This power point is a master piece ,dedicated to give inclusive knowledge on history, indications,types, modes,alarms and troubleshooting,Complicatons,weaning of mechanical ventilation

1. P R E S E N TO R : M E L A K U Y E T B A R E K ( R I )
M O D E R ATO R S : D R . E N D A S H AW ( I N T E R N I S T,
A S S I S TA N T P R O F E S S O R )
D R . D E J E N E ( A N E S T H E S I O L O G I S T, A S S I S TA N T
P R O F E S S O R )
Mechanical Ventilatory Support
10/18/2020
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2. Outline
 Introduction
 Indications
 Ventilator Circuit
 Types
 Modes
 MV Settings
 MV alarm setting and troubleshooting
 Complications
 Weaning
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3. Introduction
 Mechanical ventilation (MV) is used to assist or replace
spontaneous breathing
 It is implemented with special devices that can support
ventilatory function and improve oxygenation through the
application of high-oxygen-content gas and positive
pressure.
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4. Introduction
History:
 Galen, 2nd century A.D, Greek physician, may have been
the first to describe mechanical ventilation
 Vesalius 1543, De Humani Corporis Fabric. “But that life
may be restored to the animal, 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 again and take air”
 George Poe 1908, demonstrated his mechanical respirator
by asphyxiating dogs and seemingly bringing them back
to life.
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5. Intro…
Negative pressure
ventilators
 Developed in 1929.
 Used widely in 1940 polio
epidemic.
 The patient’s body was
encased in an iron cylinder
and negative pressure was
generated
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6. Intro…
Positive Pressure Ventilation
 Polio epidemic in Scandinavia and the United States in
the early 1950s.
 Decrease in mortality rate from >80% to 40%
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7. Indications
The most common reasons for instituting MV are
 acute respiratory failure with hypoxemia which accounts for ~65%
of all ventilated cases, and
 hypercarbic ventilatory failure—e.g., due to coma (15%),
exacerbations of chronic obstructive pulmonary disease (COPD;
13%), and neuromuscular diseases (5%).
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8. Indications…
 MV also is used frequently in conjunction with
endotracheal intubation for airway protection to prevent
aspiration
 In critically ill patients, intubation and MV may be
indicated before the performance of essential diagnostic
or therapeutic studies
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9. Types
There are two basic methods of MV:
 Noninvasive ventilation (NIV)
 Invasive (or conventional mechanical) ventilation (MV)
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10. Non invasive mechanical Ventilation(NIV)
 Uses a completely sealed system in which air cannot be
entrained,
 CPAP/ BiPAP circuits are able to deliver a truly accurate
high concentration (FiO2=1.0) and are thus effective at
treating hypoxia.
 CPAP is indicated when alveolar recruitment may occur
 BiPAP/ NIV is required when work of breathing requires
augmentation.
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11. NIV…
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12. Indications(NIV)
 Pulmonary edema
 Asthma
 COPD
 Cardiogenic Pulmonary edema
 Chest trauma
 Assisting in early extubation
 Respiratory failure in Immunocompromised patients
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15. Invasive Mechanical Ventilation(Conventional)
 Delivers conditioned gas (warmed, oxygenated, and
humidified) through ETT to the airways and lungs at
pressures above atmospheric pressure
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16. Invasive Mechanical Ventilation
Mechanical ventilators are comprised of four main
elements:
 A source of pressurized gas including a blender for air
and O2.
 An inspiratory valve, expiratory valve and ventilator
circuit.
 A control system, including control panel, monitoring and
alarms.
 A system to sense when the patient is trying to take
breath.
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17. Invasive Mechanical…
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18. Invasive Mechanical…
ET Tubes:
 They are equipped with an inflatable balloon at the distal
end (the cuff).
 The proximal end has a standard 15 mm connector, the
tubes vary in length from 25 to 35 cm and are sized
according to their internal diameter.
 Size 8-9 mm will fit to most men and size 7-8 mm to most
women.
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21. NIV…
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22. Invasive Mechanical…
 The depth of the tube on the average is 21-23 from the
teeth for male and 19-21 for female patients
 Cuff pressure – 18-25mmHg
 >25mmHg  pressure necrosis at contact area
 <18 mmHg  air leak around ETT
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23. Invasive Mechanical…
Confirm tube position:
 Bilateral chest rise
 Auscultation of the chest
 Tube location at the teeth
 Co2 detector (Capnography)
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24. Principles
 Once the patient has been intubated, the basic goals of
MV are to optimize oxygenation while avoiding
ventilator-induced lung injury
 This concept, known as the “protective ventilatory
strategy”
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25. Principles…
 Although normalization of pH through elimination of
CO2 is desirable, the risk of lung damage associated with
the large volume and high pressures needed to achieve
this goal has led to the acceptance of permissive
hypercapnia.
 This condition is well tolerated when care is taken to
avoid excess acidosis by pH buffering
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27. Modes
 Mode refers to the manner in which ventilator breaths are
triggered, cycled, and limited
 The trigger, either an inspiratory effort or a time based
signal, defines what the ventilator senses to initiate an
assisted breath.
 Cycle refers to the factors that determine the end of
inspiration.
 Other types of cycling include pressure cycling and time
cycling.
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28. Variables that govern how a ventilator functions
and interacts with the patient
Control variable
‘The Mode of Ventilation’
Pressure, flow, or volume
controlled
Triggering variable
pressure, flow or volume
sensing that initiates
the vent cycle
Cycle variable
Pressure, volume, flow,
or time that ends the
inspiratory phase
Limit Variable
Volume, pressure or flow
can be set to be constant
or reach a maximum
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29. Modes…
 The limiting factors are operator-specified values, such as
airway pressure, that are monitored by transducers internal to
the ventilator circuit throughout the respiratory cycle;
 If the specified values are exceeded, inspiratory flow is
terminated, and the ventilator circuit is vented to atmospheric
pressure or the specified pressure at the end of expiration
(positive end-expiratory pressure, or PEEP).
 Most patients are ventilated with assist-control ventilation
(ACMV), intermittent mandatory ventilation (IMV), or PSV,
with the latter two modes often used simultaneously
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30. Assist-control ventilation (ACV) or volume control
(VC)
 Every breath is delivered with a pre-set tidal volume
and rate or minute ventilation
 Extra controlled breaths may be triggered by patient
effort; if no effort is detected within a specified amount
of time the ventilator will initiate the breath
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33. Pressure control ventilation (PCV)
 A minimum frequency is set and patient may trigger
additional breaths above the ventilator
 All breaths delivered at a preset constant inspiratory
pressure
 In traditional PCV, tidal volume is not guaranteed thus
changes in compliance and resistance affect tidal volume
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34. Synchronous intermittent mandatory ventilation
(SIMV)
 Ventilator provides controlled breaths (either at a set
volume or pressure depending on whether in VC or PCV,
respectively)
 Patient can breathe spontaneously (these breaths may be
pressure supported) between controlled breaths
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37. Pressure support ventilation (PSV)
 Patient initiates all breaths and the ventilator supports
each breath with a pre-set inspiratory pressure
 Useful for weaning off ventilator
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39. High-frequency oscillatory ventilation (HFOV)
 High breathing rate &very low tidal volumes
 Used commonly in neonatal and pediatric respiratory
failure
 Occasionally used in adults when conventional
mechanical ventilation is failing
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43. Mechanical Ventilator Settings
 Trigger
 Tidal Volume
 Respiratory Rate
 PEEP
 Flow rate
 Fraction of Inspired oxygen(Fio2)
 Flow Pattern
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44. Trigger
 There are two ways to initiate a ventilator-delivered
breath: pressure triggering or flow-by triggering.
 When pressure triggering is used, a ventilator-delivered
breath is initiated if the demand valve senses a negative
airway pressure deflection
 The trigger sensitivity should allow the patient to trigger
the ventilator easily.
 Patient-ventilator asynchrony
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45. Trigger…
 Pressure triggering can be used with the assist control or
synchronized intermittent mandatory ventilation modes of
mechanical ventilation.
 Auto-PEEP (intrinsic positive end-expiratory pressure)
interferes with pressure triggering.
 When flow-by triggering is used, a continuous flow of gas
through the ventilator circuit is monitored.
 A ventilator-delivered breath is initiated when the return
flow is less than the delivered flow, a consequence of the
patient's effort to initiate a breath
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46. Tidal Volume
 The tidal volume is the amount of air delivered with each
breath.
 The appropriate initial tidal volume depends on numerous
factors, most notably the disease for which the patient
requires mechanical ventilation.
 As an example, randomized trials found that mechanical
ventilation using tidal volumes of ≤6 mL per kg of
predicted body weight (PBW) improved mortality in
patients with acute respiratory distress syndrome (ARDS)
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47. Tidal…
 An initial tidal volume of approximately 8 mL per kg of predicted
body weight (PBW, which is the same as ideal body weight)
seems reasonable, albeit unproven and based only on clinical
experience.
 The tidal volume can then be increased or decreased
incrementally to achieve the desired pH and arterial carbon
dioxide tension (PaCO 2 ), while monitoring the auto-PEEP and
airway pressure.
 Return to the previous tidal volume is indicated if the patient
develops auto-PEEP >5 cm H 2 O or a plateau airway pressure
>30 cm H 2 O following an increase in the tidal volume.
 During volume-limited ventilation, the tidal volume is set by the
clinician and remains constant.
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48. Respiratory Rate(RR)
 An optimal method for setting the respiratory rate has not been
established.
 For most patients, an initial respiratory rate between 12 and 16
breaths per minute is reasonable, although it may be modified
according to the mode
 For patients receiving assist control, the respiratory rate is
typically set four breaths per minute below the patient's native
rate
 For patients receiving synchronized intermittent mandatory
ventilation, the rate is set to ensure that at least 80 percent of
the patient's total minute ventilation is delivered by the
ventilator
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49. RR…
 Once the tidal volume has been established, the respiratory rate can
be incrementally increased or decreased to achieve the desired pH
and PaCO 2 , while monitoring auto-PEEP.
 Return to the previous respiratory rate is indicated if the patient
develops auto-PEEP >5 cm H 2 O.
 For patients with ARDS, the required respiratory rate is higher (up
to 35 breaths per minute), in order to facilitate low tidal volume
ventilation.
 Increasing the inspiratory flow rate and the respiratory rate
simultaneously may mitigate the development of auto-PEEP.
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50. Positive end expiratory pressure(PEEP)
 Applied PEEP (extrinsic positive end-expiratory pressure)
is generally added to mitigate end-expiratory alveolar
collapse.
 A typical initial applied PEEP is 5 cm H 2 O.
 However, up to 20 cm H 2 O may be used in patients
undergoing low tidal volume ventilation for acute
respiratory distress syndrome (ARDS).
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51. PEEP…
Elevated levels of applied PEEP can have adverse
consequences, such as
 Reduced preload (decreases cardiac output),
 Elevated plateau airway pressure (increases risk of
barotrauma),
 Impaired cerebral venous outflow (increases intracranial
pressure).
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52. Flow rate
 The peak flow rate is the maximum flow delivered by the
ventilator during inspiration.
 Peak flow rates of 60 L per minute may be sufficient,
although higher rates are frequently necessary.
 An insufficient peak flow rate is characterized by
dyspnea, spuriously low peak inspiratory pressures, and
scalloping of the inspiratory pressure tracing
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53. Flow…
 The need for a high peak flow rate is particularly common
among patients who have obstructive airways disease with
acute respiratory acidosis.
 In such patients, a higher peak flow rate shortens inspiratory
time and increases expiratory time (ie, decreases the
inspiratory to expiratory [I:E] ratio).
 These alterations increase carbon dioxide elimination and
improve respiratory acidosis, while also decreasing the
likelihood of dynamic hyperinflation (auto-PEEP)
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54. Flow Pattern
 Microprocessor-controlled mechanical ventilators can deliver
several inspiratory flow patterns, including a square wave
(constant flow), a ramp wave (decelerating flow), and a
sinusoidal wave
 The ramp wave may distribute ventilation more evenly than
other patterns of flow, particularly when airway obstruction is
present
 This decreases the peak airway pressure, physiologic dead
space, and PaCO 2 , while leaving oxygenation unaltered
 The effects of the different flow patterns on potential
complications of mechanical ventilation (eg, hemodynamic
impairment, pulmonary barotrauma, ventilator-associated lung
injury) are unpredictable
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55. Fraction of Inspired Oxygen (FiO 2 )
 The lowest possible fraction of inspired oxygen (FiO 2 )
necessary to meet oxygenation goals should be used.
 This will decrease the likelihood that adverse consequences of
supplemental oxygen, Typical oxygenation goals include an
arterial oxygen tension (PaO 2 ) above 60 mmHg and an
oxyhemoglobin saturation (SpO 2 ) above 90 percent.
 In patients with ARDS, targeting a PaO 2 of 55 to 80 mmHg
and a SpO 2 of 88 to 95 percent is acceptable when the trade
off would be higher plateau pressures and an increased risk of
lung injury due to alveolar overdistension (ie, volutrauma)
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56. MV Alarm Setting&Troubleshooting
 ventilator inoperative (vent INOP)
 power failure,
 no gas delivery to the patient,
 low peak inspiratory pressure (PIP),
 low tidal volume (VT),
 low or high minute volume (MV),
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57. Alarm…
 low positive end-expiratory pressure and continuous positive airway
pressure (PEEP/CPAP),
 apnea,
 inspiratory:expiratory (I:E) ratio,
 High pressure limit,
 high respiratory rate,
 and low or high fraction of inspired oxygen (FIO2)
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58. Alarms…
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High Peak Inspiratory Pressure:
 Secretions
 Patient biting ETT
 Patient coughing
Low Pressure Alarm or low PEEP alarm:
 Disconnect (check all connections)
 Apnea
Low Tidal Volume Spontaneous:
 Circuit disconnect
 Secretions

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60. Desaturation or Hypoxia
1.Attend the patient promptly.
2. Increase the FiO2 appropriately (to 100% O2 if necessary
3. Is the patient ventilating? Check for chest wall movement
(and its synergy) visually and manually while looking at
the ventilator (for low tidal volumes/ alarms from high
pressures)
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61. Desaturation…
4.If inadequate ventilation, disconnect from the ventilator, and bag
manually on 100% O2. Then ascertain which of the possible causes
 Blocked or displaced tracheostomy or ET tube
 Tension Pneumothorax
 Mucus Plug
 Endobronchial intubation
 Massive acute Pulmonary alveolar ‘flooding’
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62. Tachypnea
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63. Patient Ventilator Asynchrony
Asynchrony occurs when there is a discrepancy between
patient and ventilator in one or more of the breathing
phases
 The trigger mechanism
 The Inspiratory flow phase
 Breath termination
 Expiratory phase
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65. Patient Management
 Once the patient’s gas exchange has been stabilized,
definitive therapy for the underlying process responsible
for respiratory failure is continued.
 Subsequent modifications in ventilator therapy must be
provided in parallel with changes in the patient’s clinical
status.
 As improvement in respiratory function is noted, the first
priority is to reduce the level of mechanical ventilatory
support.
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66. Patient…
 Patients on full ventilatory support should be monitored
frequently, with the goal of switching to a mode that
allows for weaning as soon as possible
 Patients whose condition continues to deteriorate after
ventilatory support is initiated may require increased O2,
PEEP, or one of the alternative modes of ventilation
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67. Patient…
 Oversedation must be avoided in the ICU because most
studies show that daily interruption of sedation in patients
with improved ventilatory status results in a shorter time
on the ventilator and a shorter ICU stay
 Immobilized patients receiving mechanical ventilatory
support are at risk for deep venous thrombosis and
decubitus ulcers.
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68. Patient…
 Patients for whom MV has been initiated usually require
sedation and analgesia
 Combination of a benzodiazepine and an opiate
administered intravenously.
 Medications commonly used for this purpose include
lorazepam, midazolam, diazepam, morphine, and
fentanyl.
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69. Patient…
 Venous thrombosis should be prevented with the use of
subcutaneous heparin and/ or pneumatic compression
boots.
 Fractionated low-molecular-weight heparin appears to be
equally effective for this purpose.
 To help prevent decubitus ulcers, frequent changes in
body position and the use of soft mattress overlays and air
mattresses are employed.
 Early mobilization is recommended for patients on MV,
since this approach is associated with better outcomes.
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70. Patient…
 Prophylaxis against diffuse gastrointestinal mucosal injury
is indicated for patients undergoing MV.
 Histamine-receptor (H2-receptor) antagonists, antacids,
and cytoprotective agents such as sucralfate have all been
used and appear to be effective
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71. Patient…
 Nutritional support by enteral feeding through either a
nasogastric or an orogastric tube
 Promotility agents such as metoclopramide.
 Parenteral nutrition is an alternative to enteral nutrition in
patients with severe gastrointestinal pathology who need
prolonged MV
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72. Complications
Endotracheal intubation and MV have direct and indirect
effects on
 The lung and upper airways,
 The cardiovascular
 The gastrointestinal system.
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73. Pulmonary complications
 Barotrauma,
 Nosocomial pneumonia,
 Oxygen toxicity,
 Tracheal stenosis,
 Deconditioning of respiratory muscles
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74. Pulmonary complications
 Barotrauma and volutrauma overdistend and disrupt lung
tissue; may be clinically manifest by
pneumomediastinum, interstitial and subcutaneous
emphysema, or pneumothorax
 Clinically significant pneumothorax requires tube
thoracostomy.
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75. Complications
 Hypotension resulting from elevated intrathoracic
pressures with decreased venous return
 Gastrointestinal effects of positive-pressure ventilation
include stress ulceration and mild to moderate cholestasis
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76. Weaning
The Decision to Wean
 It is important to consider discontinuation of MV once the
underlying respiratory disease begins to reverse.
 Although the predictive capacities of multiple clinical and
physiologic variables have been explored, the following
conditions indicate amenability to weaning:
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77. Weaning…
 Lung injury is stable or resolving;
 Gas exchange is adequate, with low PEEP (<8 cmH2O)
and Fio2 (<0.5);
 Hemodynamic variables are stable, and the patient is no
longer receiving vasopressors;
 The patient is capable of initiating spontaneous breaths.
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79. Weaning…
 A “wean screen” should be done at least daily.
 If the patient is deemed capable of beginning to
wean, the recommendation is to perform a
spontaneous breathing trial (SBT)
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80. Weaning…
 The SBT involves an integrated patient assessment during
spontaneous breathing with little or no ventilatory
support.
 The SBT is usually implemented with a T-piece using 1–
5 cmH2O CPAP with 5–7 cmH2O or PSV from the
ventilator to offset resistance from the endotracheal tube.
 Decide on extubation,once patient has the ability to
protect the airway, is able to cough and clear secretions,
and is alert enough to follow commands.
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81. Weaning…
 In addition, other factors must be taken into account, such as
the possible difficulty of replacing the tube if that maneuver is
required
 If upper airway difficulty is suspected, an evaluation using a
“cuff-leak” test (assessing the presence of air movement
around a deflated endotracheal tube cuff) is supported by
current evidence
 If the “cuff-leak test” suggests a risk of post-extubation stridor,
the administration of systemic corticosteroids should be
considered prior to extubation
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82. Weaning…
 Despite all precautions, ~10–15% of extubated patients
require reintubation
 Several studies suggest that NIV can be used to obviate
reintubation, particularly in patients with ventilatory
failure secondary to COPD exacerbation or congestive
heart failure
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83. Weaning…
Prolonged MV and Tracheostomy
 From 5 to 13% of patients undergoing MV will go on to
require prolonged MV (>21 days)
 In these instances, critical care personnel must decide
whether and when to perform a tracheostomy.
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84. Weaning…
 This decision is individualized and is based on the risk
and benefits of tracheostomy and prolonged intubation as
well as the patient’s preferences and expected outcomes.
 A tracheostomy is thought to be more comfortable, to
require less sedation, and to provide a more secure airway
and may also reduce weaning time.
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85. Weaning…
 However, tracheostomy carries the risk of complications,
which occur in 5–40% of these procedures
 In patients with long-term tracheostomy, complex
complications include tracheal stenosis, granulation, and
erosion of the innominate artery.
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86. Weaning…
 In general, if a patient needs MV for >10–14 days, a
tracheostomy, planned under optimal conditions, is
indicated
 Whether it is completed at the bedside or as an operative
procedure depends on local resources and experience.
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87. Weaning…
 Some 5–10% of patients are deemed unable to wean in
the ICU
 These patients may benefit from transfer to special units
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88. Weaning…
 Unfortunately, close to 2% of ventilated patients may
ultimately become dependent on ventilatory support to
maintain life
 Most of these patients remain in chronic care institutions,
although some with strong social, economic, and family
support may live a relatively fulfilling life with at-home
ventilation
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89. References
 Uptodate,2018
 Harrison’s Principles of Internal Medicine,2018
 Hand book of Mechanical Ventilation, User’s guide
 Practical Guide for Mechanical Ventilation,4th
edition
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