The Basics of The Basics of VentilatorsVentilators

Richard M. Ford BS Richard M. Ford BS RRTRRT

UCSD Respiratory CareUCSD Respiratory Care

Why Important ?Why Important ?

Managing the Managing the Patient/Ventilator system is Patient/Ventilator system is less difficult with an less difficult with an understanding of the understanding of the fundamentals of operation, fundamentals of operation, alarms, and capabilities.alarms, and capabilities.

Where to Start ?Where to Start ?ASV, APRV, AutoFlow, AutoMode, AutoPEEP, BiLevel, BiPAP, Closed Loop, CPAP, Control Variables, Demand Flow, Differential Output, Duty Time, EPAP, Flow Control Valves, Fluid Logic, HFJV, HFOV, HFFI, HFPV, IPAP, Linear Drive Piston, Mandatory Breath, MAP, MMV, NEEP, PEEP, PIP, Phase Variables, Pplateau, PCV, PCIRV, PRVS, PRVC, PSV, PV, Proportional Amplifier, PAV, Rotary Drive Piston, Static Compliance, SIMV, Threshold Resistor, Total Cycle Time, Trigger Variable, Variable Pressure Control, VCIRV, Volume Support, WOB…from SP Pilbeam, Respiratory Care Equipment, Mosby

Beyond Basic-Beyond Basic-Today's TechnologyToday's Technology BMTI - Bird and BearBMTI - Bird and Bear Drager Medical TechnologiesDrager Medical Technologies Hamilton MedicalHamilton Medical Mallinckrodt IncMallinckrodt Inc Newport NMINewport NMI PulmoneticPulmonetic SiemensSiemens

From the ManufacturersFrom the Manufacturers

Smart Breath Delivery, Dual View, San Box, Smart Alert, Interactive Automode, Advanced Rules Based Strategic Modes, Virtual Controls

GUI Interface, soft keys, configurable

Safety, upgradability, portability

Objectives Objectives

Understand how ventilators Understand how ventilators control breath delivery - phase, control breath delivery - phase, type and control variables.type and control variables.

Understand the basic adjuncts Understand the basic adjuncts and modes of ventilation. and modes of ventilation.

Basic Ventilator Basic Ventilator ParametersParameters

FiOFiO22

Fractional Fractional concentration of concentration of inspired oxygen inspired oxygen delivered expressed delivered expressed as a % (21-100)as a % (21-100)

Breath Rate (f)Breath Rate (f)The number of The number of

times over a one times over a one minute period minute period inspiration is inspiration is initiated (bpm)initiated (bpm)

Tidal volume (VTidal volume (VTT))The amount of gas that The amount of gas that

is delivered during is delivered during inspiration expressed in inspiration expressed in mls or Liters. Inspired or mls or Liters. Inspired or exhaled.exhaled.

FlowFlowThe velocity of gas flow The velocity of gas flow

or volume of gas per or volume of gas per minute minute

Phase VariablesPhase Variables Trigger (start)- begins inspiratory flowTrigger (start)- begins inspiratory flow Cycling (end)- ends inspiratory flowCycling (end)- ends inspiratory flow Limiting (continue)- places a maximum Limiting (continue)- places a maximum

value on a “control variable”value on a “control variable”pressurepressurevolumevolumeflowflow

timetime

Breath Type… Only Two (for Breath Type… Only Two (for now)!now)!

MandatoryMandatoryVentilator does the workVentilator does the workVentilator controls start and stopVentilator controls start and stop

SpontaneousSpontaneousPatient takes on workPatient takes on workPatient controls start and stopPatient controls start and stop

Trigger Variable- Trigger Variable- Start of a BreathStart of a Breath

Time - Time - control ventilationcontrol ventilationPressure - Pressure - patient assistedpatient assistedFlow - Flow - patient assistedpatient assistedVolume - Volume - patient assistedpatient assistedManual - Manual - operator controloperator control Impedance - Impedance - patient assistedpatient assisted

The Control Variable-The Control Variable-Inspiratory Breath DeliveryInspiratory Breath Delivery

Flow (volume) controlledFlow (volume) controlledpressure may varypressure may vary

Pressure controlledPressure controlledflow and volume may varyflow and volume may vary

Time controlled (HFOV)Time controlled (HFOV)pressure, flow, volume may varypressure, flow, volume may vary

If compliance decreases the pressure increases to maintain the same Vt

Volume Control Breath TypesVolume Control Breath Types

11 22 33 44 55 66

SECSEC

11 22 33 44 55 66

PPawaw

cmHcmH2200

6060

-20-20

120120

120120

SECSEC

INSPINSP

EXHEXH

FlowFlowL/minL/min

Many Dual Modes start out looking like PCV

A New Twist…A New Twist…Volume TargetedVolume Targeted

1 2 3 4 5 6

SEC

1 2 3 4 5 6

Paw

cmH20

60

-20

120

120

SEC

INSP

EXH

FlowL/min

Volume TargetedVolume Targeted(Pressure Controlled)(Pressure Controlled)

As compliance changes - flow and volumes change

1 2 3 4 5 6

SEC

1 2 3 4 5 6

Paw

cmH20

60

-20

120

120

SEC

INSP

EXH

FlowL/min

Pressure then raises to assure that the set tidal volume is delivered

New Volume Targeted Breath New Volume Targeted Breath Pressure Variability is ControlledPressure Variability is Controlled

1 2 3 4 5 6

SEC

1 2 3 4 5 6

Paw

cmH20

60

-20

120

120

SEC

INSP

EXH

FlowL/min

Inspiratory - delivery limitsInspiratory - delivery limits

Maximum value that can be Maximum value that can be reached but will not end the reached but will not end the breath-breath-VolumeVolumeFlowFlowPressurePressure

End of Insp…cycle End of Insp…cycle mechanismsmechanisms

The phase variable used to The phase variable used to terminate inspiration-terminate inspiration-VolumeVolumePressurePressureFlowFlowTimeTime

Expiratory - baselineExpiratory - baseline

PPositive ositive EEnd nd EExpiratory xpiratory PPressureressureExpiratory RetardExpiratory RetardNNegative egative EEnd nd EExpiratory xpiratory PPressureressureExpiratory HoldExpiratory HoldTime Limited Exhalation (APRV)Time Limited Exhalation (APRV)

PEEPPEEP DefinitionDefinition

Positive end expiratory pressurePositive end expiratory pressure Application of a constant, positive pressure such that at Application of a constant, positive pressure such that at

end exhalation, airway pressure does not return to a 0 end exhalation, airway pressure does not return to a 0 baselinebaseline

Used with other mechanical ventilation modes Used with other mechanical ventilation modes such as A/C, SIMV, or PCVsuch as A/C, SIMV, or PCV

Referred to as CPAP when applied to spontaneous Referred to as CPAP when applied to spontaneous breathsbreaths

PEEPPEEP

Increases functional residual Increases functional residual capacity (FRC) and improves capacity (FRC) and improves oxygenationoxygenationRecruits collapsed alveoliRecruits collapsed alveoliSplints and distends patent alveoliSplints and distends patent alveoliRedistributes lung fluid from alveoli to Redistributes lung fluid from alveoli to

perivascular spaceperivascular space

5 cm 5 cm HH22OO

PEEPPEEP

CPAPCPAP DefinitionDefinition

Continuous positive airway pressureContinuous positive airway pressureApplication of constant positive pressure Application of constant positive pressure

throughout the spontaneous ventilatory cyclethroughout the spontaneous ventilatory cycle

No mechanical inspiratory assistance is No mechanical inspiratory assistance is provided provided Requires active spontaneous respiratory driveRequires active spontaneous respiratory drive

Same physiologic effects as PEEPSame physiologic effects as PEEP

CPAPCPAP

May decrease WOBMay decrease WOB

Tidal volume and rate determined by Tidal volume and rate determined by patientpatient

Often final form of support before Often final form of support before extubationextubation

10 cm 10 cm HH22O O

PEEPPEEP

TimeTime

Basic Modes of VentilationBasic Modes of Ventilation

Control Control Assist, Assist/ControlAssist, Assist/Control(S)IMV(S)IMVPCVPCVPSVPSVServo Servo

ControlControl

Delivery of a Delivery of a mandatory mandatory breath at a set breath at a set time interval - time interval - time is the time is the trigger to start trigger to start the breaththe breath

F

P

Safety Issue - Control Safety Issue - Control

Control mode should never be Control mode should never be deliberately set as the ventilator deliberately set as the ventilator should never be insensitive to a should never be insensitive to a patients inspiratory effortspatients inspiratory efforts

Control ventilation is a patient driven Control ventilation is a patient driven function and new ventilators do not function and new ventilators do not even incorporate a pure “control” even incorporate a pure “control” functionfunction

Assist, Assist ControlAssist, Assist Control

Patient is Patient is able to able to trigger the trigger the start of start of inspirationinspiration F

P

Safety Issue - Assist Safety Issue - Assist ControlControl

The control rate must be set high The control rate must be set high enough to insure that minute enough to insure that minute ventilation will be adequateventilation will be adequate

Apnea ventilation will also serve as a Apnea ventilation will also serve as a back up back up

As rate increases expiratory time will As rate increases expiratory time will shorten and gas trapping may occurshorten and gas trapping may occur

Synchronize Intermittent Synchronize Intermittent Mandatory Ventilation - Mandatory Ventilation - SIMVSIMV

A minimum A minimum mandatory mandatory breath rate is set breath rate is set with spontaneous with spontaneous breathing breathing supported supported between the between the mandatory cyclesmandatory cycles

F

P

SIMVSIMV

AdvantagesAdvantagesSynchronized breaths may Synchronized breaths may

improve patient comfortimprove patient comfortIncrease patient control/regulationIncrease patient control/regulationEnhances blood flowEnhances blood flowHyperventilation less of a concern Hyperventilation less of a concern

compared to A/Ccompared to A/C

Volume vs…Volume vs… Pressure Control Ventilation Pressure Control VentilationVolume VentilationVolume Ventilation

Volume delivery Volume delivery constantconstant

Inspiratory pressure Inspiratory pressure variesvaries

Inspiratory flow Inspiratory flow constantconstant

Inspiratory time Inspiratory time determined by set flow determined by set flow and V and VTT

PressurePressure VentilationVentilation

Volume delivery Volume delivery varies varies

Inspiratory pressure Inspiratory pressure constantconstant

Inspiratory flow variesInspiratory flow varies Inspiratory time set Inspiratory time set

by clinicianby clinician

Pressure Control Pressure Control Ventilation - PCVVentilation - PCV

The ventilator The ventilator delivers a set delivers a set pressure limit pressure limit over a set over a set inspiratory inspiratory timetime

F

P

Pressure Control Pressure Control Ventilation - PCV, with Ventilation - PCV, with Inverse Ratio IRVInverse Ratio IRV

The ventilator The ventilator delivers a set delivers a set pressure limit pressure limit over a set over a set inspiratory time, inspiratory time, however however inspiration is inspiration is longer than longer than expirationexpiration

F

P

Pressure Control Pressure Control VentilationVentilation

AdvantagesAdvantagesLimits risk of barotraumaLimits risk of barotraumaMay recruit collapsed alveoliMay recruit collapsed alveoliImproved gas distributionImproved gas distribution

DisadvantagesDisadvantagesTidal volumes vary when patient Tidal volumes vary when patient

compliance changes (i.e. ARDS, compliance changes (i.e. ARDS, pulmonary edema)pulmonary edema)

With increases in I-time, patient may With increases in I-time, patient may require sedation and/or paralysis require sedation and/or paralysis

Pressure Support Pressure Support Ventilation - PSVVentilation - PSVThe ventilator The ventilator

delivers a set delivers a set pressure limit pressure limit with end with end inspiration inspiration driven by the driven by the patientpatient

F

P

Safety Issue - PSVSafety Issue - PSV

PSV is a spontaneous mode of PSV is a spontaneous mode of ventilation, therefore the patient ventilation, therefore the patient must demonstrate they can trigger must demonstrate they can trigger the ventilator and that volumes are the ventilator and that volumes are appropriateappropriate

High and low rate, apnea, and high High and low rate, apnea, and high and low tidal volume alarms need to and low tidal volume alarms need to be assessedbe assessed

Bi LevelBi Level

Is a Is a spontaneous spontaneous breathing breathing mode in which mode in which two levels of two levels of pressure and pressure and hi/low are sethi/low are set

F

P

What is BiLevel What is BiLevel Ventilation?Ventilation? Enabled utilizing an active exhalation valveEnabled utilizing an active exhalation valve

Substantial improvements for spontaneous Substantial improvements for spontaneous breathingbreathing better synchronization, more options for supporting better synchronization, more options for supporting

spontaneous breathing, and potential for improved spontaneous breathing, and potential for improved

monitoringmonitoring Spontaneous Breaths

P

T

Spontaneous Breaths

Synchronized Transitions

What is BiLevel What is BiLevel Ventilation?Ventilation? At either pressure level the patient can At either pressure level the patient can

breathe spontaneouslybreathe spontaneously spontaneous breaths may be supported by PS spontaneous breaths may be supported by PS if PS is set higher than PEEPif PS is set higher than PEEPHH, PS supports , PS supports

spontaneous breath at upper pressure spontaneous breath at upper pressure

TT

PEEPPEEPHigh High + PS + PS

PP

PEEPPEEPLL

PEEPPEEPHH

Pressure SupportPressure Support

Bi Level -APRV Bi Level -APRV Airway Pressure ReleaseAirway Pressure Release

Is a Bi-level form of Is a Bi-level form of ventilation with ventilation with sudden short releases sudden short releases in pressure to rapidly in pressure to rapidly reduce FRC and allow reduce FRC and allow for ventilationfor ventilation

Can work in Can work in spontaneous or spontaneous or apneic patientsapneic patients

F

P

Then What Is APRV?Then What Is APRV? APRV is similar but utilizes a very short expiratory time for APRV is similar but utilizes a very short expiratory time for

PRESSURE RELEASEPRESSURE RELEASE this short time at low pressure allows for ventilationthis short time at low pressure allows for ventilation

APRV always implies an inverse I:E ratioAPRV always implies an inverse I:E ratio

All spontaneous breathing is done at upper pressure levelAll spontaneous breathing is done at upper pressure level

Spontaneous Spontaneous BreathsBreaths

PP

TT

““ReleaseRelease” ”

Safety Issue - IRV and Safety Issue - IRV and APRVAPRV

Pronged inspiratory times with Pronged inspiratory times with pressure transmission to the pressure transmission to the surrounding chest structures may surrounding chest structures may significantly reduced cardiac outputsignificantly reduced cardiac output

Decrease in expiratory time may Decrease in expiratory time may result in intrinsic PEEP which must result in intrinsic PEEP which must be consideredbe considered

Safety Issues - Safety Issues - AlarmsAlarms

Alarms must be re-assessed with Alarms must be re-assessed with every primary ventilator changeevery primary ventilator change

Alarm silence should only be used Alarm silence should only be used when the alarm condition is clear when the alarm condition is clear and attended toand attended to

The most important back up is a The most important back up is a skilled clinician with a resuc bagskilled clinician with a resuc bag

Potential Complications of Potential Complications of MVMV Ventilator malfunctionVentilator malfunction

Manually ventilate patientManually ventilate patient BarotraumaBarotrauma

Alveolar rupture due to overdistentionAlveolar rupture due to overdistentionMonitor PIP, breath sounds PulmonaryMonitor PIP, breath sounds Pulmonary

Oxygen toxicityOxygen toxicitygoal: FIOgoal: FIO22 << .50 and PaO .50 and PaO22 >> 70 70

Cardiovascular compromise/arrhythmiasCardiovascular compromise/arrhythmiasMonitor vital signsMonitor vital signs

Potential Complications of Potential Complications of MVMV InfectionInfection

ET tube bypasses natural airway defense mechanismsET tube bypasses natural airway defense mechanisms– Nosocomial pneumonia, aspiration pneumoniaNosocomial pneumonia, aspiration pneumonia

Good handwashing, provide mouth and tube careGood handwashing, provide mouth and tube care

PsychologicalPsychological Patients may be extremely anxious and/or agitatedPatients may be extremely anxious and/or agitated Give consistent, calming explanations, offer Give consistent, calming explanations, offer

reassurancereassurance Sedation, anti-anxiety agents frequently indicatedSedation, anti-anxiety agents frequently indicated

From Basics to From Basics to Advanced...Advanced... Microprocessor controlled/GUI’sMicroprocessor controlled/GUI’s Proportional solenoid control of gas delivery Proportional solenoid control of gas delivery New exhalation valve technologyNew exhalation valve technology Fast response times - low work of breathingFast response times - low work of breathing Ability to compensate for leaks/ET tubesAbility to compensate for leaks/ET tubes Broaden performance with pediatric and/or Broaden performance with pediatric and/or

infant capabilitiesinfant capabilities New smart breathing algorithms/modes that New smart breathing algorithms/modes that

automatically adjust to changing patient automatically adjust to changing patient conditionsconditions

Servo Regulated ModesServo Regulated Modes Mandatory Minute Ventilation Mandatory Minute Ventilation Pressure Regulated Volume ControlPressure Regulated Volume Control Volume SupportVolume Support AutoFlowAutoFlow Proportional Assist VentilationProportional Assist Ventilation Adaptive Support VentilationAdaptive Support Ventilation Volume Assured Pressure SupportVolume Assured Pressure Support Proportional Pressure SupportProportional Pressure Support