Stoelting Study 10 Anesthesia Systems

Front 1

3. What is the purpose of the fail-safe valve? What triggers the fail-safe valve on the anesthesia machine?

Back 1

3. The purpose of the fail-safe valve on the anesthesia machine is to prevent the continued delivery of gases when the oxygen supply to the machine has malfunctioned. The fail-safe valve on the anesthesia machine is triggered when the pressure of oxygen in the delivery line falls to 28 psi. When the fail-safe valve is triggered, it either shuts off or proportionally decreases the flow of all other supply gases, depending on the anesthesia machine. Note, it is only the pressure of oxygen that the fail-safe valve responds to

Front 2

8. How is an erroneous hook·up of a gas cylinder to the anesthesia machine minimized?

Back 2

8. An erroneous hook-up of a gas cylinder to the anesthesia machine is minimized in two ways. First, the cylinders are color-coded. Second, and more importantly, the connections of the cylinders to the anesthesia machine are via hanger yoke assemblies. The hanger yoke assembly functions to support and orient the cylinder, provide a gas-tight seal, and provide for the unidirectional flow of gases into the machine. The hanger yoke assembly connections are made gasspecific by the Pin Index Safe~ System. The Pin Index Safety System consists of two metal pins that fit with two corresponding holes in the gas cylinder. Thus the connection IS s~d to be pin·indexed. Each gas has its own specific pin arrangement thereby minimizing the risk of misconnection

Front 3

10. How is the pressure of oxygen related to the volume of oxygen in an oxygen gas cylinder?

Back 3

10. The pressure of oxygen is directly proportional to the volume of oxygen in an oxygen gas cylinder, allowing the volume of gas in an oxygen cylinder to be estimilted based on the oxygen pressure. 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.

Front 4

11. How is the pressure of nitrous oxide related to the volume of nitrous oxide in a cylinder containing nitrous oxide gas?

Back 4

ll. The pressure of nitrous oxide is unrelated to the volume of nitrous oxide in the cylinder. The pressure gauge on a nitrous oxide cylinder will continue to read about 750 psi despite what the volume of nitrous oxide is In the cylinder. This is because nitrous oxide exists partially as a gas and partially as a liquid in the cylinder. The vapor pressure of the liquid is 750 psi, so as long as there is any liquid left in the cylinder the pressure will remain the same. When the stores of nitrous oxide become so depleted that there is no liquid left, the pressure in the ;~:;~~~!~~::n~:;::~;1;1~~~~;~~:O~~:~~;:;'~!;~~;~;~~;; oxide in a cylinder becomes fully vaporized to gas when it is approximately ) depleted. Therefore, when a decrease in pressure is noted in a cylinder of of oxide, the cylinder must be near empty.

Front 5

17 What is the purpose of the oxygen flush valve?

Back 5

17. The purpose of the oxygen flush valve is to provide large volumes of oxygen to the patient quickly. Oxygen delivered to the patient when the oxygen flush valve is depressed bypasses pressure regulators, the flowmeters, and the manifold.

Front 6

18. What is the flow of oxygen delivered to the patient when the oxygen flush valve is depressed?
What is the risk of this?

Back 6

18. The flow of oxygen that is delivered to the patient via the oxygen flush valve is 35 to 75 L/min

Front 7

21. What is vapor pressure? What influence does temperature have on vapor pressure:

Back 7

21. Placement of a volatile liquid in a closed container will result in liquid molecules reaching a steady-state equilibrium with gas molecules in the container over time. The vapor pressure is the pressure exerted by the gas on the walls of the container at equilibrium. An increase in temperature increases the amount of liquid molecules that become gas molecules, thus increasing the pressure exerted by the gas on the container. An increase in temperature therefore results in an increase in the vapor pressure.

Front 8

22. What is the heat of vaporization?

Back 8

22. The heat of vaporization is the heat required to convert 1 g of a liquid to a gas at a given temperature

Front 9

23. Describe how a vaporizer for a volatile anesthetic works.

Back 9

After passing through the fiowmeters, gases mix in the common manifold, then enter the vaporizers. Once in the vaporizer there are three different streams of flow that the gases can take. The gases may be diverted by a temperature-compensating bypass valve, they may enter the mixing bypass chamber, or they may enter the vaporizing chamber The temperature-compensating bypass valve adjusts the amount of gas that enters the other two chambers. When the temperature of the vapor is warm, more gas IS directed to the vaporizer outlet than when the temperature is relatively cooler. The opposite occurs when the temperature of the vapor is cool. That is, more of the gas is directed toward the other two chambers. The temperature-compensating valve allows the vaporizer to compensate for changes in temperature so the desired concentration of volatile anesthetic is maintained.

Front 10

25. What does the term 10. The pressure of oxygen is directly proportional to the volume of oxygen in an oxygen gas cylinder, allowing the volume of gas in an oxygen cylinder to be estimated based on the oxygen pressure. 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 variable-bypass refer to?

Back 10

25. The term variable-bypass refers to the division of gas into either the mixing bypass chamber or the vaporizing chamber based on the dialed concentration.

Front 11

50. What is the purpose of unidirectional valves in the circle system? What would occur if one of the unidirectional valves should become incompetent?

Back 11

50. The purpose of unidirectional valves in the circle system is to prevent the patient from rebreathing carbon dioxide or from breathing gases that have not been supplemerted with more oxygen. Incompetence of one of the unidirectional valves can result in hypercarbia or, if the valves were to become stuck, occlusion of the entire circuit.

Front 12

54. What is the purpose of the adjustable pressure limiting valve, or pop-off, on the circle system?

Back 12

54. The adjustable pressure limiting valve, or pop-off valve, on the circle system allows the anesthesiologist to increase the pressure in the circuit to assist or control ventilation of the lungs

Front 13

56. What is the purpose of the bellows on the anesthesia machine ventilator? What is the advantage to bellows that ascend during exhalation instead of inhalation?

Back 13

56. Bellows on the anesthesia machine ventilator deliver the anesthetic gases to the patient when compressed by air or driven by electricity. An advantage to bellows that ascend during exhalation instead of inhalation is that the bellows fill with gas during expiration. If there is a leak: in the circuit, there will not be a sufficient amount of gas to fill the bellows and the bellows will not ascend. This gives the anesthesiologist a signal that there is a leak or a disconnection in the anesthetic breathing system. In contrast, bellows that descend during exhalation may descend by the entrainment of room air by gravity during exhalation when there is a leak in the circuit. Therefore, bellows that descend during exhalation continue to cycle up and down even with a leak in the circuit. Most contemporary ventilators have ascending bellows.

Front 14

57. Are most anesthesia ventilator machines time cycled or volume cycled?

Back 14

57. Most anesthesia ventilator machines are time-cycled.

Front 15

63. Are inspired concentrations of oxygen more or less predictable when nitrous oxide is also being delivered in a closed circle anesthetic breathing system? Why?

Back 15

63. Inspired concentrations of oxygen are less predictable when nitrous oxide is also being deliveled in a closed circle anesthetic breathing system bec~use the of uptake of nitrous oxide decreases with time. This results in an increase in the exhaled concentration of nitrous oxide, and a concomitant decrease in the inhaled concentration of oxygen if the dialed concentration of oxygen for delivery is unchanged this results in a decrease in the proportional concentration of oxygen that is being inhaled by the patient.

Front 16

71. What does soda lime consist of?

Back 16

71. Soda lime corsists of approximately 94% calcium hydroxide, 5% sodium hydroxide, and 1 % potassium hydroxide. The sodium hydroxide and potassium hydroxide act as activators. I

Front 17

76. What is the optimal carbon dioxide absorbent granule size?

Back 17

76. The optimal absorbent granule sire is 4 to 8 mesh.

Front 18

78. What makes the carbon dioxide absorbent granules change color with use?

Back 18

78. Carbon dioxide absorbent granules change color from colorless to violet with use as a result of the pH indicator dye ethyl violet that i5 added to the granules. The indicator dye changes from colorless to violet in response to the carbonic acids that are formed by the neutralization reaction of the absorbent granules. This provides the anesthesiologist with an indication of how many of the granules have been exhausted by neutralization reactions with carbon dioxide.

Front 19

79. What is the maximum volume of carbon dioxide that can be absorbed per 100 g of absorbent granules?

Back 19

79. A maximum volume of 26 L of carbon dioxide can be absorbed per 100 g of absorbent granules.

Front 20

80. What does channeling in the carbon dioxide absorbent granule-containing canister refer to? How does channeling in the canister affect the efficiency of carbon dioxide neutralization?

Back 20

80. The passage of exhaled gases through pathways of low resistance in the carbon dioxide canister that results in granules being bypassed is termed channeling. This can result in absorbent granules never coming into contact with exhaled gases and in a decrease in the efficiency of carbon dioxide neutralization.

Front 21

81. What is the most frequent came of channeling in the carb)n dioxide absorbent granule-containing canister? How can it be minimized?

Back 21

81. The most frequent cause of channeling is loose packing of the carbon dioxide absorbent granules. Channeling can be minimized by shaking the canister gently :fore use.

Front 22

82. What is a potentially toxic interaction between the carbon dioxide absorbent and sevoflurane?

Back 22

82. A potentially [oxic interaction between the carbon dioxide absorbent and sevotlurane is the production of compound A. This can occur with either soda lime or baralyrne, hut the risk appears to be higher with baralyme. Other factors that may increase the risk of compound A production include the low inflow of fresh gases, high concentrations of sevofiurane, higher absorbent temperatures, and fresh absorbent. Tie concern with compound A is that it has been shown · to be nephrotoxic in animals. Even so, no clinical cases of nephrotoxicity have )ccurred in humans, even with low gas inflows

Front 23

83. What is a potentially toxic interaction between the carbon dioxide absorbent and desflurane?

Back 23

83. A potentially toxic intera::tion between the carbon dioxide absorbent and desBurane is the clinically significant production of carbon monoxide. Carboxybemoglobin concentratIons can reach as high as 30%. This can occur with either soda lime or baralyme, but the production of carbon monoxide appears to be greater with baralyme. Other factors that appear to increase the production of carbon monotide include higber anesthetic concentrations, an increased temperature, and greater dryness of the absorbent. T I 84.

Front 24

84. How can inhaled gases delivered to the patient be humidified?

Back 24

Inhaled gases delivered to the patient can be humidified by the addition of water i vapor to the gases.

Front 25

87. What are some of the benefits of the humidification of inspired gases?

Back 25

87. Benefits of the humidification of inspired gases include the preservation of respiratory epithelium from damage, the prevention of the drying of secretions, and the prevention of water and heat loss from the patient. This is especially important in pediatric patients in whom heat loss can occur rapidly under general anesthesia.

Front 26

91. What is the recommendation by the National Institute of Occupational Safety and Health for the maximum atmospheric concentrations of nitrous oxide and volatile anes1hetics in parts per million?

Back 26

91. The National Institute of Occupational Safety and Health recommends that the maximum atmospteric concentrations of nitrous oxide be lower than 22 parts per million (ppm), and volatile anesthetic atmospheric concentrations should be lower than 5 ppm.

Front 27

92. What concentration of nitrous oxiide in parts per million should alert personnel to examine the anesthesia machine for leaks?

Back 27

92. A concentration greater than 200 parts per million of nitrous oxide should alert personnel to examine theaneliliesia machine for leaks. C

Front 28

96. From which part of the anesthesia breathing system are gases scavenged?

Back 28

96. Gases are scavenged from the anesthesia breathing system at the adjustable pressure limiting valve. Gases that normaly exit the anesthetic breathing system through this valve are captured by a slight suction device and umally delivered · to a central vacuum system in the hospital for disposal.