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Chapter 3 Mech Vent
Classification of Mechanical Ventilators
| Question | Answer |
|---|---|
| Compressor | a device capable of building up pressure by compressing the volume of air |
| Controller | the mechanism that provides a mode of ventilation within a specific parameter (pressure, time, volume, or flow) |
| Cycle | the length of one complete breathing cycle |
| flow triggered | a strategy that uses a combination of continuous flow and demand flow. Before inspiration the delivered flow equals the return flow. |
| microprocessor | minute computer that is designed to perform specific functions |
| pneumatic drive mechanism | operation of a ventilator with pressurized gas as a power source |
| pressure triggered | inititiation of a mechanical breath based on the drop in airway pressure that occurs at the beginning of a spontaneous inspiratory effort |
| reducing valve | a device that decreases the delivery pressure of a gas |
| servo | a feedback system that typically consists of a sensing elemnt, an amplifier, and a servo motor, used in the automatic control of the mechanical device of a ventilator |
| sine wave | a graphic representation of flow and time that has a horizontal “S” appearance |
| solenoid valve | a valve controlled by an electronic switching device that is used to regulate the specific functions of a ventilator |
| time triggered | initiation of a mechanical breath based on the set time interval for one complete respiratory cycle |
| What was the name of the 1st volume controlled mechanical ventilator made in 1951? | Engstrom 100 |
| The Chatburn system classifies mechanical ventilators based on what? | related features, physics, and engineering |
| The pressure required to deliver the tidal volume is referred to as what? | the "load" either the muscles or the ventilator must work against |
| The "elastic load" is proportional to _______ and inversely proportional to ______ | volume; compliance |
| The "resistance load" is proportional to _____ and ______ _____ | Raw; inspiratory flow |
| What is the equation of motion for the respiratory system? | Muscle pressure + Ventilator pressure= [Volume/Compliance] + (Resistance x Flow) |
| What is the definition of Compliance? | a change in volume divided by a change in pressure |
| What is the definition of Flow? | a unit of volume divided by a unit of time |
| What is Resistance? | the force that must be overcome to move gas through the conducting airways |
| What best describes resistance? | Poiseuille's law |
| Mechanical ventilators may be classified based on these 7 categories | Input power, Drive mechanism, Control circuit, Control variables, Phase variables, Output waveforms, and alarm systems |
| Mechanical ventilators may first be classified by what? | the power source that is used to provide the energy required to support the patients ventilation |
| 3 types of input power for mechanical ventilators | pneumatically, electrically, and combined pneumatic and electric |
| What type of ventilators use compressed gas as an energy source? | pneumatically powered |
| 5 examples of pneumatically powered ventilators | Bennett PR-2, Bird Mark 7, Percussionaire IPV, Monaghan 225/SIMV, and Percussionaire VDR |
| Ventilators may also be electrically powered, utilizing what for power source? | 120 V 60 Hz alternating current (AC) or 12 V direct current (DC) |
| 4 examples of electrically powered ventilators | Emerson 3-MV, Puritan-Bennett LP-10 and LP-20, and the Bear medical systems Bear 33 |
| 3 examples of 3rd generation combined pneumatic and electrically powered ventilators | BEAR 1000, Hamilton Veolar, Puritan-Bennett 840 |
| What is the drive mechanism? | system used by the ventilator to transmit or convert the input power to useful ventilatory work |
| What 2 things on newer ventilators allows them to produce a variety of user-selected inspiratory flow or pressure patterns? | microprocessors and proportional solenoid valves |
| 4 kinds of drive mechanisms | pistons, bellows, reducing valves, and pneumatic circuits |
| Pistons are usually driven by what type of power source? | electrically powered |
| 2 different types of piston drive mechanisms | rotary-driven and linear driven |
| 3 ways a Bellows drive mechanism may be compressed | a spring, a weight, or by gas pressure if it is in a sealed chamber |
| An example of a ventilator that uses a reducing valve drive mechanism | Bennett PR-2 |
| Multiprocessor controlled pneumatic mechanisms use | programmed algorithms in the microprocessors to open and close the solenoid valves to mimic virtually any flow or pressure waveform |
| Technically both pistons and bellows are what type of systems? | pneumatic |
| What is the control circuit? | the system that governs or controls the ventilator drive mechanism or output control valve |
| Classifications of control circuits | open or closed loop, mechanical, pneumatic, fluidic, electric, and electronic |
| What is an open loop control circuit? | the desired output is selected and the ventilator achieves the desired output without any further input from the clinician or ventilator itself |
| What is a closed loop control circuit? | ventilator measures a specific parameter or variable (flow, pressure or volume) continuously, and the input is constantly adjusted to match the desired output selected |
| Closed loop control circuit is AKA | servo controlled |
| Which type of control circuits emply simple machines such a levers, pulleys, or cams to control the drive mechanism? | mechanical |
| These type of control circuits were very durable but lacked flexibility by being an open loop control system | mechanical |
| Pneumatic devices used as control circuits include | valves, nozzles, ducted ejectors, and diaphragms |
| 3 ventilators that use pneumatic control circuits | IPPB, Percussionaire IPV and VDR |
| What is fluidics? | the application of gas flow and pressure to control the direction of other gas flows and to perform logic functions |
| How to fluidic elements control the direction of flow and perform logic functions? | use a flow splitter located beside adjacent walls |
| Fluidic elements operate using the _____ effect | Coanda |
| This ventilator uses fluidics | Monaghan 225 |
| This type of control circuits use simple switches to control the drive mechanism? | electric |
| This ventilator uses electric control circuits to control 2 microswitches to control inspiratory and expiratory time | Emerson 3-MV |
| 5 devices of electronic control circuits | resistors, diodes, transistors, integrated circuits, and microprocessors |
| What are the 4 variables mechanical vents can control during inspiration? | pressure, volume, flow, and time |
| What are the 2 different types of pressure controlled ventilators? | positive(when airway pressure rises above baseline) and negative(body surface pressure below baseline) |
| What pressure gradient is the biggest determiner of depth or volume of inspiration? | transrespiratory pressure |
| A positive pressure ventilator requires the use of what? | a tight fitting mask or artificial airways |
| This type of control variable is usually unaffected by changes in the patients compliance or resistance | pressure controller |
| What must occur to classify a vent as volume controlled? | volume must be measured and used as a feedback signal to control the output (volume) delivered |
| What type of controller allows pressure to vary with changes in compliance and resistance while volume delivery remains constant? | volume controller |
| Volume controllers can measure volume by the ___ or ____ that serves as the ventilators drive mechanism | pistons or bellows |
| 3 examples of volume controlled ventilators | Bennett MA-1 and MA-2+2 and the Emerson 3-MV |
| Which type of controllers allow pressure to vary with changes in the patients compliance and resistance while directly measuring and controlling flow? | Flow controllers |
| 4 things that measure flow in flow controlled ventilators | vortex sensors, heated wire grids, venture pneumotachometers, and strain gauge flow sensors |
| Time controllers are ventilators that measure and control what? | inspiratory and expiratory time |
| What type of ventilators allow pressure and volume to vary with changes in pulmonary compliance and resistance? | time controlled |
| What are the 4 phases of ventilator supported breaths? | the change from expiration to inspiration, inspiration, the change from inspiration to expiration, and expiration |
| When a variable (pressure, volume, flow, and time) is observed during a particular phase it is called what? | a phase variable |
| What is a Trigger variable? | variable that determines the start of inspiration |
| 3 types of trigger variables | time triggered, pressure triggered, or flow triggered |
| The amount of negative pressure below a patients baseline airway pressure (or end-expiratory pressure), a patient must generate to trigger the ventilator into inspiration is called? | sensitivity level |
| What is the range of acceptable sensitivity levels for pressure triggering below the patients baseline pressure? | -1 to -5 cm H2o |
| Changing the sensitivity setting on a ventilator from -3 cmH2o to -5 cmH2o is ______ the sensitivity setting | decreasing (it takes more patient effort to trigger inspiration) |
| Which time of trigger is more sensitive and responsive to a patients effort, Flow triggered or Volume triggered? | Flow triggered |
| 3 examples of ventilators than can be flow triggered | CMV, SIMV, and PSV |
| One infant ventilator (Sechrist IV-200) uses ___ _____ to initiate a ventilator supported breath | inductive plethysmography |
| What is a limit variable? | when 1 or more of the variables (pressure, flow, or volume) is not allowed to rise above a preset value during inspiratory time |
| 4 types of cycle variables | pressure cycled, flow cycled, volume cycled, time cycled |
| The variable that is controlled during the expiratory phase or expiratory time is called the? | baseline variable |
| Most commonly, ____ is controlled during the expiratory phase | pressure |
| Application of PEEP and CPAP are used to do what 3 things? | increased FRC, improve gas distribution, and oxygenation |
| Baseline pressure is AKA | ambient pressure |
| What pressures, when applied above baseline pressure during exhalation, maintain the lungs in a partially inflated state? | PEEP and CPAP |
| What are conditional variables? | patterns of variables that are controlled by the ventilator during the ventilatory cycle |
| What are output waveforms? | graphical representations of the control or phase variables in relation to time |
| Output waveforms are typically presented in what order? | pressure, volume, flow |
| The ____ determines the shape of the control variable, whereas the other 2 depend on what? | ventilator; patients compliance and resistance |
| Waveforms can assist clinician in detecting inadvertent _____, the patients _____ _____, resistance, and compliance | PEEP; ventilatory work |
| 4 types of pressure waveforms | rectangular, exponential, sinusoidal, and oscillating |
| This type pf waveform is characterized by a near instant rise to a peak pressure value that is held to the start of exhalation. During exhalation pressure rapidly drops to baseline | rectangular |
| This type of waveform is depicted by a gradual increase in pressure, is common in some infant vents and has become an option in some adult vents.Vent settings such as flow and inspiratory time regulate how steep the waveform rises toward PIP | exponential |
| This type of waveform is produced by ventilators having a rotary-driven piston drive mechanism | sinusoidal |
| 2 types of volume waveforms | ascending ramp and sinusoidal |
| This type of volume waveform is produced by a constant (rectangular) inspiratory flow pattern. The shape is characterized by a linear rise to the PIP value | ascending ramp |
| This type of volume waveform is ventilators that have a rotary driven piston drive mechanism | sinusoidal |
| 5 ventilators that produce sinusoidal waveforms d/t rotary driven piston drive mechanism | Emerson 3-MV, Respironics PLV-100, BEAR 33, Puritan- Bennett LP-10 and LP-20 |
| 4 types of flow waveforms | rectangular(constant), ascending ramp, descending ramp, and sinusoidal |
| This type of flow waveform is produced when volume is the control variable | rectangular flow waveform |
| If flow rises as the breath is delivered, this type of flow waveform is seen | ascending ramp |
| If flow falls during the ventilator supported breath, this type of flow waveform is seen | descending ramp |
| 3 types of alarm systems on mechanical ventilatiors | Input power alarm, control circuit alarm, and output alarms |
| Most battery backup alarms are powered by what? | nickel cadmium batteries that are recharged when AC power is available |
| What type of alarms are employed in oxygen blenders? | pneumatic reed alarms |
| Control circuit alarms alert the clinician to what? | settings or parameters that are not within acceptable ranges or specifications, or that the vent has failed some part of a self-diagnostic test |
| 6 subdivisions of output alarms | pressure, volume, flow, time, inspiratory, and expiratory gas |
| This type of output alarm includes high/low peak and mean and baseline airway pressures | pressure |
| This type of output alarm includes high/low exhaled tidal volumes for both vent-supported breathing and spontansous breathing | volume |
| This type of output alarm is limited to exhaled minute volume | flow |
| This type of output alarm includes high/low frequency or rate, excessive or inadequate inspiratory time, and excessive or inadequate expiratory time | Time |
| Inspiratory and expiratory time alarms may alert the clinician to what? | circuit obstructions or malfunctions, changes in gas distribution, or inappropriate vent settings |
| What do inspired gas alarms alert the clinician to? | changes in oxygen concentration or gas temperature |
| What can be monitored by the expiratory gas alarm? | exhaled oxygen tension or end tidal carbon dioxide tension |
| The exhaled gas monitoring system can assist the clinician in determining what 2 things? | Vd/Vt gas exchange, and the respiratory exchange ration (R) |
Created by:
Dibsy