Ventilator Management

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Ventilator Management

Michael Schmitz, DO, MS

Emergency Medicine/Internal Medicine

October 10, 2007


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Objectives: To review differences in ventilator modes To review how to interpret ventilator settings

and readings

To discuss the protocol for assessing a

ventilated patient who is in distress

To review the pathophysiology of the

obstructive lung diseases To discuss guidelines for ventilator settings for

patients with obstructive lung disease


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25

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14

5050

5

18

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BUY EASY TIGER by RYAN ADAMS

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Nomenclature

A/C 600/14/50%/+5


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Volume Cycled Ventilation

A/C Ventilation

SIMV


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Pressure Cycled Ventilation

Pressure Support

(PSV)

Airway Pressure

Release (APRV)


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Flow Rate / I:E Ratio Flow Rate: a measure of the rate of delivery of

oxygen through the system to the patient.

(usually 60 liters per minute)

I:E Ratio: a measure of total inspiratory time toexpiratory time. (1:3) is ideal

Inspiratory time = Tidal Volume / Inspiratory flow

An increase in flow rate will shorten inspiratory time anddecrease I:E

Insufficient flow rates contribute to patient dyspnea

Insufficient expiratory time increases mean airwaypressure, the likelihood of barotrauma and auto-PEEP.


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Trigger Mode/Sensitivity Trigger Mode- (A/C)

Most common is pressuretriggering; the patient must

generate a sufficient NE

Tnegative airway pressure inorder to receive a breath

Sensitivity- the set

negative pressure thepatient must overcome toopen the demand valveand trigger a breath


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Flow Pattern

Constant (square)

Decelerating (ramp)-possibly better in

COPD

Sinusoidal


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PEAK VS. PLATEAU PRESSURES

Peak Pressure:Pressure at the end of inspiration.

Determined by inflation volume, airway resistance

and the elastic recoil of the lungs and chest wall

Plateau Pressure: Measured when airflow is

stopped. It is directly proportional to the elasticity of

the lungs and chest wall


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PEAK VS.

PLAT

EAUP

RESSURES


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Positive End-Expiratory

Pressure

PEEP: an elevation in

alveolar pressure

above atmospheric

pressure at the end ofexhalation

Extrinsic PEEP(ePEEP): applied

through a mechanical

ventilator

ACV without PEEP

ACV with PEEP


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Positive End-Expiratory Pressure

improves gas exchange by

opening small airways inthe dependent lung zonesand distributing inspiredgas homogeneously.

decreases expiratory flow

limitation and dynamichyperinflation.

decreases oxygenconsumption

Physiologic:(3-5 cm H20) overcomes the decreasein functional residual capacity due to endotracheal

intubation (glottis has been bypassed):


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PressureSupraphysiologic PEEP:(>5 cm H20)

Offsets auto-PEEP in patients with obstructivelung disease

Improves oxygenation in patients with hypoxemicrespiratory failure

Improves oxygenation and cardiac performancein patients with cardiogenic pulmonary edema

Caution in: focal lung disease, pulmonary embolism,hypotension, patients with increased ICP, hypovolemia,bronchopleural fistula


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Pressure


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Auto-P

EEP

Intrinsic PEEP(iPEEP, aka occult, vent-

associated) occurs because of incompleteventilation: Initiating a new breath prior to

complete exhalation causes air-trapping


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Auto-P

EEP

Causes: high minute

volume ventilation,

expiratory flow

limitation or increasedexpiratory resistance

Hypoxemia,

hypotension and

barotrauma can occur

as a result


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Auto-PEEP


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PEEP

Applying PEEP can decrease the magnitude of

negative pressure that the patient must generate to

trigger the ventilator, which reduces work done by

the muscles of inspiration


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Consequences of MV Positive pressureventilation preferentiallyinflates the more compliant,non-dependent upper lung

zones Uneven gas distribution

contributes to barotraumaand auto-PEEP, with apreference for damaging

normal alveoli Occurs in ARDS, asthma

and chronic interstitial lungdisease


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Consequences of MV Barotrauma causes

damage to adjacent

alveoli via stretching andshearing forces.

High peak airway

pressures are directly

correlated with

barotrauma


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Consequences of MV Complications of

alveolar rupture can be

devastating: Pulmonary interstitial

emphysema

Pneumomediastinum

SQ Emphysema Pneumothorax

Pneumoperitoneum


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Ventilator Synchrony

Setting the ventilator to cycle with the patients respiratory

rhythm

Requires close patient monitoring

Try to prevent ineffective triggering

Adjust oxygen flow rate in proportion to tidal volume

* may increase peak airway pressure Adequate sedation is critical

Any increased sense of effort (fatigue vs. forced exhalation) on the

part of the patient contributes to sensation of dyspnea


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CaseP

resentation 65 year-old man BIBEMS

c/o increasing dyspnea

over3 days associated with

temperature of100.3 andincrease in thickened,

green sputum. He has a

history of emphysema, is

on home oxygen and hasbeen using his inhalers

without relief.


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The Decision

To Intubate

Initiation of mechanical ventilation in COPD

patients is associated with high patient mortality

and poor potential for weaning

Indications:(E.B.M. vs. clinical gestalt)

Patient failed conservative management

Severe, persistent acidosis

Continued arterial hypoxemia despite initial therapy

Patient fatigue

Altered mental status

Additional major illness (pulmonary embolism, AMI)


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The usual vent settings are applied

Some time passes.


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5

60

0.6

14

50%

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63

3:1

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WARNING: LOW EXHALED VOLUME

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Respiratory Distress in MV Ventilator: Malfunction or Circuit Leak

Ventilator: Inadequate ventilator settings: Inadequate Tidal volume, FiO2, Flow rate, Positive end

expiratory pressure (PEEP) or over/undersensitivity

Airway:(increased Ppeak-Pplat) ENDOTRACHEAL TUBE MIGRATION, patient biting

tube, balloon cuff leak, deflation or rupture Bronchospasm, increased airway resistance imposed by

heat and moisture exchanger, obstruction by secretions,blood or foreign object


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Respiratory Distress in MV Lungs:(Ppeak-Pplat unchanged or

decreased): pneumonia, atelectasis,pulmonary edema, aspiration of gastric

contents, pneumothorax, pleural effusion,pulmonary embolus,ENDOTRACHEAL TUBE MIGRATION!

Extrapulmonary: Abdominal distension,delerium, anxiety, pain, stroke, seizure


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Respiratory Distress in MV


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What to Do?

Protocol


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Goals for CO

PD patients

Adequate patient monitoring

Optimize ventilator settings to minimize

excessive work of breathing Assure Synchrony

Detect auto-PEEP and prevent barotrauma

Prevent further respiratory muscle atrophy Intubate using the widest diameterET tube

possible (R = 8nl / r4)


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ObstructiveLung Diseases

Asthma

Chronic bronchitis

Emphysema

Congenital bullous

lung disease


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Pathophys COPD


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Pathophys Emphysema


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VentG

uidelines Emphasis on assisted modes of ventilation

(patient initiated), institution preference for

A/C vs. IMV with PSV (to overcome ET tube)

SIMV: probably causes excess work, b/c of

high resistance circuit but debatable;

requires close patient monitoring


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Vent Guidelines


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VENTGuidelines

Higher flow rates are highly beneficial


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VentG

uidelines


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VentG

uidelines Tidal Volume:5-7 ml/kg

Set Rate: 4 less than spontaneous rate

FiO2: adjust to PaO2 of at least 60 mmHg

Triggering:-1 to -2 cm H2O

Prevent Auto-PEEP with sufficient PEEP

Flow rate: Increase to provide increased expiratory

time (70-90 lpm)

Continue inhaled medications: requires sufficient

tidal volume and inspiratory time


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Pathophys Asthma

Airway narrowing causedby smooth musclecontraction, wall thickeningand increased secretionscombine to reduce air flowrates

Primarily a disease of theAIRWAYS with decreased

elastic recoil of the lungsduring attack

ABG for PaCO2 to identifyrespiratory failure


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Pathophys Asthma


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Vent Settings Asthma Respiratory rate 10 to 14 breaths/min

(allows more time for exhalation)

Tidal volume less than 8 mL/kg Minute ventilation less than 115 mL/kg

Inspiratory flow of 80 to 100 L/min

Extrinsic postive end-expiratory pressureless than 80 percent of the intrinsic PEEP

Continue inhaled medications and steroids


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Vent Settings Asthma Intubate with largest diameter tube possible!(8.0 mm and up)

F

irst priority is to minimize auto-PEEPand keep plateau pressures low!

Lower respiratory rate and tidal volume maybe necessary causing PaCO2 to increase

(permissive hypercapnia) Sedation, then paralysis to force synchrony

Heliox


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Osteopathic Considerations Findings reflect anatomical changes related

to increased lung volumes and impairedventilation

Thoracic Vertebral Dysfunction

Rib Dysfunction (stuck in exhalation)

Diaphram Dysfunction (stuck down)

Law of LaPlace T = Pr Lymphatic obstruction: lymphatic drainage

impaired by positive pressure


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Summary

The need to initiate mechanical ventilation in patients with

obstructive lung disease in the emergency department isassociated with a higher inpatient mortality

Patients with obstructive lung disease require closemonitoring of all physiologic parameters to preventcomplications associated with positive pressure ventilation

Assessing a distressed ventilator dependent patient requiresan organized approach

In general: low tidal volumes, higher flow rates andapplication of a conservative amount ofPEEP are appropriateinitial settings for patients with obstructive lung disease


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References The ICU Book Marino PL, 2nd Edition Respiratory Physiology West JB, 5th Edition

Pulmonary Pathophysiology Grippi MA Textbook of Medical Physiology Guytonand Hall 9th Edition

Chest Radiology Companion Stern EJ,

White CS Harrisons Principles of Internal Medicine 16th

Edition

R f


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References

www.utdol.com :

principles of mechanical

ventilation, alternate modes of

mechanical ventilation,

positive end expiratorypressure, pathophysiologic

consequences of positive

pressure ventilation,

mechanical ventilation in acute

respiratory failure complicatingCOPD, mechanical ventilation

in adults w/ status asthmaticus


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