VALLEY: EQUIPMENTS & INSTRUMENTATION Flashcards
In which publication is the purity of medical
gases specified? What agency enforces the
purity of medical gases in the United States?
The purity of medical gases is specified in the United States Pharmacopoeia and is enforced by the Food and Drug Administration (FDA).
Which United States government agency
regulates matters affecting the safety and
health of employees in all industries
The U.S. government regulates matters affecting the safety and health of employees in all industries through the Department of Labor
In 1970, the U.S. Congress passed the Occupational Health and Safety (OSHA) Act. Which two executive-branch agencies were created to carry out the provisions of OSHA
The Occupational Health and Safety Act (OSHA) created two separate executive- branch agencies to carry out the provisions of the act: ( 1) the National
Institute of Safety and Health (NIOSH), an agency with the Centers for Disease Control and Prevention under the Department of Health and Human Services, and OSHA. under the Department ofLabor.
Who controls such processes as the filling
and manufacturing of gas cylinders
The US Department ofTransportation {DOT).
What is the role of the Federal Food and
Drug Administration (FDA) in the regulation
of compressed gas cylinders?
The FDA enforces regulations of the Federal Food, Drug and Cosmetic Act. FDA inspectors inspect medical gas and liquefaction plants every other year. Oxygen cylinders and nitrous oxide tanks have been recalled
for numerous reasons including improper labeling, inappropriate testing, filling of cylinders with the wrong gases, and contamination of gases with ammonia, rusty water, oil, or chlorine.
List the responsibilities of the Department
of Transportation when dealing
with compressed gases.
The Department of Transportation has set requirements for the manufacturing, marking, labeling, filling, qualification, transportation, storage,handling, maintenance, requalification and disposition of medical gas cylinders and containers
How often should cylinders be inspected?
At least every five years, or, with special permit, up to every ten years
What is the working pressure of the
hospital pipeline system?
5O psig
Describe the diameter index safety system
(DISS), and state its purpose.
The pipeline inlet fittings are gas specific DISS threaded body fittings. The DISS provides threaded non-interchangeable connections for medical gas lines, and
this minimizes the risk of misconnection
- What are common contaminants of
medical gas lines? Which contaminant is
most common?
Common contaminants of medical gas lines are oil, water, bacteria, particulate matter, and residual sterilizing solutions. Water is the most common contaminant of medical gas lines
- Which two gases are in liquid form in
pressurized cylinders?
N20 and C02
- What is fusible plug?
The fusible plug is a thermally operated, non-reclosing pressure-relief device with the plug held against the discharge channel. It offers protection from
excessive pressure caused by a high temperature but not from overfilling. The yield temperature is the temperature at which the fusible material becomes
sufficiently soft to extrude from its holder so that cylinder contents are discharged.The fusible plug has supplanted Wood’s metal.
What is the capacity (L) and pressure A full E cylinder of oxygen ( 0 2) has a capacity of 660 L under a pressure of(psig) of a full E cylinder of oxygen (02)?
A full E cylinder of oxygen ( 0 2) has a capacity of 660 L under a pressure of 1900
What is the capacity (L) and pressure A full H cylinder of oxygen (02) has a capacity of 6,900 L under a pressure
(psig) of a full H cylinder of oxygen of 2200 psi.
A full H cylinder of oxygen (02) has a capacity of 6,900 L under a pressure 2200
Think about an E-cylinder of oxygen what do pressures of 2000, 1000, and 500 psi corresponds to>
2000 full
1000 half
500 quarter
If the pressure gauge of an e-cylinder reads 700 psi, how much gas remain in the cylinder
210 L
At what pressures should the O2 E-cyliner on an aensthesia machine be changed
less than 1000psi
What is the capacity and pressure of a full e cylinder of nitrous oxide
A full E cylinder of nitrous oxide {N 20) has a capacity of 1590 L under 745 psi.
What is the capacity (L) and pressure of a full H cylinder of nitrous ?
A full H cylinder of nitrous oxide {N20) has a capacity of 15,800 L under a pressureof745 psi. [
(psig)
Nitrous oxide {N20) is stored as a liquid
in cylinders, as you know. What does
the gauge pressure of745 psi actually ture.
Since nitrous oxide {N20) is stored as a liquid, the cylinder pressure of 745 psi represents the vapor pressure of liquid nitrous oxide at room temperature
What is the capacity (L) and pressure .
{psig) of a full E cylinder of air?
A full E cylinder of air has a capacity of 625 L under a pressure of 1900 psi
What is the capacity (L) and pressure
(psig) of a full H cylinder of air? psi.
A full H cylinder of air has a capacity of 6,550 L under a pressure of 2,200
Because the pressure on a nitrous oxide cylinder remains relatively constant (745
oxide in the cylinder, what is the only
way to know the amount of liquid in the
cylinder of nitrous oxide?
In a cylinder containing a liquefied gas, the pressure depends on the vapor pressure of the liquid-weight must be used to determine the amount of in cylinders that store liquefied gas.
What is the weight of an empty EE cylinder
cylinder?
An empty weighs 14 pounds. [
During the case, the wall oxygen pressure fails. The E-cylinder registers 2000 psig, but within a few breaths falls to zero pressure. What should you do?
Open the valve on the e-cylinder. The E-cylinder gauge may read 2000 psig after the e-cyliinder valve is turned off if the pressure in the line was not vented (bled) when the wall pressure of oxygen fails, the oxygen in the line form the closed E-cylinder “bleeds” quickly and the pressure fall abruptly.
The gauge on an E cylinder of nitrous oxide reads 740 psi. Explain the significance of this pressure reading.
Since nitrous oxide is stored as a liquid, the nitrous oxide cylinder pressure gauge remains at 745 psi until the liquid is gone; at this point, the cylinder is more than three-quarters empty. After all the liquid nitrous oxide isgone, the pressure rapidly declines until the cylinder is exhausted.
Before installing a gas cylinder on the anesthesia machine, the valve is “cracked:’ How and why is the cylinder
valve “cracked?”
A gas cylinder valve is “cracked” by slowly and briefly opening the valve with the port pointed away from the user or any other persons. The purpose of “cracking” the valve is to remove dust, dirt, metal shavings and other foreign matter from the valve port. This reduces the possibility of flash fire or explosion when the valve is later opened with the fittings in place.
What prevents back-flow pressure in the
gas cylinder
The check valve on the hanger yoke prevents back-flow pressure in a gas cylinder.
Explain the purpose of the pin index
system
The pin index system ensures that the cylinders will be non-interchangeable.
For example, an oxygen cylinder cannot be attached to a nitrous oxide yoke. [
Identify the four ( 4) components of the
anesthesia gas machine that are exposed
to high pressures (cylinder pressure
The four components of the anesthesia gas machine that are exposed to high-pressure (cylinder pressure) are: (1) hanger yoke, (2) yoke block with check valves, (3) cylinder pressure gauge, and (4) cylinder pressure regulators.
Identify the eight (8) components of the
anesthesia gas machine that are exposed
to intermediate pressures {pipeline pressure,
SO psi).
The eight components of the anesthesia gas machine that are exposed to
intermediate pressures (pipeline pressure, SO psi) are: ( l) pipeline inlets,(2) check valves, (3) pressure gauges, (4) ventilator power inlet, (S) oxygen
pressure-failure device, (6) flowmeter valve, (7) oxygen second-stageregulator, and (8) flush valve.
Identify the four ( 4) components of the
anesthesia gas machine that are exposed
to low pressures (distal to flowmeter
needle valve).
The four components of the anesthesia gas machine that are exposed to low
pressures are all distal to the flowmeter needle valve. The components are: ( l)
flowmeter tubes, (2) vaporizers, {3) check valves, and (4) common gas outlet.
What do pressure reducing devices
(regulators) do?
Pressure reducing regulators reduce the high and variable pressure in a
cylinder to a lower pressure ( 40 to 48 psig). Gas flow is maintained constant
without changing the supply pressure.
What is the name of the cylinder
pressure gauge that is found on cylinder
tanks? Does it measure relative or absolute
pressure?
High cylinder pressures are measured by the Bourdon gauge. The Bourdon
gauge measures pressure relative to the atmosphere.
When the Bourdon gauge reads zero,
what is the pressure in the tank?
One atmosphere
What do second stage reducing devices
(regulators) do?
Second stage regulators receive gas from either the pipeline or the cylinder reducing device (regulator) and reduce the pressure further to 26 psig for nitrous oxide and 14 psig for oxygen. The purpose of this second stage regulator is to eliminate fluctuations in pressure, so flow remains constant.
Besides reducing line pressure, what
other function does a second-stage
regulator provide?
In addition to reducing line pressure, the second-stage regulator maintains constant flow with changing supply pressure. In other words, the second stage regulator eliminates fluctuations in pressure.
What is a variable orifice, variable area,
or Thorpe tube mechanical indicator?
The mechanical tube indicator is the tapered (variable orifice) tube with an indicator bobbin that is part of the constant-pressure variable-orifice flowmeter found in anesthesia machines.
The Thorpe tube of the variable-orifice flowmeter is tapered, as you know. Describe the tapering of the Thorpe tube and the Thorpe tubes location in the anesthesia machine.
The Thorpe tube (variable orifice tube) is located in the manifold area of the anesthesia machine and is tapered, with the smallest diameter at the bottom of the tube and the largest at the top
What type of flowmeter uses rotating
indicator?
Variable orifice flow meters use rotating indicators (rotamer).
Why do some modern gas machines
have 2 flowmeter tubes whereas other
machines have one flowmeter tube?
The flowmeter arrangement on modern gas machines must account for both low and high flow rates. A machine with 2 flowmeter tubes in series- one for low flow rates and one for high flow rates- allows a single flowmeter to indicate both high and low flow rates. A machine with a single flowmeter tube actually has dual tapers in the tube one to accurately reflect low flow rates and the other for high flow rates. (Recall that the Thorpe tube flowmeter is a tapered tube.) Memory phrase: single taper dual tubes or dual taper-+ single tube
At what point on the float (plumb-bob
or ball types) of the flowmeter is flow
rate read?
Flow rate is read from the top of plumb-bob or skirted floats and from the middle of the ball-type float. Principle: read flow rate at the highest and widest portion of the float
What is the function of an auxiliary
flowmeter on the gas machine? What is
the advantage of an auxiliary flowrneter?
Auxiliary flowmeters are useful for attaching supplemental oxygen delivery devices, such as a nasal cannula, to the gas machine. The auxiliary flowmeter is advantageous because the breathing circuit and gas delivery hose remain intact while supplemental oxygen is delivered to a spontaneously breathing patient. Another advantage is that an oxygen source is readily available for the Ambu bag if the patient needs to be ventilated manually for any reason during the case.
What is the primary disadvantage of an
auxiliary flowmeter
If pipeline supply has lost pressure or has been contaminated, the auxiliary flowmeter becomes unavailable. Another disadvantage is that the fraction
of inspired inspiration cannot be varied with the auxiliary
Calibration oftlowmeters is based upon
what physical property of gases: density
or viscosity?
Flowmeters are calibrated for specific gases based upon the gas viscosity ( ‘f) at low flows and the gas density (p) at high flows. Recall that with low flow rates, laminar flow is typically favored and the fluid viscosity is a key determinant of laminar flow. At high flow rates turbulent flow is more likely and the fluid density effects the flow.
How is the oxygen flowmeter knob
distinguished from other flowmeter
knobs? (Hint: there are 3 distinguishing
characteristics … )
Flowmeter controls are touch and color coded (knobs must look and feel different}. The oxygen flowmeter control knob is distinct from other flowmeter
control knobs in the following 3 ways: the oxygen flowmeter control knob (1) is distinctively fluted (all other knobs must be round). (2) projects beyond control knobs for other gases, and (3) is larger in diameter than
other control knobs.
Describe the placement of the oxygen
flowmeter tube in relation to the other
flow tubes in the side-by-side array
The oxygen flowmeter tube should be placed downstream or to the right of other flowmeter tubes. Another description is that the oxygen flowmeter tube must be nearest the manifold outlet
What five features are characteristic of
anesthesia workstation vaporizers?
Anesthesia workstation vaporizers ( 1) must be concentration calibrated, (2) must have an interlock, (3) must indicate the liquid level in order to prevent overfilling, (4) should use keyed-filler devices, and (5) must not discharge liquid anesthetic from the vaporizer, even at maximum fresh gas
What volatile agents are delivered from
variable-bypass vaporizers? What are
three characteristics of variable-bypass
vaporizers?
The volatile agents that are delivered from variable-bypass vaporizers are isoflurane, and sevoflurane. Variable-bypass vaporizers are: (1) agent specific, (2) temperature-compensated, and (3) flow over (carrier gas flows over anesthetic liquid in the vaporizing chamber). The gas delivered to the variable-bypass vaporizer is divided into carrier gas, which flows over liquid anesthetic in the vaporizing chamber, and non-carrier gas, which
leaves the vaporizer unchanged. Because the gas flowing into the modern day vaporizer is divided into two streams, it is also known as a variable-bypass vaporizer.
Where should variable-bypass vaporizers
be located? Why?
Variable bypass vaporizers should be located outside the circle system,between the flow meters and common gas outlet. This placement lessens the likelihood of concentration surges during use of the oxygen flush valve.
What volume of anesthetic vapor is
produced by 1 milliliter of volatile anesthetic
liquid
One milliliter ofliquid volatile anesthetic produces - 200 milliliters of anestheticvapor at 20 °C and 1 atmosphere. [
What is the transport (“T”) dial setting
on a Drager Vapor 2000 gas machine?
What is the equivalent of this on other
gas machines?
The Drager Vapor 2000 gas machine has a transport (“T”) dial setting the helps prevent tipping-related problems. This function is provided by the
vaporizer cassette systems of other modern gas machines
What system prevents filling a vaporizer
with the incorrect agent?
The keyed filling port system on modern vaporizers lessens the chance of filling with the incorrect agent.
Most contemporary anesthesia gas machines have variable-bypass vaporizers. Which modern gas machine does not have a variable-bypass vaporizer? What is the appropriate description of this vaporizers operation?
Unlike most contemporary vaporizers, the Tee 6 desflurane vaporizer is not a variable-bypass vaporizer. The Tee 6 vaporizer is best called a dual-gas •
blender vaporizer
What is the temperature and pressure in
the desflurane vaporizer? Is the desflurane
vaporizer a flow-over vaporizer?
Desflurane is delivered from a heated (39 degrees C) and pressurized ( 1300
mm-Hg) vaporizer. The desflurane vaporizer is not a flow-over vaporizer
State two reasons why desflurane needs
a specially-designed vaporizer?
Desjlurane’s vapor pressure of 669 mm Hg is near atmospheric pressure. so it almost boils at sea level; (2) desflurane is only one-fifth as potent as the other volatile agents, so a relatively large volume of vapor must be delivered to the patient.
Which vaporizer is a “dual-circuit”
gas-vapor blender? To what feature does
the “dual-circuit” apply?
The Tee 6 vaporizer is an electrically heated, thermostatically controlled, constant-temperature. pressurized, electromechanically coupled dual circuit,
gas-vapor blender. The pressure in the vapor circuit is electronically regulated to equal the pressure in the fresh gas circuit. At a constant fresh gas flow rate, the operator regulates vapor flow using a conventional concentration
control dial. When the fresh gas flow rate increases, the working pressure increases proportionally. For a given concentration setting even when varying the fresh gas flow rate, the vaporizer output is constant because the amount of flow through each circuit remains proportional.
The Tee 6 desflurane vaporizer is a
dual-gas blender, as you know. What are
the implications of this type of vaporizer
when a change in altitude is encountered?
Because the Tee 6 vaporizer is a dual-gas blender, the Tee 6 will maintain a constant concentration of vapor output(% v/v), not a constant partial pressure. regardless of ambient pressure. This means that at high altitudes. the
partial pressure of desflurane (Pd.,) will be decreased in proportion to the atmospheric pressure. The Tee 6 vaporizer requires manual adjustment of the concentration control dial at altitudes other than sea level to maintain a constant Pd …
Desflurane is heated to 39°C in the TEC 6 vaporizer, as you well know. What is the source of heat and what is the saturated vapor pressure (SVP) of destlurane
at this temperature? Also describe the location of the heated desflurane reservoir in relation to the common outlet and shut-off valve.
In the TEC 6 vaporizer, desflurane is electrically heated in a sump that is upstream of both the common outlet and shut-off valve. Heating of desflurane to 39 °C creates a saturated vapor pressure of 2 atmospheres, which
drives the agent towards the fresh gas flow. In contrast to other vaporizers, no fresh gas flow goes through the desflurane sump. i.e., fresh gas flow never
comes in contact with liquid desflurane
Does the TEC 6 desflurane vaporizer
automatically compensate for changes in
elevation? What are the implications of
this for the anesthetist?
The Tee 6 desflurane vaporizer does not automatically compensate for changes in elevation. The concentration of desflurane is unaffected by elevation, but the partial pressure decreases. At high elevations, the anesthetist
must increase the concentration on the control dial to raise the partial pressure to the desired level. Since the partial pressure of agent delivered to the patient is what counts, you would need to increase the concentration
setting when you are in the mountains so as to deliver an equivalent partial pressure of desflurane to the patient.
Calculate the partial pressure of desflurane delivered from the Tee 6 vaporizer at sea level (atmospheric pressure= 760 mm Hg) and also in the mountains where the atmospheric pressure is 600 mm Hg. Do your calculations explain why delivering 5% in the mountains results in lighter anesthesia?
If you set the dial on the Tee 6 at 5% and you are at sea level, the partial
pressure of desflurane going to the patient is 0.05 x 760 mm Hg :: 38 mm
Hg (Dalton’s law of partial pressures permits this calculation); but, if you
go up into the mountains where the total atmospheric pressure is, let’s
say, 600 mm Hg, the partial pressure of desflurane delivered to the patient
when you set the Tee 6 dial at 5% is O.OS x 600 mm Hg = 30 mm Hg. These
calculations explain why setting the dial at S% results in lighter anesthesia
in the mountains than it does at sea level. The partial pressure going to the
patient for a given dial setting is lower in the mountains
Tech 5 vaporizer designs were susceptible to a "pumping effect." Describe this pumping effect. What was the result of this effect in terms of anesthetic delivery?
Early vaporizer designs were susceptible to a pumping effect: intermittently fluctuating pressure in the breathing system, such as that generated by positive pressure ventilation or by intermittent pressing and releasing of
the 0 2 flush valve, caused fluctuating back pressure to be transmitted into the low-pressure system. The “pumping effect” is more pronounced at low flow rates. The result of this pumping effect was an increased concentration
of anesthetic delivered
How is the pumping effect (see previous
question) prevented in more modern
anesthetic vaporizers?
New anesthetic vaporizers incorporate mechanisms that decrease the size
of the vaporizing chamber relative to the bypass channel and increase the
volume of the inflow channel. Vapor-saturated gas cannot make its way
back into the bypass channel, and thus the pumping effect is prevented
State six ( 6) hazards of modern vaporizers that persist, despite advancements in vaporizer design.
Six hazards of modern vaporizes that remain, despite advances in design, are: (1) incorrect agent administration, (2) tipping, (3) overfilling with agent, (4) leaks, (5) electronic failure, and (6) reliance on breath-by-breath gas analysis rather than preventative maintenance.
Describe three functions of the interlock
system on the anesthesia machine.
Contemporary vaporizers are secured to the anesthesia machine in mani· folds that hold 2-3 units. The interlock system, also known as the vaporizer exclusion system, prevents more than one vaporizer from being turned on
at a time. In other words, the operator is prevented from delivering more than any one agent simultaneously. The interlock system also ensures that all vaporizers are locked in such that leaks are decreased, and trace vapor
output is minimal when the vaporizer is off.
What is the main function of the check
valve(s) in a gas machine?
Check valves, also called unidirectional or one-way valves, prevent retrograde flow {back flow) during positive pressure ventilation, therefore minimizing the effects of downstream intermittent pressure fluctuations
on inhaled anesthetic concentration
List 3 functions of the anesthesia machine
check valve
The anesthesia machine check valve: ( l) prevents “back-flow” from
high-pressure to low-pressure sides (prevents “pumping action” of gases),
(2) allows for an empty cylinder to be exchanged for a full one with minimal
loss of gas, and (3) minimizes leakage from an open cylinder to the
atmosphere.
Describe the purpose of the fail.safe valve on the anesthesia machine.
The fail·safe valve prevents the delivery of hypoxic gas mixtures from the machine in the event of failure of the oxygen supply. The fail-safe valve goes by many other names- the oxygen failure safety valve, oxygen failure •
safety device, low·pressure guardian system, oxygen failure protection device, pressure sensor shutoff system or valve, pressure sensor system, and
nitrous oxide shutoff valve
Which anesthetic gas has no fail-safe valve?
Oxygen
During an anesthetic the fail· safe valve shuts down all non·oxygen gas flow.What happened?
The oxygen pressure fell below 2S-30 psi. When oxygen pressure falls below 20- 30 psi (roughly SO% of normal), a fail-safe valve automatically doses the nitrous oxide and other gas lines to prevent accidental delivery of
a hypoxic gas mixture to the patient. A gas whistle or electric alarm sounds to alert the anesthetist to this occurrence.
List eight (8) required monitors on the anesthesia workstation
The eight required monitors on the anesthesia workstation are: (1) exhaled volume
(2) inspired oxygen, with a high-priority alarm within 30 seconds of oxygen falling below 18% (or a user-defined adjustable limit);
(3) oxygensupply failure alarm;
(4) a hypoxic guard system that must protect against
less than 21 % inspired oxygen if nitrous oxide is in use; (S) anesthetic vapor
concentration;
(6) pulse oximetry
; (7) blood pressure monitoring; and,
(8) electrocardiogram
What is the maximum time a high·priority
alarm may be silenced?
High-priority alarms may not be silenced for more than 2 minutes
What are your actions when the oxygen low-pressure alarm sounds?
When the oxygen low·pressure alarm sounds-indicating profound loss of 01 pipeline pressure-fully open the E cylinder, disconnect the pipeline, and consider use of low fresh gas flows
How frequently does the scavenging system need to be checked?
The scavenging system needs to be checked daily as outlined by the FDA in 1993
Name five components of the scavenging system.
The gas· collecting system; (2) the transfer tubing; (3) the scavenging interface; (4) the gas disposal tubing; and (5) an active or passive gas disposal assembly.
Where is the valve of the scavenging system located?
Waste gas scavengers dispose of gases that have been vented from the breathing circuit by a pressure release valve located in the breathing circuit or the ventilator. Either of these valves is connected to hoses leading to the
scavenger system. [
To what is the outlet of the scavenging system
connected?
The outlet of the scavenging system can be a direct line to the outside or a connection to the hospital’s vacuum system
What are indications that the scavenging system is malfunctioning?
When a scavenging system malfunctions or is misused, positive or negative pressure can be transmitted to the breathing system. This is more likely to
occur with dosed interfaces
What is the purpose of each of the two
pressure relief valves of the scavenger
system?
One relief valve is for negative pressure and one is for positive pressure
When does the positive pressure relief
valve of the scavenger system open?
If flow of waste gases into the vacuum source is insufficient and the reservoir
bag distends, the positive pressure valve opens and vents some of the
exhaled gases into room.
