Ventilators Flashcards
Why are ventilators important?
Gas exchange
What is qualitative and quantities ventilation?
Qualitative ( efficiency of ventilation, CO2 elimination, oxygenation)
Quantitative ( breathing in and out respiratory rate Tidal volume)
How is ventilation different to spontaneous breathing?
Ventilation forces air into the lungs
Spontaneous breathing generates negative pressure allowing the lungs to fill with air
What is the tidal volume?
Normal volume of lungs
Can exaggerate insp and esp if need be
How do you calculate minute volume?
Tv x respiratory rate
What is compliance of the lungs?
Change in volume for any given pressure (ability to stretch)
What controls ventilation within the dog and cat?
Respiratory centre in the medulla and pons
There are stretch receptors in the lungs and peripheral chemoreceptors that will alter ventilation if the pH and CO2 alters
What are the indications for quantitative and qualitative ventilation?
Quantitative failure to breath (drugs, control damage, cervical lesion, tetanus)
Qualitative drug induced depression V/Q mismatch
Lung disease
Prevent respiratory exhaustion
What two ways can you give ventilation?
IPPV ( manuallynor mechanically)
Negative pressure ventilation
(HF jet ventilation)
How do you control ventilation what are the types of ventilation and the types of breath?
Manually vs mechanically
Controlled and assisted
Volume controlled and pressure controlled breath
Name the two types of ventilation?
Rebreathing ambu bag (demand valve, short inspiration, assess thoracic movements)
Ventilators
What are the pros and cons of using a rebreathing bag?
Pros Easy economic does not depend on conditions can be less harmful than ventilators Cons Depends on operator Irregular administration of breaths Poor control of ventilatory parameters
What are the pros and cons of ventilators?
Pros Automatic Set regular breaths Allows different types of ventilation Additional features PEEP CPAP Cons Requires equipment and power More complicated to operate Risk of injuries
Describe spontaneous breathing and how it is controlled?
Inspiratory flow determined by the patient
Breath terminated by the patient
Breath initiated by the patient
Describe assisted ventilation and how it is controlled?
Inspiratory flow determined by the ventilator
Breath terminated by the ventilator
Breath initiated by the patient
Describe supported ventilation and how it is controlled?
Inspiratory flow is controlled by the ventilator
The breath is ended via the patient
The breath is started via the patient
Describe mandatory controlled ventilation and how it is controlled?
Inspiratory volume is controlled by the ventilator
Breath is ended by the ventilator
Breath is started by the ventilator
Describe the types of mandatory ventilation?
Continuous mandatory
intermittent mandatory
What are the additional features of the mandatory ventilator?
Pressure support ventilation ( flow delivered by ventilator)
Positive End Expiration Pressure ( Small amount of air left in the lungs)
Continuous Positive Airway Pressure (CAP) same as PEEP but always on spontaneous breathing
What are the two methods of controlling IPPV?
Pressure controlled (dangerous if open thorax) Volume controlled (set volume at the end of inspiration)
What are the risk of IPPV to the cardiovascular system?
Decreased cardiac output decreased venous return Direct affect on the heart Poor perfusion of the organs increased sympathetic, RAA and ADH (increase blood pressure)
What are the risks of IPPV directly on the lungs?
Trauma (barotrauma)
Very high pressure required in supported lungs
volumtrauma
Shear stress effect
volutrauma/atelectotrauma (ventilator induced lung injury, large scale inflammation)
oxygen effects ( 100% less than 6 hours reduce o2 to 30/40% to reduce free radicals)
Risks of IPPV acid base disturbances?
Sympathetic effect of high CO2 affect on cerebrl perfusion <20mmhg vasconstriction and poor perfusion >60mmhg vasodilation, affect on ICP metabolic impact
What are the ventilators variables and settings?
Breathing frequency Tidal volume/minute volume I:E ratio Inspiratory time/expiratory time inspiratory flow rate Peak inspiratory pressure Positive End Expiratory pressure
What is the calculation for minute volume?
Tv X RR
What is the calculation for respiratory rate?
60/ (inspiratory time+expiratory time)
What is the calculation for tidal volume|?
inspiratory time X inspiratory flow rate
What are the three control phases of breathing for ventilators?
Cycling-end of inspiration
Triggering_end of expiration
Limitting-maximum
What re they types of triggering ventilators that you can get?
Time triggered (Set expiratory time) Pressure triggered (negative pressure generated by the patient) Volume triggered (set expiratory volume) Flow triggered (detection of decreased expiratory flow)
What are the types of ventilators that are cycling?
Time-cycled (set inspiratory time) Pressure cycled (changeover when pre-determined pressure is reached) Volume-cycled (change over when determined volume is reached) Flow- cycled (changeover when flow decreases to pre-determined value)
What are the types of ventilators that are limiting?
Safety, set maximum value pressure-limiting (max pressure) Volume-limiting (max volume) Flow limiting (max flow) can stop inspiration prematurely (before set value)
List the four different types of ventilators?
Bag squeezer (horizontal, Ascending, descending)
Intermittent blower
Mechanical thumb
Volume divider
List the different types of bag squeezer and the type of ventilator that they are?
Mie ventmaster (time-cycled, can set up exp and insp time, volume will set flow)
Hallowell EMC 2000
Time-cycled pressure limited (alarm will sound)
JD medical (equine)
pressure-cycled pressure limited
Describe the characteristics of a bag squeezer
bag in a bottle (bellow) connected to a bag port
Mimics the effect of a hand regularly pressing on the bellow
if the bag doesn’t fill full there is a leak in the system
Describe the characteristics of the mechanical Thumb
T-piece valve is occluded on expiratory limb
Newton valve - action depends on flow from ventilator, associated with ventilator
Air is forced back into the patient inspiration time is the time the valve is occluded for
Tidal volume= flow rate and occlusion
Name a mechanical thumb ventilator
Vetronic SAV03
change flow rate impact on the volume and pressure on the airways
Describe the characteristics of the intermittent blower
Proportional flow valve (electronically timed and activated).
or pneumatically timed oscillator (powered by both gas and electricity)
Divides the driving gas up into tidal volumes of a set size and rate
List two intermittent blowers and their characterisitcs
Merlin
microprocessor-control precision piston
time, pressure or volume (piston pushes air in and out, will stop if patient starts fighting it)
Nuffield
Pneumatic oscillator (driving gas makes ventilator work tidal volume= exspiratory flow and inspiratory flow
time-cycled
set inspiratory time, flow
Describe the characteristics of a minute volume divider
continuous flow of gas into reservoir air is delivered to the patient via positive pressure pressurised reservoir by a weight fresh gas flow= intended minute volume divided up into the required BPM expensive in terms of gas flow FGF over one minute= minute volume
Name a minute volume divider
Manley MP3 spontaneous= mapelson D main bellow/storage bellow volume triggered (when storage full) volume-cycled set tidal volume and insp time
How do you start ventilation?
NMBA
decrease co2 ( drops below the level which triggers breathing give an extra breath)
decrease sensitivity to co2 (drugs, opiods, midazolam )
How do you set up a ventilator?
t-piece connect it to expiratory limb
Bain, circle connect to the re breathing bag port
close the apl valve
adjust the flow rate
How do you set up the minute volume for a ventilator?
tidal volume 10-15ml (start smaller in compromised patients, increase progressively, adjust according to monitoring|)
breathing rate pre-op (may need to be higher initially to control breathing)
adjust according to monitoring
How do you set up the inspiration and expiration volume for a ventilator?
Short inspiration long expiration I:E ration 1:2 adjust according to RR
Inspiration shorter if RR higher
Expiration is passive and gives the lungs time to recoil
What monitoring equipment should you use whilst ventilating?
Spirometery
capnography
Spo2
blood gas analysis
How does spirometery work?
Volumes and pressures administered effectively
dynamics of ventilation (compliance)
Visualisation of PEEP
How doe a capnograph work during ventilation?
EtCO2 value hypo/hyperventilation
adjust on qualitative basis
detects problem with the system rebreathing, occlusion
How is blood gas monitoring used during ventilation?
Best way to assess ventilation/oxygenation
Discontinuous monitoring
How do you stop ventilation?
Make sure spontaneous breathing is possible
antagonise NMBA
decrease/stop resp depressant drugs
allow CO2 to rise decrease ventilation
