weaning and discontinuation of ventilatory support
DESCRIPTION
Weaning and Discontinuation of Ventilatory Support. 215a. Educational Objectives. Differentiate between weaning , discontinuation , and extubation List the causes of ventilator dependence List the patient parameters evaluated and the values required prior to initiating weaning. - PowerPoint PPT PresentationTRANSCRIPT
Weaning and Discontinuation of Ventilatory Support
215a
Educational Objectives
• Differentiate between weaning, discontinuation, and
extubation
• List the causes of ventilator dependence
• List the patient parameters evaluated and the values
required prior to initiating weaning
Educational Objectives
• Describe the various techniques of weaning, with
the advantages and disadvantages of each
• Describe the overall factors associated with
successful weaning
• List the steps of extubation
Definitions
• Weaning
– The process of gradually reducing ventilatory support
and its replacement with spontaneous ventilation in
an incremental manner
• Discontinuation
– The permanent removal of the ventilator
Definitions
• Extubation
– Removal of the artificial airway
• Ventilatory Demand
– The level of ventilation required to meet the patient’s
need for elimination of carbon dioxide
Definitions
• Ventilatory capacity
– The level of the patient’s drive (CNS) to breathe
and the ability of the respiratory muscles to
maintain this drive (strength and endurance)
Causes of Ventilator Dependence
• Ventilatory demand in excess of ventilatory
capacity
• Non-respiratory factors
• Psychological factors
• Nutritional needs
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Increased CNS drive
• Hypoxia• Acidosis
• Pain
• Fear/anxiety
• Stimulation of J receptors
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Increased metabolic rate
• Increased carbon dioxide production
• Fever
• Shivering
• Trauma
• Infection/sepsis
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Decrease in lung compliance
• Atelectasis
• Pneumonia
• Fibrosis
• Pulmonary edema
• ARDS
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Decreased thoracic compliance
• Obesity
• Ascites
• Abdominal distention
• Pregnancy
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Increased airway resistance
• Bronchospasm
• Mucosal edema
• Secretions
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Artificial airways
• Endotracheal tube
• Tracheostomy tube
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors increasing ventilatory demand
– Mechanical factors
• Ventilator circuits
• Demand flow systems
• Inappropriate ventilator settings
–Flow
–Sensitivity
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors affecting ventilatory capacity
– Decreased PaCO2
– Metabolic alkalosis
– Pain
– Electrolyte imbalance
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors affecting ventilatory capacity
– Respiratory depressants
• Narcotics
• Sedatives
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors affecting ventilatory capacity
– Fatigue
• Overall fatigue
• Malnutrition
• Atrophy of respiratory muscles
Ventilatory Demand in Excess of Ventilatory Capacity
• Factors affecting ventilatory capacity
– Decrease in metabolic rate
– Carbon dioxide retention
– Neurologic or neuromuscular disease
Non-Respiratory Factors
• Cardiovascular factors
– Myocardial ischemia
– Heart failure
– Hemodynamic instability
– Arrhythmias
Non-Respiratory Factors
• Neurological factors
– Decreased central drive
– Decreased peripheral nerve transmission
Psychological Factors
• Confusion/altered mental status
• Fear and anxiety
• Stress
• Depression
• Support from staff and family
Nutritional Needs
• Preferably, patient is not on hyperalimentation
• No excessive carbohydrates
– Increased carbohydrate intake increases respiratory
quotient > 0.8
– Results from increase in carbon dioxide production
Factors Affecting Readiness For Weaning
• Reversal or stabilization of underlying disease
causing initiation of support
• Stable vital signs
– Afebrile
– Pulse, blood pressure within normal limits
Factors Affecting Readiness For Weaning
• Adequate cardiovascular reserves
– Absence of acute myocardial ischemia
– Minimal requirement for vasopressors to maintain blood
pressure
– No significant arrhythmias
Factors Affecting Readiness For Weaning
• Adequate blood gas results
– PaO2 ≥ 60 mmHg with FIO2 < 0.5 and PEEP ≤ 5 cmH2O
– pH > 7.25
– PaCO2 at patient’s normal level (may be greater than 45
mmHg for COPD patients)
Factors Affecting Readiness For Weaning
• Adequate ventilatory status
– Spontaneous respiratory rate < 30 breaths/min
– Spontaneous tidal volume > 5 mL/kg
– Vital capacity > 10 – 15 mL/kg
Factors Affecting Readiness For Weaning
• Adequate respiratory muscle strength
– Maximum inspiratory force
– MIF < −30 cmH2O
Factors Affecting Readiness For Weaning
• Adequate ventilatory reserve
– Maximum voluntary ventilation
– MVV > 20 L/min or two times minute
ventilation
Factors Affecting Readiness For Weaning
• Adequate ventilatory reserve
– Rapid Shallow Breathing Index (RSBI)• Respiratory rate divided by tidal volume in liters
(f/VT)
• Calculated during one minute of unsupported,
spontaneous breathing
• Pressure support reduces predictive value
Factors Affecting Readiness For Weaning
• Adequate ventilatory reserve
– Rapid Shallow Breathing Index (RSBI)
• Most predictive for patients on ventilatory
support less than eight days
• f/VT < 105 predictor of weaning success; < 80
associated with 95% success
Approaches to Weaning
• Spontaneous breathing trials (SBT)
• Synchronized intermittent mandatory ventilation
• Pressure support ventilation
• Extubation
Spontaneous Breathing Trials (SBT)
• Method
– Prepare the patient psychologically
– Set FIO2 either at the ventilator setting or 10% above
setting
– Patient placed on T piece or left on ventilator with no
backup rate and CPAP set at zero
Spontaneous Breathing Trials (SBT)
• Method
– Start with five minutes off the ventilator (or less, if
not tolerated by patient); may increase initial time
up to 120 minutes if tolerated well
Spontaneous Breathing Trials (SBT)
• Method
– Response is monitored; trial discontinued if changes
observed
• f > 35 breaths/min
• SPO2 < 90%
• Heart rate > 140 beats/min or increase by 20%
Spontaneous Breathing Trials (SBT)
• Method
– Response is monitored; trial discontinued if changes
observed
• BP ≥ 20% change; systolic >180 mmHg and
diastolic > 90 mmHg
• Diaphoresis
• Increased anxiety
Spontaneous Breathing Trials (SBT)
• Method
– If first trial unsuccessful and patient has auto-PEEP
secondary to airway obstruction, may add 5 cmH2O
– If patient has nasal ET tube or small ET tube,
5 to 7 cmH2O pressure support may be added
– If patient fails SBT, patient replaced on ventilatory
Support to rest for one to four hours
Spontaneous Breathing Trials (SBT)
• Method
– Increase duration of spontaneous breathing trials
– Some patients may tolerate the procedure so well
that they do not have to resume ventilator use at all
Spontaneous Breathing Trials (SBT)
• When weaning is difficult, process can last weeks or
months
• Generally, ventilatory support is resumed overnight
Synchronized Intermittent Mandatory Ventilation
• Method
– Initially, respiratory rate and tidal volume set to
provide full ventilatory support
– Initiation of weaning by SIMV
• May wait until patient’s condition has improved
considerably
• May begin as soon as patient’s condition allows
Synchronized Intermittent Mandatory Ventilation
• Method
– Rate decreased in increments of two with assessment
of patient following each adjustment
– May be reduced more rapidly as patient condition
improves
– Once rate is equal to 4 breaths/min and can be
tolerated at least two to four hours, the patient may
be extubated
Synchronized Intermittent Mandatory Ventilation
• Decreases respiratory muscle atrophy and
discoordination
• Minimizes chance of barotrauma through rapid
reduction of mean airway pressure
Pressure Support Ventilation
• Mode of ventilatory support that assists the
patient’s spontaneous inspiratory effort with
a level of positive airway pressure
Pressure Support Ventilation
• Mode works best for short-term weaning (< 72
hours); if used for long-term weaning, increase
support to near maximum at night to allow patient
to rest
Pressure Support Ventilation
• Technique
– Begin with pressure support level at which
respiratory rate and tidal volume are close to
full support
– Gradually reduce support as tolerated by patient
Pressure Support Ventilation
• Technique
– Continue to reduce support until a minimum level of
between 5 and 10 cmH2O can be tolerated
– When patient can maintain this level for a minimum
of two and four hours, the patient is considered
weaned
Extubation
• Decision to wean and decision to extubate are
separate decisions
Extubation
• Guidelines for extubation
– No immediate need for mechanical ventilation
– Achievement of adequate oxygenation and
ventilation during spontaneous breathing
Extubation
• Guidelines for extubation
– Minimal risk of upper airway obstruction
• Minimal upper airway edema; perform cuff
leak test
–Suction upper airway above cuff
–Deflate cuff
Extubation
• Guidelines for extubation
– Minimal risk of upper airway obstruction
• Minimal upper airway edema; perform cuff leak
test
–Briefly occlude endotracheal tube
– If patient is unable to breathe around the
occluded endotracheal tube with the cuff
deflated, laryngeal edema may be present
Extubation
• Guidelines for extubation
– Minimal risk of upper airway obstruction
• No evidence of mass obstructing airway
– Minimal risk of aspiration
– Adequate protection of airway
– Adequate clearance of pulmonary secretions
Failure to Wean
• Approximately 25% of patients removed from
ventilatory support experience enough respiratory
distress to require reinstitution of support
Causes of Weaning Failure
• Oxygenation problems
– Decreased ventilation/perfusion ratio
• Asthma
• Emphysema
• Chronic bronchitis
• Bronchospasm
Causes of Weaning Failure
• Oxygenation problems
– Increase in shunt
• Atelectasis
• Pneumonia
• ARDS
• Pulmonary edema
Causes of Weaning Failure
• Oxygenation problems
– Low oxygen content of mixed venous blood
Causes of Weaning Failure
• Ventilation problems
– Central hypoventilation
• Neurological injury
• Drugs
– Impaired neuromuscular function
Causes of Weaning Failure
• Ventilation problems
– Increased dead space
• Embolism
• ARDS
• Emphysema
Causes of Weaning Failure
• Ventilation problems
– Increased carbon dioxide production
• Increased carbon dioxide production from
increased muscle activity
• Carbohydrate overfeeding
• Fever
Causes of Weaning Failure
• Cardiovascular problems
– Left ventricular failure
– Hemodynamic instability
Terminal Weaning
• Discontinuation of ventilatory support in the
presence of catastrophic or irreversible illness
Terminal Weaning
• Decision to terminally wean made by family in
conjunction with physician and according to
established ethical and legal guidelines
– Patient’s prior known desire to not continue life
support
– Predictions of a low chance of survival
Terminal Weaning
• Decision to terminally wean made by family in
conjunction with physician and according to
established ethical and legal guidelines
– Likelihood of significant future cognitive impairment
– Inability to maintain blood pressure without
continuous need for medication
Terminal Weaning
• Patient is discontinued from ventilator after all
procedures to ensure as much comfort as possible
for the patient have been performed