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Mechanical Ventilation (101)

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This is one of my mechanical ventilation presentations which covers the basics regarding Physical Characteristics of Ventilators & Components of Mechanical Ventilators, Basic Component of Breath Delivery, Classification of Modes of Ventilation and Clinical Application.

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Mechanical Ventilation (101)

  1. 1. Mechanical Ventilation (101) 1st Respiratory Care Comprehensive Review Course 1
  2. 2. Mastering Mechanical Ventilation 1st Respiratory Care Comprehensive Review Course 2 Physical Characteristics of Ventilators & Components of Mechanical Ventilators Normal Physiology of Ventilation & Spont. Breathing and Lung Mechanics Basic Component of Breath Delivery Classification of Modes of Ventilation Initiation MonitoringManagement Clinical Application
  3. 3. Physical Characteristics of Ventilators & Components of Mechanical Ventilators 1st Respiratory Care Comprehensive Review Course 3
  4. 4. Ventilator characteristics • Input power (Electrical, pneumatic) • Power conversion and transmission • Control system • Output (flow: Pressure and volume) conversion transmission and Control system Input power Output 1st Respiratory Care Comprehensive Review Course 4
  5. 5. Components of a Ventilator Those components are: • User interface • Breath Delivery [Patient] Unit • Backup power supply [Rechargeable batteries] • Air compressor.  Physical characteristics  Ventilator power source • Electrically powered ventilator • Pneumatically powered ventilator • Combined Power Ventilators  Positive or negative pressure  Control systems and circuits  Open- and closed-loop systems  Control panel: user interface  Pneumatic circuit (internal and patient circuit)  Drive mechanism  Compressor or Blowers  displacement  Flow control valves  Output  Pressure, volumes, and flow scalars 1st Respiratory Care Comprehensive Review Course 5
  6. 6. Power Source • Ventilator power source • Electrically powered ventilator • Pneumatically powered ventilator • Combined Power Ventilators • Combined Power Ventilators • Current ICU ventilators use microprocessor control and 50 psi sources of oxygen and air and are Combined Power Ventilators • Current ICU ventilators are classified as Electrically Powered- Pneumatically Driven-Microprocessor Controlled Ventilators 1st Respiratory Care Comprehensive Review Course 6
  7. 7. Pressure Delivery • Negative-pressure ventilators • Iron lung • Chest cuirass • Positive-pressure ventilators • Most ventilators used today are positive-pressure ventilators • Examples include: Puritan Bennett 840, Servoi, and Hamilton G-5 • Combined Pressure Devices • High-frequency oscillators 1st Respiratory Care Comprehensive Review Course 7
  8. 8. Negative-Pressure Ventilators • Attempt to mimic normal spontaneous ventilation • When negative pressure is applied, thoracic volume is increased and air enters lungs • During exhalation, negative pressure is removed and air leaves lungs 1st Respiratory Care Comprehensive Review Course 8
  9. 9. Negative-Pressure Ventilators (Cont.) 1st Respiratory Care Comprehensive Review Course 9
  10. 10. Negative-Pressure Ventilators (Cont.) • Types of negative-pressure ventilators: • Chest cuirass: chest shell applies negative pressure only to chest • Tank ventilator: applies negative pressure to entire body • Negative-pressure ventilators rarely used in ICU • Sometimes used in home care setting 1st Respiratory Care Comprehensive Review Course 10
  11. 11. Combined Pressure Devices • Most common application is high-frequency oscillator • Sinusoidal pressure wave includes positive and negative pressure applied to airway 1st Respiratory Care Comprehensive Review Course 11
  12. 12. High-frequency oscillators 1st Respiratory Care Comprehensive Review Course 12
  13. 13. Control System & Circuit  Control systems and circuits Open- and closed-loop systems (Control level) Control panel: user interface Pneumatic circuit (internal and patient circuit) 1st Respiratory Care Comprehensive Review Course 13
  14. 14. Control Type (level of control) Open loop control system • An open-loop system cannot distinguish between the volume actually delivered and the set volume and respond to this difference. • Operator sets parameter that is delivered by ventilator • No assurance that volume or pressure is actually delivered to lungs Closed loop control system • Closed-Loop systems are an intelligent system • Flow/volume or pressure are set & measured, with feedback to drive mechanism altering output to maintain desired (set) levels • Microprocessor is used to control ventilation • When specific tidal volume is set, ventilator adds to volume if there is leak in circuit • Ventilator adjusts delivered volume or pressure to ensure that set parameter is delivered 1st Respiratory Care Comprehensive Review Course 14
  15. 15. Pneumatic Circuit • Consists of two series of tubing: 1. Internal Circuit: directs flow within the ventilator. It can be single or double circuit. 2. The External Circuit (Patient Circuit): directs the flow from the ventilator to the patient. 1st Respiratory Care Comprehensive Review Course 15
  16. 16. Internal Circuit (Single-circuit design) • Single circuit: gas moves through ventilator and is delivered to patient circuit. Most commonly used 1st Respiratory Care Comprehensive Review Course 16
  17. 17. Internal Circuit (Double-circuit design) • Double circuit includes bellows or a bag containing desired tidal volume • Bag is compressed and desired tidal volume is delivered to lungs 1st Respiratory Care Comprehensive Review Course 17
  18. 18. The External Circuit (Patient Circuit) 1st Respiratory Care Comprehensive Review Course 18
  19. 19. Control Panel • Referred to as user interface • It contains all controls used to set the ventilation and monitoring parameters • As well as It displays other important parameters and graphics 1st Respiratory Care Comprehensive Review Course 19
  20. 20. Control Panel (Cont.) 1st Respiratory Care Comprehensive Review Course 20
  21. 21. Drive mechanism (Power Transmission System) • Drive mechanism is part of the breath delivery unit. • Responsible for breath delivery to the patient • Develop and control pressure gradient between ventilator and patient • It contains pneumatic and electronic modules that control the breath delivery to the patient • Electrically powered ventilators use compressors, blowers, or other volume displacement devices • Pneumatic systems use compressed gas from wall to deliver volume to lung 1st Respiratory Care Comprehensive Review Course 21
  22. 22. Compressors or Blowers • Can be driven by pistons, rotating blades, moving diaphragms, or bellows • Most common type of compressor: rotary compressor • Examples: • Viasys Avea • LTV ventilators 1st Respiratory Care Comprehensive Review Course 22
  23. 23. Volume Displacement Designs • Use displacement devices to deliver specific volume • Includes pistons, bellows, or bag in chamber mechanisms • Spring-Loaded Bellows • Operator adjusts tension on spring that is used to compress bellows • Not commonly used 1st Respiratory Care Comprehensive Review Course23
  24. 24. Flow-Control Valves • Three types of flow controlling valves 1. Proportional solenoid valve 2. Stepper motors with valve 3. Digital valves with on/off configuration • Current ICU ventilators use Proportional solenoid valve. 1st Respiratory Care Comprehensive Review Course 24
  25. 25. Fluidic Ventilators • Use fluidics to deliver gas to patient • Do not use moving parts or electricity to function • Used on Bio-Med MVP 10 • Compatible with use during MRI • Two basic principles: • Beam deflection • Wall attachment (Coanda effect) 1st Respiratory Care Comprehensive Review Course 25
  26. 26. Expiratory Valves 1st Respiratory Care Comprehensive Review Course 26
  27. 27. Expiratory Valves • Close during inspiration to direct gas flow to patient • Open during exhalation allowing patient to exhale gas into atmosphere • PEEP is used to improve oxygenation • PEEP is provided by threshold resistor or flow resistance • Both valves prevent complete exhalation of expired tidal volume 1st Respiratory Care Comprehensive Review Course 27
  28. 28. Spring-Loaded Valves • Can be used to provide PEEP • Spring is used to adjust amount of pressure applied against exhalation valve to prevent complete exhalation 1st Respiratory Care Comprehensive Review Course 28
  29. 29. Diaphragm Expiratory Valve • Diaphragm over exhalation valve closes during inspiration • During exhalation, pressure on diaphragm is released • When PEEP is used, pressure against diaphragm is maintained thus preventing complete exhalation 1st Respiratory Care Comprehensive Review Course 29
  30. 30. Diaphragm Expiratory Valve (Cont.) 1st Respiratory Care Comprehensive Review Course 30
  31. 31. Electromagnetic Valves • Amount of electrical current is adjusted to regulate amount of force applied to expiratory flow • The higher the level of current, the more force applied to exhaled gas • Increases PEEP level 1st Respiratory Care Comprehensive Review Course 31
  32. 32. Heated wire flow sensor • As flow passes through the sensor, the ventilator tries to keep the wire temperature constant • The electric currant consumed to keep this temperature is proportional to gas flow • This type of sensors is affected by condensate, secretion and calcification. • An example of a ventilator using this type of sensors is Dräger Evita XL™ 1st Respiratory Care Comprehensive Review Course 32
  33. 33. Differential pressure flow sensor • As flow passes through the sensor’s resistive element a pressure deference develop • Using Boyle’s Law [P1V1 = P2V2] the gas flow can be calculated • This type of sensors can be affected by condensate, secretion and calcification. • An example of a ventilator using this type of sensors is Hamilton G5 & S1 1st Respiratory Care Comprehensive Review Course 33
  34. 34. Ultrasonic Flow Sensor 1st Respiratory Care Comprehensive Review Course 34 Ultrasonic transducer technology: T2 - T1 = Tdiff Tdiff is proportional to the gas flow New measurement every 4 ms
  35. 35. CPAP Devices • FIO2 is regulated with blender • Inspired gas is warmed and humidified • Threshold resistor prevents complete exhalation to maintain positive pressure in airway • Problems with CPAP Systems • Inadequate gas flow to patient • Leaks in system • Loss of source gas flow • Jamming or obstruction of expiratory flow resistor 1st Respiratory Care Comprehensive Review Course
  36. 36. Basic Component of Breath Delivery 1st Respiratory Care Comprehensive Review Course 36
  37. 37. Primary Ventilator Control Variables • Primary variable ventilator controls to cause inspiration • 3 possible explicit primary variables 1. Pressure controlled 2. Volume controlled 3. Flow controlled • Only one can be controlled; other two become dependent variables 1st Respiratory Care Comprehensive Review Course 37
  38. 38. Pressure Controller • Ventilator controls pressure (P), but volume & flow vary with changes in compliance (C) & resistance (Raw) • Pressure waveform will be square (constant) during inspiration • Positive or negative pressure controlled • i.e., iron lung controls with negative P 1st Respiratory Care Comprehensive Review Course 38
  39. 39. Volume & Flow Controllers • Volume controller • Ventilator controls volume so will be constant • Flow is volume/time, so flow is also constant • Pressure will vary with changes in C & Raw • Flow controller • As above, flow & thus volume constant • Pressure varies with changes in C and Raw • Old neonatal ventilators used flow interruption to deliver volume during inspiration 1st Respiratory Care Comprehensive Review Course 39
  40. 40. Two Breath Types • Spontaneous • Patient triggers & cycles the breath • Patient effort may be supported by manual or mechanical ventilator • Mechanical • Mandatory breath: breath is initiated by ventilator • Assisted breath: breath is triggered by patient but is delivered by ventilator 1st Respiratory Care Comprehensive Review Course 40
  41. 41. Types of Breath 1st Respiratory Care Comprehensive Review Course 41
  42. 42. Types of Breath (Spontaneous breath) • Without Support (CPAP) • With Support (PSV) 1st Respiratory Care Comprehensive Review Course 42
  43. 43. Primary Breath Control Variable • Volume control: VT/flow set, while P depends on those settings & pulmonary mechanics • Pressure control: P set, VT /flow depend on P setting & pulmonary mechanics • Dual control: Mixture of volume & pressure • Either starts breath in volume control & ends with pressure control or the reverse 1st Respiratory Care Comprehensive Review Course 43
  44. 44. Components (phases) of Breath Delivery • End of expiration and beginning of inspiration • Delivery of inspiration • End of inspiration and beginning of exhalation • Expiratory phase 1st Respiratory Care Comprehensive Review Course 44
  45. 45. Phase Variables • Ventilator uses variables to initiate or limit each phase of ventilation • Initiation of inspiration (E to I) • Inspiration • End of inspiration (I to E) • Expiration 1st Respiratory Care Comprehensive Review Course 45
  46. 46. Initiation of Inspiration • Trigger variable • Machine triggered • Time: determined by rate control • Patient triggered • Pressure • Flow (least work for patient to trigger) • Volume (rare) • Most ventilators provide a manual breath button that operator activates • Patient triggering: breath is triggered because of patient effort • Trigger sensitivity: amount of effort required by patient to initiate machine breath 1st Respiratory Care Comprehensive Review Course 46
  47. 47. Time Triggering • Ventilator triggers breath at preset intervals • Time for mandatory breath is based on cycle time • Cycle time is calculated by dividing 60 by set rate • Example: Set rate is 12 breaths/min • Cycle time = 60/12 • Cycle time = 5 seconds 1st Respiratory Care Comprehensive Review Course 47
  48. 48. Pressure Triggering • Ventilator breath is triggered by decrease in pressure below baseline • Sensitivity is usually set at –0.5 to 1.5 cm H2O • Common locations for pressure sensor: • Internal ventilator circuit where main gas flow leaves ventilator • Where expired gas flow returns from patient to ventilator • At proximal airway (near wye connector) 1st Respiratory Care Comprehensive Review Course 48
  49. 49. Flow Triggering • Base or bias flow, present during exhalation, is set • Common level is 5 to 10 L/min • Flow trigger is set at 1 to 5 L/min • When patient decreases flow to set level of flow trigger, an assisted breath is delivered 1st Respiratory Care Comprehensive Review Course 49
  50. 50. Other Triggering Methods • Manual triggering: operator triggers ventilator breath • Neural triggering: monitors electrical activity of diaphragm • Method is used with neurally adjusted ventilatory assist (NAVA) 1st Respiratory Care Comprehensive Review Course 50
  51. 51. Inspiration: Target (Limit) Variable • Limits inspiration but does not terminate the phase • Pressure limited • Limits peak inspiratory pressure (PIP) during inspiration • Volume limited • Limits amount of tidal volume (VT) delivered during inspiration to set amount • Flow limited • Limits the amount of flow during inspiration 1st Respiratory Care Comprehensive Review Course 51
  52. 52. Target Variable 1st Respiratory Care Comprehensive Review Course 52
  53. 53. Inspiratory Phase (Cont.) • Sloping or ramping • Ability to adjust how quickly flow is delivered during set inspiratory time • This feature is referred to as: • Ramping • Inspiratory rise time • Flow acceleration • Slope adjustment • Sloping 1st Respiratory Care Comprehensive Review Course 53
  54. 54. Maximum Safety Pressure • Sets maximum pressure that can be delivered during inspiration • Upper pressure limit is set 10 cm H2O above peak inspiratory pressure (PIP) • Terms for this setting: • Pressure limit • Upper pressure limit • Normal pressure limit • High pressure limit • Peak/maximum pressure 1st Respiratory Care Comprehensive Review Course 54
  55. 55. Maximum Safety Pressure (Cont.) • Events that occur with activation of upper pressure limit: • Activation of visible and/or audible alarm • Termination of delivery of inspiratory breath • Decrease in inspiratory time 1st Respiratory Care Comprehensive Review Course 55
  56. 56. End of Inspiration • Cycle variables terminate inspiratory phase • Pressure cycled • Inspiration terminates as preset pressure reached (hit alarm level) • Volume cycled • Inspiration terminates at preset VT • Flow cycled • Inspiration terminates when flow drops to preset value (PSV) • Time cycled • Inspiration terminates when set inspiratory time is reached • Includes any inspiratory holds 1st Respiratory Care Comprehensive Review Course 56
  57. 57. Pressure Cycling • When preset pressure is reached, inspiratory flow ends and expiratory flow begins • In pressure control ventilation, preset pressure is maintained for set inspiratory time • Only application of pressure cycled ventilation is administration of intermittent positive-pressure breathing (IPPB) • Pressure cycling also occurs if upper pressure limit is reached in volume- or pressure-targeted ventilation 1st Respiratory Care Comprehensive Review Course 57
  58. 58. Time Cycling • Length of inspiration is set by operator; then followed by ventilator ending inspiration and beginning expiration • If inspiratory time is decreased, expiratory time is increased and I:E ratio is increased • If inspiratory time is increased, expiratory time is decreased and I:E ratio is decreased 1st Respiratory Care Comprehensive Review Course 58
  59. 59. Inspiratory Pause • Extension of inspiratory time by exhalation valve remaining closed after set tidal volume has been delivered • Also referred to as: • Inflation hold • Inspiratory plateau • Can be used with pressure or volume ventilation • Common application is to obtain plateau pressure to calculate effective static compliance in VCV. • In pressure-controlled ventilation, inspiratory time is long enough for pressure to equilibrate within lungs 1st Respiratory Care Comprehensive Review Course 59
  60. 60. Inspiratory Pause (Cont.) 1st Respiratory Care Comprehensive Review Course 60
  61. 61. Volume Cycling • When preset volume is delivered, ventilator ends inspiration and begins expiration • Most ventilators accomplish this by calculation of the amount of flow to deliver a set volume during the set inspiratory time • Amount of volume actually delivered to patient may be less because of volume lost due to tubing compression 1st Respiratory Care Comprehensive Review Course 61
  62. 62. Tubing Compression • During inspiration, tubing is distended and returns to normal size during exhalation • Most adult ventilator circuits have tubing compression factor of 1 to 3 cm H2O • Many current ventilators calculate volume lost to tubing compression and add this to delivered tidal volume 1st Respiratory Care Comprehensive Review Course 62
  63. 63. Flow Cycled • Inspiration ends when preset flow is reached • Pressure support ventilation (PSV) is most common application of flow cycling • In PSV, breaths end when inspiratory flow decreases to set percentage of initial flow rate • When PSV was first developed, breaths ended when flow dropped to 25% of initial flow • In current ventilators, pressure support breaths can be ended at percentages of expiratory flow ranging from 5% to 80% of initial inspiratory flow rate 1st Respiratory Care Comprehensive Review Course 63
  64. 64. Expiration: Baseline Variable • Defined by how baseline or end expiratory pressure (EEP) relates to atmospheric pressure • PEEP Positive or supra- atmospheric EEP • NEEP Negative or sub-atmospheric EEP • ZEEP Zero EEP equals sub-atmospheric pressure 1st Respiratory Care Comprehensive Review Course 64
  65. 65. Baseline Pressure • Pressure at which inspiration begins • Zero baseline pressure is equal to atmospheric pressure • PEEP: resistance applied during exhalation preventing complete exhalation • Applications of PEEP: • Increases FRC • Increases mean airway pressure • Improves lung recruitment • Improves oxygenation 1st Respiratory Care Comprehensive Review Course 65
  66. 66. Baseline Pressure (Cont.) • CPAP • Baseline pressure is elevated • Patient is breathing spontaneously • Applications for CPAP are same as PEEP 1st Respiratory Care Comprehensive Review Course 66
  67. 67. Negative End-Expiratory Pressure • Developed to minimize effects of positive pressure on blood flow • Used during expiration during high-frequency oscillation 1st Respiratory Care Comprehensive Review Course 67
  68. 68. Continuous Gas Flow During Exhalation • Referred to as “base flow” or “bias flow” • Provides flow to patient during last portion of exhalation to the beginning of inspiratory effort • Most current ventilators use bias flow to provide flow triggering 1st Respiratory Care Comprehensive Review Course 68
  69. 69. Expiratory Hold/End Expiratory Pressure • Used to estimate amount of pressure in lungs caused by trapped air • Pressure of trapped air is referred to as “auto-PEEP” • Conditions increasing risk of developing auto-PEEP: • High minute volumes (>10 L/minute) • Patients with high airway resistance • Patients with active exhalation 1st Respiratory Care Comprehensive Review Course 69
  70. 70. Waveforms and Graphics • Scalar graphics • Pressure-time • Volume-time • Flow-time • Loop graphics • Flow-volume • Pressure-volume 1st Respiratory Care Comprehensive Review Course 70
  71. 71. Scalar Graphics During Volume-Controlled Ventilation 1st Respiratory Care Comprehensive Review Course 71
  72. 72. Scalar Graphics During Pressure-Controlled Ventilation 1st Respiratory Care Comprehensive Review Course 72
  73. 73. Scalar Graphics During Pressure-Support Ventilation 1st Respiratory Care Comprehensive Review Course 73
  74. 74. Loop graphics: Flow-volume A Inspiratory curve B Expiratory curve C Begin inspiration D End expiration E Point on volume axis where I begins and E ends. Note: C, D, and E should all be the same point. F Peak inspiratory flow rate (VI) G Peak expiratory flow rate H Point on volume axis of maximum VT and end I I Begin E 1st Respiratory Care Comprehensive Review Course 74
  75. 75. Loop graphics: 1st Respiratory Care Comprehensive Review Course 75
  76. 76. Mechanical Ventilation (2) 1st Respiratory Care Comprehensive Review Course 76
  77. 77. Classification of Modes of Ventilation 1st Respiratory Care Comprehensive Review Course 77
  78. 78. History • Control variable • Volume • Pressure • Breath sequence • Continuous mandatory ventilation (CMV) • Intermittent mandatory ventilation (IMV) • Continuous spontaneous ventilation (CSV) 1st Respiratory Care Comprehensive Review Course 78 • PCV or VCV • A/C VC or PC • SIMV VC or PC • PSV Basic Modes of Ventilation • PRVC • CMV Autoflow • VSV • ASV • PAV • VC+ Advanced Modes of Ventilation
  79. 79. Chatburn’s Classification of Ventilator Modes • Breathing pattern • Control variable • Volume • Pressure • Breath sequence • Continuous mandatory ventilation (CMV) • Intermittent mandatory ventilation (IMV) • Continuous spontaneous ventilation (CSV) 1st Respiratory Care Comprehensive Review Course 79
  80. 80. Chatburn’s Classification of Ventilator Modes (Cont.) • Targeting scheme: Described as feedback control function of ventilator • Set-point • Dual • Servo • Adaptive • Optimal • Intelligent 1st Respiratory Care Comprehensive Review Course 80
  81. 81. Types of Targeting • Set-point: operator sets target parameter, such as a tidal volume; ventilator delivers that volume • Dual targeting: operator sets pressure and volume target. If desired volume is not reached with pressure; ventilator will increase pressure to reach volume target 1st Respiratory Care Comprehensive Review Course 81
  82. 82. Types of Targeting (Cont.) • Servo targeting: output of ventilator is adjusted based on input • Examples: • Proportional assist ventilation • Automatic tubing compensation • Neutrally adjusted ventilatory assist 1st Respiratory Care Comprehensive Review Course 82
  83. 83. Types of Targeting (Cont.) • Adaptive Targeting: One target is adjusted automatically to achieve another target • Examples: • Pressure-Regulated Volume Control (PRVC): pressure is adjusted to obtain desired tidal volume • Mandatory minute ventilation 1st Respiratory Care Comprehensive Review Course 83
  84. 84. Types of Targeting (Cont.) • Optimal Targeting: Target of ventilator is adjusted automatically to optimize target following predetermined model • Used with adaptive support ventilation on Hamilton ventilators 1st Respiratory Care Comprehensive Review Course 84
  85. 85. Types of Targeting (Cont.) • Intelligent Targeting: Modes and targets are adjusted according to patient needs • SmartCare found on Dräger ventilators • Monitors patient’s PetCO2, spontaneous tidal volume, and spontaneous respiratory rate • Ventilator automatically adjusts ventilator parameters to maintain above parameters at acceptable levels 1st Respiratory Care Comprehensive Review Course 85
  86. 86. 1st Respiratory Care Comprehensive Review Course 86
  87. 87. Modes Used in Ventilator Classification • VC-CMV • PC-CMV • VC-IMV • PC-IMV • CSV 1st Respiratory Care Comprehensive Review Course 87
  88. 88. 1st Respiratory Care Comprehensive Review Course 88
  89. 89. Continuous Mandatory Ventilation with Set- Point Targeting • Use of time triggered volume-targeted or pressure-targeted breaths • All breaths are time triggered or patient triggered • Patient guaranteed minimum respiratory rate • Sensitivity determines amount of effort required to trigger assisted breath 1st Respiratory Care Comprehensive Review Course 89
  90. 90. Pressure-Controlled Inverse Ratio Ventilation • Inspiratory time exceeds expiratory time • All breaths are pressure targeted • Inverse ratios are used to increase mean airway pressure and improve oxygenation • Increases risk of developing auto-PEEP • Alveolar pressure (plateau pressure) should not exceed 30 cm H2O to prevent lung injury 1st Respiratory Care Comprehensive Review Course 90
  91. 91. Intermittent Mandatory Ventilation with Set- Point Targeting • Can be volume or pressure targeted • Patient is allowed to breathe spontaneously between assisted breaths • Volume-targeted IMV • Set target tidal volume, flow or inspiratory time, and mandatory rate • Pressure-targeted IMV • Set pressure above PEEP, mandatory rate, and inspiratory time 1st Respiratory Care Comprehensive Review Course 91
  92. 92. Airway Pressure Release Ventilation • Form of PC-IMV • Uses two levels of CPAP, allowing spontaneous breathing at both levels • Airway pressure release ventilation (APRV) is used to control mean airway pressure and improve oxygenation in patients with significant lung injury • High level CPAP (PHIGH) is usually set at a level close to mean airway pressure (20 to 25 cm H2O) • Pressure is allowed to decrease low level CPAP (PLOW) for a brief period of time (0.2 to 1.0 seconds) • Allows ventilation to occur 1st Respiratory Care Comprehensive Review Course 92
  93. 93. Settings Used in APRV • CPAP High (PHIGH) • CPAP Low (PLOW) • Time High (THIGH) • Time Low (TLOW) 1st Respiratory Care Comprehensive Review Course 93
  94. 94. Dual Targeting • Ventilator delivers pressure-targeted breath with decelerating flow curve; inspiratory time is preset • Exhaled volume is monitored • If volume does not meet minimum volume, pressure is increased or decreased in increments so desired tidal volume is delivered 1st Respiratory Care Comprehensive Review Course 94
  95. 95. CMV with Adaptive Targeting • Also referred to as “dual control mode” • Pressure is adjusted up or down to achieve target tidal volume • Pressure is adjusted up or down in increments of 1 to 3 cm H2O • Maximum safety pressure is determined and pressure is not allowed to exceed this level • This level is 5 cm H2O below upper pressure limit 1st Respiratory Care Comprehensive Review Course 95
  96. 96. Pressure-Controlled CSV with Intelligent Targeting • Used with SmartCare found on Dräger ventilators • Spontaneous VT, spontaneous rate, and PetCO2 are monitored • Ventilation is adjusted to patient needs based on these values • Used as a weaning mode • Found to be as effective as weaning done by experienced providers in CCU 1st Respiratory Care Comprehensive Review Course 96
  97. 97. Volume-Controlled IMV with Adaptive Targeting • Described as “mandatory minute ventilation” • Rate or pressure support level is adjusted automatically to ensure preset minute volume • If patient reaches volume target, no support is provided • Available on Dräger ventilators 1st Respiratory Care Comprehensive Review Course 97
  98. 98. Pressure-Controlled IMV with Adaptive Targeting • Examples: • Maquet PRVC-IMV • Dräger SIMV + Autoflow • Hamilton PC-SIMV + Adaptive Pressure Ventilation • CareFusion PRVC SIMV • GE Engstrom Care Station SIMV 1st Respiratory Care Comprehensive Review Course 98
  99. 99. Pressure-Controlled IMV with Optimal Targeting • Example: adaptive support ventilation • Mandatory rate and tidal volume are adjusted to minimize patient’s work of breathing • Mandatory and spontaneous breaths are pressure limited • Ventilator determines dynamic compliance 1st Respiratory Care Comprehensive Review Course 99
  100. 100. Pressure-Controlled IMV with Optimal Targeting (Cont.) • Following parameters are set: • Patient’s IBW and percentage of minute volume operator wants ventilator to provide • Maximum pressure limit and PEEP level • Pressure or flow trigger • Rise time 1st Respiratory Care Comprehensive Review Course 100
  101. 101. Pressure-Controlled IMV with Optimal Targeting (Cont.) • When patient is spontaneously breathing, ventilator adjusts pressure to keep rate and VT in optimum range 1st Respiratory Care Comprehensive Review Course 101
  102. 102. Pressure-Controlled IMV with Optimal Targeting (Cont.) 1st Respiratory Care Comprehensive Review Course 102
  103. 103. Pressure-Controlled CSV • Patient is breathing spontaneously and support is adjusted to control work of breathing • All breaths are patient triggered, pressure limited, and flow cycled • Commonly referred to as “BiPAP” 1st Respiratory Care Comprehensive Review Course 103
  104. 104. Volume Delivered in Pressure Support • Affected by three factors: • Set pressure • Patients’ compliance and resistance • Patients’ inspiratory efforts 1st Respiratory Care Comprehensive Review Course 104
  105. 105. Applications of Pressure Support • Decreasing imposed work of breathing associated with artificial airway and ventilator circuit • Supplementing patients’ spontaneous tidal volume to decrease work of breathing 1st Respiratory Care Comprehensive Review Course 105
  106. 106. Types of Patients Who Are Candidates for PSV • Patients with artificial airway and any of the following conditions: • Artificial airways smaller than optimal size • Spontaneous respiratory rates greater than 20 breaths/min (adults) • Minute volumes greater than 10 L/min 1st Respiratory Care Comprehensive Review Course 106
  107. 107. Types of Patients Who Are Candidates for PSV (Cont.) • Patients supported with IMV/SIMV or CPAP and any of the following conditions: • History of chronic obstructive pulmonary disease (COPD) • Evidence of ventilatory muscle weakness requiring ventilatory support 1st Respiratory Care Comprehensive Review Course 107
  108. 108. Volume Support Ventilation • Breaths are patient triggered, pressure limited, and flow cycled • Level of pressure support is adjusted to ensure delivery of mandatory tidal volume • If patient becomes apneic, ventilator changes to pressure-regulated volume control (PRVC) • Found on Maquet Servoi 1st Respiratory Care Comprehensive Review Course 108
  109. 109. Proportional Assist Ventilation • Amount of work of breathing assumed by ventilator is adjusted • Found on Covidien PB 840 ventilator • Pressure, flow, and volume are automatically adjusted to ensure ventilator provides percentage of work of breathing 1st Respiratory Care Comprehensive Review Course 109
  110. 110. Proportional Assist Ventilation (Cont.) 1st Respiratory Care Comprehensive Review Course 110
  111. 111. Automatic Tubing Compensation • Use of pressure support to overcome resistance of endotracheal tube • Amount of pressure support necessary is calculated by measuring pressure at distal end of endotracheal tube • Found on Dräger and Covidien PB 840 ventilators 1st Respiratory Care Comprehensive Review Course 111
  112. 112. Neurally Adjusted Ventilatory Assist • Electrical activity of diaphragm is measured, determining amount of support necessary • Specialized nasogastric tube is used to monitor electrical activity of diaphragm • Ventilator begins inspiration as soon as diaphragm begins depolarization • Depth of ventilation and length of breath are determined by electrical activity of diaphragm 1st Respiratory Care Comprehensive Review Course 112
  113. 113. Benefits of NAVA • Reduced work of breathing • Fewer trigger efforts missed • Intrinsic PEEP does not affect triggering • Improved synchrony and oxygenation • Reduced need for sedation and paralysis • Improved ventilation 1st Respiratory Care Comprehensive Review Course 113
  114. 114. Clinical Application 1st Respiratory Care Comprehensive Review Course 114
  115. 115. Criteria for Mechanical Ventilation RTS 363: MECHANICAL VENTILATION
  116. 116. Objectives of Mechanical Ventilation RTS 363: MECHANICAL VENTILATION
  117. 117. Acute Respiratory Failure • Recognizing the patient in distress • Determine the patient’s level of consciousness. • Assess the appearance and texture of skin. • Evaluate the patient’s vital signs. • Respiratory rate • Heart rate • Blood pressure • Body temperature • Oxygenation status RTS 363: MECHANICAL VENTILATION
  118. 118. Physical Signs of Distress RTS 363: MECHANICAL VENTILATION CAUSE Sudden Onset of Dyspnea SIGNS What Do YOU See? What Would Patient Complain OF ? What Would YOU Find out? What About Panic Attack?
  119. 119. Respiratory Failure Acute Hypoxemic Respiratory Failure (TYPE1) • Definition • Causes Acute Hypercapnic Respiratory Failure (TYPE 2)• Definition • Causes RTS 363: MECHANICAL VENTILATION Failure to Recognize Patient in Acute & Impending RF May Lead to Cardiac Dysrhythmias Ventricular Fibrillation Cardiac Arrest
  120. 120. 1st Respiratory Care Comprehensive Review Course 120
  121. 121. 1st Respiratory Care Comprehensive Review Course 121
  122. 122. Physiologic Measurements • Bedside measurements • MIP • VC • PEFR • FEV1 • Respiratory frequency (fb) • Expired volume per minute (VE) • (VE = VT  fb) RTS 363: MECHANICAL VENTILATION
  123. 123. Physiologic Measurements—cont’d • Partial pressure of carbon dioxide in arteries (PaCO2) • Is the best indicator of adequate ventilation. • Suggests that VD is increased relative to VT. • Partial pressure of oxygen in arteries (PaO2) • Is a good indicator of oxygenation status. • Oxygen saturation measured by pulse oximeter (SpO2) • Arterial content of oxygen (CaO2) • PaO2/PAO2 • Ratio of arterial PO2 to FIO2 (PaO2/FIO2) RTS 363: MECHANICAL VENTILATION
  124. 124. Selecting the Patient Interfaces • NIPPV • CPAP • NIV • Pressure-triggered, pressure-limited, flow-cycled devices • Critical-care ventilators • Invasive positive-pressure ventilation RTS 363: MECHANICAL VENTILATION
  125. 125. Full and Partial Ventilatory Support • Full ventilatory support • Partial ventilatory support • Intermittent mandatory ventilation (IMV) • PSV • PAV • MMV RTS 363: MECHANICAL VENTILATION
  126. 126. Volume-Targeted Ventilation Advantages • Guarantees a Specific MV regardless of the lungs mechanics Disadvantages • Variable PIP based on the lungs mechanics • Related to flow and sensitivity setting which may lead to patient- ventilator asynchrony. HOW? RTS 363: MECHANICAL VENTILATION Maintains a certain level of PaCO2 Constant Flow may not match patient demand Inappropriate Sensitivity setting may make it difficult for patient to trigger
  127. 127. Pressure-Targeted Ventilation Advantages • Allow clinicians to set a maximum pressure level. • Decelerating flow pattern. • More comfortable for patient who can breath spontaneously. • Helps reduce WOB. HOW? Disadvantages • Volume delivery varies • Clinicians are less familiar with Pressure-Control Ventilation. • VT & VE decrease when lung characteristics deteriorate. RTS 363: MECHANICAL VENTILATION
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  129. 129. To select initial ventilator settings you should take the following steps: 1. Identify the patient’s underline acute condition, history, gender, and height. 2. Identify or calculate the patient’s IBW or use the BSA if given. IBW male = 106 + 6 (H – 60) IBW female = 105 + 5 (H – 60) Height in inches and weight will be in lb to convert to Kg divide by 2.2 3. Calculate the appropriate MV based on IBW or BSA and gender IBW X 100 ml/Kg (male and female) BSA X 4 male BSA X 3.5 female Note: Correct the MV based on body temperature and respiratory acid/base status 4. Calculate the appropriate TV based on IBW and gender, and patient condition 5. Then from the MV and the TV you can calculate the appropriate Rate 6. PEEP is generally accepted to start with 3 to 5 cm H2O for optimal PEEP settings go to your reference book 7. Desired FiO2 you can start with the same FiO2 which patient was receiving if PaO2 and SaO2 are acceptable or higher if not. You can also use the following formula for estimated Desired FiO2 = Known FiO2 X Known PaO2 / Desired PaO2 8. For the initial PC settings can be estimated by given VC breathes to patient with same baseline pressure then use the plateau pressure as an initial pressure on PC ventilation. Or to start with 10 to 15 cm H2O then assess the exhaled TV to adjust the PC level to achieve the optimal TV. 9. For PSV is well accepted way is to use the difference (PIP – Pplat) then assess the exhaled TV to 4 to 8 ml/Kg IBW 10. Mode can be selected based on the patient condition or what therapist is more confidant with. Selecting Ventilator Initial Settings 1st Respiratory Care Comprehensive Review Course 129
  130. 130. Sensitivity (Trigger) • Trigger sensitivity: amount of effort required by patient to initiate machine breath • Pressure Triggering • Ventilator breath is triggered by decrease in pressure below baseline • Sensitivity is usually set at –0.5 to 1.5 cm H2O • Flow Triggering • Base or bias flow, present during exhalation, is set • Common level is 5 to 10 L/min • Flow trigger is set at 1 to 5 L/min • When patient decreases flow to set level of flow trigger, an assisted breath is delivered 1st Respiratory Care Comprehensive Review Course 130
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  132. 132. Humidification • HMEs • Active Humidification 1st Respiratory Care Comprehensive Review Course 132
  133. 133. ALARMS • Low-pressure alarms are usually set about 5 to 10 cm H2O below PIP. • High-pressure alarms are set about 10 cm H2O above PIP. • Total Respiratory Rate alarm set about : high 10 Breaths above the patient total rate; low as low as 6 to 8 BPM • Low PEEP/continuous positive airway pressure (CPAP) alarms are usually set about 2 to 5 cm H2O below the PEEP level. • Apnea alarms are used to monitor mandatory or spontaneous breaths. An apnea period of 20 seconds is the highest accepted maximum. In some situations, apnea alarms are set so the patient will not miss two consecutive machine breaths (apnea time > total cycle time [TCT] and < [TCT × 2]). • Low exhaled VT: 10% to 15% below set VT. • Low exhaled minute volume: 10% to 15% below average minute volume. • FIO2: 5% above and below set oxygen percentage. 1st Respiratory Care Comprehensive Review Course 133
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  135. 135. Monitoring • Mode • Sensitivity • Tidal Volume, Rate, and Minute Ventilation • Monitoring Airway Pressures • Peak Inspiratory Pressure • Plateau Pressure • Set Pressure • Transairway Pressure: PIP Minus Pplateau • Mean Airway Pressure • End-Expiratory Pressure • Pressure Limit • Checking the Circuit: Checking for Leaks • Vital Signs, Blood Pressure, and Physical Examination of the Chest • Heart Rate • Temperature • Systemic Arterial Blood Pressure • Central Venous Pressure • Pulmonary Artery Pressure • Physical Examination of the Chest • Management of Endotracheal Tube and Tracheostomy Tube Cuffs • Cuff Pressure Measurement • Tube and Mouth Care • Monitoring Compliance and Airway Resistance • Static Compliance • Dynamic Characteristic (Dynamic Compliance) • Airway Resistance 1st Respiratory Care Comprehensive Review Course 135
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  141. 141. Adjusting Ventilator Settings Ventilation: to maintain acceptable PaCO2 and/or pH according to patient status or treating team plan - Increasing MV to eliminate CO2 and improve respiratory acidosis: 1. You target the TV as long as you still have space to increase it based on the patient IBW and Pplat should not exceed 30 cm H2O Volume Control Modes: Desired TV = Known TV X Known PaCO2 / Desired PaCO2 Pressure Control Modes: Adjusting PC Based on Cs. Desired PC = Desired TV/Cs Example if the current TV is 400 ml and Cs is 35 ml/cm H2O and you need to increase the volume to 500 ml Desired PC= 500/35 = 14 cm H2O 2. Increase the Rate as long as enough time is available for expiration or I:E is less than 1:1. - Decreasing MV to resolve respiratory alkalosis: 1. Decreasing the mandatory rate or switch from full support to partial support. 2. Decreasing the TV if possible (maintaining acceptable TV for the patient) Oxygenation: the goal is to maintain acceptable level of PaO2 more than 60 mm Hg and SaO2 more than 90%. - Increasing the FiO2: 1. Desired FiO2 = Known FiO2 X Known PaO2 / Desired PaO2 2. When increasing FiO2 you have to evaluate the risk of high FiO2 on the patient condition. Maintaining FiO2 ≤ 60% should be applied as long as possible to avoid oxygen toxicity and absorption atelectasis. 3. If FiO2 higher than 60% is required conceder increasing the PEEP - Increasing PEEP: 1. Initial PEEP of 3 to 5 cm H2O is acceptable in most cases 2. Therapeutic PEEP range of 5 cm H2O or higher 3. When increasing the PEEP, Pplat should always be maintained at ≤ 30 cm H2O Increase the PEEP by 3 to 5 cm H2O for adults and by 2 to 3 for infants then watch for the effect on the patient (optimal PEEP study) 1st Respiratory Care Comprehensive Review Course 141
  142. 142. Weaning Mechanical Ventilation Support (Evidence-Based Weaning) • Criteria for weaning: • Problem requiring ventilation resolved • Measurable criteria met for the patient’s readiness to discontinue • Successful SBT 1st Respiratory Care Comprehensive Review Course 142
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  144. 144. Facts to Consider • Patients may require support during weaning • Supplemental O2 and PEEP may be required • Require an artificial airway • Extubation is different from discontinuation of support • May require one or all of the above
  145. 145. Methods of Titrating Ventilator Support During Weaning • Three approaches 1. Intermittent mandatory ventilation (IMV) 2. Pressure-support ventilation (PSV) 3. T-piece weaning
  146. 146. Intermittent Mandatory Ventilation (IMV) • Theory is that the patient’s respiratory muscles work during spontaneous breaths and rest during mandatory breaths • Common practice • Reduce the mandatory rate at a pace that matches the patient’s improvement • Usually in steps of 1 or 2 breaths/min • PSV can be added • 5-10 cm H2O • PEEP of 3 to 5 cm H2O
  147. 147. Pressure-Support Ventilation (PSV) • Patient controls the rate, timing, and depth of each breath • Patient triggered, pressure limited, and flow cycled • ICU ventilators allow form monitoring and alarm systems • Establishing the level of PSV • Pressure support levels of 5-15 cm H2O • Attempt to re-establish the patient’s baseline RR (15-25 breaths/min) and VT (300-600 mL)
  148. 148. Pressure-Support Ventilation (PSV)—cont’d • During weaning • Clinician gradually reduces level of support • Usually until about 5 cm H2O • Need to monitor patient for signs of distress
  149. 149. T-Piece Weaning • Oldest technique • Humidified gas source connected to a T-piece (Briggs adapter) with large-bore tubing • Then attached to ET tube • Another piece of large-bore tubing attached to the exhalation side of T-piece • Requires high level of staff attention • When T-piece is used through a ventilator, CPAP is used
  150. 150. T-Piece Weaning—cont’d • Not tolerated well in patient with • Underlying heart disease • Severe muscle weakness • Inclined to panic • Preexisting chronic lung conditions
  151. 151. Closed-Loop Control Modes for Ventilator Discontinuation • Automatic tube compensation (ATC) • Volume-targeted pressure-support ventilation • Automode and variable pressure support/variable pressure control • Mandatory minute ventilation (MVV) • Adaptive support ventilation • Artificial intelligence systems
  152. 152. Weaning Mechanical Ventilation Support 1st Respiratory Care Comprehensive Review Course 152
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  154. 154. Weaning Mechanical Ventilation Support • Removal of an Artificial Airway • Conceder factors that may contribute to extubation failure • Extubation equipment and procedure • Postextubation difficulties 1st Respiratory Care Comprehensive Review Course 154
  155. 155. Weaning Mechanical Ventilation Support 1st Respiratory Care Comprehensive Review Course 155
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  157. 157. 1. Pilbeam’s mechanical ventilation : physiological and clinical applications / J.M. Cairo.— 6th edition, 2016. 2. Egan's Fundamentals of Respiratory Care / Robert M. Kacmarek, James K. Stoller, and Al Heuer. – 10th Edition, 2013 3. A Taxonomy for Mechanical Ventilation: 10 Fundamental Maxims / Robert L Chatburn MHHS RRT-NPS FAARC, Mohamad El Khatib PhD MD RRT FAARC, and Eduardo Mireles-Cabodevila MD / RESPIRATORY CARE • NOVEMBER 2014 VOL 59 NO 11 4. Principles And Practice of Mechanical Ventilation / Martin J. Tobin, 3rd Edition / 2013 5. Mosby, 2013 1st Respiratory Care Comprehensive Review Course 157

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