Phys, Machines, Monitors Flashcards
The risk of radiation exposure
Inversely related to the square of the distance from radiation source
Risk = 1/square root of feet’s
Hagen-poiseuille’s equation
It investigate the steady flow of liquid through a capillary tube. (Describes the glow of fluids through IV cath)
States the flow (Q) of fluid is related to a number of factors:
Inversely to
- Viscosity (n) of fluid (increases with increasing H/H and decreases temp -> hence the benefiting using warmers)
- Length (L) -> shorter increases flow
Directly
- Pressure gradient across the tubing (P) -> elevating IV bags or squeezing it
- Diameter (r) of tube (increases flow rate by 16 folds)
Turbulent gas flow increases with increasing … and ….
In other words; Turbulent flow resistance depends on …. and …
Gas density and gas flow rate
- decreasing gas desensitized with helix instead of air helps to relieve airway obstruction (e.g. tracheas stenosis)
- decreasing gas flow rate as taking slower deep breaths also helps ventilation in obstructed patient
So decreasing density (decreasing resistance) and flow rate (decreasing Reynolds’s number) improves gas flow.
Reynold’s number > 2100, has become turbulent
Laminar has flow resistance depends on ….
Gas viscosity
What property of Heliox increases flow to laminar?
By reducing Reynolds number due to its lower density, heliox changes the turbulent to laminar
Heliox 70% and O2 30% mixture ( it has lower density than O2 but it’s viscosity is the same as O2)
The density of the gas … at high altitude, but viscosity….
Decreases and viscosity remains the same.
So the high flow will be affected in high altitude and the flowmeters will over read higher flows because the higher the flow the density decreases in high altitude
Where there is no effect at low flows as the flow is laminar and depends on viscosity which is unaffected by high altitude
Colors of cylinders
Green Blue Yellow Gray Black Brown
O2 N2O Air CO2 Nitrogen Helium
Volumes and pressured
O2
Air
N2O
625 L. 2000 PSI
625 L. 2000 PSI
1590 L 750 PSI
Characteristics of N2O cylinder
Stored as both liquid and compressed gas
As vaporized nitrous leaves the cylinder, more nitrous is vaporized.
Therefore, the pressure in the cylinder remains the same as long as there is any nitrous remaining in cylinder.
When the pressure begins to decrease, approximately 400L of nitrous remains in the cylinder
Dead space in circle system starts from … and can be reduced by placing a ….
From the Y piece
By placing a septum in the Y piece
The ideal position of circle system structure position from expiratory to inspiration
Expiratory unidirectional valve > pop off valve > circle absorber > fresh gas flow > inspiratory unidirectional valve
Best action When major crossover of O2 and N2O pipelines suspected
D/C patient from machine and ventilate with ambu bag with room air.
Maintain anesthetic with TIVA
(Turning on the backup O2 cylinder is not an option because it could be filled with N2O earlier before the suspicion)
Action when pipeline O2 fails and your backup O2 cylinder is low with O2
Turn of the ventilator and start manual ventilation
Because continuousventilationwith even low flows will empty the O2 early from the back up cylinder
What’s the most important safety feature in machine to prevent the delivery of hypoxia mixture
The inspired O2 analyzer
The best monitor to detect the expired limb disconnection during spontaneous ventilation is
Inspired oxygen analyzer
Mapleson’s A circuit vs Mapleson’s D circuit
A: prevents rebreathing during SPONTANEOUS ventilation
D: prevent rebreathing during CONTROLLED ventilation ( in order to prevent rebreathing during spontaneous, fresh gas need to be increased 3 times the minutes ventilation)
Bellows and circuit disconnection
Ascending va descending bellows
Ascending-> rose during expiration, will not fill during circuit d/c and therefore identify any disconnection
Descending-> falls during expiration, continues to raise and fall in event of circuit d/c and therefore can’t recognize a circuit d/c
When there is hope in the bellows, what effect or change seen on FIO2 in
O2 powered ventilation
Air powered ventilation
Increase in FIO2
Decreases
What is the saturated vapor pressure and what it depends on?
It’s the pressure exerted on the wall of the container at equilibrium
Depends on Temp of liquid and liquid physical characteristics (not on the barometric pressure).
Vaporizer output and its relationship to fresh gas flow?
The vapor output will decrease weather in low or high fresh gas flow rate
Vaporizer output at high altitude increases or decreases?
Increases (except Desflurane) as the potency decreases due to decrease in density of vapor, therefore no need to change the dial.
Desflurane remains the same as its electrically heated (boiling point for Desflurane is 23 degree and its heated to 39)
When Desflurane vaporizer alarms?
- agent level less than 20 ml
- tilting of vaporizer grater than 10 degrees
- power failure
To agents has the same saturated vapor pressure?
Halothane + isoflurane (~240 mmHg)
So they are the least error to occur in terms of vapor output if mistakenly filled with wrong agent
When is the sub-ambient pressure alarm identified? and what common cases of negative pressure?
The sub-ambient pressure alarm is intended to identify a breathing system pressure of
