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Mechanical Ventilation Mind Map 2, How does the ICU decide on ventilator…
Mechanical Ventilation
Mind Map 2
What patients need intubation or
mechanical ventilation?
Respiratory failure (despite max therapy)
Not tolerating NIV
After major surgery/haemodynamically unstable
Sepsis
Impaired mental state
Indications on ABG
PaO2 <60 (hypoxic)
PaCO2 >60 (T2RF)
pH <7.25
Indication on Obs
RR >35/min
Reduced tidal volumes
Increased WOB
Severe dyspnoea, paradoxical breathing
Ventilator settings that Physio
needs to assess
PIP (peak insp
pressure)
Usual setting (adult) <40cmH2O
PEEP
Indicated with PaO2 and Fio2 >0.49
Increases FRC
Improves PaO2 but takes a while to build up (when disconnected/removed, PaO2 drops quickly -->
clinical consideration
PEEP to overcome deadspace of tubes 3-5cmH20
Precautions: barotrauma, increase ICP, over-extending lung tissue, reduce cardiac output, increase pulmonary vascular resistance
Usual setting 5-15cmH2O
Tidal Volumes
Usual setting 6-8ml/kg
Resp rate
12 for adults
Flow
Usual setting 50-100L/min
I:E ratio
and time
Healthy population (2:3), ICU usually 1:3
IE can be
inverted
to improve gas distribution and oxygenation.
clinical consideration
: avoid breath stacking is patient exp phase is not long enough
Sensitivity (for breath triggering)
Pressure
Support (PS)
Usual setting for adult 5-20cmH2O
Modes of Ventilation
Controlled Mandatory Ventilation
Patient gets preset number of breaths
Patient effort
DOES NOT
trigger mechanical breath
Ventilator performs all WOB
Indications:
Patients with no resp effort (eg C2 spinal cord injury, Gullian-Barre)
Fail-safe method of ventilating patient for backup (eg under anaesthesia)
Disadvantages
Patient-vent asynchrony if patient tries to take a breath
Resp muscle weakness from not being used
SIMV
Set number of breaths of a set tidal volume (VT)
Patients can have a spontaneous breath then vent delivers mandatory breath in synchrony
Allows patient to set own RR
Advantages
Less atrophy of resp muscles
better distribution of gas during spont breathing
Disadvantages
SIMV associated with longest weaning and lowest success rate
Pressure
Support (PS)
Patient's SPONT breathing effort is assisted by vent by delivering set amount of insp positive pressure
No set tidal volume - variable with patient effort, PS, lung compliance
Advantages
overcome resistance of breathing into artificial airway
Patient retains control over RR, insp time and VT. Better patient-vent synchrony
Good to use at end of weaning = lets patient do more work
Disadvantages
VT is variable = aleolar ventilation is not guaranteed if compliance changes
Pressure Control
Preset RR and set amount of breath delivered to insp pressure
No set VT. VT is variable based on insp pressure, insp time, compliance and resistance
Protects airways from injury
Indicated for people with very poor lung compliance and have high airway pressures
Advantages
Constant pressure of air
maintains open airways and improves gas distribution
splints airways
reduced risk of barotrauma
Disadvantages
Mean airway pressure increases (sustained at PIP throughout inspiration) = can reduce cardiac output due to lung distention
Pressure
Regulated
Volume Control
(PRVC)
Preset no. of breaths at present VT. Vent aim to get target VT breath using lowest possible pressure
Re-assesses breath volumes based on calculated pressure to deliver VT
Vent always goes to lowest pressure to get desired VT
For patient safety, upper pressure limit should be set as low as possible
suitable patient who don't have reliable resp drive, non-compliant lungs, patients with changing compliance
Disadvantages
Vent may continue to deliver breaths if there is an cuff leak or pneumothorax (keep pushing air in)
Complications of
Mechanical Ventilation
Barotrauma leading to pneumothorax, pneumopericardium, pneumomediastinum
Infection (ventilator acquired pneumonia)
Oxygen toxicity
Resp mm weakness
tracheal trauma
Reduced cardiac output
What are the effects of long
term ICU admissions and mechanical
ventilation?
Physical
Bed rest = loss of mm strength (reduction in sarcomeres, reduction in mitochondria, decrease in motor unit firing time), reduced bone density
CAN LAST FOR 1 YEAR
Reduced FVD and PaO2, exertion dyspnoea, reduced pulmonary function
Communication
Effects of tracheostomy/ETT, damage to larynx
Speaking value on tracheostomy
Difficulty writing/speaking due to cognitive changes
Social
Increased supports on d/c from hospital
More reliance on family
More dependent with PADLs and ADLs
Sensory
Changes in vision/hearing, pain problems
Cognition
Consider: Older ICU population due to ageing
Loss of memory, attention deficits
Sequencing problems, disinhibition, poor insight
reduced executive functioning
Psychological
Anxiety, depression, PTS related symptoms
Withdrawal, delusions, hallucinations, nightmares
Considerations for Rehab & Long Term Management of Mechanically ventilated patients
All mechanically ventilated patients should be reviewed by MDT after D/C from ICU
Start rehabilitation as early as possible
Set short and long term goals for patients
Educate on the long term effects of ICU admission
Functional reassessment at 2-3 months after patient's discharge (community follow up)
How does the ICU decide on ventilator settings?