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Weaning from Mechanical Ventilation

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Weaning from Mechanical Ventilation Powered By Docstoc
					Mechanical Ventilation
    PROBLEMS

                       Patiparn Toomtong
           Department of Anesthesiology
      Siriraj Hospital Mahidol University
Although life-saving, IPPV may
be associated with many
complications, including:
   Consequences of PPV
   Aspects of volutrauma
   Adverse effects of intubation and
   tracheostomy
Optimal Ventilatory Care
       Requires
Attention to minimizing
adverse hemodynamic effects
Averting volutrauma
Effecting freedom from IPPV
as early as possible
       Common Scenarios
•   New development of hypotension
•   Acute respiratory distress (fighting)
•   Repeated sounding of High pressure alarm
•   Hypoxaemia
•   Blood from the endotracheal tube
•   Problem of diagnosing VAP
 Barotrauma or Volutrauma
• High Paw alone insufficient to cause
  alveolar rupture
• Excessive alveolar volume the likely
  factor leading to alveolar rupture and air
  dissection
• More frequent in younger age group
• May be difficult to detect if small in CXR
• “Stretch-induced” Acute lung injury
  Patient-ventilator Synchrony
Flow-targeted breath requires careful
adjustment
Constant flow of 40-60 lpm not always
adequate
Monitor: patient response, airway
pressure/flow graphics
Using decelerating flow pattern may be
helpful
 Patient-ventilator Synchrony
Pressure-targeted breath is better?
• Rapid pressurisation of the airway
with high initial gas flow
• Match Ppl change quicker than
flow pattern
• Flow is continuously adjusted by
the ventilator to maintain a constant
airway pressure
  Patient-ventilator Synchrony
Any problems from pressure
breaths?
• Max initial flow may not be optimal in all
patients depending on drive
• Adjustment of the rate of rise may be
beneficial
• Pressure of what? Proximal airway vs Ppl by
muscular effort
• So! Carinal or pleural triggering helpful
• variable minute ventilation!
   Weaning from
Mechanical Ventilation
     Definition of Weaning
       The transition process from
        total ventilatory support
       to spontaneous breathing.
This period may take many forms ranging
    from abrupt withdrawal to gradual
   withdrawal from ventilatory support.
             Weaning
   Discontinuation of IPPV is achieved
  in most patients without difficulty
 up to 20% of patients experience
  difficulty
 requires more gradual process so
  that they can progressively assume
  spont. respiration
 the cost of care, discontinue IPPV
  should proceed as soon as possible
     Reversible reasons for
prolonged mechanical ventilation

• Inadequate respiratory drive
• Inability of the lungs to carry
  out gas exchange effectively
• Psychological dependency
• Inspiratory fatigue
             Weaning
• Patients who fail attempts at weaning
  constitute a unique problem in critical
  care
• It is necessary to understand the
  mechanisms of ventilatory failure in
  order to address weaning in this
  population
  Why patients are unable to
sustain spontaneous breathing

 • Concept of Load exceeding
   Capacity to breathe
 • Load on respiratory system
 • Capacity of respiratory system
    Balance Load vs Capacity
• Most patients fail the transition from
  ventilator support to sustain spont.
  breathing because of failure of the
  respiratory muscle pump
• They typically have a resp muscle
  load the exceeds the resp
  neuromuscular capacity
 Load on Respiratory System
• Need for increase ventilation
     increased carbon dioxide production
     increased dead space ventilation
     increased respiratory drive
• Increased work of breathing
 Causes of Inspiratory respiratory
         muscle fatigue
• Nutrition and metabolic deficiencies: K,
  Mg, Ca, Phosphate and thyroid hormone
• Corticosteroids
• Chronic renal failure
• Systemic disceases; protein synthesis,
    degradation, glycogen stores
• Hypoxemia and hypercapnia
Capacity of respiratory system
• Central drive to breathe
• Transmission of CNS signal via Phrenic
  nerve
• Impairment of resp muscles to generate
  effective pressure gradients
• Impairment of normal muscle force
  generation
 Evidence based medicine

• When to start weaning process?
• Decision making, any guideline?
  How long it will take?
When to begin the weaning process?
• Numerous trials performed to develop
  criteria for success weaning, however, not
  useful to predict when to begin the weaning
• Physicians must rely on clinical judgement
• Consider when the reason for IPPV is
  stabilised and the patient is improving and
  haemodynamically stable
• Daily screening may reduce the duration of
  MV and ICU cost
  Evidence-based medicine
Recommendation 1. Search for all the
 causes that may contribute to
 ventilator dependence in all patients
 with longer than 24 h of MV support,
 particularly who has fail attempts.
 Reversing all possible causes should
 be an integral part of discontinuation
 process.
         Daily Screening
• Resolution/improvement of patient’s
  underlying problem
• Adequate gas exchange (SaO2 > 90%,
  PaO2/FiO2 >200)
• Respiratory rate < 35/ min
• Absence of fever, temperature < 38C
• Adequate haemoglobin concentration, >
  8-10 g/dl
• Stable cardiovascular function: heart
  rate < 140/min, 180>SBP>90
   Daily Screening (cont.)
• Indices suggesting an adequate
  capacity of the ventilatory pump:
  respiratory rate of less than 30/
  min, Maximum inspiratory pressure
  < -20 to -30 cmH2O
• Correction of metabolic and
  electrolyte disorders
• Normal state of consciousness
  Evidence-based medicine
Recommendation 2. Patients receiving
 MV for respiratory failure should
 undergo a formal assessment of
 discontinuation potential if the criteria
 are satisfied.
Reversal of cause, adequate oxygenation,
 haemodynamic stability, capability to
 initiate respiratory effort. The
 decision must be individualized.
Predictions of the outcome
        of weaning
Variables used to predict weaning
  success: Gas exchange
• PaO2 of > 60 mmHg with FiO2 of < 0.35
• A-a PaO2 gradient of < 350 mmHg
• PaO2/FiO2 ratio of > 200
Weaning success prediction
Ventilation Pump
• Vital capacity > 10- 15 ml/kg BW
• Maximal negative insp pressure
  < -30 cmH2O
• Minute ventilation < 10 l/min
• Maximal voluntary ventilation more
  than twice resting MV
Weaning success prediction
•   Tidal volume            > 325 ml
•   Tidal volume/BW        > 4 ml/kg
•   Dynamic Compliance > 22 ml/cmH2O
•   Static compliance       > 33 ml/cmH2O
•   Rapid shallow breathing index < 105
    breaths/min/L
    Clinical observation of
   the Respiratory Muscles
• Initially thought to be reliable in predicting
  subsequent weaning failure
• from inductive plethysmographic studies
  not necessary
• a substantial increase in load will effect on
  the rate, depth, and pattern of breathing
• a manifestation of fatigue
Both respiratory rate and minute
ventilation initially increase, may
   be followed by a paradoxical
  inward motion of the anterior
abdominal wall during inspiration
 which indicates the insufficient
  diaphragmatic contraction to
descend and move the abdominal
        content downward
  Cyclic change in breathing
patterns with either a chest wall
  motion or a predominantly
  abdominal wall motion are
    another indicator, called
      respiratory alternans
          Fatigue Criteria
Duration of weaning prior to initial episode of
fatigue (days)              2.5 (0.25–7.5)
Fatigue criteria
Hypoxia (PaO2 < 60, SpO2 <90%) 11 (31%)
Hypercarbia (PaCO2 > 50 mmHg) 9 (25%)
Pulse rate > 120/min                  17 (47%)
SBP > 180 or < 90 mmHg                 2 (6%)
Respiratory rate > 30/min              33 (92%)
Clinical respiratory distress           27 (75%)
Parameters that assess airway
   patency and protection
1. Maximal expiratory pressure
2. Peak expiratory flow rate
3. Cough strength
4. Secretion volume
5. Suctioning frequency
6. Cuff leak test
7. Neurological function (GCS)
  Evidence-based medicine
Recommendation 3. The removal of the
 artificial airway from a patient who
 has successfully been discontinued
 from ventilatory support should be
 based on assessment of airway
 patency and the ability of the patient
 to protect the airway.
Methods of Weaning
•   Abrupt Discontinuation
•   T- tube trials
•   SIMV
•   Pressure support
   Spontaneous breathing protocol
• Communicate with patient, weaning is
  about to begin, allow pt to express fear
  whenever possible
• Obtain baseline value and monitoring
  clinical parameters; vital signs, subj
  distress, gas exchange, arrhythmia
• Ensure a calm atmosphere, avoid sedation
• Sit the patient upright in bed or chair
• Fit T-tube with adequate flow, observe
  for 2 hr
For How long I will have to
monitor the weaning process
with SBT in my patient?
 Evidence-based medicine
Recommendation 4. Formal assessments
should be done during SBT rather than
receiving substantial support. The
criteria to assess patient tolerance
during SBTs are respiratory pattern, gas
exchange, hamodynamics stability and
patient comfort. The tolerance of SBTs
lasting 30 to 120 minutes should prompt
for permanent ventilator
discontinuation.
                SIMV Protocol
• Switch to SIMV from assist mode or decrease RR
• Begin with RR 8/min decrease SIMV rate by two
  breaths per hour unless clinical deterioration
• if assume to fail, increase SIMV rate to previous
  level, until stable
• if stable at least 1 hour of rate 0/ min extubate
• in patient without respiratory disorders,
  decrease rate with half an hour interval, 2 hr
  extubate
    Pressure Support Protocol
• Switch to PSV or decrease PS
• Begin PSV at 25 cmH2O, decrease PS by 2-4
  cmH2O every hour unless clinical deterioration
  appears, adjust pressure until stable, if stable of
  PSV = 0 for at least one hour fit with T-tube or
  CPAP and then observe
• In patient without resp problems, decrease
  pressure at half an hour interval, if able to
  tolerate PSV = 0 for 2 hours, can be extubated
          Failed to Wean
• Associated with intrinsic lung disease
• Associated with prolonged critical
  illness
• Incidence approximately 20%
• Increased risk in patient with longer
  duration of mechanical ventilation
• Increased risk of complications,
  mortality
 Evidence-based medicine
Recommendation 5. Patients receiving
MV who fail an SBT should have the
cause determined. Once causes are
corrected, and if the patient still
meets the criteria of DS, subsequent
SBTs should be performed every 24
hours.
Evidence-based medicine
Recommendation 6. Patients
receiving MV for respiratory
failure who fail an SBT should
receive a stable, nonfatiguing,
comfortable form of ventilatory
support.
  Weaning Protocol
Reduced ventilator time
Reduced weaning time; early
beginning by non-physician
healthcare workers
Reduced cost
Reduced complications: VAP
Evidence-based medicine
Recommendation 7. Weaning
protocols designed for nonphysician
health care professionals should be
developed and implemented by ICUs.
Protocols aimed at optimizing
sedation should also be developed and
implemented.
Evidence-based medicine
Recommendation 8. Tracheostomy
should be considered after period of
stabilization on the ventilator when it
becomes apparent that the patient
will require prolonged MV.
Tracheostomy should be performed
when the patient appears likely to
gain one or more benefits from the
procedure.
 Evidence-based medicine,
          cont.
• Required high levels of sedation to
  tolerate tube
• With marginal respiratory mechanics,
  lower resistance
• Derive psychological benefit from the
  ability to eat orally, communicate by
  articulated speech, enhanced mobility
• Assist physical therapy efforts
Evidence-based medicine
Recommenation 9. Unless there is
evidence for clearly irreversible
disease, a patient requiring prolonged
MV should not be considered
permanently ventilator-dependent
until 3 months of weaning attempts
have failed.
Patient subgroups
Evidence-based medicine
Recommendation 10.
Anaesthesia/sedation strategies
and ventilator management aimed
at early extubation should be
used in postsurgical patients.
 SEMIQUANTITATIVE ASSESSMENT OF NEED FOR AIRWAY CARE
Spont. cough          Gag               Sputum Quantity
0 Vigorous       0 Vigorous            0 None
1 Moderate       1 Moderate            1 1 pass
2 Weak           2 Weak                2 2 passes
3 None           3 None                3 > 3 passes
Sputum Viscosity Suctioning Frequency Sputum Character
                   ( per last 8 h)
0 Watery         0 >3 h                0 Clear
1 Frothy         1 q 2-3 h             1 Tan
2 Thick          2 q 1-2 h             2 Yellow
3 Tenacious      3 <q1h                3 Green
            EXUTBATION DELAY IN THE 136 PATIENTS
                                           No Delay      Delay       p Value
n (%)                                      99 (73%)     37 (27%)
Days of delay                                 NA         3 (2-17)    NA
Intubation duration at readiness day, d     2 (1-8)      2 (1-6)     0.03
Spontaneous cough
  Readiness date                            1 (0-3)      1 (0-3)     0.34
  Extubation date                           1 (0-3)      1 (0-3)     0.29
Gag
  Readiness date                            1.0 (0-3)   1.5 (0-2)    0.04
  Extubation date                           1.0 (0-3)   2.0 (0-3)    0.002
Sum of airway care assessments
  Readiness date                           8.0 (1-12)   9.0 (5-11)   0.04
  Extubation date                          7.5 (1-12)   9.0 (2-16)   0.01
Glasgow Coma Scale (GCS)
  Readiness date                           10 (4-11)     7 (3-11)    < 0.001
  Extubation date                          10 (4-11)     8 (3-11)    0.006
Coma (GCS < 8)
  Readiness date                          31/99 (31%) 29/37 (78%) < 0.001
  Extubation date                         28/99 (28%) 21/37 (57%) 0.002
    EXBUTATION DELAY AND OUTCOME
                   No Delay    Delay      p
n (%)              99 (73%) 37 (27%)
Pneumonia (%)      21.2%       37.8%    0.048
ICU length of stay  3 (1-15) 8 (3-22)  < 0.001
Hospital LOS       11 (1-39) 17 (3-61)  0.009
Cost, $              41,824    70,881 < 0.001

Mortality, n (%)      12.1%       27.0%    0.04
Tracheotomy, n (%)   4 (4.0%)   0 (0.0%)   0.6
     FACTORS ASSOCIATED WITH SUCCESSFUL EXTUBATION
IN NEUROSURGICAL PATIENTS AFTER FIRST EXTUBATION ATTEMPT
                Univariate Analysis                     Multivariate Analysis

Parameter     OR       95% CI          p Value   OR            95% CI            p Value


GCS score    1.35     (1.2-1.5)       < 0.0001   1.24          (1.1-1.4)        0.0006
f/VT ratio   0.99    (0.98-0.99)      < 0.0001   0.99       (0.985-0.997)       0.0050
P/F ratio    1.01    (1.00-1.01)      0.0001     1.01       (1.002-1.007)       < 0.0001
MV           0.89    (0.85-0.94)      < 0.0001   0.92       (0.845-0.981)       < 0.0116
GCS and prediction of successful weaning, AJRCCM 2001
      ODDS OF SUCCESSFUL EXTUBATION FOR
  NEUROLOGIC AND RESPIRATORY PREDICTORS
Parameters                       OR 95% CI p Value
f/VT ratio < 105                 10.3 1.2-87  0.02
P/F ratio > 200                   3.3 1.8-6   0.0001
GCS score > 8                     4.9 2.8-8.3 < 0.001
P/F ratio, GCS score, f/VT ratio 5.1 3.1-8.4 < 0.001
P/F ratio, GCS score              4.8 2.9-8   < 0.001
f/VT ratio, GCS score             4.9 2.9-8.5 < 0.001
Nursing role in Weaning
         from
 mechanical ventilation

   Nurse-led weaning
Psychological preparation
         Nurse-led weaning
• ICCN 2001: Limited evidence suggesting
  that nurse-led weaning may reduce
  ventilation time; however, not clear
  whether it was nurse-led aspect or the
  clinical protocol that produced the effect
• Superior to doctor-led weaning, has huge
  implications for intensive care practice
        Nurse-led weaning
• ICCN 2002; Retrospective study in
  patients with MV longer than 7 days,
  reduced average duration of MV support
• Some delays occurred: sedation; protocol
  needed, epidural analgesia, tracheostomy;
  surgical vs percutaneous, some staff
  lacked confidence and knowledge:
  continuous education programme
         Daily Screening
• Resolution/improvement of patient’s
  underlying problem
• Adequate gas exchange (SaO2 > 90%,
  PaO2/FiO2 >200)
• Respiratory rate < 35/ min
• Absence of fever, temperature < 38C
• Adequate haemoglobin concentration, >
  8-10 g/dl
• Stable cardiovascular function: heart
  rate < 140/min, 180>SBP>90
   Daily Screening (cont.)
• Indices suggesting an adequate capacity
  of the ventilatory pump: respiratory rate
  of less than 30/ min, Maximum
  inspiratory pressure < -20 to -30
  cmH2O
• Correction of metabolic and electrolyte
  disorders
• Normal state of consciousness

  Oriented, Mental ease, Positive attitude
    Psychological preparation
• Knowing the patient; personal resources,
  motivation levels, and styles of coping,
  comes from continued and close contact
  with the patient
• Oriented; understanding what will happen
  and being informed of progress, able to
  control negative responses
• Mental ease; absence of anxiety and fear
  arising from being informed, reassured and
  supported
• Positive attitude; being motivated and co-
  operating
    Last year Meeting (2oo3)
• SIMV 2nd CPAP 3rd, T-piece 1st choice
• SIMV 25%, CPAP 19.82%, T-piece
  50.29%
• Physician-led weaning approx. Nurse-led
  weaning
• T-piece duration 15 min to 4 hours
• Mainly tidal volume less than 10 ml/kg.

				
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