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Chapter 42 Mechanical Ventilators. Learning Objectives. Discuss the basic design features of ventilators. Classify ventilators and describe how they work. Define what constitutes a mode of ventilation. Classify and discuss modes of ventilation. Learning Objectives (cont.). - PowerPoint PPT Presentation
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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Chapter 42
Mechanical Ventilators
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 2
Learning Objectives
Discuss the basic design features of ventilators.
Classify ventilators and describe how they work.
Define what constitutes a mode of ventilation. Classify and discuss modes of ventilation.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 3
Learning Objectives (cont.)
Explain the indications for the basic modes of ventilatory support.
Describe the application of selected modes of ventilatory support.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 4
Mechanical Ventilator (MV)
4 basic functions1. Input power
• Electrical, pneumatic, manual
2. Power transmission & conversion
3. Control system
4. Output
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Control System
5
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 6
All of the following are functions of mechanical ventilation, except:
A. Turbo power
B. Input power
C. Power transmission and conversion
D. Control system
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 7
Power Transmission & Conversion
Drive mechanism Generates force needed to deliver gas to patient
under pressure Mechanisms can either be
• Gas from pressure-reducing valve
• Driven by electric motor or compressor
Output control valve Regulates flow of gas to patient Can be just on/off valve or one that modifies output
waveform
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Volume & Pressure Ventilation:Characteristic Waveforms
8
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 9
Control Circuit
System that allows ventilator to manipulate pressure, volume, & flow
May be composed of mechanical, pneumatic, electric, electronic, or fluidic components Most modern vents combine two or more May be advantages to components used
• MRI: Fluidic controls have no metal & are immune to failure due to electromagnetic interference
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 10
Control Circuits may be composed of all of the following components, except:
A. Mechanical
B. Pressure
C. Electric
D. Pneumatic
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 11
Control Variables
Primary variable ventilator controls to cause inspiration
3 possible explicit variables1. Pressure controlled
2. Volume controlled
3. Flow controlled Only one can be controlled; other two
become dependent variables
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 12
All of the following are possible explicit variables except:
A. Pressure controlled
B. Volume controlled
C. Flow controlled
D. Loop controlled
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Control Variables (cont.)
13
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Control Variables (cont)
14
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 15
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
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 16
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
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 17
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
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Phase Variables
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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 19
All of the following are variables that initiate or limit each phase of ventilation, except:
A. Initiation of inspiration (E to I)
B. Inspiration
C. End of inspiration (I to E)
D. End of expiration
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 20
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
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 21
Inspiration: Target 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
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Target Variable
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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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
23
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 24
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
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All of the following are all baseline variables, except:
A. ZEEP
B. MEEP
C. PEEP
D. NEEP
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 26
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
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Two Breath Types
Spontaneous Patient triggers & cycles the breath Patient effort may be supported by manual or
mechanical ventilator Mandatory
Ventilator initiates and/or cycles breath See Box 42-2.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 28
Modes of Ventilation 3 possible sequences of breaths
1. CMV: all breaths mandatory, “full support”• Patient & machine-initiated breaths are same
2. CSV: all breaths spontaneous• Patient triggers & cycles all breaths
3. IMV: Breaths can be mandatory or spontaneous When tied to control variable, nine possible
combinations
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Breath Sequence
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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Breath Sequence
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Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Modes of Ventilation (cont.)
31
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 32
Control Type
Open loop control: Most basic early ventilators were flow, volume, or pressure, are determined by pulmonary mechanics & ventilator system
Closed loop control: Flow/volume or pressure are set & measured, with feedback to drive mechanism altering output to maintain desired (set) levels
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 33
Importance of Defining Modes
Modern ventilators, modes may look similar on graphics but must be set up differently
Clear understanding & definition of each mode will avoid potentially dangerous patientventilator mismanagement
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 34
Ventilator Waveforms
Ventilator graphics are to ventilator management , what ECGs are to managing the heart, or pressure waveforms from a PA catheter are to hemodynamic management
Graphics provide wealth of information at a glance
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Ventilator Waveforms (cont.)
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