A Synchrony During Mechanical Ventilation

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Asynchrony During

Mechanical VentilationKaren J. Bosma, MD, FRCPC


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Disclosure Statement I have received research funding from

Covidien to support a clinical research

assistant


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October 30, 2012

ObjectivesTo define patient-ventilator asynchrony

To understand why it occursTo recognize major types of asynchrony

To learn ways to manage asynchrony


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SynchronySimul taneous occurrence of events

Critical Care Western

AsynchronyEvents no t coord inated in t ime


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Assisted Spontaneous Breathing

Pvent + Pmus = (Flow * Resistance) + (Volume * Elastance)


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Definition

Patient-Ventilator Asynchrony occurs when thetiming of the ventilator cycle is not simultaneous

with the timing of the patients respiratory cycle

Neural Ti Ventilator Ti Neural Te Ventilator Te


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Associated with Weaning Failure

Patients with high level of asynchrony:

Longer duration of MV

Higher incidence of tracheostomy

Less likely to successfully wean from MV

Longer ICU LOS

Longer Hospital LOS

Less likely to be discharged home

Thille, Intensive Care Med (2006) 32:1515-22, Chao, CHEST (1997) 112:1592-99

De Wit, Critical Care Medicine (2009) 37: 2740-45


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Patient-ventilator

interaction:

-Mechanical propertiesof lung and chest wall

-Neural function

-Clinical input


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Key Phases of Each Breath

Jolliet and Tassaux, Crit Care (2006) 10:236-42

Triggersensitivity

(PEEPi)

Initial

flow rate

Set pressure

Control of flow(responsiveness to

patient demand)

Set Ti

% of peak flow(elastance and

resistance)


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Case 1

Asynchrony During Mechanical Ventilation


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Case 1

Mr. H., 63 year old male with emphysema admittedto ICU with COPD exacerbation

Current active issue: Prolonged weaning frommechanical ventilation.


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Case 1 continued

Progress: Remains on PSV 16-18 cmH2O ; at every attempt toreduce PSV below 15 cmH2O, RR 40, and is therefore placedon higher PSV at which RR 18-22. The airway pressure andflow tracings seen on the ventilator are shown below.


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PSV 16 (Paw (cmH2O) top and Flow (L/sec) bottom)

PSV 12 (Paw (cmH2O) top and Flow (L/sec) bottom


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Ineffective Efforts

Flow

Pao

Peso

Ineffective Efforts (IE) Patient 1 Ventilator 0


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COPD ( Auto-PEEP )


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Measures to Reduce PEEPi

Reduce resistance in airways Bronchodilators and steroids

Tube patency remove secretions

Prolong expiratory time Reduce inspiratory time (cycle sooner)

Decrease respiratory rate

Decrease Tidal Volume

Decrease pressure support


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D l d C li


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Flow

Pao

Peso

Mechanical Ti > Neural Ti

Delayed Cycling (DC) Patient 2 Ventilator 1

Delayed Cycling


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Delayed Cycling


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Delayed Cycling


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Delayed Cycling


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Ad ff t f b th


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Adverse effects of both

insufficient and excessive levels

of pressure support

Goal: provide optimal unloadingof the respiratory muscles


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Case 2



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Case 2

A 24 year old woman is admitted with ARDS

10 days later the patient is improving.

FiO2 has been weaned to 0.40 and PEEP is at 10 cmH2O

CXR, although improved, still shows bilateral airspace disease You would like to start weaning the patient from the ventilator

and order sedation to be weaned.

However, when sedation is lightened, the patient does not

tolerate pressure support and looks asynchronous on assistcontrol.


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Case 2 continued

Flow (L/sec) (top) and Airway Pressure (cmH2O) (bottom)

shown below:

Do ble Triggering
http://ccn.aacnjournals.org/content/vol29/issue6/images/large/41fig1.jpeg


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Double Triggering

Flow

Pao

Peso

Mechanical Ti < Neural Ti

Double Triggering (DT) Patient 1 Ventilator 2


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Premature Cycling

25%

10%

Cycle

setting

Neural Ti


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Measures to Reduce

Double Triggering

Double triggering occurs in setting of high

ventilatory demand and short ventilator

inspiratory time (ACV more common than PSV)

Aim for ways to reduce ventilatory demand

Increase Vt

Sedation

Increase Ti Reduce cycling criterion (Esens), or increase Ti


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Case 3



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Case 3

An 80 year old woman, admitted to ICU withpneumonia, dehydration and weight loss.

PMHx: congestive heart failure

The nurse calls you to the bedside. The ventilatorkeeps alarming for high respiratory rate. Thepatients respiratory rate is 35 to 40.

The RRT has tried assist control/ pressure control,assist control/volume control and pressure support,

but cannot get the patient to settle. The nurse would like an order for more sedation and

asks if you are considering paralyzing the patient.


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Case 3 continued The patient is awake, with a high respiratory rate, but

no other signs of distress.

The airway pressure (bottom) and flow tracings (top)seen on the ventilator are shown below.

A i i


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Auto-triggering

Flow

Pao

Peso

Autotriggering (AT) Patient 0 Ventilator 1


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Auto-triggering

The delivery of a mechanical breath in the absence of a clearcontraction of the respiratory muscles.


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Auto-triggering

Circuit leak Water in the circuit

Cardiac oscillations

Nebulizer treatments Negative suction applied through chest tube

Fix leak, empty water from circuit Increase Trigger sensitivity

Change from flow to pressure triggering


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Case 3 continued

You increase the trigger threshold (make it less sensitive) andthe RR immediately drops to 24, and the patient, appearingmore comfortable, drifts off to sleep. However, soon thenurse is calls to let you know that now the ventilator isalarming for apnea. Although the patient is on fentanyl at 50

ug/hr, she arouses easily and obeys commands.

ABG: pO2 89, pCO2 30, pH 7.50, HCO3- 24

P i di B thi


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Periodic Breathing

Flow

Pao

Peso

10 seconds

Central apnea


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Summary



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Types of Gross Asynchrony

Patient

Breath

Ventilator

Breath

Triggering Problem

Ineffective Efforts (IE) 1 0

Autotriggering (AT) 0 1

Cycling off Problem

Double Triggering (DT) 1 2

Delayed Cycling (DC) 2 1


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Bedside Management

Respir Care. 2011;56(1):61

72.

Type Correction

Ineffective triggering

weak inspiratory effort

High PEEPi (COPD)

Decrease trigger threshold

Reduce sedation

Reduce the potential for intrinsic PEEP

(decrease VT, VE, increase TE)

Delayed Cycling

-Low elastic recoil (emphysema)

-High resistance (COPD)

Increase cycling criterion (Esens)

Decrease Ti

Auto-triggering

cardiogenic oscillations or circuit leaks

absence of patient effort

Increase trigger threshold

Switch from flow to pressure triggering

Avoid hyperventilation

Double-triggering

-high ventilatory demand, and-short ventilator inspiratory time (ACVmore common than PSV)

Aim for ways to reduce ventilatory

demand.

Is VT too small? TI too short?

Decrease cycling criterion (Esensitivity)


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Patient-ventilator

interaction:

-Mechanical propertiesof lung and chest wall

-Neural function

-Diaphragm contraction

-Clinical input


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PAV

Flow

Pao

Peso

Pmus = Flow*Rtot + Vt*Est

PAV instantaneously

measures the flow andvolume being pulled in by

the patient, and, knowing the

elastance and resistance of

the respiratory system,

determines how muchpressure to provide for each

breath.


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NAVA


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FutureResearch



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Asynchrony

may be costly

Critical Care Western


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Reducing patient-ventilator asynchrony may improve outcome

IF

THEN

Delirium

Duration MV

ICU LOS

Hospital LOS Mortality

Asynchrony

Sleep Quality

? Sedation

? VIDD

Asynchrony


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[email protected]

Key issues of patient ventilator interaction during


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Key issues ofpatient-ventilator interaction during

Variable Gas Flow Delivery (PSV)


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Delays in Flow Delivery


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Active Exhalation Initiating Cycling


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Neurally Adjusted Ventilatory Assist

Documents

A Synchrony During Mechanical Ventilation