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Ventilator Management

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SQ Emphysema. Pneumothorax. Pneumoperitoneum. Ventilator Synchrony ... He has a history of emphysema, is on home oxygen and has been using his inhalers ... – PowerPoint PPT presentation

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Title: Ventilator Management


1
Ventilator Management
  • Michael Schmitz, DO, MS
  • Emergency Medicine/Internal Medicine
  • October 10, 2007

2
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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BUY EASY TIGER by RYAN ADAMS

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4
Nomenclature
  • A/C 600/14/50/5

5
Volume Cycled Ventilation
  • A/C Ventilation
  • SIMV

6
Pressure Cycled Ventilation
  • Pressure Support
  • (PSV)
  • Airway Pressure Release (APRV)

7
Flow Rate / IE Ratio
  • Flow Rate a measure of the rate of delivery of
    oxygen through the system to the patient.
  • (usually 60 liters per minute)
  • IE Ratio a measure of total inspiratory time to
    expiratory time. (13) is ideal
  • Inspiratory time Tidal Volume / Inspiratory
    flow
  • An increase in flow rate will shorten inspiratory
    time and decrease IE
  • Insufficient flow rates contribute to patient
    dyspnea
  • Insufficient expiratory time increases mean
    airway pressure, the likelihood of barotrauma and
    auto-PEEP.

8
Trigger Mode/Sensitivity
  • Trigger Mode- (A/C)
  • Most common is pressure triggering the
    patient must generate a sufficient NET negative
    airway pressure in order to receive a breath
  • Sensitivity- the set negative pressure the
    patient must overcome to open the demand valve
    and trigger a breath

9
Flow Pattern
  • Constant (square)
  • Decelerating (ramp)
  • -possibly better in COPD
  • Sinusoidal

10
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

11
PEAK VS. PLATEAU PRESSURES

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13
Positive End-Expiratory Pressure
  • PEEP an elevation in alveolar pressure above
    atmospheric pressure at the end of exhalation
  • Extrinsic PEEP (ePEEP) applied through a
    mechanical ventilator

ACV without PEEP
ACV with PEEP
14
Positive End-Expiratory Pressure
Physiologic (3-5 cm H20) overcomes the decrease
in functional residual capacity due to
endotracheal intubation (glottis has been
bypassed)
  • improves gas exchange by opening small airways in
    the dependent lung zones and distributing
    inspired gas homogeneously.
  • decreases expiratory flow limitation and dynamic
    hyperinflation.
  • decreases oxygen consumption

15
Positive End-Expiratory Pressure
  • Supraphysiologic PEEP (gt 5 cm H20)
  • Offsets auto-PEEP in patients with obstructive
    lung disease
  • Improves oxygenation in patients with hypoxemic
    respiratory failure
  • Improves oxygenation and cardiac performance in
    patients with cardiogenic pulmonary edema
  • Caution in focal lung disease, pulmonary
    embolism, hypotension, patients with increased
    ICP, hypovolemia, bronchopleural fistula

16
Positive End-Expiratory Pressure
17
Auto-PEEP
  • Intrinsic PEEP (iPEEP, aka occult,
    vent-associated) occurs because of incomplete
    ventilation Initiating a new breath prior to
    complete exhalation causes air-trapping

18
Auto-PEEP
  • Causes high minute volume ventilation,
    expiratory flow limitation or increased
    expiratory resistance
  • Hypoxemia, hypotension and barotrauma can occur
    as a result

19
Auto-PEEP
20
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

21
Consequences of MV
  • Positive pressure ventilation preferentially
    inflates the more compliant, non-dependent upper
    lung zones
  • Uneven gas distribution contributes to barotrauma
    and auto-PEEP, with a preference for damaging
    normal alveoli
  • Occurs in ARDS, asthma and chronic interstitial
    lung disease

22
Consequences of MV
  • Barotrauma causes damage to adjacent alveoli via
    stretching and shearing forces.
  • High peak airway pressures are directly
    correlated with barotrauma

23
Consequences of MV
  • Complications of alveolar rupture can be
    devastating
  • Pulmonary interstitial emphysema
  • Pneumomediastinum
  • SQ Emphysema
  • Pneumothorax
  • Pneumoperitoneum

24
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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26
Case Presentation
  • 65 year-old man BIBEMS c/o increasing dyspnea
    over 3 days associated with temperature of 100.3
    and increase in thickened, green sputum. He has a
    history of emphysema, is on home oxygen and has
    been using his inhalers without relief.

27
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)

28
  • The usual vent settings are applied
  • Some time passes.

29

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WARNING LOW EXHALED VOLUME
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30
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

31
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

32
Respiratory Distress in MV
33
What to Do?
  • Protocol

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Goals for COPD 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 diameter ET tube
    possible (R 8nl / pr 4)

38
Obstructive Lung Diseases
  • Asthma
  • Chronic bronchitis
  • Emphysema
  • Congenital bullous
  • lung disease

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41
Pathophys COPD
42
Pathophys Emphysema
43
Vent Guidelines
  • 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

44
Vent Guidelines
45
VENT Guidelines
  • Higher flow rates are highly beneficial

46
Vent Guidelines
47
Vent Guidelines
  • 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

48
Pathophys Asthma
  • Airway narrowing caused by smooth muscle
    contraction, wall thickening and increased
    secretions combine to reduce air flow rates
  • Primarily a disease of the AIRWAYS with decreased
    elastic recoil of the lungs during attack
  • ABG for PaCO2 to identify respiratory failure

49
Pathophys Asthma
50
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 pressure less
    than 80 percent of the intrinsic PEEP
  • Continue inhaled medications and steroids

51
Vent Settings Asthma
52
Vent Settings Asthma
  • Intubate with largest diameter tube possible!
    (8.0 mm and up)
  • First priority is to minimize auto-PEEP and keep
    plateau pressures low!
  • Lower respiratory rate and tidal volume may be
    necessary causing PaCO2 to increase (permissive
    hypercapnia)
  • Sedation, then paralysis to force synchrony
  • Heliox

53
Osteopathic Considerations
  • Findings reflect anatomical changes related to
    increased lung volumes and impaired ventilation
  • 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

54
Summary
  • The need to initiate mechanical ventilation in
    patients with obstructive lung disease in the
    emergency department is associated with a higher
    inpatient mortality
  • Patients with obstructive lung disease require
    close monitoring of all physiologic parameters to
    prevent complications associated with positive
    pressure ventilation
  • Assessing a distressed ventilator dependent
    patient requires an organized approach
  • In general low tidal volumes, higher flow rates
    and application of a conservative amount of PEEP
    are appropriate initial settings for patients
    with obstructive lung disease

55
References
  • The ICU Book Marino PL, 2nd Edition
  • Respiratory Physiology West JB, 5th Edition
  • Pulmonary Pathophysiology Grippi MA
  • Textbook of Medical Physiology Guyton and Hall
    9th Edition
  • Chest Radiology Companion Stern EJ, White CS
  • Harrisons Principles of Internal Medicine 16th
    Edition

56
References
  • www.utdol.com
  • principles of mechanical ventilation,
    alternate modes of mechanical ventilation,
    positive end expiratory pressure,
    pathophysiologic consequences of positive
    pressure ventilation, mechanical ventilation in
    acute respiratory failure complicating COPD,
    mechanical ventilation in adults w/ status
    asthmaticus

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