Chapters 6-13 Equiptment Flashcards
What is the splitting ratio when it comes to modern vaporizers?
Some of the gas passes through the vaporizing chamber and the rest of it goes to a bypass chamber. The ratio of the bypass:vaporizing channel depends on the concentration dial.
Most vaporizers are calibrated using O2 as the gas carrier. If you add NO2 to the carrier gas, what happens?
Temporarily reduced vapor concentrations
At high altitude and therefore low pressure, what happens to the partial pressure and percent concentration on modern vaporizers?
variable bypass concentration-calibrated vaporizers will deliver the same approximate partial pressure, but this will be at a higher volume percent.
What principle governs the flow of a bobbin through the thorpe tube and what is the equation?
Poisuilles Law.
Q= change in P*pi*r^4/8*viscosity*L Flow= change in pressure*pi*radius^4/8*viscosity*Length
What physical property of the gas determines flow in a Thorpe tube both at the top and at the bottom.
Low= Laminar= viscosity High= turbulent=density
Lonely Little Viking Has Tons of Dogs
What will make a Thorpe tube inaccurate?
Significant changes in pressure and temperature
If your Thorpe tube is not recalibrated at high altitudes, what will happen to the amount of flow you deliver?
Barometric pressure decreases, gives you more flow than you would expect.
At low flows, the gas flow is dependent on viscosity which is independent of altitude–this should be more accurate than at high flows where the gas flow is dependent on density
Where is the greatest accuracy on a Thorpe tube?
in the middle
In which position should the O2 be situated in relation to the NO2 and Air flowmeter sequence?
It should be positioned as far downstream, and therefore, to the right.
What type of circuit is the most efficient for controlled ventilation in terms of low flows?
Mapelson D (Bain circuit)
What type of circuit is the most efficient for spontaneous ventilation in terms of low gas flows?
Mapleson A
What are common circumstances in which rebreathing of CO2 may occur in a circle system?
Absortant problems (channeling, malfunction of color indictator)
Unidirectional valve problem
~inspiratory valve stuck open= during expiration alveolar gas can backfill the inspiratory limb
~expiratory valve stuck open= ONLY IN SPONTANEOUS BREATHING PATIENT, negative pressure generated by the patient can entrain alveolar gas from the expiratory limb.
What are potential complications of doing mainstream sampling for CO2 capnography?
placed close to ET tube, must be heated to 40degrees, can burn a patient.
**Benefit- response time is faster
What are ways of doing CO2 measurement?
1) Infrared spectrometry- analyzing infrared absorption through the gas sample and compares with known values. Water vapor can interfere and lead to falsely elevated CO2 levels.
2) Mass spectrometry- can measure gases O2 and N2 that infrared spect cannot measure. Disadvantages- cost, size and warm up time.
3) Colorimetric detection- pH sensitive paper
What are the 4 phases in a capnograph waveform?
Phase I= valley= inspriation and CO2 should be 0
Phase II= beginning of expiration with CO2 rising rapidly as we are looking at deadspace ventilation
Phase III= top of plateau- alveolar gar
Phase IV= beginning on inhalation with steep descent
