The Basics of VentilatorsThe Basics of Ventilators

Richard M. Ford BS RRTRichard M. Ford BS RRTUCSD Respiratory CareUCSD Respiratory Care

Why Important ?Why Important ?

➤Managing the Patient/Ventilator Managing the Patient/Ventilator system is less difficult with an system is 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 ParametersBasic Ventilator Parameters

➤ FiOFiO22

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

➤ Breath Rate (f)Breath Rate (f)➥The number of times The number of times

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

➤ Tidal volume (VTidal volume (VTT))➥The amount of gas The amount of gas

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

➤ FlowFlow➥The velocity of gas The velocity of gas

flow or volume of gas flow or volume of gas per minute per 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”➥pressurepressure➥volumevolume➥flowflow

➥timetime

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

➤MandatoryMandatory➥Ventilator does the workVentilator does the work➥Ventilator controls start and stopVentilator controls start and stop

➤SpontaneousSpontaneous➥Patient takes on workPatient takes on work➥Patient controls start and stopPatient controls start and stop

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

➤Time - Time - control ventilationcontrol ventilation➤Pressure - Pressure - patient assistedpatient assisted➤Flow - Flow - patient assistedpatient assisted➤Volume - Volume - patient assistedpatient assisted➤Manual - Manual - operator controloperator control➤Impedance - Impedance - patient assistedpatient assisted

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

➤Flow (volume) controlledFlow (volume) controlled➥pressure may varypressure may vary

➤Pressure controlledPressure controlled➥flow 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-➥VolumeVolume➥FlowFlow➥PressurePressure

End of Insp…cycle mechanismsEnd of Insp…cycle mechanisms

➤The phase variable used to The phase variable used to terminate inspiration-terminate inspiration-➥VolumeVolume➥PressurePressure➥FlowFlow➥TimeTime

Expiratory - baselineExpiratory - baseline

➤PPositive ositive EEnd nd EExpiratory xpiratory PPressureressure➤Expiratory RetardExpiratory Retard➤NNegative egative EEnd nd EExpiratory xpiratory PPressureressure➤Expiratory HoldExpiratory Hold➤Time Limited Exhalation (APRV)Time Limited Exhalation (APRV)

PEEPPEEP

➤ DefinitionDefinition➥Positive end expiratory pressurePositive end expiratory pressure➥Application of a constant, positive pressure such that Application of a constant, positive pressure such that

at end exhalation, airway pressure does not return to at end exhalation, airway pressure does not return to a 0 baselinea 0 baseline

➤ 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 Referred to as CPAP when applied to spontaneous breathsspontaneous breaths

PEEPPEEP

➤ Increases functional residual capacity Increases functional residual capacity (FRC) and improves oxygenation(FRC) and improves oxygenation➥Recruits collapsed alveoliRecruits collapsed alveoli➥Splints and distends patent alveoliSplints and distends patent alveoli➥Redistributes 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 pressure➥Application 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 patientTidal volume and rate determined by patient

➤ Often final form of support before extubationOften final form of support before extubation

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)IMV➤PCVPCV➤PSVPSV➤Servo 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 ControlSafety Issue - Assist Control

➤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 - SIMVMandatory Ventilation - SIMV

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

F

P

SIMVSIMV

➤ AdvantagesAdvantages➥Synchronized breaths may Synchronized breaths may

improve patient comfortimprove patient comfort➥Increase patient control/regulationIncrease patient control/regulation➥Enhances blood flowEnhances blood flow➥Hyperventilation 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 Vand VTT

PressurePressure VentilationVentilation

➤ Volume delivery varies Volume delivery varies ➤ Inspiratory pressure Inspiratory pressure

constantconstant➤ Inspiratory flow variesInspiratory flow varies➤ Inspiratory time set by Inspiratory time set by

clinicianclinician

Pressure Control Ventilation - Pressure Control Ventilation - PCVPCV

➤The ventilator The ventilator delivers a set delivers a set pressure limit pressure limit over a set over a set inspiratory timeinspiratory time

F

P

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

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

F

P

Pressure Control VentilationPressure Control Ventilation

➤ AdvantagesAdvantages➥Limits risk of barotraumaLimits risk of barotrauma➥May recruit collapsed alveoliMay recruit collapsed alveoli➥Improved gas distributionImproved gas distribution

➤ DisadvantagesDisadvantages➥Tidal volumes vary when patient compliance Tidal volumes vary when patient compliance

changes (i.e. ARDS, pulmonary edema)changes (i.e. ARDS, pulmonary edema)➥With increases in I-time, patient may require With increases in I-time, patient may require

sedation and/or paralysis sedation and/or paralysis

Pressure Support Ventilation - Pressure Support Ventilation - PSVPSV

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

F

P

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

spontaneouslyspontaneously➥ 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 sudden short releases in pressure releases in pressure to rapidly reduce to rapidly reduce FRC and allow for FRC and allow for ventilationventilation

➤ 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 APRVSafety Issue - IRV and APRV

➤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 be result in intrinsic PEEP which must be consideredconsidered

Safety Issues - AlarmsSafety Issues - Alarms

➤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 and when the alarm condition is clear and attended toattended 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 MVPotential Complications of MV

➤ Ventilator malfunctionVentilator malfunction➥Manually ventilate patientManually ventilate patient

➤ BarotraumaBarotrauma➥Alveolar rupture due to overdistentionAlveolar rupture due to overdistention➥Monitor PIP, breath sounds PulmonaryMonitor PIP, breath sounds Pulmonary

➤ Oxygen toxicityOxygen toxicity➥goal: FIOgoal: FIO22 << .50 and PaO .50 and PaO22 >> 70 70

➤ Cardiovascular compromise/arrhythmiasCardiovascular compromise/arrhythmias➥Monitor vital signsMonitor vital signs

Potential Complications of MVPotential Complications of MV

➤ 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 reassuranceGive consistent, calming explanations, offer reassurance➥Sedation, anti-anxiety agents frequently indicatedSedation, anti-anxiety agents frequently indicated

From Basics to Advanced...From Basics to 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