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Mechanical Ventilation: The Basics and Beyond

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Title: Mechanical Ventilation: The Basics and Beyond


1
Mechanical Ventilation The Basics and Beyond
  • Presented By
  • Diana Gedamke, BSN, RN, CCRN
  • Marion College - Fond du Lac

2
Mechanical Ventilation
  • an opening must be attempted in the trunk of
    the trachea, into which a tube of reed or cane
    should be put you will then blow into this, so
    that the lung may rise againand the heart
    becomes strong
  • Andreas Vesalius (1555)

3
Mechanical Ventilation
  • First described in 1555
  • First used in patient care during the polio
    epidemic of 1955
  • Medical students became human ventilators
  • First positive pressure ventilator was used at
    Massachusetts General Hospital

4
Indications for MV
  • Acute Respiratory Failure (66)
  • Coma (15)
  • Acute Exacerbation of COPD (13)
  • Neuromuscular Disorders (5)
  • Esteban et al. How is mechanical ventilation
    employed in the intensive care unit? An
    international utilization review. Am J Respir
    Crit Care Med 2000161 1450 - 8.

5
Indications for MV
  • Acute Respiratory Failure
  • ARDS
  • Heart Failure
  • Pneumonia
  • Sepsis
  • Complications of Surgery
  • Trauma

6
Objectives of MV
  • Decrease WOB
  • Reverse life-threatening hypoxemia or acute
    progressive respiratory acidosis
  • Protect against ventilator-induced lung injury
  • Wean and extubate as soon as possible

7
Caring for the Mechanically Ventilated Patient
  • Endotracheal tube
  • Position
  • Stability
  • Cuff inflation
  • Patency
  • Oral cavity
  • Trauma to lip and palate
  • Secretions

8
Caring for the Mechanically Ventilated Patient
  • Patient Position
  • Patient-Ventilator Synchrony
  • Physical Assessment
  • VS, General assessment, breath sounds
  • Ventilator Mode
  • Alarms
  • Reason for intubation
  • MV in disease states
  • Does patient still need to be intubated and
    mechanically ventilated?

9
Endotracheal Tube
  • Nasal or oral
  • Size (6 8.5 cm)
  • Position
  • 21 cm from the teeth in women 23 cm in men
  • Confirm position by CXR (even when breath sounds
    are bilateral)
  • 3 - 5 cm above carina
  • Affects of head position

10
Endotracheal Tube
  • Position
  • End Tidal CO2 to confirm ETT placement

11
Normal Airway
12
Endotracheal Tube Positioning
13
Complications of Intubation and Mechanical
Ventilation
  • Sinusitis - occurs in gt 25 of patients
    ventilated gt 5days nasal gt oral subtle findings
    (unexplained fever leukocytosis), polymicrobial
  • Laryngeal damage - ulceration, granulomas, vocal
    cord paresis, laryngeal edema
  • Aspiration/Ventilator-associated pneumonia -
    occurs despite cuffed tube
  • Tracheal necrosis - tracheal stenosis,
    tracheomalacia
  • Death ventilator malfunction/inadvertent
  • disconnection/endotracheal tube
    dysfunction/VAP

14
Preventing Infection
  • Sterile suctioning
  • assess as routine part of assessment only
    suction when patient needs it
  • Elevate HOB to 45 degrees

15
Positive Pressure Ventilation
  • Volume-cycled ventilation
  • Pressure-preset ventilation

16
PB 7200
17
Volume-cycled Ventilation
  • Delivers a preset volume of gas with each machine
    breathairway pressures increase in response to
    the delivered breath
  • Airway pressures are higher in patients with low
    compliance or high resistancehigh pressures
    indicate risk of ventilator-induced lung injury

18
Spontaneous Breathing vs. Positive Pressure
Ventilation
19
Volume-cycled Ventilation
  • Assist Control (AC)
  • Synchronized Intermittent Mandatory Ventilation
    (SIMV)

20
Assist-control (AC)
  • Most widely used mode of MV
  • Delivers a minimum number of fixed-volume breaths
  • Patients can initiate extra assisted breaths
    (will get full set volume with each effort)

21
Pressure-time TracingsAssist Control Mode
22
Synchronized Intermittent Mandatory Ventilation
(SIMV)
  • Delivers preset number of fixed-volume breaths
  • Patient can breathe spontaneously between breaths
    (rate and depth determined by patient)
  • Patients often have trouble adapting to
    intermittent nature of ventilatory assistance

23
Pressure-time TracingsSIMV Mode
24
Pressure-preset Ventilation
  • Delivers a predefined target pressure to the
    airway during inspiration
  • Resulting tidal volume (VT) and inspiratory flow
    profile vary with the impedance of the
    respiratory system and the strength of the
    patients inspiratory efforts
  • Includes pressure-control (PC) and Pressure
    support (PS)

25
Pressure-control (PC) Ventilation
  • Delivers a preset gas pressure to the airway for
    a set time and at a guaranteed minimum rate
  • Patient can breathe in excess of set rate
  • Tidal volume achieved depends on pressure level,
    lung mechanics, and patient effort
  • Inspiratory flow rate variable

26
Pressure Support (PS)
  • Delivers preset airway pressure for each breath
  • Variable parameters Inspiratory and expiratory
    times (respiratory rate), flow rate, and tidal
    volume (VT)

27
SIMV PS
  • Spontaneous breaths allowed in SIMV are assisted
    by PS

28
New Modes of MV
  • New modes often introduced
  • Involves nothing more than a modification of the
    manner in which positive pressure is delivered to
    the airway and of the interplay b/n mechanical
    assistance and patients resp effort
  • Goals enhance respiratory muscle rest, prevent
    deconditioning, improve gas exchange, prevent
    lung damage, improve synchrony, foster lung
    healing

29
Ventilator Settings
  • Respiratory rate
  • Tidal volume
  • FiO2
  • InspiratoryExpiratory (IE) ratio
  • Pressure limit
  • Flow rate
  • Sensitivity/trigger
  • Flow waveform

30
Inspiratory Flow (V) Waveform
  • Square waveform Decelerating
    Waveform
  • (constant flow)
    (decelerating flow)

31
Inspiratory Flow (V) Waveform
  • Square waveform volume of gas is evenly
    distributed across inspiratory time. Has highest
    peak pressure and lowest mean airway pressure.
    Ideal for those at risk for autopeeping due to
    short inspiration time

32
Inspiratory Flow (V) Waveform
  • Decelerating waveform Volume of gas flow is
    high at the beginning of inspiration then tapers
    off toward the end of the breath. Has lowest
    peak pressure and highest mean airway pressure.
    Increased inspiratory time useful in ARDS.

33
Patient-Ventilator Synchrony
  • Check for
  • Symmetric chest inflation
  • Regular breathing pattern
  • Respiratory rate lt 30 bpm
  • Synchrony between patient effort and machine
    breath
  • Paradoxical breathing

34
Patient-Ventilator Synchrony
  • Inspiratory effort expended by patients with
    acute respiratory failure is 4 - 6 x normal
  • Dont eliminate respiratory effort causes
    deconditioning and atrophy

35
Patient-Ventilator Asynchrony
  • Possible causes
  • Anxiety or pain
  • Ventilator settings may not be appropriate
    check ABG and alert individual responsible for
    ventilator orders
  • Auto-PEEP
  • Pneumothorax

36
Ventilator Alarms and Common Causes
High Pressure Low Pressure Low Exhaled Volume
Kink in tubing Patient biting ETT Ventilator disconnected from ETT Pressures exceeding high pressure limit
Secretions Cuff leak Cuff leak
Coughing Extubation Ventilator disconnected
Bronchospasm
Foreign body
37
Definitions
  • PEEP positive-end-expiratory pressure applied
    during mechanical ventilation
  • CPAP - continuous positive airway pressure
    applied during spontaneous breathing

38
PEEP
  • Improves oxygenation - increases functional
    residual capacity (FRC) above closing volume to
    prevent alveolar collapse
  • permits reduction in FIO2
  • Reduces work of breathing
  • Increases intrathoracic pressure - decreases
    venous return to right heart - decreases CO
  • Titrate to least amt. necessary to achieve O2 sat
    gt 90 or PO2 gt 60 mm Hg with FiO2 lt 0.6

39
Auto-PEEP
  • Auto-PEEP/intrinsic PEEP (PEEPi)/inadvertent
    PEEP/occult PEEP - positive end expiratory
    alveolar pressure occurring in the absence of set
    PEEP. Occurs when expiratory time is inadequate.

40
Assessing Flow Waveform for Presence of Auto-PEEP
41
Resistance and Compliance
42
Definitions
  • Peak Airway Pressure (Ppk)
  • An increase in Ppk indicates either an increase
    in airway resistance or a decrease in compliance
    (or both).
  • Plateau Pressure (Ppl) - end-inspiratory alveolar
    pressure

43
Airway Pressure Analysis
44
Ventilator-Induced Lung Injury
  • High volumes and pressures can injure the lung,
    causing increased permeability pulmonary edema in
    the uninjured lung and enhanced edema in the
    injured lung
  • Alveolar overdistention repeated collapse and
    re-opening of alveoli

45
Mechanical Ventilation in Obstructive Lung Disease
  • resistance to expired flow
  • results in air trapping/hyperinflation
  • hyperinflation may result in cardiopulmonary
    compromise
  • Goal meet minimal requirements for gas exchange
    while minimizing hyperinflation
  • Allow increased time for expiratory flow

46
Increasing Time for Exhalation
  • Decrease inspiratory time
  • Increase flow rate
  • Square waveform
  • Decrease minute ventilation (VE)
  • RR x TV

47
Monitoring Patients with Obstructive Lung Disease
Requiring Mechanical Ventilation
  • Monitor plateau pressure in general, Pplat lt
    30 cm H20 to decrease risk of hyperinflation and
    alveolar overdistension
  • Permissive hypercapnia

48
Respiratory Failure Due to Asthma
  • Watch for overventilation post intubation
  • High Ppk common
  • May require sedation to establish synchronous
    breathing with ventilator
  • Avoid paralytics
  • Ventilate as stated above (Increase exhalation
    time by decreasing RR and TV, increasing
    inspiratory flow rate, and using square waveform)
  • May want to use SIMV

49
Respiratory Failure Due to COPD
  • Ppk typically not as elevated as in asthma when
    it is, think other pathologic processes
  • Many patients with COPD have chronic hypercapnia
    ventilatory support titrated to normalize pH and
    not PCO2
  • Small levels of set PEEP may decrease WOB
  • May try NIPPV

50
Noninvasive Positive Pressure Ventilation (NIPPV)
  • Cooperative patient
  • Functionally intact upper airway
  • Minimal amount of secretions
  • Done by full face or nasal mask
  • Watch for gastric distension may increase risk
    of aspiration
  • May use standard ventilators
  • Monitor patients closely for decompensation and
    need for intubation

51
ARDS A Three Lung Unit Model
Normal
Non-recruitable
Recruitable
52
Respiratory Failure Due to ARDS
  • Refractory hypoxemia
  • Avoid ventilator induced lung injury
  • pressure-limited approach
  • keep Pplat lt 30 cm H20
  • small tidal volumes (6 ml/kg)
  • permissive hypercapnia
  • Avoid O2 toxicity apply moderate levels of PEEP

53
ARDS
  • May need to increase inspiratory time
  • Inverse ratio ventilation (IRV)
  • IE gt 11
  • May require sedation/paralysis
  • Use as second-line strategy if PEEP fails to
    improve oxygenation

54
Mechanical Ventilation in Patients with
Neuromuscular Weakness
  • Present with acute or subacute respiratory
    failure, usually with hypercapnia
  • progressive neurologic dysfunction (amyotrophic
    lateral sclerosis, muscular dystrophies,
    Guillain-Barre, CNS dysfunction due to head
    injury or drug ingestion)
  • usually ventilated without difficulty unless RF
    is complicated by secondary conditions
    (atelectasis or pneumonia)
  • lung compliance and gas exchange remain
    relatively normal

55
Does My Patient Still Need to Be Intubated and
Mechanically Ventilated?
  • Evaluate daily when patient is hemodynamically
    stable and improving
  • Use weaning checklist

56
Discontinuation of MV
  • Most (80 - 90) are able to have MV discontinued
    after reversal of physiologic process requiring
    support
  • No single approach to weaning has been shown to
    be better than any other
  • A particular approach, when improperly applied,
    can prolong process
  • General rules work, rest, feed, allow to sleep

57
Weaning Checklist
  • 1. Patient status
  • Reversal of physiologic derangements requiring
    ventilatory support
  • Globally improving patient
  • 2. Mental status
  • Alert, cooperative, able to follow commands
  • 3. Secretions/airway protection
  • Absence of copious, thick, secretions
  • Patient ability to handle secretions/protect
    airway/intact gag reflex

58
Weaning Checklist
  • 4. Oxygenation
  • In general, need Pa02 gt 60 torr (SaO2 gt90) on
    FiO2 lt 0.4 and PEEP lt 5.0 cm H2O
  • Ventilation
  • Baseline PCO2 achieved with Ve lt 12 L/min
  • Rapid shallow breathing index, f/VT lt 100 during
    spontaneous breathing (VT is in liters, e.g.
    25/.4 62.5 with Ve 10 L/min is predictive of
    success)

59
Weaning Checklist
  • If criteria 1 5 are met, decrease ventilatory
    support by, decreasing pressure support, or a
    trial of CPAP or t-piece. If tolerating after 2
    hours, extubate.
  • If any of the above criteria are not met,
    continue ventilatory support and correct
    physiologic derangements (see below).
  • With regard to 5 (ventilation), if f/VT gt 100,
    there is inadequate strength (assessed by NIF) or
    excessive ventilatory load (assessed by
    compliance) or both. (The patient must be strong
    enough for any given load to maintain spontaneous
    respirations.)

60
Weaning Checklist
  • NIF must be more negative than 25 cm H2O
  • If not, increase strength (check TFTs, nutrition,
    Ca, Mg, PO4, K, avoid fatigue, avoid lung
    hyperinflation,? paralytics, ? aminoglycosides, ?
    critical illness polyneuropathy)
  • Increased ventilatory load what is causing
    decreased compliance? (ARDS, pulmonary edema,
    pneumonia, atelectasis)

61
Weaning Methods
  • 1. Trials of spontaneous breathing alternating
    with full ventilatory support
  • 2. SIMV (longer than spontaneous breathing and
    PS)
  • 3. PS

62
Weaning
  • Monitor clinical parameters HR, RR, subjective
    distress, pulse oximetry, cardiac rhythm
  • If patient deteriorates either clinically or
    physiologically, terminate weaning trial
  • In general, initiate only one weaning trial in a
    24-hour period

63
Extubation
  • Reliable indices are not available
  • LOC
  • Gag
  • Cough
  • Secretions
  • Head lift
  • Do early in day
  • Suction and re-intubation equipment
  • Laryngeal edema, laryngeal spasm

64
Re-intubation
  • 10 - 20 of patients require re-intubation
  • Mortality in these patients is gt 6x as high as
    mortality among patients who can tolerate
    extubation

65
Case Study
  • You are the ICU nurse picking up Mr. James, who
    was admitted and intubated yesterday for
    pneumonia. You enter the room and notice that he
    is tachypneic and restless. His ventilator
    settings are AC, rate 14, VT 700, FiO2 60. He
    is currently breathing at a rate of 24. His O2
    sat is 100.

66
Case Study
  • What lab test would you check to assess his
    ventilatory status?
  • ABG
  • What are possible causes of his increased
    respiratory rate?
  • Secretions, anxiety, pain, vent settings may not
    be appropriate

67
Case Study
  • ABG results pH 7.48, PCO2 28, pO2 120
  • Based on the ABG, his vent settings are changed
    to SIMV, rate 10, PS 10, VT 700, FiO2 40. How
    will these settings help Mr. James?

68
Case Study
  • You are the ICU nurse caring for a patient that
    was intubated for an exacerbation of COPD. When
    you enter the room, you notice that the patient
    is breathing out of synchrony with the ventilator
    and appears agitated and restless. The high
    pressure alarm is sounding. What could be the
    possible causes?

69
Case Study
  • Secretions, wrong vent settings (possible
    hyperinflation), anxiety

70
Case Study
  • You start your shift at 700 am and are picking
    up a patient that has been intubated for over a
    week for ARDS. You are told that he is doing
    well and may be able to be weaned today. When
    you complete your assessment, what will you
    specifically look at to report on rounds?

71
Case Study
  • Patient status
  • Mental status
  • Secretions/airway protection
  • Oxygenation
  • Ventilation

72
Case Study
  • Patient status
  • Reversal of physiologic derangements requiring
    ventilatory support
  • Globally improving patient
  • 2. Mental status
  • Alert, cooperative, able to follow commands
  • 3. Secretions/airway protection
  • Absence of copious, thick, secretions
  • Patient ability to handle secretions/protect
    airway/intact gag reflex

73
Case Study
  • Oxygenation
  • In general, need Pa02 gt 60 torr (SaO2 gt90) on
    FiO2 lt 0.4 and PEEP lt 5.0 cm H2O
  • Ventilation
  • Baseline PCO2 achieved with Ve lt 12 L/min
  • Rapid shallow breathing index, f/VT lt 100 during
    spontaneous breathing (VT is in liters, e.g.
    25/.4 62.5 with Ve 10 L/min is predictive of
    success)

74
Case Study
  • Increase strength check TFTs, nutrition, Ca,
    Mg, PO4, K, avoid fatigue, avoid lung
    hyperinflation,? paralytics, ? aminoglycosides, ?
    critical illness polyneuropathy
  • Decrease load ARDS, pulmonary edema, pneumonia,
    atelectasis

75
Case Study
  • Your patient with ARDS remains hypoxemic despite
    a high FIO2. What are other strategies to
    improve oxygenation?
  • Increase PEEP, check HBG, prone positioning,
    change vent settings to increase inspiratory time

76
Case Study Question
  • In caring for a ventilated patient, what
    strategies should you use to decrease the risk of
    VAP?
  • Closed suctioning only when needed
  • Frequent oral care
  • Upright patient

77
Case Study Question
  • Your intubated patient is requiring moderate
    amounts of PEEP to improve oxygenation. Discuss
    strategies to decrease the risk of complications
    from increased PEEP.
  • Increase volume, vasopressors, positive inotropic
    therapy, may need to decrease PEEP

78
Case Study
  • You are caring for a patient that was intubated
    for hypoxemic respiratory failure due to ARDS.
    Initial vent settings are AC, RR 18, TV 10 cc/kg,
    PEEP 7.5 cm H2O. On these settings, her Ppk is
    45 cm H2O and Pplat is 38 cm H2O. There is no
    auto-PEEP. ABG is PO2 70 mm Hg, PCO2 46 mm Hg,
    and pH 7.32. Which of the following ventilator
    changes would you make first?

79
Case Study
  1. decrease FiO2
  2. decrease TV
  3. increase PEEP
  4. decrease inspiratory flow rate
  5. change to pressure control

80
References
  • Tobin MJ. Advances in mechanical ventilation. N
    Engl J Med, Vol. 344, No. 26, June 28, 2001.
  • Hall et al. Principles of Critical Care (2nd
    ed). 1999. (MV chapter)
  • Campbell RS et al. Pressure-controlled versus
    volume-controlled ventilation does it matter?
    Resp Care 2002 (474)416 - 426.
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