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Ventilator Graphics: Optimizing Ventilator Settings: 

Ventilator Graphics: Optimizing Ventilator Settings Lisa Moores PCCMS

Overview: 

Overview Graphical Assessment Calculating Loads PEEP Ventilator Dysynchrony

Graphical Displays: 

Graphical Displays Four Parameters commonly monitored pressure Ventilator circuit (Paw) Esophagus (Pes) --pleural pressure flow volume time Commonly plotted as pressure, flow, and volume over time

Breath Delivery: 

Breath Delivery Four phases of ventilatory cycle trigger flow delivery cycle expiratory phase Breaths described by what determines the above phases

Triggers: 

Triggers

Flow: 

Flow

Cycling: 

Cycling

Breath Types: 

Breath Types

Breath Types: 

Breath Types

Slide11: 

Graphical Assessment Calculating Loads PEEP Ventilator Dysynchrony

Plateau Pressure: 

Plateau Pressure Lung “overstretch” has been linked to VILI An approximation of lung stretch is the “end inspiratory” pressure Must be measured in a “no flow” state

Plateau Pressure: 

Plateau Pressure

Plateau Pressure: 

Plateau Pressure

Measuring Loads: 

Measuring Loads

Measuring Loads: 

Measuring Loads

Measuring Loads: 

Measuring Loads

Overview: 

Overview Graphical Assessment Calculating Loads PEEP Ventilator Dysynchrony

PEEP and Compliance: 

PEEP and Compliance

PEEP Interaction Between Applied and Intrinsic: 

PEEP Interaction Between Applied and Intrinsic

PEEPi and Flow Limitation: 

PEEPi and Flow Limitation

PEEPi and Flow Limitation: 

PEEPi and Flow Limitation

Overview: 

Overview Graphical Assessment Calculating Loads PEEP Ventilator Dysynchrony

Patient Related Factors: 

Patient Related Factors Anxiety Pain Secretions Bronchospasm Pulmonary edema Dynamic hyperinflation Abnormal respiratory drive Drugs Nutrition

Ventilator Related Causes: 

Ventilator Related Causes Ventilator disconnection System leak Circuit malfunction Inadequate FiO2 Inadequate ventilator support

Ventilator Support: 

Ventilator Support Minute ventilation has a quadratic relationship to work of breathing Patient with increased drive, asynchrony may result from: overly sensitive trigger inadequate peak flow or peak flow rate prolonged inspiratory time inadequate pressure support inadequate expiratory time

Background: 

Background Total vs partial support Interactive modes can be either synchronous or asynchronous with patient efforts Synchronizing is important to avoid “imposed” muscle loading

Overview: 

Overview Mechanical breath parameters breath triggering (trigger criteria) ventilator delivered flow pattern (target criteria) ventilator flow termination (cycling criteria) Imposed expiratory loads (ET tube, PEEP valve) “Backup” ventilator breaths (if not timed appropriately with patient efforts)

Breath Triggering: 

Breath Triggering Ventilator must sense a spontaneous effort to initiate flow sensitivity (trigger phase) responsiveness (post-trigger phase) Inherent asynchrony pleural pressure change dampened avoid “autocycling” demand valve delay

Breath Triggering Minimizing Asynchrony: 

Breath Triggering Minimizing Asynchrony Microprocessor flow controls Inspiratory pressure support Sensors in the pleural space or on the phrenic nerve Does the type of triggering matter? Pressure Flow

Auto-PEEP and Triggering: 

Auto-PEEP and Triggering In the setting of PEEPi, the elevated alveolar pressure at end inspiration can serve as a significant triggering load The addition of extrinsic PEEP may help with triggering, but will not affect the degree of hyperinflation

Auto-PEEP and Triggering: 

Auto-PEEP and Triggering PEEPi = 10 PEEPi = 10 PEEPnet = 12 PEEPe = 10 PEEPe = 12 PEEPe = 0

Effect of Delivered Flow: 

Effect of Delivered Flow Interactive breaths can be “assisted”, “supported”, or “unassisted” Ventilator breaths can meet one of three goals after triggering fully unload the ventilatory muscles partially unload the ventilatory muscles not affect ventilatory muscle loads

Effect of Delivered Flow: 

Effect of Delivered Flow Inadequate flow rates may cause the patient to sense “air hunger” and lead to greater work of breathing Flow rates exceeding demand are also poorly tolerated and can lead to increased ventilatory drives and “double cycling”

Fully Unloaded Breaths: 

Fully Unloaded Breaths Goal is to deliver adequate flow over the entire inspiratory effort to unload the contracting muscles Assess by comparing the pressure pattern of a patient and machine triggered breath

Fully Unloaded Breaths: 

Fully Unloaded Breaths Synchrony requires careful selection of flow rate and pattern Patients with high respiratory drives often require high initial flow rates Pressure targeted breaths may be easier high initial flows flow is continuously adjusted

Fully Unloaded Breaths: 

Fully Unloaded Breaths Problems with pressure targeting: patients with lower drives require lower flows pressure target is the proximal airway…thus there is inherent under-responsiveness Studies comparing pressure and flow targeted breaths are lacking Proportional assist may be an alternative in the future

Breaths to Partially Unload: 

Breaths to Partially Unload Intermittently shift work between patient and ventilator Patient triggers the breath and then “shares” the work of the breath Studies directly comparing the two methods are lacking….though IMV tends to increase overall work done by the patient

Slide43: 

Flow Dysynchrony in a Volume Targeted Breath

Slide44: 

Flow Dysynchrony in a Pressure Targeted Breath

Flow Termination: Cycling: 

Flow Termination: Cycling Cycling should be done in accordance with patient demand and adequate tidal volume Premature termination may lead to decreased tidal volume or inspiratory load Delayed termination may result in increased tidal volume or expiratory load

Flow Termination: Cycling: 

Flow Termination: Cycling With pressure targeted breaths, termination may be accomplished in several ways: 25-30% of peak flow (duration and magnitude of patient effort can affect Ti) PS level and rate of pressure rise can also affect Ti Pressure assisted breaths….set Ti

Most Common Reasons for Dysynchrony: 

Most Common Reasons for Dysynchrony ACV: Inappropriate flow settings IMV: Little breath-breath adaptation…as back-up rate decreases, WOB increases PSV: prolongation of inspiratory flow beyond patient’s neural inspiratory time…this may also lead to PEEPi and triggering difficulty

Slide52: 

Patient comfort, synchrony with the ventilator is important to avoid imposed loads on the respiratory system Must consider trigger, flow, and cycling criteria when the patient “fights” the ventilator If problem unclear from the airway pressure tracing, consider placing an esophageal balloon

Overview: 

Overview Graphical Assessment Calculating Loads PEEP Ventilator Dysynchrony