Principles of Mechanical Ventilation RET 2284 Module 7.0 Discontinuation From Mechanical...
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Transcript of Principles of Mechanical Ventilation RET 2284 Module 7.0 Discontinuation From Mechanical...
Principles of Mechanical Ventilation
RET 2284 Module 7.0Discontinuation From Mechanical Ventilation
Discontinuation From Mechanical Ventilation
Discontinuation (ACCP/SCCM/AARC) The process of withdrawing mechanical
ventilatory support and transferring the work of breathing from the ventilator to the patient whose condition is improving AKA
Weaning Gradual reduction Liberation
Can be accomplished Abruptly Gradually
Discontinuation From Mechanical Ventilation
DiscontinuationOnce the need for mechanical ventilation has been resolved, ventilation can be discontinued
About 80% of patients requiring temporary mechanical ventilation do not require a slow withdrawal process and can be disconnected within a few hours or day of initial support
Postoperative – recovery from anesthesia Uncomplicated drug overdose Exacerbations of asthma
Discontinuation From Mechanical Ventilation
Discontinuation The ventilator and airway should be
discontinued as soon as possible to avoid the risks associated with mechanical ventilation Ventilator induced lung injury (VILI) Nosocomial pneumonia Airway trauma form ET Unnecessary sedation
Premature discontinuation also is associated with a higher mortality rate
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Criteria for Weaning – Three Key Points
The problem that caused the patient to require ventilation has been resolved
Certain measurable criteria should be assessed to help establish a patient’s readiness for discontinuation of ventilation
A spontaneous breathing trial should be performed to establish readiness for weaning
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Pathology of Ventilator Dependence
Primary pathology that led to ventilatory support must be corrected
In patients who require mechanical ventilation for >24 hours, a formal search should be made for all causes that may be contributing to ventilator dependence
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Weaning Criteria
When a patient’s condition is stable, alert, and cooperative, clinicians commonly evaluate certain ventilatory mechanic and gas exchange values to help assess readiness for weaning
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Measurement of Adequacy of Oxygenation
PaO2 60 mm Hg (FiO2 <0.40) PEEP 5 – 8 cm H2O PaO2/FiO2 >200 mm Hg P(A-a)O2 <350 mm Hg (FiO2 of 100%) % OS/QT <20% - 30%
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Measurement of Ventilation
PaCO2 <50 mm Hg VE (spont.) <10 – 15 L/min VD/VT <0.6 VT >5 mL/kg RR (spont.) ≤35 min. or >6 – 10 min. Resp Pattern Regular
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Respiratory Mechanics
MIP ≤ 20 cm H2O VC >10 – 15 mL/kg (needed for
effective cough) CS ≥ 30 mL/cm H2O
CD ≥ 22 mL/cm H2O P0.1 ≤ 6 cm H2O
Discontinuation From Mechanical Ventilation
Evaluation of Clinical Criteria for Weaning Integrated Indices
Respiratory Frequency/Tidal Volume Ratio (f/VT) Failure to wean may be related to spontaneous
breathing that is rapid (high respiratory rate) and shallow (low tidal volume)
Procedure Disconnect the spontaneous breathing patient
from the ventilator and oxygen for 1 minute VE, respiratory frequency, VT are measured Calculate f/VT
RSBI < 105 associated with successful weaning
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
Ventilator support can be reduced as patients become increasingly able to resume part of the work of breathing
Three Common Approaches Synchronized Intermittent Mandatory Ventilation
(SIMV) PSV – Pressure Support Ventilation (PSV) Spontaneous Breathing Trial (SBT)
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
SIMV – Synchronized Intermittent Mandatory Ventilation
Common practice is to reduce the mandatory rate progressively (1 – 2 breaths/min) at a pace that matches the patients improvement
Pressure support can be added to unload spontaneous breaths through circuit and ET (helps prevent fatigue)
PEEP of 3 – 5 cm H2O is also used to help compensate for changes in FRC
Studies done clearly show that weaning took longer with SIMV when compared to PSV and T-piece methods
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of titrating Ventilator Support
SIMV – Synchronized Intermittent Mandatory Ventilation
Measurements of flow, volume, airway pressure, and esophageal pressure in a patient ventilated with SIMV. The esophageal pressure swings reflect the changes in pleural pressure and are the result of respiratory muscle contraction. These pressure swings are nearly as large during a mandatory breath as during spontaneous breaths. (From Hess DR: Respir Care 47:1007, 2002.)
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
PSV – Pressure Support Ventilation Patient triggered, pressure limited, flow
cycled Patient controls the rate, timing and depth of
each breath
Theoretically, PSV allows the clinician to adjust the ventilatory workload for each spontaneous breath to enhance endurance conditioning of the respiratory muscles without causing fatigue
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
PSV – Establishing PS level Set PS level to 5 – 15 cm H2O until a reasonable
ventilatory pattern for the patient is accomplished
Or Reestablish patient’s baseline respiratory rate
(15 – 25 breaths/min) VT (300 – 600 mL/min)
Inappropriate PS level will produce tachycardia, hypertension, tachypnea, diaphoresis, excessive use of accessory muscles, paradoxical breathing, respiratory alternans
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
PSV – Weaning Gradually reduce PS level as long as an
appropriate spontaneous respiratory rate and VT are maintained and no distress is evident
When PS is reduced to 5 cm H2O it is not high enough to contribute to ventilatory support, but will help overcome the work imposed by the ventilator system and ET
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
Spontaneous Breathing Trial (SBT) - Abrupt Method Patient is removed from full ventilatory support and
placed one of the following for a few minutes to assess their ability to perform a more extended spontaneous breathing trial:
T-Piece Low level of CPAP (e.g., 5 cm H2O) and/or low
level of PS (e.g., 5 – 8 cm H2O) – on ventilator Automatic Tube Compensation (ATC) – on
ventilator
Considered a screening phase
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
Spontaneous Breathing Trial (SBT) - Abrupt Method
During the SBT the patient’s ability to tolerate unsupported ventilation is determined
Respiratory pattern Adequacy of gas exchange Hemodynamic stability Subjective comfort
A patient is considered ready for ventilator discontinuation when they can tolerate an SBT of 30 – 120 minutes
Discontinuation From Mechanical Ventilation
Weaning Techniques Methods of Titrating Ventilator Support
Spontaneous Breathing Trial (SBT) - Gradual Method Patient is removed from full ventilatory support and
placed on T-Tube, ATC, CPAP and/or PS for 5 and minutes and returned to full support for the remainder of the hour
Repeat process with progressively more time on T-Tube, ATC, CPAP and/or PS, working up to 20 – 30 minutes, and less time on full support
Full ventilatory support at night to rest patient
A patient is considered ready for ventilator discontinuation when they can tolerate an SBT of 30 – 120 minutes
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
Clinical Signs and Symptoms Indicating Problems RR >30 – 35 bpm Increases in RR >10 bpm from baseline, or RR <8
bpm Use of accessory muscles VT below 250 – 300 mL Blood Pressure
20 mm Hg systolic 30 mm Hg systolic Systolic values >180 mm Hg Diastolic values change 10 mm Hg
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
Clinical Signs and Symptoms Indicating Problems Heart Rate
>20% from baseline >140 bpm
PVCs – sudden onset (>4 – 6/hr) Diaphoresis, pallor, cyanosis Deterioration of ABG or SpO2 Agitation, anxiety, drowsiness
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
Clinical Signs and Symptoms Indicating Problems
Patients should not be allowed to experience extreme exhaustion during the SBT
Unnecessary prolongation of a failed SBT can result in muscle fatigue, hemodynamic instability, discomfort and worsening gas exchange
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
If the patient fails an SBT, the causes of the failure must be determined and corrected when possible
When the reversible causes of SBT failure have been corrected, and if the patient still meets the criteria for discontinuation of ventilation, an SBT should be performed every 24 hours
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
The clinical focus for the 24 hours after a failed SBT should be on maintaining adequate muscle unloading, optimizing comfort (and thus sedation needs), and preventing complications, rather than on aggressive ventilatory support reduction
When a patient fails an SBT, repeated testing the same day is of no benefit
Discontinuation From Mechanical Ventilation
Weaning Techniques SBT
To date no studies offer any evidence that a gradual support reduction strategy is better than providing full, stable support between once daily SBTs
Discontinuation From Mechanical Ventilation
Weaning Techniques Nonrespiratory Causes That May Complicate
Weaning Cardiac Factors
Acute CHF Acid-Base Factors
Patients with chronic hypercapnia fail to wean in the presence of relative hyperventilation, respiratory alkalosis and subsequent renal compensation, leading to a decrease in bicarbonate
Discontinuation From Mechanical Ventilation
Weaning Techniques Nonrespiratory Causes That May Complicate
Weaning Metabolic Factors
Electrolyte Imbalances Hypophosphtemia – muscle weakness Hypomagnesemia – muscle weakness
Hyopthyroidism – directly impair diaphragmatic function
Pharmacological Agents Opioids, tranquilizers, hypnotic agents
Depress central ventilatory drive Must be minimized for weaning to be successful
Discontinuation From Mechanical Ventilation
Weaning Techniques Nonrespiratory Causes That May Complicate
Weaning Nutritional
Inadequate nutrition may blunt response to hypercarbia and hypoxemia
Underfeeding may cause muscle wasting Overfeeding
Carbohydrates – Causes increased O2 consumption, CO2 production, and VE
Discontinuation From Mechanical Ventilation
Weaning Techniques Nonrespiratory Causes That May Complicate
Weaning Psychological Factors
Psychological ventilator dependence Anxiety, fear, delirium Agitation and/or panic during attempt to reduce or
D/C ventilatory support Lack of Motivation
Depression Effects of drugs Organic brain dysfunction Preexisting personality factors