Dr Priyanka

1
Ventilatory Care of Critically ill Patient and
Weaning from Mechanical Ventilation

• Dr Priyanka

University College of Medical Sciences GTB
Hospital, Delhi
2
Contents

• Introduction
• Stages of weaning
• Weaning criteria
• Weaning procedure
• Weaning protocols
• Pathophysiology of weaning failure
• Specialised weaning units (SWUs)

3
Weaning

• Process of withdrawal of mechanical ventilatory
  support that transfers the work of breathing from
  ventilator to the patient
• This period may take many forms ranging from
  abrupt to gradual withdrawal from ventilatory
  support
• The aim of ventilatory support is to unload the
  patients respiratory pump, while weaning is the
  process of reloading the respiratory pump

4

• 75 of mechanically ventilated patients are easy
  to be weaned off the ventilator with simple
  process
• 10-15 patients require use of a weaning protocol
  over a period of 24-72 hours
• 5-10 require a gradual weaning over longer time
• 1 of patients become chronically dependent on
  ventilator
• Out of the total time that a patient spends on
  ventilator, 40 of the time is spent on weaning
  process

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Decreases the availability of ICU beds
Increased cost
Increased hospital length of stay
Increased risk of VAP
Why Wean early ???
Increased ICU length of stay
Increased morbidity mortality
Can adversely affect the patient outcome
6
Different stages Of Weaning in Mechanically
Ventilated pts
failure should be avoided whenever possible
because the need for reintubation carries an
8-fold higher odds ratio for nosocomial
pneumonia99 and a 6-fold to 12-fold
increased mortality risk. reintubation rates
range from 4 to 23 for different ICU populations
In contrast, the maintenance of unnecessary
ventilator support carries its own burden
of patient risk for infection and other
complications
1. Treatment of ARF
3. Assessing readiness to wean
5. Extubation
6. Reintubation
2. Suspicion
4. SBT
Admit
Discharge
7
Classification of patients according to the
weaning process
Group/ category Definition
Simple weaning Patients who proceed from initiation of weaning to successful extubation on the first attempt without difficulty
Difficult weaning Patients who fail initial weaning and require up to three SBT or as long as 7 days from the first SBT to achieve successful weaning
Prolonged weaning Patients who fail at least three weaning attempts or require gt7 days of weaning after the first SBT
8
Evaluating Patients to Be Weaned from Mechanical
Ventilator

• A daily routine follow up should be done in every
  patient receiving mechanical ventilation and
  exploring the following condition
• Resolution/improvement of the underlying disease
• Stop sedation
• Core temperature below 38 ºC
• Stable haemodynamics (HR lt 140/min, stable BP)
  with no/minimal need of vasoactive drugs, absence
  of active myocardial ischemia
• Adequate haemoglobin ( Hb gt 8 g/dL)
• Adequate mentation ( arousable, GCS gt 13)
• No major metabolic and/or electrolyte
  disturbances

9
Weaning Criteria

• Clinical Criteria

• Objective Criteria

• Adequate cough
• Absence of excessive tracheobronchial secretions
• Resolution of the disease acute phase for which
  the patient was intubated

• Ventilatory criteria
• Oxygenation criteria
• Pulmonary reserve
• Pulmonary measurements
• Other factors

10
Ventilatory Criteria

• PaCO2 lt 50 mmHg with
  normal pH
• Vital Capacity gt 10 to 15 ml/kg
• Spontaneous VT gt 5 to 8 ml/kg
• Spontaneous RR lt 30/min
• Minute ventilation lt 10 l/min

PaCO2 most reliable indicator VC and spon VT
indicate mechanical cond of lungs A high spon RR
and MV indicate ? WOB
11
Oxygenation Criteria

• PaO2 gt 60 mmHg _at_FiO2 lt 0.4,
• PEEP lt 5 cm H2O
• SaO2 gt 90 _at_ FiO2 lt
  0.4
• PaO2/FiO2 gt 200 mmHg
• P(A-a)O2 lt 350 mmHg
  (corresponds to 14 shunt)
• Qs/Qt lt 20

Qs/Qt estimate wasted pulmonary
perfusion P(A-a)O2 is related to degree of
hypoxemia/shunt In pts with anemia or dysfunct
Hb, PaO2 and SaO2 dont reflect true
oxygenation status So arterial oxygen content
should be measured
12
Pulmonary Reserve
Pulmonary reserve requires active pt
cooperation Pulmonary measurements indicate
workload needed to support spont. ventilation

• Max. voluntary ventilation 2 MV_at_FiO2 upto
  0.4
• Max. Insp. Pressure (MIP) lt -20 to -30 cmH2O

13
Pulmonary measurements

• Static compliance gt 30 ml/cm H2O
• Airway resistance observe trend
• Vd/Vt lt 0.6

14

• Weaning is more likely to succeed if a patient
  meets most of the criteria.
• If a patient can meet only one or two of the
  weaning criteria, the success rate is likely to
  be low.
• Though not fool proof, all patients who fit most
  of the criteria can undergo a formal spontaneous
  breathing trial (SBT).

15
Combined weaning indices
Since respiratory failure is multifactorial
individual predictors may be unrelaible
predictors of weaning outcome

• Since respiratory failure is multifactorial,
  individual parameters are unreliable predictors
  of weaning outcome
• Indices integrating several physiological
  variables may be more effective predictors of
  weaning outcome
• RSBI (Rapid shallow breathing index)
• CROP Index
• SWI Index

16
RSBI ( Rapid shallow breathing index)

• Index of rapid and shallow breathing f/Vt
• RSBIlt105 predicts successful weaning attempts
• First described by Yang and Tobin in 1991
• The RSBI measurement is performed immediately
  after discontinuation of ventilatory support with
  the patient still intubated and spontaneously
  breathing room air for 1 min
• More accurate predictor of weaning success than
  any other parameter studied
• Disadvantage excessive false ve

17
RSBI
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RSBI Rate

• A measure of change of RSBI over time
• Calculated by obtaining the difference between
  the initial RSBI and the final RSBI, and then
  dividing the result by the initial RSBI. The
  resulting number is then multiplied by 100.
• RSBI Rate (RSBI2 RSBI1)/RSBI1 x100
• It was shown that RSBI Rate of less than 20 was
  over 90 sensitive and 100 specific for
  predicting weaning success.

19
CROP Index( Compliance Rate Oxygenation Pressure
Index)

• Evaluates pulmonary gas exchange and balance b/w
  respiratory demands and respiratory neuromuscular
  reserve
• CROP Index ( Cd MIP PaO2/PAO2)/f
• Where Cd dynamic compliance
• MIP maximum inspiratory pressure
• PaO2 Arterial oxygen tension
• PAO2 Alveolar oxygen tension
• f spontaneous respiratory rate per minute
• Should be gt 13 ml/breath/min for successful
  weaning
• Widespread application limited by complicated
  calculation no. of variables involved

20
SWI (Simplified Weaning Index)

• Evaluates efficiency of gas exchange and
  ventilatory endurance
• SWI ( fmv (PIP PEEP)/MIP) PaCO2/40
• Where PIP peak inspiratory pressure
• PEEP Peak end expiratory pressure
• MIP Maximal inspiratory pressure
• fmv ventilatory frequency
• PaCO2 Arterial CO2 tension while on ventilator
• Value lt 9/min ? successful weaning outcome

21
Other Criteria

• P 0.1 (Maximal occlusion pressure)
• Airway occlusion pressure measured 100 msec after
  a maximal inspiratory effort against an occluded
  airway
• It is effort independent and correlates well with
  central respiratory drive
• Patients with P0.1 gt6 cm H2O tend to be difficult
  to wean
• Impractical as equipment required for its
  measurement is not available routinely in ICU
• P 0.1 / MIP lt 0.3 - a good early predictor of
  weaning success

22
Other Criteria

• Pressure time product
• Integral of the difference between pleural
  pressure during assisted breathing and the recoil
  pressure of the chest during passive breathing
• Measures work of breathing
• Limitation cumbersome measurements ? not widely
  applied
• Tension time index
• Product of transdiaphragmatic pressure during
  tidal breathing as a proportion of the maximal
  transdiaphragmatic pressure and the duration of
  inspiration
• Accounts for isometric contraction
• Correlates well with oxygen cost of breathing
• Requires esophageal and gastric balloons ?
  impractical

23
Other criteria
It is found to be a better predictor of weaning
success than traditional parameters and RSBI

• Gastric intramucosal pH( pHi)
• Periods of increased respiratory muscle activity
  are associated with decreased splanchnic blood
  flow and decrease in gastric mucosal pH
• pHi estimated using gastric juice PCO2 before and
  during SBT ? Gastric pHi gt 7.30 or a change of
  lt0.09 predicts successful extubation
• Criticism ? Gastric juice PCO2 is extremely
  unstable ? unreliable measurement

24
Weaning Procedure

• Rapid ventilator discontinuation
• Spontaneous breathing trials
• Pressure support ventilation (PSV)
• SIMV
• Other Modes used for weaning

25
Rapid ventilator discontinuation
Sbts are superior to both SIMV and PS in both
duration of weaning and likelihood of success
after weaning

• Considered in patients with no underlying
  cardiovascular, pulmonary, neurologic, or
  neuromuscular disorders and patients receiving
  ventilatory support for short periods e.g.
  post-op patients

Patient on ventilator for lt 72 hrs
Good spont RR, MV, MIP, f/Vt
SBT for 30 to 120 min.
EXTUBATE if no other limiting factor
26
Spontaneous Breathing Trial

• SBT can be in the form of T tube trial or PSV
  of 5-10 cm H2O or CPAP 5-7 cmH2O
• T-Tube trial allows spontaneous breathing
  interspersed with periods of full ventilatory
  support

• ADVANTAGES
• Tests pts spontaneous breathing ability
• Allows periods of work and rest
• Weans faster than SIMV

• DISADVANTAGES
• Abrupt transition difficult for some pts
• No alarms, unless attached to vent.
• Requires careful observation.

27
T Tube Adapter
A T-piece (or trach-collar) trial involves the
patient breathing through a T-piece (essentially
the endotracheal tube (ett) plus a flow of
oxygen-air and no ventilatory assistance) for a
set period of time. The work of breathing is
higher than through a normal airway (although
this simulates laryngeal edema/airway narrowing).
If tolerated, the chances of successful
extubation are high. If not reattachment to a
ventilator is simple. Gas flow to inspiratory
limb should be at least twice that of the
patients spontaneous minute ventilation in order
to meet the patients peak inspiratory flow rate.
An extension piece of about 12 inches should be
added to the expiratory limb to prevent
entrainment of room air.
28
Weaning protocol for SBT with a T-Tube
There is evidence that the detrimental effects of
ventilatory muscle overload, if it is going to
occur, often occur early in the
SBT.73,108,110,128 Thus, the initial few
minutes of an SBT should be monitored closely
before a decision is made to continue (this is
often referred to as the screening phase of an
SBT). Thereafter, the patient should continue the
trial for at least 30 min but for not 120 min102
to assure maximal sensitivity and safety. It
also appears that whether the SBT is performed
with low levels of CPAP (eg, 5 cm H2O), low
levels of pressure support (eg, 5 to 7 cm H2O),
or simply as T-piece breathing has little
effect on outcome.101,129131 CPAP, however,
conceivably could enhance breath triggering in
patients with significant auto-PEEP.132,133
Optimize the patients medical condition
suction, adequate humidification, bronchodilator
therapy, good nutrition, optimal position,
psychological counseling, adequate staff,
equipment, no sedatives
Prepare for T-Tube trial
3 min. screening trial
Measure TV,RR Measure MIP thrice selecting the
best
If signs of intolerance are present
. Formal SBT for 30 120 min
MIP lt -20 cm H20 TV spon. gt 5 ml/kg RR spon. lt
35/min.
Put the patient back on previous ventilator
settings
no signs of intolerance
Repeat next trial after 24 hrs
extubate
29
SBT with CPAP

• CPAP circuit overcomes some of the work of
  breathing through the tracheal tube and prevents
  airway collapse.
• CPAP may improve lung mechanics and reduce the
  effort required by mechanically ventilated
  patients with air flow obstruction and may
  enhance breath triggering in patients
• with significant auto-PEEP.

30
SBT with Pressure Support

• Trachea can be extubated directly from PS as PS
  overcomes the tube resistance
• 7cmH2O of pressure support is required to
  overcome the resistance through a size 7.5mm
  (internal diameter) endotracheal tube
• 3cmH2O PS is required through a tracheostomy
• If a smaller tube is in place, pressure support
  of 10 cmH2O is required.

31
Weaning with SIMV

• Breaths are either spontaneous or mandatory
• Mandatory breaths are synchronized with
  patients own efforts

• ADVANTAGES
• Gradual transition
• Easy to use
• Minimum MV guaranteed
• Alarm system may be used
• Should be used in comb.
• with PSV/CPAP

• DISADVANTAGES
• Prolongs weaning
• May worsen fatigue

32
Protocol of SIMV Weaning
Start with SIMV rate at 80 of full support

• Monitor patients appearance , respiratory rate
  , SpO2, BP, obtain ABG sample

f is then decreased by 2 4 breaths twice
daily
If deterioration ? ? SIMV rate
If the patient tolerates an SIMV rate of 2-4
breaths forgt 2 hrs
Allow pts resp msls to rest at night by ?ing
SIMV rate
Consider extubation
33
Weaning with PSV

• Pressure support is given with each spontaneous
  breath to ensure an adequate TV

• ADVANTAGES
• Gradual transition
• Prevents fatigue
• Increased pt comfort
• Weans faster than SIMV alone
• Pt can control cycle length, rate
• and inspiratory flow.
• Overcomes resistive WOB d/t
• ET tube and circuit.

• DISADVANTAGES
• ?ed MAP versus T-Tube
• TV not guaranteed

34
Protocol of PSV weaning
PSV is adjusted to deliver TV 10-12 ml/kg,
(PSVmax)
Monitor patients appearance , respiratory rate ,
SpO2, BP, obtain ABG sample
PSV level is decreased by 2-4 cm H2O twice daily
to maintain TV
If patient tolerates PSV level of 5-8 cm H2O
for greater than 2 hrs
Consider extubation
35
Weaning with SIMV PSV

• The addition of pressure support with SIMV can
  overcome the work of breathing during
  spontaneous breaths due to endotracheal and
  tracheostomy tubes, demand flow systems and
  ventilator circuits
• The pressure support level needed to overcome
  the imposed work of breathing during IMV weaning
  can be estimated as
• PSV (PIP-Pplat) V max
• Vmech
• PIP peak inspiratory pressure during a machine
  delivered breath
• Pplat pateau pressure during a mechanical
  inspiratory volume hold
• Vmech flow during a machine breath
• Vmax patients spontaneous peak inspiratory
  flow

36
Weaning protocol for SIMV PSV
SIMV rate is set at 2 breaths/min lower than the
rate given by A/C mode PSV 15-20 cmH2O
Reduce SIMV rate in steps of 1-3 breaths/min
PSV 15-20 cm H2O
Monitor patients appearance , respiratory rate ,
SpO2, BP, obtain ABG sample
When SIMV rate becomes 5 breaths/min, stop SIMV
and continue with PSV 15-20 cm H2O
Allow pts resp msls to rest at night by ?ing
SIMV rate
Reduce PSV in steps of 2 cm H2O until PSV is 5-6
cmH2O
Extubate the patient
37
Weaning Selecting an Approach!!!

• Many studies have compared the different methods
  of weaning
• Common conclusions are
• No clear superiority exists between T-tube
  weaning and pressure support based weaning
• SIMV is the least efficient technique of weaning

38
Weaning Selecting an Approach!!!
39
Weaning Selecting an Approach!!!
To summarize, there are advantages and
disadvantages to each of the weaning methods
.however, the best appraoch may be the one with
which the clinician is most familiar anf is based
on a sound rationale
40
Other Modes used for weaning

• Non invasive ventilation (NIV)
• Biphasic positive airway pressure (BiPAP)
• Automatic tube compensation (ATC)
• Volume support (VS)
• Volume assured pressure support (VAPS)
• Mandatory minute ventilation (MMV)
• Servo controlled ventilation ( Automatic
  Ventilatory Support)

41
Non invasive Ventilation

• Used to support ventilation without the use of an
  
• artificial airway
• Useful as a bridge to total withdrawal of
  ventilatory support
• Suggested Indications
• Alternative weaning technique for patients who
  failed conventional weaning sp COPD pts
• NIV as a prophylactic measure for patients with a
  high risk for reintubation
• NIV for the treatment of respiratory
  insufficiency after extubation (post-extubation
  failure)

TECHNIQUE OF PROVIDING ventilation without the
use of an artificial airway It is used
successfully in patients with OSA, acute
ventilatory failure or impending ventilatory
failure
42

• For some subgroups (hypercapnic respiratory
  insufficiency, especially in COPD patients) NIV
  may be helpful in expediting the weaning process.
  
• However, its use cannot be recommended for all
  patients failing a SBT.
• Clear criteria for discontinuation of NIV must be
  defined.
• Positive effects of prophylactic NIV treatment in
  patients at risk for reintubation seem likely,
  but larger studies have yet to confirm this
  observation.

43
Weaning with BiPAP
44
Weaning with BiPAP...
45
Volume support

• The machine measures the delivered volumes and
  adjusts the pressure support to meet desired
  goal
• Allows automatic weaning of P support as
  compliance alters.

Preset constant
C V P
changes during weaning guides P support level
P support dependent on C
compliance ? - P support ? ? - P support ?
Deliver desired TV
46
Volume support

• Advantages
• Provides a controlled tidal volume
• Increases patient comfort
• Helps in weaning or during awakening from
  anaesthesia

47
Volume assured pressure support
We set the desired minimum tidal volume and
pressure support level . Once a breath is
triggered vent tries to achieve the desired tidal
volume at the earliest by increasing the fflow .
If the desired tidal volume equals the set tidal
volume breath is considered as a pressure support
breath if the delivered volume is less than the
preset volume, the ventilator switches from a
pressure limited breath to a volume limited
breath..
48
Volume assured pressure support

• Disadvantages
• May prolong the inspiratory times leading to air
  trapping and undesirable cardiovascular effects

• Advantages
• Assures a stable tidal volume

49
Automatic tube compensation

• A ventilatory method aimed at compensating for
  nonlinear pressure drop across the endotracheal
  tube during spontaneous breathing.
• Overcomes the imposed work of breathing due to
  artificial airways.
• Provides dynamic ventilatory support of each
  spontaneous breath by delivering the exact amount
  of pressure necessary to overcome the resistive
  load of the endotracheal tube for the flow
  measured at the time, so-called variable pressure
  support.
• At least as successful as use of simple T-tube or
  low-level PS for weaning from mechanical
  ventilation.

50
Automatic tube compensation
High circuit pressure
Low carinal pressure
Pressure drop across the circuit is the cause of
WOB with an endotracheal tube ATC raises the
carinal pressure and hence decreases the work of
breathing
?P (P support) a (L / r4 ) a flow a WOB
51
Automatic tube compensation

• Indications for ATC
• Patients with compromised respiratory function
  COPD, malnutrition
• Patients with failed previous extubation
  attempts
• May be beneficial if an SBT fails because of a
  particularly narrow endotracheal tube
• Difficult to wean patients
• However, for groups 2 and 3 patients, there is a
  lack of controlled trials to make any meaningful
  recommendations about the use of ATC.

52
Mandatory Minute Ventilation

• Provides predetermined minute ventilation when
  pts spontaneous breathing effort becomes
  inadequate
• Desired minimum minute volume which is slightly
  lesser than that required to normalize PaCO2 is
  preset on the ventilator
• Mandatory RR increases when actual MV lt preset MV
• All mandatory breaths are volume cycled

53
Mandatory Minute Ventilation

• ADVANTAGES
• Backup ventilation ensured
• Potential to speed weaning
• compared with SIMV
• Prevents hypoventilation and
• respiratory acidosis in
• final stages of weaning

• DISADVANTAGES
• May not ensure efficient
• pattern of breathing
• Rapid shallow breathing
• possible with MMV.
• Requires close monitoring

54
Servo controlled ventilation

• Automatic ventilatory modes
• Rapid adaptation of the ventilatory support to
  the changing demands of a patient
• Includes two modes
• Adaptive support ventilation (ASV)
• Knowledge-based expert system (Smartcare)

55
Adaptive support ventilation

• Based on a computer-driven closed-loop regulation
  system of the ventilator settings which is
  responsive to changes in both respiratory system
  mechanics and spontaneous breathing efforts
• The clinician enters patients body weight and
  sets the desired percentage of minute ventilation
  (100 being equal to 100 mL/kg body weight/min in
  adult patients), as well as the FIO2, level of
  PEEP and maximal inspiratory pressure
• Thereafter, mechanical ventilation starts with
  closed-loop regulation algorithms based on
  real-time determination of the expiratory time
  constant

56

• Adjustment of inspiratory pressure and RR (to
  ensure RR and minute ventilation within defined
  limits) may improve patientventilator
  interactions
• Any spontaneous breathing efforts trigger either
  a pressure-controlled breath or a spontaneous
  breath with inspiratory PS, the level of which is
  adjusted to meet the target RR/VT combination.
• ASV can thus manage the spectrum of ventilatory
  support ranging from controlled mechanical
  ventilation to PS, up to the pre-extubation
  weaning trial.

57
Knowledge-based expert system (Smartcare)

• Follows two main goals
• The first is a real-time adaptation of the level
  of pressure support to maintain the patient
  within a comfort zone (RR 1530 /min, VT gt
  250-300 ml and EtCO2 lt 55 mmHg or 65 mmHg in
  patients with COPD).
• To reach these targets, the level of PS is
  periodically adapted by the system in steps of
  2-4 cmH2O.
• Secondly, the device also includes an algorithm
  of a stepwise decrease of PS with the aim of
  automatically performing an SBT.
• Additional studies are needed to evaluate its
  efficacy in difficult weaning.

58
Extubation

• Discontinuation of invasive PPV involves 2 steps
  
• separation of pt. from ventilator.
• removal of artificial airway.

based on assessment of airway patency and
protection
Parameters for airway protection Effective
cough Secretion volume Mental status
Parameters for airway patency Cuff leak
test Qualitative Quantitative audible
air leaklt 110 ml air leak

59
Cuff leak test
used to assess the patency of the upper airway
(cuff leak test).134 In a study of
medical patients,135 a cuff leak of 110 mL (ie,
average of three values on six consecutive
breaths) measured during assist control
ventilation within 24 h of extubation
identified patients at high risk for
postextubation stridor
60
Weaning Protocols

• Weaning protocols provide structured guidance
  regarding weaning of patients on mechanical
  ventilation.
• Intended to provide more consistent and efficient
  practice by following an expert consensus to
  reduce variation produced by the application of
  individual judgment and experience.
• Protocols are usually presented as written guides
  or algorithms, and ventilator settings are
  manually adjusted by healthcare professionals.

61
Weaning Protocols...

• 3 components
• A list of objective criteria (often referred to
  as readiness to wean criteria)
• Structured guidelines for reducing ventilatory
  support e.g. abrupt/gradual using different
  weaning modes
• A list of criteria for deciding if the patient is
  ready for extubation

62
Cochrane systematic review and meta-analysis, 2011

• Protocol based weaning is more efficient than one
  based on subjective evaluation because subjective
  judgment is not sensitive enough to detect the
  fact that a patient is ready for extubation.
• There is evidence of a reduction in the duration
  of mechanical ventilation, weaning, and stay in
  the intensive care unit when standardised weaning
  protocols are used
• Compared with usual care, use of weaning
  protocols can reduce the duration of mechanical
  ventilation by 25, weaning duration by 78, and
  length of stay in intensive care unit by 10

63
Walsh et al. BJA 200492793-9

• A simple checklist can assist assessment of
  suitability for weaning and could be used as a
  trigger to commence a weaning protocol.
• The weaning checklist used
• Cooperative and pain free
• Good cough reflex to tracheal suctioning
• PaO2/FIO2 ratio gt24 kPa
• PEEP lt10 cm H2O
• Hb gt7 g/dl
• Axillary temperature between 36 and 38.5C
• Plasma K concentration gt3.0 and lt5.0 mmol/litre
• Plasma Na concentration gt128 and lt150 mmol/litre
• Inotropes reduced or unchanged over previous 24 h
• Spontaneous ventilatory frequency gt6/min

64
Weaning failure

• Weaning failure is defined as either the failure
  of SBT or the need for reintubation within 48 h
  following extubation.

65
Indicators of weaning failure

• Inadequate gas exchange
• Arterial oxygenation saturation (SaO2) lt85 - 90
• PaO2 lt50 60 mmHg
• pH lt 7.32
• Increase in PaCO2 gt10 mmHg
• Unstable ventilatory/respiratory pattern
• Respiratory rate gt30 35 breaths/minute
• Respiratory rate change over 50

66
Indicators

• Hemodynamic instability
• Heart rate gt120 140 beats/minute
• Heart rate change greater than 20
• Systolic blood pressure gt180 mmHg or lt90 mmHg
• Blood pressure change greater than 20
• Vasopressors required

67
Indicators

• Change in mental status
• Coma
• Agitation
• Anxiety
• Somnolence
• Signs of increased work of breathing
• Nasal flaring
• Paradoxical breathing movements
• Use of accessory respiratory muscles

68
Pathophysiology of weaning failure
Need for ventilatory support depends upon the
balance between ventilatory muscle demands and
capabilities
69
Factors which may increase ventilatory workload

• Increased ventilatory demand
• Increased CNS drive hypoxia, acidosis, pain,
  fear, anxiety and stimulation of J receptors (
  pulmonary edema)
• Increased metabolic rate increased CO2
  production, fever, shivering, agitation, trauma,
  infection, and sepsis
• Increased dead space COPD, pulmonary embolus
• Decreased compliance
• Decreased lung compliance atelectasis,
  pneumonia, fibrosis, pulmonary edema, and ARDS
• Decreased thoracic compliance obesity, ascites,
  abdominal distension, pregnancy

70

• Increased resistance
• Increased airway resistance bronchospasm,
  mucosal edema, and secretions
• Artificial airways endotracheal, tracheostomy
  tube
• Other mechanical factors ventilator circuits,
  demand flow systems, and inappropriate ventilator
  flow and/or sensitivity settings

71
Non-respiratory factors

• Cardiac load
• Neuromuscular
• Neuropsychological
• Metabolic
• Nutrition
• Anaemia

72
Non-respiratory factors...

• Cardiac load
• Increased cardiac workload leading to myocardial
  dysfunction dynamic hyperinflation increased
  metabolic
• demand unresolved sepsis
• Neuromuscular
• Depressed central drive metabolic alkalosis
  sedative/hypnotic medications
• Peripheral dysfunction primary causes of
  neuromuscular weakness critical illness
  neuromuscular abnormalities (CINMA )

73
Non-respiratory factors...

• Metabolic
• Metabolic disturbances -hypokalemia,
  hypomagnesemia, hypophosphatemia, hypothyroidism,
  hypoadrenalism
• Role of corticosteroids
• Hyperglycaemia
• Nutrition
• Overweight
• Malnutrition
• Ventilator-induced diaphragm dysfunction
• Neuropsychological
• Delirium
• Anxiety, depression

74
Specialised weaning units (SWUs)

• Specialised acute respiratory care units
  dedicated for the purpose of weaning patients on
  prolonged mechanical ventilation
• 2 types
• step-down units or noninvasive respiratory care
  units within acute care hospitals
• regional weaning centres that serve several acute
  care hospitals within the region
• The type of unit preferably will depend on the
  healthcare structure and financing system of each
  individual region or country

75
Specialised weaning units (SWUs)

• Advantages
• Offer specialised teams of personnel (e.g.
  nurses, physiologists, respiratory therapists,
  nutritionists, etc.)-ensure better level of care
• appropriate bridge to home environment for
  such patients and their families (e.g. privacy,
  daytime activity, longer visiting hours and
  undisturbed sleep)
• Provide more focus on patient care as compared to
  the conventional ICUs
• cost-effective

76
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