Ventilators Flashcards
What are the four methods of ventilator cycling?
Time, volume, pressure, flow
The ventilator is ____ controlled and ____ driven.
The ventilator is electronically controlled and pneumatically driven.
What are the 3 ventilator modes?
Pressure Control, Volume Control, SIMV
What should the flow rate be set at?
5 times the minute ventilation
What is the physiologic I:E ratio?
1:2
What is the equation for time of inspiration?
TV/ Flow Rate
How much O2 does one gram of fully saturated hemoglobin combine to?
1.39ml
How do you calculate dissolved O2 based on PaO2?
0.003ml O2/100 ml blood/mmHg
How do you calculate dissolved CO2 based on PaCO2?
0.067ml CO2/100ml blood/mmHg
Is IMV ventilator setting synced with patient breaths?
NO- used for weaning
Is SIMV synced with patient breaths?
YES- used for waking pt up in OR
What is the difference between AC and SIMV?
Assist control delivers the same TV( or pressure) for each patient initiated or time initiated breath. SIMV does not deliver a set TV for any additional breaths taken by the patient about the set rate.
How are vents mainly classified?
By their inspiratory flow characteristics and method of cycling
What are some examples of inspiratory characteristics?
Constant flow, non-constant flow and constant pressure
What are some methods of cycling?
Time cycled, volume cycled, pressure cycled, flow cycled.
What are some possible power sources for ventilators?
Compressed gas only, piston power only, compressible bellows-gas and power
What are some possible drive mechanisms for ventilators?
Double circuit bellows compressed by driving gas, piston-bellows compressed by electricity
Define pressure, where is pressure encountered, what is the amount of backpressure generated a result of?
Pressure is the impedance to gas flow rate, impedance is encountered in the breathing circuit as well as the patient’s airways and lungs. The amount of backpressure generated as a result of airway resistance and lung-thorax compliance
Describe an inspiratory pause/sigh.
The volume of gas delivered to the pt is held in the patients lungs to increase inspiratory time by 25%
What does the low pressure alarm detect?
A drop in peak circuit pressure like there would be during a disconnect
What is the most important monitor on the machine?
The oxygen analyzer. Calibrate at 21% O2.
What monitor can be used to reveal a disconnect?
ETCO2
What are some differences between ICU vents and Anesthesia vents?
ICU vents are more powerful allowing for greater inspiratory pressures and tidal volumes, anesthesia vents have a CO2 absorber, ICU vents have more modes of ventilation, gas supplied by the ICU ventilator directly ventilates the patient while the anesthesia driving gas never reaches the patient, bellows are essential in the anesthesia vent
Describe the IMV vent setting.
The machine delivers a set tidal volume at a set time. The patient can still breath spontaneously. It is not synched with the patient. Fixed rate. Used as a weaning technique
Describe the SIMV vent setting
Like IMV but synched with the patient’s effort. The patient breaths spontaneously and at a predetermined interval the spontaneous breath is assisted by the machine
Describe AC ventilation
Intermittent mode of positive pressure ventilation. The patient’s inspiratory effort triggers the vent to deliver a preset TV. If the patient’s rate drops below a preset minimum rate the machine takes over. Can be pressure controlled or volume controlled, all breaths the patient takes are fully assisted by the ventilator
Describe pressure support ventilation
Aids in normal breathing with a predetermined level of positive airway pressure. Decreases the work of breathing and delays muscle fatigue.
Describe high frequency ventilation.
Low tidal volumes with a high rate. 100-200bpm typical. Goal is to maintain gas exchange at lower mean airway pressures
Describe pressure control ventilation
Patient or time triggered pressure limited, time-cycled mode of ventilation. Gas flow decreases as airway pressure rises and ceases when airway pressure equals the set peak pressure. TV is not fixed.
Describe CPAP
Continuous positive pressure is maintained during inspiration and expiration.
