Physics And Equipment Flashcards
Why is Helium useful in cases of airway constriction/masses?
Helium has a much lower density and will improve turbulent flow
Describe N2O Gas Cylinders
Blue
Contain 1590L of gas at 750PSI
Gauge will continue to read 750PSI, until only 1/4 of gas (~400L) remains
What is Laplace’s Law?
Tension = (Pressure x Radius) / Thickness
The surface tension of a sphere is directly proportional to the radius and pressure within the sphere
Describe the 4 Main Gas Laws
Henry’s Law - at constant temperature, the concentration of a dissolved gas is directly proportional to the partial pressure of that gas (i.e. increasing the dial on a gas vaporizer)
Boyle’s Law - a fixed mass of gas at constant temperature will have a constant pressure-volume relationship (P1V1=P2V2)
Gay-Lussac’s Law - the pressure of a given mass of gas is directly proportional to its temperature when at a constant volume (i.e. pressure of an ETT cuff increasing with increased temperature)
Dalton’s Law - the total pressure exerted by a mixture of gases is the sum of the individual gases’ partial pressure (i.e. requiring higher concentrations at higher altitudes)
Describe O2 Gas Cylinders
Green
Contains 625L at 2000PSI
What are the roles of 1st- and 2nd-stage regulators?
1st-stage regulators reduce pressured to 45PSI
2nd-stage regulators reduce pressure to around 15PSI
What is the anesthesia machine fail safe valve?
Also called the pressure sensor shut off valve
Functions to prevent delivery of hypoxic gas mixtures
When O2 pressure drops below 25PSI, valve discontinues the flow of N20
How does transducer level effect A-line blood pressure readings?
A difference of 10cm results in a change of 7mm Hg
List the volatile agent vapor pressures
Sevoflurane = 160 Enflurane = 172 Isoflurane = 240 Halothane = 243 Desflurane = 669
What is the formula for anesthetic volatile concentration delivered?
(vapor pressure x flow through vaporizer) / [(barometric - vapor pressure) x (flow through vaporizer + dilutent flow)]
Describe the phases of the CO2 Capnogram
4 Phases:
1) Inspiratory baseline
2) Expiratory upstroke - mixing of gas from dead space and alveoli
3) Expiratory baseline - CO2 rich alveolar gas
4) Inspiratory downstroke
What is the maximum FiO2 that can be delivered via nasal cannula?
45%
4% per liter (up to 6L) over the 21% found in room air
Describe pacemaker nomenclature
First letter identifies the chamber paced
Second letter identifies which chamber is sensed
Third letter describes the response
What is the reason for the difference between EtCO2 and arterial CO2?
Alveolar dead space
What is the difference between minute ventilation and alveolar ventilation?
Minute ventilation = tidal volume x respiratory rate
Alveolar ventilation = (tidal volume - dead space) x respiratory rate