Ventilators Flashcards
Generic anesthesia machine (not ventilator) included what 5 things?
A gas source (N2O, O2, air [cylinder & pipeline]), means to keep the patient asleep, gases get delivered to the circuit, valves/regulators (to regulate flows & pressures), & fail-safe valve/device (prevents a hypoxic mixture)
Ventilator includes what 3 things?
Gas delivery system, patient breathing system, waste gas scavenging system (prevents atmospheric contamination)
Ventilator types
Bellows (pneumatic), piston (electric)
Describe a bellows ventilator
Electrically controlled (need power), pneumatically driven, bellows have outer compartment where the driving gas enters to compress the bellow, inner compartment delivers gas to the patient breathing circuit
Describe pneumatically driven (how it works) ventilator
Pneumatically driven- pneumatic force compresses a bellows which empties it’s content (gas from flowmeters & vaporizer) into the circuit. The driving gas is oxygen, air or a venturi mix of oxygen & air
Descending versus Ascending bellows
Descending are weighted - during exhalation the bellows fall no matter what, ascending bellows filling is depending on exhaled gases from a tight circuit
Complications from descending bellows
If it becomes disconnected have no signal, may entrain air in the bellows and aspiration of air could create negative pressure in the lungs
What if there is a leak in the ascending bellows?
Bellows will not come up
How does a piston ventilator work?
Driven by compression from an electric motor - do not require driving gas. The tidal volume is equal to the surface area of the piston x the distance the piston moves to ventilate the patient
Piston advantages/disadvantages
Quieter, no baseline PEEP, greater precision, no gas necessary
Bellows advantages/disadvantages
Able to see disconnect, always have a PEEP of 3-5 in ascending bellows
Explain volume control ventilation
You set tidal volume & RR, minute ventilation remains constant, peak pressure will vary. Patient will never become hypoventilated unless their metabolic needs change, must monitor peak pressure (could cause barotrauma)
What are some reasons you would see a peak pressure rise?
Having laryngospasm, laparoscopic and belly is bigger, obstruction
Normal tidal volume
5-7 mLkg
Normal tidal volume delivered
8-10 mL/kg
Explain pressure control ventilation
You set peak pressure & RR, minute ventilation & tidal volume vary. You get a better volume for your pressure due to compensation in flow - total flow will fluctuate depending on lung compliance - volume will fluctuate depending on how much flow is required to reach the target pressure
If you have poor lung compliance in volume controlled ventilation, what will your pressure, flow & volume waveform look like?
Pressure will increase, the other 2 remain the same
If you have poor lung compliance in pressure controlled ventilation, what will your pressure, flow & volume waveform look like?
Volume will decrease and flow will decrease, pressure remains
Explain Pressure Control - Volume Guarantee (Aisys)
Delivers desired tidal volume with the lowest possible pressure using a decelerating flow pattern, vent automatically adjusts the pressure to achieve the volume that you would like it to achieve. Will determine patient compliance based on first volume controlled breath. Tidal volume not delivered warning will alert if tidal volume is not achievable at the pressure max less than 5 cm H2O of what you set
Explain Synchronized Intermittent Mandatory Ventilation
Combo of spontaneous & mandatory breathing- can set TV & RR or pressure & RR, supplements patient’s own respiratory effors
Explain pressure support ventilation
Used for spontaneously breathing patients, vent provides constant pressure to the airway to relieve the work of breathing once the vent senses an inspiratory effort
Explain pressure support ventilation-Pro
Has back up ventilation incase the patient stops breathing (15-30 seconds), set a minimum mandatory RR & pressure - in between mandatory breaths, patient receives support
