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 functions 1. 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 variables 1. 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 18

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 (V T ) 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 22

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 V T  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

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 25 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: V T /flow set, while P depends on those settings & pulmonary mechanics  Pressure control: P set, V T /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

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 27 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 29

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. Breath Sequence 30

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 patient  ventilator 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.) 35