The document discusses the process of weaning patients from mechanical ventilation, emphasizing the assessment of readiness, criteria for weaning, and the various methods involved, such as spontaneous breathing trials (SBT) and progressive withdrawal of mechanical support. It outlines important indicators, contraindications, and factors contributing to difficult weaning, and establishes the criteria necessary for successfully transitioning patients off mechanical ventilators. The document also highlights the significance of monitoring patient response during weaning trials to ensure safety and effectiveness.

1. WEANING
Prepared by :
Ms Rita Magar
Ms Sujata k.c.
BNS 3rd year

2. General objective:
At the end of this discussion BNS 3rd year student will be able to explain
about weaning from mechanical ventilator.

3. Specific objectives:
At the end of this sessions BNS 3rd student will be able to:
• introduce weaning
• enlist indication and contraindication of weaning
• stat assessment of readiness for weaning
• describe weaning criteria
• state difficult weaning
• describe methods of weaning
• describe weaning protocol
• describe weaning failure.

4. Weaning from mechanical ventilation

5. Introduction
• Weaning from mechanical ventilation , also called ventilator liberation, refers to
the process of the patient assuming more and more of the work of breathing and
finally demonstrating that ventilator support is no longer required.
• Simply it means the process of withdrawing mechanical ventilatory support and
transferring the work of breathing from the ventilator to the patient . Weaning can
be accomplished with an endotrachel tube ( ETT) or a tracheostomy tube in place.
• In the case of the ETT, the final step in the process is the removal of the tube(
extubation). With a tracheostomy, the final step may be the ability to breath
spontaneously for a designated period of time with the tube in place.

6. Contd..
• Weaning success is defined as absence of ventilatory support 48 hours following
the extubation.
• While the spontaneous breaths are unassisted by mechanical ventilation,
supplemental oxygen, bronchodilators, low level pressure support ventilation or
continuous positive airway pressure (CPAP) may be used to support and maintain
adequate spontaneous ventilation and oxygenation.

7. Purpose
• The purpose is to assess the probability that mechanical ventilation can be
successfully discontinued.
as
• 75% of mechanically ventilated patients are easy to be weaned off the
ventilator with simple process.
• 10-15% of patients require a use of a weaning protocol over a 24-72 hours.
• 5-10% require a prolonged weaning plan.
• 1% of patients become dependent on chronic mechanical ventilation.

8. Indication
• Improvement of the cause of respiratory failure.
• Absence of major system dysfunction.
• Appropriate level of oxygenation.
• Adequate ventilatory status.
• Intact airway protective mechanism.

9. Contraindications of weaning
• Altered sensorium either drowsiness or restlessness.
• Spo2 ˂90%
• Rising PaCO2 with drop in PH
• Tachypnoea ˃35/ min
• Tachycardia ˃120 /min
• Drop in systolic blood pressure
• Sweating
• Cold clammy skin
• Signs of diaphragmatic weakness
• Paradoxical abdominal wall movement

10. Assessment of readiness for weaning
• Hemodynamic stability
 Minimum inotropic support
Adequate cardiac output
Afebrile
Hematocrite greater than 25%

11. Respiratory stability
• Improved chest x-ray
• Arterial oxygen tension (PaO2) greater than 60mm Hg with fraction of inspired oxygen (
FiO2) less than 0.5
• PaO2/FiO2 greater than 300 mm Hg
• Positive end expiratory pressure (PEEP) less than 0-5 cm H2O
• Vital capacity (VC) 10-15ml/kg
• Spontaneous tidal volume (VT) 5ml/Kg
• Respiratory rate less than 30 breaths/mim
• Minute ventilation 5-10 L/min
• Negative inspiratory pressure greater than -20cm H2O
• Rapid shallow breathing index (RSBI) less than 105

12. Metabolic factors stable
• Electrolytes within normal range.
• ABGs( Arterial blood gases) normalized
Other
• Adequate management of pain and anxiety.
• Patient is well rested

13. WEANING CRITERIA
• Weaning criteria are used to evaluate the readiness of a patient for a weaning trial
and the likelihood of weaning success.
Clinical criteria
Ventilatory criteria
Oxygenation criteria
Pulmonary reserve and measurements

14. Clinical criteria
• Resolution of acute phase of disease
• Adequate cough
• Absence of excessive secretion
• Cardiovascular and hemodynamic stability
• Patient is arousable, or Glasgow Coma Score ≥13

15. Ventilatory criteria
Spontaneous breathing trial Tolerates 20-30 min
PaCO2 < 50mmHg with normal pH
Vital capacity >10ml/kg
Spontaneous VT >5ml/kg
Spontaneous f (frequency) <35/min
f/VT <100 breath/min/L
Minute ventilation <10L with satisfactory ABG

16. Oxygenation criteria
Pao2 without PEEP >60mm Hg at FiO2 up to 0.4
PaO2 with PEEP (<5cm H2O) >100mm Hg at FiO2 up to 0.4
SaO2 (Arterial oxygen saturation) >90% at FiO2 up to 0.4
PaO2/FiO2 (P/F) ≥300 mm Hg
Qs/Qt (Physiolgic shunt) <20%
P(A-a)O2 (Alveolar arterial oxygen
tensiion gradient)
<350mm Hg at FiO2 of 1.0

17. Pulmonary reserve and measurements
Pulmonary reserve Vital capacity >10ml/kg
Max. inspiratory
pressure (MIP)
> -30cmH2O in sec
Pulmonary
measurements
Static compliance >30ml/cm H2O
Airway resistance Stable or improving
VD /VT
(physiologic dead
space to tidal
volume)
<60% while
intubated

18. DIFFICULT WEANING
Factors responsible for difficult weaning may be grouped under the following
headings:
1. Respiratory
a. Poor lung compliance.
b. Poor chest wall compliance.
c. Increased resistive load.

19. Contd…
2. Neuromuscular
a. Decreased central respiratory drive (e.g., coma, obesity
hypoventilation syndrome, myxoedema)
b. Decreased airway reflexes (e.g., toxin- or drug-related, bulbar
neurological dysfunction
c. Neuromuscular weakness (e.g., neuromyopathy, myasthenia)

20. Contd…
3. Neuropsychiatric
a. Delirium, anxiety, sleep disturbance
4. Metabolic
a. Hypokalaemia, hypophosphataemia, hypomagnesaemia
5. Cardiac failure

21. WHEANS NOT
Ely suggested the ‘WHEANS NOT’ mnemonic to aid clinicians in identifying such
issues:
• Wheeze (especially COPD and asthma)
• Heart disease and fluid overload
• Electrolytes and metabolic derangement
• Anxiety and delirium
• Neuromuscular disease and weakness
• Sepsis
• Nutrition insufficiency
• Opioid and other sedatives
• Thyroid disease

22. WEANING THE PATIENT FROM THE
VENTILATOR
• Considerable effort has been devoted to finding the best method of
weaning from mechanical ventilation, but research has not established
which method is best .
• Weaning can be done using:
A. Spontaneous Breathing Trial
B. Progressive with drawl of mechanical ventilation

23. WEANING USING SPONTANEOUS
BREATHING TRIALS(SBT)
• The SBT is the major diagnostic test to determine if patients can be successfully
extubated and weaned from mechanical ventilation.
• SBT assesses the patient’s ability to breath while receiving minimal or no
ventilator support.
• During an SBT, the physician evaluates the patient’s ability to breath on his or her
own. To accomplish this, the patient is placed either on a T-piece or on the CPAP
mode, typically set at 5cm H2O pressure support.
• Low level pressure support, CPAP, Or automatic tube compensation (ATC) may
be used along with SBT to augment a patient’s spontaneous breathing efforts.
• Duration is generally at least 30 minutes, but no more than 120 minutes. A
decision to extubate is made with the conclusion of a successful trial.

24. SBT criteria
• Stable hemodynamics
 Mean arterial pressure (MAP) greater than 60mmHg
Heart rate less than 120 b/min.
• No significant dysrhythmias
• PH >7.28
• PCO2 < 60mmHg
• PaO2 > 60mm Hg
• SPO2 >92%
• FiO2 ≤ 0.50
• PEEP ≤ 5cm H2O
• RASS score ≥ -2
• Temperature < 102F

25. Process of SBT
• During an SBT, the physician evaluates the patient’s ability to breathe on his or
her own (i.e., spontaneously) . To accomplish this, the patient is placed either on a
T-piece or on the CPAP mode, typically set at 5 cmH2O PEEP, and supplemented
with 5–10 cmH2O pressure support.

26. T- Piece
• The term “T-piece” stems from its shape. One arm of the T-shaped piece connects
to the ETT, one arm connects to the fresh gas flow, and the third arm serves as the
exhalation limb of the apparatus. The exhalation tubing should be at least 25 cm
long to prevent entrainment of room air, and the fresh gas flow should equal at least
twice the patient’s spontaneous minute ventilation to eliminate rebreathing.

27. Contd…
• T-piece method of weaning involves removing the patient from the mechanical
ventilator and attaching an oxygen source to the artificial airway with a T- piece for
a SBT.
• The advantage of this method of weaning is that the resistance to breathing is low,
because no special valves need to be opened to initiate gas flow.
• This method of weaning is usually used when the patient is awake and alert, is
breathing without difficulty, has good gag and cough reflex and is
hemodynamically stable.
• Signs of exhaustion and hypoxia correlated with deterioration in the blood gas
measurements indicate the need for ventilator support.

28. CPAP
• CPAP mode allows the patient to breath spontaneously, while
applying positive pressure (5cm H2O) throughout the
respiratory cycle to keep the alveoli open and promote
oxygenation.
• Most SBTs are now performed using the CPAP mode with the
patient still connected to the ventilator apparatus. Advantages
of this setup include the collection of more complete and
continuous monitoring of many parameters, including tidal
volume, RR, and minute ventilation, as well as ease of
transition from baseline ventilatory support to the SBT.

29. Contd…
• Resistance created by the ETT, ventilator tubing, and circuit valves can be
overcome by the addition of a minimal amount (i.e., 5 cmH2O) of pressure
support. Insufficient pressure support will result in increased work of breathing
(WOB) due to the high resistance of the relatively narrow ETTs .
• The optimal duration of the SBT for predicting weaning success is unclear
because no large randomized, controlled trials (RCTs) exist. The Spanish Lung
Failure Collaborative Group reported a 30-minute trial to be just as effective as a
two-hour trial in predicting weaning outcome.

31. Performing an SBT
• Turn off sedation
• Reduce pain medication to the minimal effective dose
• Change the ventilator to a pressure support mode (no mandatory breaths)
 Set pressure support and PEEP:
 Pressure support should be minimal (0–5 cm H2O) to overcome resistance in the
tubing
The smaller the ET tube, relative to the size of the person (eg, #6 tube in a 6″
male), the higher the pressure support
Physiologic PEEP is used (5 cm H2O)

32. • The patient is observed for 3 minutes, screening for initial intolerance (ie,
immediate failure), too quick to reflect respiratory failure secondary to abnormal
pulmonary mechanics or function
• Initial intolerance (< 3min) is typically caused by delirium, pain, or persistent
sedative effect

33. • Diagnosis hinges on directly observing and interacting with the patient during
the spontaneous breathing attempt
1. Apnea, the most common reason for initial SBT intolerance, occurs in either
awake or sleeping patients
• Awake Apnea” is almost always secondary to the patient being alkalotic at the
start of the SBT (often evident on the morning of ABG)
• However, the respiratory alkalosis may occur just prior to the SBT, when sedation
and pain medication are stopped/weaned

34. Contd..
• The patient should be given more time to allow CO2 to rise and pH to fall
(the normal stimulus for ventilation)
• Though often unnecessary, the patient can be preoxygenated to ensure
desaturation will not occur
• “Sleeping Apnea” implies oversedation (± narcotic effect) and is managed
by waiting more time, decreasing narcotics, and then reattempting an SBT

35. Contd..
2. Ineffective respirations are the next most common cause of initial SBT
intolerance, occurring with either agitation or sleepiness
• Agitation, in this context, implies delirium and should be treated with either
haloperidol or dexmedetomidine (as described below)
• Sleepiness, in this context implies persistent sedative effect, and patients should be
given more time to wake up before repeat SBT

36. Contd…
3. Signs of adrenergic distress (increased HR and BP):
• Tachycardia and hypertension occur in agitated individuals and may
represent pain or delirium, occurring as sedation and analgesia are
weaned, in preparation for the SBT
• Agitated patients on mechanical ventilation should always be queried
about pain
• When pain is endorsed, narcotic dosing should be increased
• The SBT can be reattempted when pain is better controlled

37. • If the patient demonstrates initial SBT tolerance, he or she should be
observed for 30–120 minutes and screened for the development of a
pathologic rapid shallow breathing pattern indicative of diaphragmatic
fatigue and impending hypercapnic respiratory failure (ie, an RSBI > 105)
• If the patient does well for 30–120 min, then consider extubation (no ABG
required), specifically if the following are true of the patient:
RSBI < 105
Awake and following commands
Denies dyspnea
Audible cuff leak

38. Clinical signs of SBT failure
• Tachypnea
• Tachycardia
• Hypertension
• Hypotension
• Hypoxemia
• Acidosis
• Arrhythmias

39. Clinical criteria related to SBT failure
• PaO2 ≤ 60mm Hg
• FiO2 ≤ 50%
• PaCO2 >50mm HG
• Ph <7.32
• F/VT >100 breaths/ min/L
• F> 35 breaths/Min
• Heart rate >140b/m
• Systolic BP > 180 mm Hg and < 90mm Hg
• Presence of cardiac arrhythmias

40. Physical signs of SBT failure
• Agitation
• Distress
• Diminished mental status
• Diaphoresis
• Increased work of breathing

41. Rapid shallow breathing index (RSBI):
• RSBI is used to evaluate the spontaneous breathing pattern.
• Rapid shallow breathing index (RSBI): The RSBI (f/VT index) is calculated
by dividing the spontaneous breathing frequency (breaths/min) by the
average spontaneous VT (L).
• Absence of rapid shallow breathing, as defined by an f/VT ratio of less than
105breaths/ min/L, is an accurate predictor of weaning success.
• When the RSBI or f/VT index is greater than 105 breaths/min/L, it
correlates with weaning failure.

42. PROGRESSIVE WITHDRAWAL
OF
MECHANICAL VENTILATION

43. When initial attempts at spontaneous breathing fail to achieve
the goal of liberation from mechanical ventilation, clinicians
must choose appropriate mode(s) of ventilatory support which:
1) maintain a favourable balance between respiratory system
capacity and load;
2) attempt to avoid diaphragm muscle atrophy; and
3) aid in the weaning process.

44. The choices for these patients include the following:
• synchronized intermittent mandatory ventilation (SIMV)
•pressure support ventilation (PSV)
• T-piece trials
• Continuous positive airway pressure (CPAP)

45. Synchronized Intermittent Mandatory
Ventilation (SIMV) Weaning
•In SIMV weaning, the goal is a step-by-step reduction in
mechanical support, promoting the patient’s own ventilatory
efforts (and strength), by sequentially decreasing the number
of machine delivered breaths .

46. SIMV (not
recommended as a
stand-alone mode
for weaning)
(1)Reduce SIMV (ventilator) frequency by 1 to 3
breaths per min;
(2)Monitor SpO2, obtain ABG as needed;
(3)Reduce SIMV frequency further until a
frequency of 2 to 4/min is reached. This may
take only hours for patients with normal
cardiopulmonary functions but days for those
with abnormal functions;
(4)If patient tolerates step (3), consider extubation
when blood gases and vital signs are
satisfactory.

47. •The patient is evaluated at each level of ventilatory support,
both clinically and with the use of weaning parameters, and
laboratory data (i.e., arterial blood gas).
•The patient is considered successfully weaned and ready to
evaluate for extubation if he/she is tolerating an SIMV rate of
2 to 4 breaths/min for at least 120 minutes.
•Pressure support (5 cmH2O) may be added to overcome the
resistance created by the ventilator tubing and valves in the
circuit during the spontaneous breaths.

48. •One of the disadvantages of both SIMV weaning and T-piece
weaning is the absence of automatic adjustments for changes
in a patient’s ventilatory demands (i.e., there is no
compensation if the patient’s minute ventilation declines).
•This implies that the patient cannot be left unattended during
SIMV (or T-piece) weaning.
•So far, no study has proven any of these claims or shown
superiority of SIMV weaning over any other modes

49. Pressure Support Ventilation ( PSV) Weaning
•PSV helps to reduce the airflow resistance imposed on the
patient by the endotracheal tube and ventilator circuit.
•Some clinicians advocate weaning with pressure support as
a stand-alone mode.

50. PSV (1)PSV may be used in conjunction with spontaneous
breathing or SIMV mode;
(2)Start PSV at a level of 5 to 15 cm H2O (up to 40
cm H2O) to augment spontaneous VT until a
desired VT (10 to 15 mL/kg) or spontaneous
frequency (<25/min) is reached;
(3)Decrease pressure support (PS) level by 3 to 6 cm
H2O intervals until a level of close to 5 cm H2O
is reached;
(4)If patient tolerates step (3), consider extubation
when blood gases and vital signs are satisfactory.

51. T-Tube Trials
• The oldest weaning technique is to
undertake trials of spontaneous
breathing through a T-tube circuit.
• It is usual to limit a T-tube trial to 2
hours or less. Typically, extubate a
patient who does not develop distress
during a 30-minute T-tube trial.
• If a patient fails a T-tube trial, we wait
24 hours before we undertake a
subsequent trial.

52. •This method of weaning is usually used when the patient is
awake and alert, is breathing without difficulty, has good gag
and cough reflexes, and is hemodynamically stable.
•During the weaning process, the patient is maintained on the
same or a higher oxygen concentration than when on the
ventilator.
•While on the T-piece, the patient should be observed for signs
and symptoms of hypoxia, increasing respiratory muscle
fatigue, or systemic fatigue.

53. •These include restlessness, increased respiratory rate greater
than 35 breaths/min, use of accessory muscles, tachycardia
with premature ventricular contractions, and paradoxical
chest movement (asynchronous breathing, chest contraction
during inspiration and expansion during expiration).
•Fatigue or exhaustion is initially manifested by an increased
respiratory rate associated with a gradual reduction in tidal
volume; later there is a slowing of the respiratory rate.

54. •If the patient appears to be tolerating the T-piece trial, a
second set of arterial blood gas measurements is drawn 20
minutes after the patient has been on spontaneous ventilation
at a constant FiO2 pressure support ventilation. (Alveolar–
arterial equilibration takes 15 to 20 minutes to occur.)
•If clinically stable, the patient usually can be extubated within
2 or 3 hours of weaning and allowed spontaneous ventilation
by means of a mask with humidified oxygen.

55. Continous Positive Airway Pressure(CPAP)
•The continuous positive airway pressure (CPAP) mode allows
the patient to breathe spontaneously, while applying positive
pressure throughout the respiratory cycle to keep the alveoli
open and promote oxygenation.
•Providing CPAP during spontaneous breathing also offers the
advantage of an alarm system and may reduce patient anxiety
if the patient has been taught that the machine is keeping track
of breathing.

56. •It also maintains lung volumes and improves the patient’s
oxygenation status. CPAP is often used in conjunction with
PSV.
•Nurses should carefully assess for tachypnea, tachycardia,
reduced tidal volumes, decreasing oxygen saturations, and
increasing carbon dioxide levels.

57. RESTING MODE: ASSIST CONTROL
MODE
• The rest mode should be a stable, nonfatiguing, and
comfortable form of support for the patient.
• Assist–control may be used as the resting mode for patients
undergoing weaning trials.
• This mode provides full ventilatory support by delivering a
preset tidal volume and respiratory rate; if the patient takes a
breath, the ventilator delivers the preset volume. The cycle
does not adapt to the patient’s spontaneous efforts.

58. •With recent advances in technology, new features on
ventilators like Automatic Tube Compensation (ATC) have
been developed
•ATC compensates for the pressure drop across the
endotracheal or tracheostomy tube by delivering exactly the
amount of pressure necessary to overcome the resistive load
imposed by the tube for the flow measured at the time
• ATC has been shown to decrease the work of breathing
necessary to overcome endotracheal tube resistance more
effectively than PSV or CPAP

59. WEANING PROTOCOL

60. •In general, they often include three elements:
- the patient condition in which weaning may be attempted,
- the detailed process of weaning, and
- the evaluation of weaning outcomes.

61. STEP CRITERIA RESULTS
1. Does the patient show:
• Evidence of some reversal of underlying
cause for ventilatory failure?
• Presence of inspiratory effort?
• Hemodynamic stability? (absence of
myocardial ischemia, hypotension, use of
vasopressor)
• Adequate oxygenation and acid-base status?
(PaO2/FiO2 >150 mm Hg, PEEP < 8 cm
H2O and pH >7.25)
• Light sedation or better? (brief eye contact
to voice command)
If YES to all
five questions,
proceed to
STEP 2. If NO
to any one
question,
postpone
weaning until
next day.

62. STEP CRITERIA RESULTS
2. Perform and measure rapid shallow breathing
index (RSBI or f/VT) with mandatory
frequency turned off and pressure support <8
cm H2O, PEEP <5cm H2O, measurements
taken following >3 min of spontaneous
breathing. Is RSBI (f/VT) < 100 breaths/min/L?
If YES, proceed to
STEP 3. If NO,
postpone weaning until
next day.
3 Can patient tolerate: Spontaneous breathing trial
for up to 30 minutes without termination? (See
termination criteria* below.)
If YES, proceed to
ventilator
discontinuance or
evaluate for extubation.
If NO, repeat weaning
until next day.

63. Termination criteria
•Spontaneous frequency > 35/min for 5 min;
• SpO2 < 90%,
• Heart rate > 140/min or 120% of baseline;
• Systolic pressure >180 mm Hg or < 90 mm Hg;
• Signs of anxiety or use of accessory muscles.

64. Care of the Patient Being
Weaned From Mechanical
Ventilation

65. 1. Assess patient for weaning criteria:
Vital capacity—10 to 15 mL/kg
Maximum inspiratory pressure (MIP) at least –20 cm H2O
Tidal volume—7 to 9 mL/kg
Minute ventilation—6 L/min
Rapid/shallow breathing index—below 100 breaths/minute/L
PaO2 greater than 60 mm Hg with FiO2 less than 40%

66. 2. Monitor activity level, assess dietary intake, and monitor
results of laboratory tests of nutritional status.
3. Assess the patient’s and family’s understanding of the
weaning process and address any concerns about the process.
- Explain that the patient may feel short of breath initially and
provide encouragement as needed.
- Reassure the patient that he or she will be attended closely
and that if the weaning attempt is not successful, it can be
tried again later.

67. 4. Implement the weaning method prescribed: A/C, IMV,
SIMV, PSV, PAV, CPAP, or T-piece.
5. Monitor vital signs, pulse oximetry, ECG, and respiratory
pattern constantly for the first 20 to 30 minutes and every 5
minutes after that until weaning is complete.
6. Maintain a patent airway; monitor arterial blood gas levels
and pulmonary function tests. Suction the airway as needed.

68. 7. In collaboration with the physician, terminate the weaning
process if adverse reactions occur.
Adverse reactions include
- a heart rate increase of 20 beats/min,
- systolic blood pressure increase of 20 mm Hg,
- a decrease in oxygen saturation to less than 90%,
- respiratory rate less than 8 or greater than 20 breaths/minute,
- ventricular dysrhythmias,
- fatigue, panic, cyanosis, erratic or labored breathing, paradoxical
chest movement

69. 8. If the weaning process continues, measure tidal volume
and minute ventilation every 20 to 30 minutes; compare with
the patient’s desired values, which have been determined in
collaboration with the physician.
9. Assess for psychological dependence if the physiologic
parameters indicate weaning is feasible and the patient still
resists.

70. WEANING FAILURE

71. • Weaning failure is defined as either the failure of
spontaneous breathing trial (SBT) or the need for
reintubation within 48 hours following extubation.
•Early signs of weaning failure include: tachypnea, use of
accessory muscles and paradoxical abdominal movements,
dyspnea, chest pain, chest-abdomen asynchrony, and
diaphoresis.

72. Indicators of Weaning Failure
• Blood Gases
- Increasing PaCO2 (>50 mm Hg)
- Decreasing pH (< 7.30)
- Decreasing PaO2 (< 60 mm Hg)
- Decreasing SpO2 (< 90%)
- Decreasing PaO2/FIO2
(< 150 mm Hg)

73. Vital Signs
Changing blood pressures (20 mm Hg systolic or 10 mm Hg
diastolic)
Increasing heart rate (by 20/min, or >110/min)
Abnormal ECG (presence of arrhythmias)

74. Respiratory Parameters
•Decreasing 𝑣𝑇 (<250 mL)
•Increasing f (>30/min)
•Increasing f/VT (>100 breaths/min/L)
•Decreasing MIP (< - 20 cm H2O)
•Decreasing static compliance (<30 mL/cm H2O)
•Increasing 𝑣𝐷/𝑣𝑇 (>60%)

75. CAUSES OF WEANING FAILURE
•Aside from the pathological conditions that lead to the need
for mechanical ventilation, weaning failure may occur when
the work of spontaneous breathing becomes too great for the
patient to sustain. Weaning failure is generally related to
(1) increase of airflow resistance,
(2) decrease of compliance, or
(3) respiratory muscle fatigue.

76. Increase of Airflow Resistance
• Normal subjects using an endotracheal (ET) tube have an
increase of 54% to 240% in the work of breathing,
depending on the size of the ET tube and ventilator flow
rate.
•To minimize the effects of an artificial airway on airflow
resistance, ET tubes of size 8 or larger should be used when
it is appropriate to the patient’s size.

77. •In addition, the ET tube may be cut to about an inch from the
patient’s lips to minimize the airflow resistance contributed
by the length of the ET tube. The cut section of the ET tube
should be displayed prominently so that others would not
presume that the ET tube had been moved deep into the
brochus.
• Other strategies for decreasing airway resistance can easily
be done by periodic monitoring of the ET tube for kinking or
obstructions by secretions, or other devices attached to the ET
tube such as a continuous suction catheter, heat and moisture
exchanger, or end-tidal CO2 monitor probe.

78. • Endotracheal suctioning to remove retained secretions
and use of bronchodilators to relieve bronchospasm
have also been used successfully to reduce the airflow
resistance.

79. Decrease of Compliance
•Low compliance makes lung expansion difficult and, it is a
major contributing factor to respiratory muscle fatigue and
weaning failure.
•In situations where the compliance gradually decreases (e.g.,
ARDS), the resultant refractory hypoxemia and increased
work of breathing may lead to muscle fatigue and
ventilatory failure.
•When this occurs to a patient undergoing a weaning trial, a
return to the mechanical ventilator is almost inevitable.

80. Respiratory Muscle Fatigue
•Respiratory work is a product of transpulmonary pressure (𝑃𝑇𝑃)
and tidal volume (𝑉𝑇). Studies have been done to evaluate the
relationship between the work of breathing and a patient’s
ability to sustain adequate spontaneous ventilation.
•Work of breathing =𝑃𝑇𝑃 X 𝑉𝑇
•The transpulmonary pressure is increased in conditions of low
compliance or high airway resistance. Normally a threshold
work value of 1.6 kg.m/min or less is needed before ventilator-
dependent patients can be weaned and assume adequate
spontaneous breathing.

81. •Prolonged full ventilatory support and muscle disuse may
lead to respiratory muscle dysfunction and diaphragmatic
atrophy.
•Retraining of atrophied muscles may be accomplished by
short T-tube trials that improve respiratory muscle strength.
Pressure support ventilation may also be tried as it increases
diaphragmatic endurance

82. POST- TEST
•The criteria used for weaning are________, _________,
_________ and ________ .
•________minutes is considered an adequate time interval for
evaluation of spontaneous breathing trial.
•RSBI __________breaths/ min/L, is an accurate predictor of
weaning success.

83. • The patient is considered successfully weaned and ready to
extubate if he/she is tolerating an SIMV rate of ___ breaths/min
for at least ___ minutes.
• PSV weaning is done by decreasing pressure support (PS) level
until a level of close to __ cm H2O is reached.
• Weaning failure is generally related to _______, _________ and
________.
• To reduce airway resistance, what size ET tube should be used?

84. References
• Hinkle, J & Cheever, K(2010). Brunner and suddarth’s Medical
Surgical Nursing (12th edition ). Reed Elsevier Pvt .Ltd: New Delhi ,
India.
• Chang, D.W. (2014). Clinical Application of Mechanical Ventilation
(4th ed.). New York: Delmar, Cengage Learning
• Landsberg, J.W. (2018). Clinical Practice Manual for Pulmonary and
Critical Care Medicine ( 1st ed.). Philadelphia: Elsevier, Inc.
• Kollef, M. & Isakow, M. (2012). The Washington Manual of Critical
Care( 2nd ed.). Philadelphia: Lippincott Williams & Wilkins.

85. • Nettina , M.S. ( 2018) . Lipincott Manual of Nursing practice (11th
ed.). New Delhi, India: Wolter Kluwer publication.
• Vincent ,J.L., Abraham, E., Moore, Patrick,M.K. & Fink,
M.P.(2017). Textbook of critical care (7thed.). Philadelphia:
Elsevier Inc.
• Wilson,W.C., Grande, C.M.,& Hoyt, D.B. (2007). Trauma Critical
Care ( 1st ed.). New york : Informa Healthcare USA, Inc.

86. IN ORDER TO
HELP PEOPLE
,
YOU HAVE
TO FIRST
LEARN HOW