Exam 1
What are the classifications of a circle system and on what does this depend?
A circle system can be classified as semiopen, semiclosed, or closed, depending on the amount of fresh gas inflow.
What is the relevance of NIOSH?
A department of the CDC, focusing on the prevention of illness and injury in the workplace
What is the most commonly used circle breathing system used in the United States?
A semiclosed system is associated with rebreathing of gases and is the most commonly used breathing system in the United States.
Name some agencies (private and federal) that regulates occupational safety
ANSI (American National Standards Institute) OSHA (Occupational Safety Health Administration) NIOSH (National Institute for Occupation Safety and Health) FDA (Food and Drug Administration) JCAHO (Joint Commission on Accreditation of Healthcare Organizations) CDC works with OSHA and NIOSH
What is the importance of ANSI
ANSI is a private agency, working to standardize equipment. This agency makes it possible for equipment to be moved from place to place and have it fit. For anesthesia, is sets standards for anesthesia machines, ETT, bronchoscopes, vaporizers, etc. Measured in millimeters
What is capacitance?
Ability to store a charge. In AC current capacitors allow continuous current to travel along the circuit even if no completed circuit exists Facilitates the flow of electrons
What is the risk of activating the oxygen flush valve during a mechanically delivered inspiration?
Activation of the oxygen flush valve during a mechanically delivered inspiration from the anesthesia machine ventilator permits the transmission of high airway pressure to the patient's lungs, with the possibility of barotrauma.
What are some advantages to the closed circle anesthetic breathing system?
Advantages of a closed circle anesthetic breathing system over a semiclosed circle anesthetic breathing system include (1) maximal humidification and warming of inhaled gases, (2) less pollution of the surrounding atmosphere with anesthetic gases, and (3) economy in the use of anesthetics.
What are some advantages of the Bain circuit anesthetic breathing system?
Advantages of the Bain circuit include (1) warming of the fresh gas inflow by the surrounding exhaled gases in the corrugated expiratory tube, (2) conservation of moisture as a result of partial rebreathing, and (3) ease of scavenging waste anesthetic gases from the overflow valve. It is lightweight, easily sterilized, reusable, and useful when access to the patient is limited, such as during head and neck surgery.
What are some advantages of the Mapleson F anesthetic breathing system?
Advantages of the Mapleson F anesthetic breathing system include its minimal dead space and resistance. This makes this system ideal for pediatric anesthesia.
How is an erroneous hookup of a gas cylinder to the anesthesia machine minimized?
An erroneous hookup of a gas cylinder to the anesthesia machine is minimized in two ways. First, the cylinders are color-coded. Second, and more importantly, the color-coded cylinders are attached to the anesthesia machine by a hanger yoke assembly, which consists of two metal pins that correspond to holes in the valve casing of the gas cylinder. This pin index safety system (PISS) makes it impossible to attach an oxygen cylinder to any yoke on the anesthesia machine other than that designed for oxygen. Otherwise, a cylinder containing nitrous oxide could be attached to the oxygen yoke, which would result in the delivery of nitrous oxide when the oxygen flowmeter was activated.
Can a hypoxic mixture be delivered from the anesthesia machine with an intact fail-safe valve? Explain.
An intact fail-safe valve is actually only a pressure-sensor valve. A hypoxic mixture may still be delivered to the patient if the fail-safe valve is sensing an adequate gas pressure in the circuit of the anesthesia machine when the oxygen flow is zero. This confirms the importance of the oxygen analyzer on the anesthesia machine. Far superior to the fail-safe valve or an oxygen analyzer is the continuous presence of a vigilant anesthesiologist.
What are two different ways in which anesthesia machine ventilators are powered?
Anesthesia ventilators are powered by compressed gas, electricity, or both
What are some features of an anesthetic breathing system that enable them to be classified as either open, semiopen, closed, or semiclosed?
Anesthetic breathing systems are classified as open, semiopen, semiclosed, and closed according to the presence or absence of: (1) a gas reservoir bag in the circuit, (2) rebreathing of exhaled gases, (3) means to chemically neutralize exhaled carbon dioxide, and (4) unidirectional valves.
How do anesthetic breathing systems impart resistance to the spontaneously ventilating patient?
Anesthetic breathing systems can add considerable resistance to inhalation because peak flows as high as 60 L/min are reached during spontaneous inspiration. This resistance is influenced by unidirectional valves and connectors. The components of the breathing system, particularly the tracheal tube connector, should have the largest possible lumen to minimize this resistance to breathing. Right-angle connectors should be replaced with curved connectors to minimize resistance. Substituting controlled ventilation of the patient's lungs for spontaneous breathing can offset the increased resistance to inhalation imparted by anesthetic breathing systems.
What does the term temperature-compensated refer to? Between what temperatures is vaporizer output reliably constant?
As the vaporizer temperature changes, a temperature-sensitive bimetallic strip or an expansion element inside the vaporizer influences proportioning of total gas flow between the vaporizing and bypass chambers. For example, as the temperature of the liquid anesthetic in the vaporizer chamber decreases, the temperature-sensing elements allow increased gas inflow into this chamber to offset the effect of decreased anesthetic liquid vapor pressure. Vaporizers are often constructed of metals with high thermal conductivity (copper, bronze) to further minimize heat loss. As a result, vaporizer output is nearly linear between 20 degrees C and 35 degrees C.
Where is the dead space in the circle system
Between the Y-piece and the patient
What are some components of an anesthesia workstation?
Components of an anesthesia workstation include what was previously recognized as the anesthesia machine, (the pressure-regulating and gas-mixing components), as well as the vaporizers, anesthesia breathing circuit, ventilator, scavenging system, and respiratory and physiologic monitoring systems (electrocardiogram, arterial blood pressure, temperature, pulse oximeter, and inhaled and exhaled concentrations of oxygen, carbon dioxide, anesthetic gases, and vapors)
Describe how contemporary vaporizers for volatile anesthetics are classified.
Contemporary vaporizers are classified as agent-specific, variable-bypass, flow-over, temperature-compensated, and out of circuit.
Why are contemporary vaporizers unsuitable for use with desflurane?
Desflurane has a vapor pressure near 1 atm (664 mm Hg) at 20 C. For this reason, a desflurane vaporizer is electrically heated to 23 C and 25 C and pressurized with a backpressure regulator to 1500 mm Hg to create an environment in which the anesthetic has a relatively lower, but predictable volatility
What are the two types of electrical currents?
Direct correct (DC): electron flow is always in the same direction; cannot travel far distances and would need repeating stations or booster stations -battery Alternation current (AC): electron flow reverses at given intervals; can travel far and is used as the electrical system at home -outlet
What are some disadvantages of the Mapleson F anesthetic breathing system?
Disadvantages of the Mapleson F system include (1) the need for high fresh gas inflow to prevent rebreathing, (2) the possibility of high airway pressure and barotrauma should the overflow valve become occluded, and (3) the lack of humidification. Lack of humidification can be offset by allowing the fresh gas to pass through an in-line heated humidifier.
What are some disadvantages of the circle anesthetic breathing system?
Disadvantages of the circle system include: (1) increased resistance to breathing because of the presence of unidirectional valves and carbon dioxide absorbent, (2) bulkiness with loss of portability, (3) enhanced opportunity for malfunction because of the complexity of the apparatus.
Anesthesia documentation
Document only what is necessary, too much detail could become inconsistent with other reports and may get a CRNA in trouble. Be concise and only document in one place.
What is disadvantageous about the corrugated tubing in the circle system?
During positive-pressure ventilation, some of the delivered gas distends the corrugated tubing and some is compressed within the circuit, which leads to a smaller delivered tidal volume.
What is the equation of electricity?
E = I x R (Ohm's Law) E= electricity I = currents (amps) R = resistance (ohms)
What are the two concepts of grounding?
Electrical power (green or bare wire that prevents you from getting the electricity as it now has somewhere else to go) Electrical equipment
Two sources of error in the OR
Equipment and Human
What does this statement mean in relation to anesthesia? "if you hammer in a screw, it will go in, but there will be a lot of damage"
Everything is designed to fit, if you are struggling, stop. There is something wrong CRNAs must fully understand all equipment they come in contact with
In a closed circle anesthetic breathing system, to what extent is the inhaled concentration of anesthetic dependent on the exhaled concentration of anesthetic? What is the potential problem with this? How can this problem be partially offset?
Exhaled gases, devoid of carbon dioxide, form a major part of the inhaled gases when a closed anesthetic breathing system is used. This means that the composition of the inhaled gases is influenced by the concentration present in the exhaled gases. The concentration of anesthetic in exhaled gases reflects tissue uptake of the anesthetic. Initially, tissue uptake is maximal, and the concentration of anesthetic in the exhaled gases is minimal. Subsequent rebreathing of these exhaled gases dilutes the inhaled concentration of anesthetic delivered to the patient. Therefore, high inflow concentrations of anesthetic are necessary to offset maximal tissue uptake. Conversely, only small amounts of anesthetic need to be added to the inflow gases when tissue uptake has decreased. The unknown impact of tissue uptake on the concentration of anesthetic in exhaled gases makes it difficult to estimate the inhaled concentration delivered to the patient through a closed anesthetic breathing system. This disadvantage can be partially offset by administering higher fresh gas inflow (3 L/min) for about 15 minutes before instituting the use of a closed anesthetic breathing system. This approach permits elimination of nitrogen from the lungs and corresponds to the time of greatest tissue uptake of anesthetic.
What is the purpose of flowmeters on an anesthesia machine?
Flowmeters on the anesthesia machine precisely control and measure gas flow to the common gas inlet.
What are some disadvantages of the Bain circuit anesthetic breathing system?
Hazards of the Bain circuit include unrecognized disconnection or kinking of the inner fresh gas tube. The outer expiratory tube should be transparent to allow inspection of the inner tube.
What is a critical incident?
Human or equipment failure that could have, if not discovered and corrected in time, or lead to an undesirable outcome ranging from extended stay or death
Describe a closed anesthetic breathing system. What is the inflow volume of fresh gases in a closed anesthetic breathing system?
In a closed anesthetic breathing system, there is total rebreathing of exhaled gases after absorption of carbon dioxide, and the APL valve or relief valve of the ventilator is closed. A closed system is present when the fresh gas inflow into the circle system (150 to 500 mL/min) satisfies the patient's metabolic oxygen requirements (150 to 250 mL/min during anesthesia) and replaces anesthetic gases lost by virtue of tissue uptake. If sidestream gas analyzers are used, the analyzed gas exiting the analyzer must be returned to the breathing system to maintain a closed system.
How is the pressure of nitrous oxide related to the volume of nitrous oxide in a nitrous oxide gas cylinder?
In contrast to oxygen, the pressure gauge for nitrous oxide does not indicate the amount of gas remaining in the cylinder because the pressure in the gas cylinder remains at 750 psi as long as any liquid nitrous oxide is present. When nitrous oxide leaves the cylinder as a vapor, additional liquid is vaporized to maintain an unchanging pressure in the cylinder. After all the liquid nitrous oxide is vaporized, the pressure begins to decrease, and it can be assumed that about 75% of the contents of the gas cylinder have been exhausted. Because a full nitrous oxide cylinder (E-size) contains about 1590 L, approximately 400 L of nitrous oxide remains when the pressure gauge begins to decrease from its previously constant value of 750 psi.
Rules of generating current
In order for current to flow there must be a circuit where electrons flow from a high to low concentration Normally 2 wires. One "hot," which is black and carries the voltage, and the other "neutral," which is white and returns the current to the source
How is the OR electrical system laid out?
In the OR electrical power is supplied via an isolation transformer, this separates the electrical system from the OR system, there is no grounding so therefore the risk of electrical shock is reduced since no circuit is created
Insulator vs. Conductor
Insulator is a substance that opposed the flow of electrons Conductor is a substance that facilitates the flow of electrons
JCAHO and healthcare
JCAHO is a private non-profit organization; they earn money through hospitals paying to get accredited Many state governments have recognized JCAHO as a certifying agency for Medicaid (if hospitals lose accreditation, they will no longer be able to accept Medicare and Medicaid reimbursement)
What is inductance?
Magnetic field that is created as electricity flows thru a coiled wire Resists the flow of electrons
How do flowmeters on an anesthesia machine work?
Measurement of the flow of gases is based on the principle that flow past a resistance is proportional to pressure. Typically, gas flow enters the bottom of a vertically positioned and tapered (the cross-sectional area increases upward from site of gas entry) glass flow tube. Gas flow into the flowmeter tube raises a bobbin or ball-shaped float. The float comes to rest when gravity is balanced by the decrease in pressure caused by the float. The upper end of the bobbin or the equator of the ball indicates the gas flow in milliliters or liters per minute.
Describe the mechanics of a conventional anesthesia machine ventilator during inspiration.
Most conventional anesthesia machine ventilators are pneumatically driven by oxygen or air that is pressurized and, during the inspiratory phase, routed to the space inside the ventilator casing between the compressible bellows and the rigid casing. Pressurized air or oxygen entering this space forces the bellows to empty its contents into the patient's lungs through the inspiratory limb of the breathing circuit. This pressurized air or oxygen also causes the ventilator relief valve to close, thereby preventing inspiratory anesthetic gas from escaping into the scavenging system.
What are the two broad categories of safety in anesthesia?
Occupational (safety of the anesthesia and OR personnel) Patient (avoidance of adverse incidents and increased safety) -be aware you are maintaining the patient's physiology and body functions
What does the term out of circuit refer to?
Out of circuit describes the fact that vaporizers are isolated from the anesthetic breathing system.
Why is oxygen preferred over air as the ventilator driving gas?
Oxygen is preferable to air as the ventilator driving gas because if there is a leak in the bellows, the fraction of inspired oxygen will be increased. If there is aleak in the bellows in a ventilator driven by 50 psi oxygen or air, the peak inspiratory pressure will rise.
Contributing factors requiring anesthesia outside of the OR
Pain management; children, elderly, or disabled patients that will not follow instructions; psychiatric disorders (anxiety and panic, claustrophobia); neurological disorders (movement and seizure disorders, cerebral palsy); trauma (unstable cardiovascular, respiratory, or neurological status); patients with significant co-morbidities that require monitoring; difficult airway
What are some occupational hazards to consider in the practice of anesthesia?
Physical, emotional (fatigue), and environmental (anesthetic gases and sharps)
Electrical Equipment Grounding
Prevents an electrical shock if the equipment happens to have a short in in, in this case the current will be carried by the ground wire and significantly reduce the electric shock -you may still get a shock, but it won't be as bad.
Are flowmeters for various gases interchangeable?
Proportionality between pressure and flow is determined by the shape of the tube (resistance) and the physical properties (density and viscosity) of the gas. The flowmeters are initially calibrated for the indicated gas at the factory. Because few gases have the same density and viscosity, flowmeters are not interchangeable with other gases.
What are environmental and situational stress that contribute to errors in the operating room?
Quick turnover Lack of time to establish rapport with the patient (have 15 minutes to get the patient to trust you)
What is frequency?
Rate, in one second, at which alternating current (AC) changes direction (back and forth direction) Commonly 60 Hz
What are sources of human error?
Rule-based errors (forgot the rules) -rules have deviated Knowledge-based errors (do not know enough) -"Closed-Mind Error"
When does patient safety in the OR begin?
Safety begins in the pre-op. Safety is everyone in the perioperative experiences responsibility. Once the patient is under anesthesia, they can no longer protect themselves; OR personnel must safeguard.
What are other names for the adjustable pressure-limiting (APL) valve?
The APL valve is also known as the overflow or "pop-off" valve.
Describe the Bain circuit anesthetic breathing system.
The Bain circuit is a coaxial version of the Mapleson D system in which the fresh gas supply tube runs coaxially inside the corrugated expiratory tubing. The fresh gas tube enters the circuit near the reservoir bag, but the fresh gas is actually delivered at the patient end of the circuit. The exhaled gases are vented through the overflow valve near the reservoir bag.
Describe the Mapleson F anesthetic breathing system. What is another name for this anesthetic breathing system?
The Mapleson F system is a T-piece arrangement with a reservoir bag and an adjustable pressure-limiting overflow valve on the distal end of the gas reservoir bag. Another name for this anesthetic breathing system is the Jackson-Rees circuit.
When is the Mapleson F system commonly used?
The Mapleson F system is commonly used for controlled ventilation during transport of endotracheally intubated patients.
What characterizes the Mapleson systems?
The Mapleson systems are characterized by the absence of valves to direct gases to or from the patient and the absence of chemical carbon dioxide neutralization.
Describe the Y-piece connector in the circle system circuit.
The Y-piece connector at the patient end of the circuit has (1) a curved elbow, (2) an outer diameter of 22 mm to fit inside a facemask, and (3) an inner diameter of 15 mm to fit onto an endotracheal tube connector.
What are the components of a circle system?
The circle system consists of: (1) a fresh gas inlet, (2) inspiratory and expiratory unidirectional check valves, (3) inspiratory and expiratory corrugated tubing, (4) a Y-piece connector, (5) an adjustable pressure-limiting (APL) valve, also referred to as an overflow or "pop-off" valve, (6) a reservoir bag, (7) a canister containing carbon dioxide absorbent, (8) a bag/vent selector switch, a mechanical anesthesia ventilator.
How does the circle system prevent rebreathing of carbon dioxide?
The circle system prevents rebreathing of carbon dioxide by chemical neutralization of carbon dioxide with carbon dioxide absorbents.
How is the delivery of erroneous gases to the anesthesia machine minimized?
The delivery of erroneous gases from the central supply source to the pipeline inlet connections on the anesthesia machine is minimized in two ways. First, the wall outlets and pressure hoses are color-coded. Second, and more importantly, the pressure hoses are connected to the wall outlet and anesthesia machine by noninterchangeable gas-specific diameter fittings. This diameter index safety system (DISS) is designed to prevent misconnections of pipeline gases.
How does the circle anesthetic breathing system get its name?
The essential components of a circle anesthetic breathing system are arranged in a circular manner
What is the flow of oxygen delivered to the patient when the oxygen flush valve is depressed?
The flow of oxygen that is delivered to the patient via the oxygen flush valve is 35 to 75 L/min
What is the function of anesthetic breathing systems?
The function of anesthetic breathing systems is to deliver oxygen and anesthetic gases to the patient and to eliminate carbon dioxide.
What is the heat of vaporization?
The heat of vaporization of a liquid is the number of calories required at a specific temperature to convert 1 g of a liquid into a vapor.
What is advantageous about the corrugated tubing in the circle system?
The inspiratory and expiratory corrugated tubes serve as conduits for delivery of gases to and from the patient. Their large bore provides minimal resistance, and the corrugations provide flexibility, resist kinking, and promote turbulent instead of laminar flow.
What are the most commonly used anesthetic breathing systems?
The most commonly used anesthetic breathing systems are: (1) Mapleson F (Jackson-Rees) system, (2) Bain circuit, and (3) circle system.
Why is the oxygen flowmeter the last flowmeter in a series on the anesthesia machine with respect to the direction in which the gas flows?
The oxygen flowmeter should be the last in the sequence of flowmeters, and thus oxygen should be the last gas added to the manifold. This arrangement reduces the possibility that leaks in the apparatus proximal to oxygen inflow can diminish the delivered oxygen concentration, whereas leaks distal to that point result in loss of volume without a qualitative change in the mixture. Nevertheless, an oxygen flowmeter tube leak can produce a hypoxic mixture regardless of the flowmeter tube arrangement.
How are oxygen, nitrous oxide, and air gases that are used in anesthesia typically delivered to the anesthesia machine? At what pressure must these gases be delivered for proper function of the anesthesia machine?
The oxygen, nitrous oxide, and air gases that are used in anesthesia are most often delivered to the anesthesia machine as compressed gases from a central supply source located in the hospital. These hospital supplied gases enter the operating room from a central source through pipelines to operating room wall outlets. Pressure hoses then connect the wall outlets to the anesthesia machine. These gases must be delivered at a pressure of about 50 psi for the anesthesia machine to function properly.
How can the potential problem of the inadequate delivery of oxygen using a closed circle anesthetic breathing system be minimized?
The potential problem of the inadequate delivery of oxygen using a closed circle anesthetic breathing system can be minimized by the use of an oxygen analyzer placed on the inspiratory or expiratory limb of the closed circle system.
How is the pressure of oxygen related to the volume of oxygen in an oxygen gas cylinder? What does this mean with regard to calculating the volume of oxygen remaining in a used oxygen cylinder?
The pressure in an oxygen cylinder is directly proportional to the volume of oxygen in the cylinder. For example, a full oxygen cylinder is evidenced by a pressure of approximately 2000 psi. If the pressure gauge on an oxygen cylinder were to read 500 psi, one fourth of the initial pressure, it can be estimated that only one fourth of the volume remains in the oxygen cylinder. The volume in the cylinder could be estimated to be 625/4, or about 155 L.
What are the dangers of the closed circle anesthetic breathing system?
The principal dangers of a closed anesthetic breathing system are delivery of (1) unpredictable and possibly insufficient concentrations of oxygen and (2) unknown and possibly excessive concentrations of potent anesthetic gases.
What is the purpose of the cylinders of oxygen and nitrous oxide that are found on the back of the anesthesia machine?
The purpose of the cylinders of oxygen and nitrous oxide that are found on the back of the anesthesia machine is for the delivery of those gases should the central gas supply fail.
What is the purpose of the fail-safe valve? What triggers the fail-safe valve on the anesthesia machine?
The purpose of the fail-safe valve is to prevent the delivery of hypoxic gas mixtures from the anesthesia machine in the event of failure of the oxygen supply. The fail- safe valve is triggered when the pressure in the oxygen delivery line decreases to less than 30 psi. When the fail-safe valve is triggered, it either shuts off or proportionally decreases the flow of all gases. Note that it is only the pressure of oxygen that triggers the fail-safe valve.
What is the purpose of the oxygen flush valve?
The purpose of the oxygen flush valve is to provide a large volume of oxygen to the patient quickly. Oxygen delivered to the patient when the oxygen flush valve is depressed bypasses the flowmeters and manifold.
What is the impact of the rebreathing of anesthetic gases in a semiclosed circle system?
The rebreathing of exhaled gases in a semiclosed circle system influences the inhaled anesthetic concentrations of these gases. For example, when uptake of the anesthetic gas is high, as during induction of anesthesia, rebreathing of exhaled gases depleted of anesthetic greatly dilutes the concentration of anesthetic in the fresh gas inflow. This dilutional effect of uptake is offset clinically by increasing the delivered concentration of anesthetic. As uptake of anesthetic diminishes, the impact of dilution on the inspired concentration produced by rebreathing of exhaled gases is lessened.
What are some advantages of the semiclosed and closed circle systems?
The semiclosed and closed circle system are both advantageous in that they allow for the rebreathing of exhaled gases. The rebreathing of exhaled gases results in (1) some conservation of airway moisture and body heat and (2) decreased pollution of the surrounding atmosphere with anesthetic gases when the fresh gas inflow rate is set at less than the patient's minute ventilation.
What is the role of the FDA within anesthesia?
They are responsible for protecting the public health by assuring the safety, efficacy, and security of human and veterinary drugs, medical devices, etc. Getting new equipment must be cleared with FDA
What happens when someone becomes a part of the circuit?
They will receive a shock. They complete the circuit. Touch the black wire, "hot."
How does tipping of a vaporizer affect vaporizer output?
Tipping of vaporizers can cause liquid anesthetic to spill from the vaporizing chamber into the bypass chamber with a resultant increased vapor concentration exiting from the vaporizer.
What is the purpose of unidirectional valves in the circle system? What would occur if one of the unidirectional valves should become incompetent?
Two unidirectional valves are situated in different limbs of the corrugated tubing in a circle system such that one functions for inhalation and the other for exhalation. These valves (1) permit positive-pressure breathing and (2) prevent the rebreathing of exhaled gases until they have passed through the carbon dioxide absorbent canister and have had their oxygen content replenished. Rebreathing and hypercapnia can occur if the unidirectional valves stick in the open position, and total occlusion of the circuit can occur if they are stuck in the closed position. If the expiratory valve is stuck in the closed position, breath stacking and barotrauma can occur.
Are inspired concentrations of oxygen more or less predictable when nitrous oxide is also being delivered in a closed circle anesthetic breathing system? Why?
Unpredictable and possibly insufficient delivered concentrations of oxygen when using a closed anesthetic breathing system are more likely if nitrous oxide is included in the fresh gas inflow. For example, decreased tissue uptake of nitrous oxide with time in the presence of unchanged uptake of oxygen can result in a decreased concentration of oxygen in the alveoli.
How is the potential risk of filling the agent-specific vaporizer with the erroneous volatile anesthetic minimized?
Use of an anesthetic-specific keyed filler device prevents placement of a liquid anesthetic into the vaporizing chamber that is different from the anesthetic for which the vaporizer was calibrated. This is uniquely important for desflurane because its vapor pressure is near 1 atm and accidental placement of desflurane in a contemporary vaporizer could result in an anesthetic overdose.
"Use error"
Using a device for other than its intended purpose Can include poor design, inherent safety deficiencies Poor or insufficient training in the proper use of equipment -report to FDA
What is vapor pressure? What influence does temperature have on vapor pressure?
Vaporization in the closed confines of a vaporizer ceases when equilibrium is reached between the liquid and vapor phases such that the number ofmolecules leaving the liquid phase is the same as the number reentering. The molecules in the vapor phase collide with each other and the walls of the container, thereby creating pressure. This pressure is termed vapor pressure and is unique for each volatile anesthetic. Vapor pressure is temperature dependent such that a decrease in the temperature of the liquid is associated with a lower vapor pressure and fewer molecules in the vapor phase. Cooling of the liquid anesthetic reflects a loss of heat (heat of vaporization) necessary to provide energy for vaporization. This cooling is undesirable because it lowers the vapor pressure and limits the attainable vapor concentration.
Why does atmospheric water vapor accumulate as frost on the outside surface of oxygen tanks and nitrous oxide tanks in use?
Vaporization of a liquefied gas (nitrous oxide), as well as expansion of a compressed gas (oxygen), absorbs heat, which is extracted from the metal cylinder and the surrounding atmosphere. For this reason, atmospheric water vapor often accumulates as frost on gas cylinders and in valves, particularly during high gas flow from these tanks. Internal icing does not occur because compressed gases are free of water vapor.
What does the term agent-specific refer to?
Vaporizers are calibrated to accommodate a single volatile anesthetic.
What do the terms variable-bypass and flow-over refer to?
Variable-bypass describes dividing (splitting) the total fresh gas flow through the vaporizer into two portions. The first portion of the fresh gas flow (20% or less) passes into the vaporizing chamber of the vaporizer, where it becomes saturated (flow-over) with the vapor of the liquid anesthetic. The second portion of the fresh gas flow passes through the bypass chamber of the vaporizer. Both portions of the fresh gas flow mix at the patient outlet side of the anesthesia machine. The proportion of fresh gas flow diverted through the vaporizing chamber, and thus the concentration of volatile anesthetic delivered to the patient, is determined by the concentration control dial.
Why do volatile anesthetics require placement in a vaporizer for their inhaled delivery to patients via the anesthesia machine?
Volatile anesthetics are liquids at room temperature and atmosphericpressure. Vaporization, which is the conversion of a liquid to a vapor, takes place in a closed container, referred to as a vaporizer. The inhaled delivery of volatile anesthetics requires that they be vaporized. The vapor concentration resulting from vaporization of a volatile liquid anesthetic must be delivered to the patient with the same accuracy and predictability as other gases (oxygen, nitrous oxide).
What is electrical power measured?
Watts; a watt is equal to the product of the voltage and the amperage. W = E x I A joule is a unit of electrical or mechanical work, defined as the amount of energy spent by one watt for one second in a resistance of one ohm
Describe the function of the APL valve when the "bag/vent" selector switch is set to "bag."
When the "bag/vent" selector switch is set to "bag," the APL (overflow or "pop- off") valve (1) allows venting of excess gas from the breathing system into the waste gas scavenging system and (2) can be adjusted to allow the anesthesiologist to provide assisted or controlled ventilation of the patient's lungs by manual compression of the gas reservoir bag. The APL valve should be fully open during spontaneous ventilation so that circuit pressure remains negligible throughout inspiration and expiration.
What are the advantages of the reservoir bag on the circle system?
When the "bag/vent" selector switch is set to "bag," the gas reservoir bag maintains an available reserve volume of gas to satisfy the patient's spontaneous inspiratory flow rate (up to 60 L/min), which greatly exceeds conventional fresh gas flows (commonly 3 to 5 L/min) from the anesthesia machine. The bag also serves as a safety device because its distensibility limits pressure in the breathing circuit to less than 60 cm H2O, even when the APL valve is closed.
What parts of a circle system are eliminated in anesthesia machine ventilators when the "bag/vent" selector switch is set to "vent"?
When the anesthesia machine ventilator "bag/vent" selector switch is set to "vent," the gas reservoir bag and APL valve are eliminated from the circle anesthetic system and the patient's ventilation is delivered from the mechanical anesthesia ventilator.
What are some common equipment errors?
breathing circuit disconnections; breathing circuit leaks; breathing circuit misconnections; breathing circuit control error; inadvertent gas flow control errors; gas supply problems; vaporizer control errors; IV drug/ fluid delivery system problems; ventilator misstating or malfunction; misuse of monitors; laryngoscope malfunction; scavenging system problems; soda lime exhaustion; sensor failure; blood warmer malfunction
What is a disadvantage to the closed circle anesthetic breathing system?
disadvantage of a closed circle anesthetic breathing system is an inability to rapidly change the delivered concentration of anesthetic gases and oxygen because of the low fresh gas inflow.
Problems that can be encountered at remote locations during anesthesia
lack of continuous electrical supply; lack of continuous supply of oxygen and nitrous oxide (only place that has nitrous oxide is in the OR); difficulty with storage of drugs and equipment; difficult in transport and supply of drugs and equipment; lack of maintenance of equipment; lack of skilled assistance
How is the delivery of two different volatile anesthetics to the same patient via the same anesthesia machine prevented?
safety interlock mechanism ensures that only one vaporizer at a time can be turned on.
What is impedance?
sum of forces that impede (oppose) electron movement in an AC circuit affected by capacitance and inductance
Electrical Power Grounding
the power comes from the electrical utility is grounded when a wire is intentionally connected to ground. Done for safety it prevents buildup of electricity in the wiring of the house preventing electrical shocks.
