Advanced Ventilation Flashcards
Platue Pressue
Is defined as airway pressure during the end expiratory pause and roughly reflects the level of alveolar over distension
Obstructive lung diseases
Cystic Fibrosis
Asthma
COPD
Bronchiectasis
Restrictive lung diseases
Lungs are restricted from fully expanding, making it difficult to inhale and fully expand the lungs
Interstitial lung disease
Sarcoidosis
Neuromuscular disease
Pulmonary fibrosis
Asbestosis
Plateau Pressure
Pressure in the alveolar at the end of inspiration prior to expiration
A useful marker of lung hyperinflation and should be maintained at less than 30cmH2O- if greater than 30 there is potential for alveolar injury
What does it indicate If there is an increasing plateau pressure?
Reducing lung compliance
An increased Peak pressure (PIP) and normal plateau pressure indicates
An increase in airway resistance
If peak pressure (PIP) and plateau pressure and increased what does this indicate?
A decreased lung compliance
Causes of increased airway resistance
Bronchospasm
Excessive secretions
Mucus plug
Foreign body aspiration
Extrinsic airway compression/biting the ETT
Causes of decreased compliance
Pulmonary oedema
Pleural effusion
Pneumothorax
Right main stem bronchus intubation
Ascites or other abdominal distension
Shunt
Perfusion without ventilation
Dead space
Ventilation without perfusion
Restrictive disease ventilation management
Increase inspiratory time
Look at pt position
Reduce PIP’s
Change to pressure control
PEEP to recruit alveoli
Permissive hypercapnia
Inspiratory hold on MV
Demonstrates compliance and any airway resistance:
Plateau pressure (P.Plat)
PIP/P.Plat
Difference
PIP
Caused by inspiratory flow rates
Tidal volume
Increased airway resistance
Decreased lung compliance
Decreased chest wall compliance
Normally set to 20-30cm
RAW
= resistance
Permissive hypercapnia
Deliberate limiting of ventilation with low tidal volumes (5mls/kg), in order to decrease alveolar overdistention
Gradual increase of PaCO2 by gradually decreasing Vt/rate
Gas tracheal insufflation may be used to reduce effects
Advantages of permissive hypercapnia
Reduction of barotrauma/voluntarism
Increased PaCO2 enhances oxygen unloading at the tissue level
Adverse effects of acidosis minimised with gradual rise of PaCO2 as metabolic compensation occurs
Disadvantages of of permissive hypercapnia
Acute rises in PaCO2 causes depressive effects on the CNS and CVS
Reduces the affinity of Hb for oxygen uptake in the lungs
Rapid rise in CO2 leads to respiratory acidosis
Prone positioning
May improve oxygenation and decrease the degree of shunt
Adverse effects associated with prone position for ventilation
Decreased enteral nutrition
ETT obstruction or dislodgement
Increased ICP
Difficulty monitoring the pt
Labour intensive
Facial oedema
Mechanical Ventilation in Asthma
Increase expiratory time:
Slow respiratory rate
Fast flows
No unnecessary inspiratory pauses
Decreased tidal volumes of plat pressure rising
Aim for MV approx 6L/min
Asthma management
Bronchodilators
Corticosteroids
NIV/NIPPV
?heliox
COPD management
Oxygen
NIPPV/NIV
Bronchodilators
Steroids
?heliox
Early nutrition
Physio therapy
Antibiotics if infective component
Mechanical ventilation in COPD
PEEP may be helpful to:
Decrease WOB
stents collapsible airways
Increases expiratory flow
Extubation
Can the patient ventilate and oxygenate?
Do they have a gag reflex
Are vitals WNL
Resolution of the process necessitating intubation
Can pt be easily roused and follow commands
Was it a difficult intubation
Minute ventilation
Vt x RR
PIP (peak pressure)
Is the highest pressure measured during the respiratory cycle.
PIP reflects airway resistance
Factors that generate PIP
Inspiratory flow rate
Tidal volume
Strategies to minimise barotrauma in obstructive lung disease
Reduce tidal volume
Reduce breath rate
Increase expiratory phase
Strategies to minimise barotrauma in restrictive lung disease
Pressure control
PEEP
inverse ratio ventilation
Prone positioning
Vent settings VC
Volume control- the ventilator delivers a preset Vt
Vent settings - PC
Pressure control- preset maximum pressure is delivered during inspiration
CMV
Continuous mandatory ventilation- preset number of mandatory breaths at a preset volume/pressure
Volume assist/control ventilation (A/C)
Preset mandatory breaths at preset volume/pressure; patient can trigger spontaneous breaths between mandatory breaths. Spontaneous breaths are “topped up” to match volume of mandatory breath.
SIMV
Synchronised intermittent mandatory ventilation. Preset number of breaths of a preset volume/pressure; patient triggers spontaneous breaths which are variable
I:E ratio
The shorter the inspiratory time the longer the expiration time
Generally set at 1:2
Eg: 1:2 means 33.33% breath cycle is inspiration and 66.66% is expiration
Flow Rate
Speed at which the Vt is delivered
Average settings 40-60L/min
High flow rate classified as >60L/min
*flow rate changed by altering inspiratory time
Decrease inspiratory time= increase flow rate
Increasing inspiratory time = decreases flow rate
Pressure support
Support spontaneous breaths when SIMV used
Generally set at 5-10cmH20
Disadvantages of Positive pressure ventilation
Decrease cerebral perfusion (CCP)
Raised ICP
Cerebral hypoxia
Lung protective strategy
Focused on low tidal volume ventilation to reduce ventilator associated lung injury such as barotrauma and volutrauma. Can be chosen on any pt except pts who have obstructive disease ( asthma, COPD)
High plateau pressures
Decrease the tidal volume 1ml/kg until plateau pressure of less than 30cmH2O is achieved. Tidal vols of 4ml are accepted.
In such cases you will likely need to increase RR to maintain PaCO2 goals.
Consider permissive hypercapnia if RR limits reached
Paediatric ventilation settings
Mode: PCV
PEEP - 5-15 (should not exceed 15)
PiP - determines the pts Vt. Can start between 15 And 20 cmH20 greater than PEEP (should not exceed 30 cmH20)
Observe chest rise and fall
The achieved Vt should be approx 6-8ml/kg IBW (lung protective ventilation)
Increased airway resistance
Asthma/bronchospasm- administer bronchodilators
Mucus plugging - airway clearance therapy
Kinked or obstructed tube
Indications for MV
Apnoea
Inability to protect airway
Respiratory distress
Inability to sustain adequate oxygenation
Respiratory acidosis
Post op respiratory failure
Shock states
