limit; ( 4) , VT higher than set VT delivered results in lower pressure; ( 5) , patient can trigger breath; ( 6) if apnea alarm is detected, ventilator switches to control mode /PRVC

30. VS vs VAPS How does volume support differ from VAPS ? In volume support, we are trying to adjust pressure so that, within a few breaths, desired V T is reached. In VAPS, we are aiming for desired V T tacked on to the end of same breath if a pressure-limited breath is going to fail to achieve V T

31. ADVANTAGES Guaranteed VT and VE Pressure supported breaths using the lowest required pressure Decreases the patient’s spontaneous respiratory rate Decreases patient WOB Allows patient control of I:E time Breath by breath analysis

32. Disadvantages Spontaneous ventilation required VT selected may be too large or small for patient Varying mean airway pressure A sudden increase in respiratory rate and demand may result in a decrease in ventilator support

33. PRESSURE REGULATED VOLUME CONTROLLED (PRVC)

34. Dual Control Breath-to-Breath pressure-limited time-cycled ventilation Pressure Regulated Volume Control Servo 300 Maquet Servo- i

35. PRESSURE REGULATED VOLUME CONTROL Ventilation that provides volume controlled breaths with the lowest pressure possible by altering the flow and inspiratory time Delivers patient or timed triggered, pressure-targeted (controlled) and time-cycled breaths

36. Ventilator measures VT delivered with VT set on the controls. If delivered VT is less or more, ventilator increases or decreases pressure delivered until set VT and delivered VT are equal PRVC provides volume support while keeping the PIP at a lowest level possible by altering the peak flow and inspiratory time in response to changing airway or compliance characteristics .

37. INDICATIONS Patient who require the lowest possible pressure and a guaranteed consistent VT ALI/ARDS Patients requiring high and/or variable ventilatory effort Patient with the possibility of changes in compliance of lung/ Resistance of airway

38. ALGORITHM

39. PRVC (Pressure Regulated Volume Control) ( 1 ), Test breath (5 cm H 2 O); ( 2) pressure is increased to deliver set volume; ( 3) , maximum available pressure; ( 4) , breath delivered at preset E , at preset f, and during preset T I ; ( 5) , when V T corresponds to set value, pressure remains constant; ( 6) , if preset volume increases, pressure decreases; the ventilator continually monitors and adapts to the patient’s needs

40. The increasing airflow resistance may be due to increasing airway resistance ( nonelastic resistance) or decreasing lung compliance (elastic resistance) At constant flow, the PIP is increased due to increasing airflow resistance. Increased Airflow Resistance ( nonelastic or elastic) : Increase PIP / Flow PRVC lowers the flow to reduce the driving pressure . Increased Airflow Resistance ( nonelastic or elastic) : PIP / Decrease Flow

41. To compensate for a lower inspiratory flow, PRVC prolongs the inspiratory time to deliver the target volume (VT - Increased Constant Flow * decreased Inspiratory Time) The ventilator will not allow delivered pressure to rise higher than 5 cm H2O below set upper pressure limit Example: If upper pressure limit is set to 35 cm H2O and the ventilator requires more than 30 cm H2O to deliver a targeted VT of 500 mL, an alarm will sound alerting the clinician that too much pressure is being required to deliver set volume

42. ADVANTAGES Maintains a minimum PIP Guaranteed V T and E Patient has very little WOB requirement Allows patient control of respiratory rate and E Variable E to meet patient demand Decelerating flow waveform for improved gas distribution Breath by breath analysis

43. DISADVANTAGES Varying mean airway pressure May cause or worsen auto-PEEP When patient demand is increased, pressure level may diminish when support is needed May be tolerated poorly in awake non-sedated patients A sudden increase in respiratory rate and demand may result in a decrease in ventilator support

44. ADAPTIVE SUPPORT VENTILATION (ASV)

45. Dual Control Breath-to-Breath adaptive support ventilation

46. ASV (Adaptive Support Ventilation) A dual control mode that that PROVIDES A MANDATORY MINUTE VENTILATION Unique: sets minimal work of breathing to deliver desired minute ventilation Control variable is pressure Uses both pressure control and pressure support to maintain a set minimum TV(volume target) using the least required settings for minimal WOB depending on the patient’s condition and effort

47. Set parameters are patient ideal body weight, minimum minute ventilation, PEEP and trigger ventilation It automatically adapts to patient demand by increasing or decreasing support, depending on the patient’s elastic and resistive loads Ventilator continuously optimizes I:E ratio to avoid any auto PEEP

48. INDICATIONS Full or partial ventilatory support Patients requiring a lowest possible PIP and a guaranteed V T ALI/ARDS Patients not breathing spontaneously and not triggering the ventilator Patient with the possibility of work changes (CL and Raw) Facilitates weaning

49. Parameter input: patient’s body weight and desired percent minute volume The body weight is used to estimate the dead space volume and to calculate the alveolar volume For an estimated minute ventilation requirement for a patient, the ventilator uses predetermined settings of 100 mL /min/kg for adults and 200 mL /min/kg for children. The therapist may select the percent minute volume, ranging from 20% to 200% of the predetermined adult or child setting ASV WORKING PRINCIPLE

50. For example, if 160% is selected for an adult, the minute ventilation delivered by the ventilator will be about 160 mL/min/kg ( 100 X 160/100) Once the target minute ventilation is set, the ventilator uses test breaths to measure the system compliance, airway resistance, and any intrinsic PEEP. Following determination of these variables, the ventilator selects and provides the frequency, inspiratory time, I:E ratio, and high pressure limit for mandatory and spontaneous breaths

51. If there is no spontaneous triggering effort, the ventilator determines and provides the mandatory frequency, tidal volume, and high pressure limit needed to deliver the preselected tidal volume, inspiratory time, and I:E ratio As the patient begins to trigger the ventilator, the number of mandatory breaths decreases and the pressure support level increases until a calculated tidal volume is able to provide adequate alveolar volume (i.e., tidal volume = alveolar volume + 2.2 mL/kg of deadspace volume)

52. Clinician enters patient data & % support Ventilator calculates needed minute volume & best rate/TV to produce least work Targeted TV’s given as pressure control or pressure support  breaths If  pt.’s f > “set” by ventilator , MODE  :  PS Ifpt’s f < “set” by ventilator , MODE : PC SIMV/PS If patient is  apneic , all breaths are PC Rate where WOB is minimal Pressure adjusts in +/‐2 cm H2O to achieve Tidal Volume

53. ADVANTAGES Guaranteed VT and E Minimal patient Work Of Breathing Ventilator adapts to the patient Weaning is done automatically and continuously Variable to meet patient demand Decelerating flow waveform for improved gas distribution Breath by breath analysis

54. Disadvantages Inability to recognize and adjust to changes in alveolar VD Possible respiratory muscle atrophy Varying mean airway pressure In patients with COPD, a longer TE may be required A sudden increase in respiratory rate and demand may result in a decrease in ventilator support

55. AUTOMODE

56. AUTOMODE The ventilator switch between mandatory and spontaneous breathing modes Combines volume support (VS) and pressure-regulated volume control (PRVC) If patient is paralyzed; the ventilator will provide PRVC. All breaths are mandatory that are ventilator triggered, pressure controlled and time cycled; the pressure is adjusted to maintain the set tidal volume. If the patient breathes spontaneously for two consecutive breaths, the ventilator switches to VS. All breaths are patient triggered, pressure limited, and flow cycled. If the patient becomes apneic for 12 seconds; the ventilator switches back to PRVC Macquet Servo 300A

57. PROPOTIONAL ASSISST VENTILATION (PAV) p

58. PROPOTIONAL ASSIST VENTILATION Advantage of improving ventilator patient synchrony Amplifies patient’s ventilatory effort giving patient freedom to adopt his own breathing pattern Unloads respiratory muscles without imposing a fixed breathing pattern thus allows synchrony Percentage of assistance to be delivered is set and other parameters are adjusted automatically according to the patients “air hunger” I:E ratio also decided by patient allowing more synchrony

59. ADVANTAGES: Better synchrony More comfort in NIV with PAV compared to PSV Low airway pressures Optimal weaning Decreased work of breathing Early/late ALI/ARDS Hypercapnic ventilatory failure

60. DISADVANTAGE: If patient worsens or improves ,the proportion of assistance needs to be readjusted according to patient’s clinical condition This disadvantage has been adjusted in newer modification “PAV + “ mode  capable of sensing patient respiratory mechanics and adjusting accordingly

61. Mandatory minute ventilation

62. MANADATORY MINUTE VENTILATION Modification of PSV Ventilator takes feedback to alter both respiratory rate and level of pressure support to achieve set minimum minute ventilation Operator sets: minimum minute ventilation (70-90% of current minute volume) ,which is readjusted according to patients clinical condition

63. Patient fails to achieve set volume then ventilator provides the deficit Reliable weaning mode Apneic patient or central drive pathology, MMV sets safety by providing a set value ventilation as mandatory ventilation Caution : MMV lower than current MV  increased WOB MMV more than required MV unloading of muscles atrophy D/A Rapid shallow breathing if RR is set too high

64. Bilevel ventilation modes

65. BiLevels BiPaP ARPC ( airway pressure release ventilation)

66. BiLevel Ventilation Is a spontaneous breathing mode in which two levels of pressure i.e. high /low are set Substantial improvements for SPONTANEOUS BREATHING Better synchronization, More options for supporting spontaneous breathing Potential for improved monitoring

67. BiLevel Ventilation Synchronized Transitions Spontaneous Breaths Spontaneous Breaths P aw cmH 2 60 -20 1 2 3 4 5 6 7 Also called Biphasic Bivent DuoPAP These modes deliver pressure-controlled breaths time-triggered time-cycled breaths using a set-point targeting scheme

68. This mode maintains a constant pressure (set point) even in the face of spontaneous breaths There are two pressures to be set P high P low There are two time intervals to be set Time spent on P high – T high Time spent on P low - T low Patient can breath spontaneously at both these pressures T high T low T high BiPAP

69. CPAP TIME T high T low T high PCV BIPAP Unrestricted spontaneous breathing Allows reduced sedation and promote weaning Phigh improves oxygenation promotes alveolar recruitment Plow Allows exhalation Maintains recruitment

70. P high & P low The volume difference between the two Two levels of functional FRC Creates a driving pressure Determines the VT Permit gas to enter the lung units Represents the difference between airway pressure (Paw) and alveolar pressure ( Palv ) T high T low T high PCV

71. Airway Pressure Release Ventilation Is a Bi-level form of ventilation with sudden short releases in pressure to rapidly reduce FRC and allow for ventilation Can work in spontaneous or apneic patients APRV is similar but utilizes a very short expiratory time for PRESSURE RELEASE this short time at low pressure allows for ventilation

72. APRV always implies an inverse I:E ratio All spontaneous breathing is done at upper pressure level

73. INDICATIONS Partial to full ventilatory support Patients with ALI/ARDS Patients with refractory hypoxemia due to collapsed alveoli Patients with massive atelectasis May use with mild or no lung disease

74. Provides two levels of CPAP and allows spontaneous breathing at both levels when spontaneous effort is present Both pressure levels are time triggered and time cycled

75. The release phase ( expiratory phase) brings down mean airway pressure and plays significant role in maintaining normocarbia. It has dual functionality: In spontaneously breathing pt  patients breathes with supported breaths thus reducing need for sedation In absence of spontaneous breathing bi-level pressure acts as time cycled inverse ratio ventilation.

76. Vt depends of upon respiratory compliance and difference between two CPAP levels

77. Airway Pressure Release Ventilation P aw cmH 2 60 -20 1 2 3 4 5 6 7 8 Spontaneous Breaths Releases

78. ADVANTAGES Allows inverse ratio ventilation (IRV) with or without spontaneous breathing (less need for sedation or paralysis) Improves patient-ventilator synchrony if spontaneous breathing is present Improves mean airway pressure

79. Improves oxygenation by stabilizing collapsed alveoli Allows patients to breath spontaneously while continuing lung recruitment Lowers PIP May decrease physiologic deadspace

80. DISADVANTAGES AND RISKS Variable VT 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 is spontaneous breaths are out of sync with release time Requires the presence of an “active exhalation valve”

81. Automatic tube compression

82. Automatic Tube Compensation Available in the Evita 4 ventilator (Dräger Medical) The PB840 ventilator has a similar feature which is called tubing compensation (TC). Can be applied in all ventilation modes A mode of ventilation that offsets and compensates for the airflow resistance imposed by the artificial airway

83. Overcome Work Of Breathing added by artificial airways It allows the patient to have a breathing pattern as if breathing spontaneously without an artificial airway Improve patient/ventilator synchrony by providing variable fast inspiratory flow

84. INDICATIONS patient who has compromised respiratory function ( COPD, malnutrition, respiratory muscle failure) Those who have failed previous extubation attempt The “difficult to wean” patient

85. Resistance due to ET Tube

86. Due to varying inspiratory flow rates, no single level of pressure support can actually fully compensate for WOB caused by the ETT. ATC uses known static resistance for each size and type of ETT/tracheal tube, and measures flow rates. Pressure is applied and continuously adjusted proportional to resistance.

87. With ATC, the pressure delivered by the ventilator to compensate for the airflow resistance is active during inspiration and expiration. It is dependent on the airflow characteristics and the flow demand of the patient. For example, when the airway diameter decreases or flow demand increases, the pressure is raised to overcome a higher airflow resistance or increased flow demand.

88. ADVANTAGES Designed to Maintain Tracheal Pressure at Baseline Does not require ongoing assessment of resistance! Pressure Applied Based Upon Resistive Properties of the Airway and Patients Inspiratory Flow Positive Pressure During Inspiration Negative Pressure During Exhalation Effectively unloads resistive effort imposed by ETT Improves patient – ventilator synchrony Reduces risk of lung injury

89. Neurally adjusted ventilatory assist (NAVA)

90. Neurally adjusted ventilatory assist (NAVA) 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 . 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 The electrodes are mounted on a disposable EAdi catheter and positioned in the esophagus at the level of the diaphragm .

91. Neural adjusted ventilator assist NAVA Neuro-Ventilatory Coupling Central Nervous System  Phrenic Nerve  Diaphragm Excitation  Diaphragm Contraction  Chest Wall and Lung Expansion  Airway Pressure, Flow and Volume New Technology Ideal Technology Current Technology Ventilator Unit

92. INDICATIONS NAVA is available for adults, children, and neonates, and it 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

93. Components

94. CATHETERS

95. SIGNAL CAPTURE All muscles (including the diaphragm and other respiratory muscles) generate electrical activity to excite muscle contraction. The electrical activity of the diaphragm is captured by an esophageal catheter with an attached electrode array. The signal is filtered in several steps and provide the input for control of the respiratory assist delivered by the ventilator.

96. In a healthy subject only 5% of maximum capacity of neuro ventilatory coupling is used to generate an adequate Vt

97. Benefits of NAVA Synchrony with least possible delay Safer and improved ventilation Leaks do not cause false initiation of breaths (unaffected by circuit) Eliminates man sleep disturbances Adapts to altered metabolic demand with consistent unloading Prevents disuse atrophy Improves NIV

98. In other modes auto-PEEP increases work of ventilator initiation in COPD and asthma , this does not effect ventilatory cycle in NAVA thus overall WOB decreases in these patients

99. Neoganesh ( smartcare )

100. NEOGANESH(SMARTCARE) Closed loop type modification of PSV WITH INREGRATED ARTIFICIAL INTELLIGENCE Adjusts ventilator assistance depending on patient,s respiratory pattern and literature based weaning protocols Based on 3 fundamental principles: Adapt PS to patient’s present clinical situation In case of stability wean off PS Initiate spontaneous breathing trials as per prerecorded clinical guidelines

101. Ventilator takes feedback from monitored RR, VT, etCO2 Trials have shown that it reduces weaning failure and also hastens weaning duration.

102.   SUMMARY Older modes & ventilators : passive  operator‐dependant tools New modes or new generation ventilators: adaptively interactive goal oriented patient centered

103. THANK YOU