Ventilators

Question 1

Generic anesthesia machine (not ventilator) included what 5 things?

Answer 1

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)

Question 2

Ventilator includes what 3 things?

Answer 2

Gas delivery system, patient breathing system, waste gas scavenging system (prevents atmospheric contamination)

Question 3

Ventilator types

Answer 3

Bellows (pneumatic), piston (electric)

Question 4

Describe a bellows ventilator

Answer 4

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

Question 5

Describe pneumatically driven (how it works) ventilator

Answer 5

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

Question 6

Descending versus Ascending bellows

Answer 6

Descending are weighted - during exhalation the bellows fall no matter what, ascending bellows filling is depending on exhaled gases from a tight circuit

Question 7

Complications from descending bellows

Answer 7

If it becomes disconnected have no signal, may entrain air in the bellows and aspiration of air could create negative pressure in the lungs

Question 8

What if there is a leak in the ascending bellows?

Answer 8

Bellows will not come up

Question 9

How does a piston ventilator work?

Answer 9

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

Question 10

Piston advantages/disadvantages

Answer 10

Quieter, no baseline PEEP, greater precision, no gas necessary

Question 11

Bellows advantages/disadvantages

Answer 11

Able to see disconnect, always have a PEEP of 3-5 in ascending bellows

Question 12

Explain volume control ventilation

Answer 12

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)

Question 13

What are some reasons you would see a peak pressure rise?

Answer 13

Having laryngospasm, laparoscopic and belly is bigger, obstruction

Question 14

Normal tidal volume

Answer 14

5-7 mLkg

Question 15

Normal tidal volume delivered

Answer 15

8-10 mL/kg

Question 16

Explain pressure control ventilation

Answer 16

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

Question 17

If you have poor lung compliance in volume controlled ventilation, what will your pressure, flow & volume waveform look like?

Answer 17

Pressure will increase, the other 2 remain the same

Question 18

If you have poor lung compliance in pressure controlled ventilation, what will your pressure, flow & volume waveform look like?

Answer 18

Volume will decrease and flow will decrease, pressure remains

Question 19

Explain Pressure Control - Volume Guarantee (Aisys)

Answer 19

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

Question 20

Explain Synchronized Intermittent Mandatory Ventilation

Answer 20

Combo of spontaneous & mandatory breathing- can set TV & RR or pressure & RR, supplements patient’s own respiratory effors

Question 21

Explain pressure support ventilation

Answer 21

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

Question 22

Explain pressure support ventilation-Pro

Answer 22

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