Ventilators and ventilation Flashcards
What is spontaneous ventilation?
air is drawn into the lungs under negative pressure
What is manual ventilation?
using a breathing system to deliver breaths to your patient
What type of ventilation is manual and mechanical ventilation?
positive pressure ventilation
What does manual and mechanical ventilation do?
forces air into the lungs and is no longer being drawn in under negative pressure, it is pushed in under positive pressure
What factors affect spontaneous ventilation?
- anatomical/physiological such as airway obstruction stenotic nares, excess tissue around airway, hypoplastic trachea and obesity
- external factors such as the ET tube and external restriction such as sandbags
- effusions
What are the indications fo assisted ventilation?
reduced drive to ventilate and inability to ventilate or ventilate effectively
What can cause decreased ventilatory drive?
- anaesthetic drugs
- central nervous system disease such as raised ICP, encephalopathy and hypothermia
What causes the inability to ventilate?
- open thoracic cavity
- muscle failure (NMBAs peri and post, myasthenia gravis)
- nerve failure - intercostal and diaphragmatic
- external factors effecting lung inflation
How do you recongise the need to ventilate?
- ventilatory pattern
- tidal/minute volume - spirometry
- blood gases
- end tidal carbon dioxide
- pulse oximetry
What are the advantages of manual ventilation?
easy to perfrom and cheap as it doesnt need much equipment
What are the disadvantages of manual ventilation?
- dependant on the operator
- poor control of airway pressures
- each breath may be different
- operator fatigue
- can be boring as time consuming
What are the advantages of mechanical ventilation?
allows a hands-free anaesthetic and ensures appropriate volumes of gas are administered
What are the disadvantages of mechanical ventilation?
- not always available
- expensive
- requires skill
What are the cardiovascular side effects of IPPV?
- decreased cardiac output (due to increased pressure within thorax)
- decreased venous return
- reduced stroke volume
- reduced pre-load
- reduced BP
What effects on the lungs are there due to IPPV?
barotrauma
What other effects of IPPV are there?
sheer stress effect and oxygen toxicity
What is the renin angiotensin aldosterone system?
- sympathetic nervous system notices decreased blood pressure
- triggers increased heart rate
- increased heart rate leads to increased cardiac work load
- increased cardiac work load leads to increased oxygen requirement
- RAA system kicks in leading to vasoconstriction/urine retention and ADH release
How can you monitor the efficacy of ventilation?
- observation
- auscultation
- capnography
- pulse oximetry
- arterial blood gas
When observing efficaacy of ventilation, what are you observing?
- thoracic movements
- the way abdomen rises and falls
When observing efficaacy of ventilation, what are you auscultating?
- can you hear air entering both lungs
What should you consider if you cannot hear sounds/air entering both lungs?
- bronchial intubation
- atelectasis
- mass affecting lung expansion
- fluid or other material in pleural space
What should you do if there is high ETCO2?
increase minute volume
What should you do if there is low ETCO2?
reduce minute volume
What is a ventilator?
a medical ventilator is a machine designed to provide mechanical ventilation to a patient, by moving air into and out of the lungs
Why might we need a ventilator?
- apnoeic/poorly ventilated patient
- neuromuscular blocking agents
- thoractomy
- diaphragmatic rupture
What ventilator settings are there?
- frequency of breathing
- tidal volume/minute volume
- I:E ratio
- inspiratory flow rate
- PIP (peak inspiatory pressure)
- PEEP (positive end pressure ventilation)
What is PIP / peak inspiratory pressure?
the highest pressure measured during the respiratory cycle
What is PEEP / positive end pressure ventilation?
pressure applied by the ventilator at the end of each breath to ensure that alveoli are not prone to collapse
What is ventilation cycling?
the change from inspiration to expiration
What are the four variables used to determine when to cycle expiration?
1 - pressure
2 - volume
3 - time
4 - flow
What is pressure controlled ventilation?
- the ventilator maintains a set airway pressure for a set inspiratory time
- inspiratory flow of gas is delivered until a trigger pressure is reached and this will cause insiratory cut off and will begin expiratory cycle
When should you avoid pressure controlled ventilation?
thoractomy
What is volume controlled ventilation?
- set tidal volume
- set pressure limit
- set rate, inspiratory time or I:E ratio
What does volume controlled ventilation not rely on?
airway compliance change
What is time controlled ventilation?
time cycling indicated that the ventilator breath has switched from inspiration to expiration after a set time is reached
How do you use time controlled ventilation?
set the rispiratory rate, inspiratory time, or ins:exp ratio
What is flow cycling?
when the ventilator delivers a set flow until the total volume has been delivered
What is assist control mode?
the breath is initiated by the patient
What is control mdoe?
the breath is controlled by the machine
What are inspiratory:expiratory ratios I:E?
refers to the ratio of inspiratory:expiratory time in normal spontaneous breathing
What is the standard I:E ratio?
1:2
How can you remember what the I:e is?
the expiratory time is usually approximately twice the inspiratory time
What types of ventilators are there?
- bag squeezer (ascending, descending and horizontal bellow)
- mechanical thumn (like a t-piece)
- intermittent blower
- volume divider
What is a bag squeezer ventilator?
- sets volume, I:E time
- pressure guage
- can set tidal volume
- connected to bag port
What is a hallowell EMC 2000?
time cycle and pressure limited
What is a JD medical bag squeezer?
pressure cycled and limited
What is a mechanical thumb?
essentially a thumb on a t-piece and used in small anaesthesia
What does an intermittent blower do?
takes the driving gas and divides it into smaller volumes and uses that to push the gas into the patient
What is a merlin intermittent blower?
microprocessor - controlled precision pistol, time pressure or volume set
How can you care for a patient during long periods of ventilation?
- mouth care
- humidification of gases
- endotracheal tube care - suction, deflate cuff and reposition
- monitoring efficacy of ventilation
- periodic sigh?
- physiotherpay
- turning patient
- eye care
- limb mobilisation
