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
