VALLEY: EQUIPMENTS & INSTRUMENTATION Flashcards

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

The check valve on the hanger yoke prevents back-flow pressure in a gas cylinder.

Answer 5

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. [

Answer 6

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.

Answer 7

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.

Answer 8

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.

Answer 9

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.

Answer 10

High cylinder pressures are measured by the Bourdon gauge. The Bourdon gauge measures pressure relative to the atmosphere.

Answer 11

One atmosphere

Answer 12

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.

Answer 13

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.

Answer 14

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.

Answer 15

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

Answer 16

Variable orifice flow meters use rotating indicators (rotamer).

Answer 17

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

Answer 18

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

Answer 19

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.

Answer 20

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

Answer 21

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.

Answer 22

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.

Answer 23

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

Answer 24

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

Answer 25

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.

Answer 26

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.

Answer 27

One milliliter ofliquid volatile anesthetic produces - 200 milliliters of anestheticvapor at 20 °C and 1 atmosphere. [

Answer 28

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

Answer 29

The keyed filling port system on modern vaporizers lessens the chance of filling with the incorrect agent.

Answer 30

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

Answer 31

Desflurane is delivered from a heated (39 degrees C) and pressurized ( 1300 mm-Hg) vaporizer. The desflurane vaporizer is not a flow-over vaporizer

Answer 32

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.

Answer 33

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.

Answer 34

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 ...

Answer 35

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

Answer 36

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.

Answer 37

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

Answer 38

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

Answer 39

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

Answer 40

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.

Answer 41

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.

Answer 42

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

Answer 43

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.

Answer 44

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

Answer 45

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.

Answer 46

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

Answer 47

High-priority alarms may not be silenced for more than 2 minutes

Answer 48

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

Answer 49

The scavenging system needs to be checked daily as outlined by the FDA in 1993

Answer 50

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.

Answer 51

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. [

Answer 52

The outlet of the scavenging system can be a direct line to the outside or a connection to the hospital's vacuum system

Answer 53

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

Answer 54

One relief valve is for negative pressure and one is for positive pressure

Answer 55

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.

Answer 56

If the flow of waste gases into the vacuum system is too high and the bag collapses, the negative valve opens and lets in room air

Answer 57

A proportioning system on the anesthesia workstation is a hypoxia prevention safety device. Manufacturers equip anesthesia workstations with proportioning systems in an attempt to prevent creation and delivery of a hypoxic mixture. Nitrous oxide and oxygen are mechanically and/or pneumatically linked so that the minimum oxygen concentration at the common gas outlet is between 23 to 2S% depending on manufacturer.

Answer 58

The Link-25 system is found on conventional Datex-Ohmeda machines. The heart of the system is the mechanical integration of the nitrous oxide and oxygen flow control valves. It allows independent adjustment of either valve, yet automatically intercedes to maintain a minimum 2S% oxygen concentration with a maximum nitrous oxide-oxygen flow ratio of 3: 1. The combination of the mechanical and pneumatic aspects of the system yields the final oxygen concentration. The Link-25 proportioning system can be thought of as a system that increases oxygen flow when necessary to prevent delivery of a fresh gas mixture with oxygen concentration ofless than 25

Answer 59

The following five situations can lead to delivery of hypoxic gas mixtures on workstations equipped with proportioning systems: (1) wrong supply gas, (2) defective pneumatics or mechanics, (3) leaks downstream, (4) inert gas administration, and (5) dilution of inspired oxygen concentration by volatile inhaled anesthetics.

Answer 60

An inert, third gas, such as He, N2 or C02, can cause delivery of a hypoxic mixture because contemporary proportioning systems link only nitrous oxide and oxygen. Use of an oxygen analyzer is mandatory (or preferentially a multigas analyzer, when available) if the operator uses a third gas

Answer 61

Double-circuit ventilators (bellows in a box, bag in a bottle), in which one circuit contains patient gas and the other circuit contains drive gas, are used most commonly on modem anesthesia workstations. The bellows is housed in a pressure chamber, and the inside of the bellows is connected to the breathing system. The double-circuit separates breathing system gas from driving gas. Generally, these conventional ventilators are pneumati· cally driven.

Answer 62

In pressure control mode, the ventilator is set so that the inspiratory pressure is greater than the positive end·expiratory pressure. In this mode, tidal volume fluctuates (varies) with alterations in patient pulmonary compliance, pulmonary resistance, and with patient-ventilator asynchrony

Answer 63

Operation of the jet ventilator is based on the Venturi effect and Bernoulli principle.

Answer 64

Pressure ventilators terminate the inspiratory phase when a pre·selectedpressure is achieved in the ventilator circuit. When this pressure is reached, the ventilator cycles

Answer 65

Decreasing PEEP could be helpful. Increasing the I:E ratio means that the positive airway pressure will be maintained for a longer period of time during each ventilatory cycle, which further decreases venous return, cardiac output and blood pressure. Likewise, changing to CPAP will cause airway pressure to be positive throughout the ventilatory cycle, which could further decrease venous return, cardiac output and blood pressure.

Answer 66

CPAP: {I) increases lung compliance, which decreases the work of breathing; (2) diminishes ventilation:perfusion mismatching; and (3) increases tidal volume above dosing volume

Answer 67

(l) CPAP of 5- 10 cm H20 is commonly applied when patients are intubated. It helps to maintain FRC and may prevent atelectasis since the normal mechanism for maintaining airway and alveolar patency (mild resistance to airflow by the epiglottis and upper airway structures} is bypassed by the endotracheal tube. (2} CPAP is used to maintain FRC in the postoperative period. (3) CPAP to the non-dependent lung may be useful during one-lung anesthesia; this reduces shunt.

Answer 68

(l) CPAP ofS- 10 cm H20 is commonly applied when patients are intubated. It helps to maintain FRC and may prevent atelectasis since the normal mechanism for maintaining airway and alveolar patency (mild resistance to airflow by the epiglottis and upper airway structures} is bypassed by the endotracheal tube. (2} CPAP is used to maintain FRC in the postoperative period. (3) CPAP to the non-dependent lung may be useful during one-lung anesthesia; this reduces shunt.

Answer 69

Ifloss oflung volume is significant, CPAP is very effective for restoring (increasing} or maintaining FRC

Answer 70

The goal of optimal positive end-expiratory pressure ventilation (PEEP) is to achieve optimal arterial oxygenation with an F102 $ 0.5 with the least decrement in cardiac output and tissue perfusion. The 2 universal pulmonary effects of PEEP are redistribution of extravascular water and increased FRC, through maximal alveolar recruitment. As FRC increases, oxygenation increases. Remember: FRC is an oxygen reservoir/reserve

Answer 71

PEEP, because it compresses alveolar capillaries, decreases return of blood to the left ventricle (decreases preload), and hence stroke volume, cardiac output, and systemic arterial blood pressure all decrease. Arterial hypotension may occur. Central venous pressure may increase.

Answer 72

(l) Pulmonary barotrauma; (2) increased extravascular lung water; (3) redistribution of pulmonary blood flow.

Answer 73

With prophylactic PEEP. 1-5 cm of water is used to increase functional residual capacity in order to prevent atelectasis and to decrease shunting.

Answer 74

With conventional PEEP. 5- 20 cm of water is applied if Pa02 is less than 60 mm Hg with Fi02 exceeding 50%. The best PEEP is defined as the level of PEEP with the highest oxygen transport, which is the product of cardiac output and oxygen content. This PEEP correlates with the highest total respiratory compliance, the highest mixed venous oxygen tension, and the lowest VD/VT.

Answer 75

The level of PEEP that produces maximal arterial blood oxygenation without over-distention of alveoli, as reflected by static Jung compliance, is known as "best" PEEP. Initially, PEEP is added in 2.5-5 cm water increments while breathing less than 50% 01. The goal is to deliver the amount of PEEP that maximally improves Pa02 without substantially decreasing cardiac output or increasing risk of pulmonary barotrauma

Answer 76

High PEEP is defined as the level of PEEP with the lowest intrapulmonary shunt and without compromising cardiac output. The PEEP used in this report is so-called high or super PEEP, more than 25 cm H10

Answer 77

Positive pressure ventilation at 25 cm H20 would not be enough pressure to ventilate if: (1) the upper airway is obstructed, (2) the patient has sufficient muscle tone to prevent chest expansion, (3) the individual has decreased pulmonary compliance, or ( 4) the individual has increased pulmonary resistance.

Answer 78

Intermittent positive pressure ventilation (IPPV) causes compression of pulmonary capillaries with a shift of blood from capillaries to pulmonary arteries and veins. [

Answer 79

Intermittent positive pressure ventilation (IPPV) causes compression of pulmonary capillaries with a shift of blood from capillaries to pulmonary arteries and veins.

Answer 80

Intermittent positive pressure ventilation (IPPV) decreases venous return to the left ventricle, decreases cardiac output and decreases arterial blood pressure; it may increase heart rate (reflex).

Answer 81

Intermittent mandatory ventilation (IMV) allows a patient to breath spontaneously around a baseline pressure (PEEP) in between mandatory breaths. IMV circuits provide a continuous supply of fresh gas flow for the spontaneous breaths between mechanical breaths. Note: with IMV the patient is breathing above the set minute ventilation

Answer 82

Intermittent mandatory ventilation is often used to wean a patient from mechanical ventilation. NB: Barash makes the point that "weaning from mechanical ventilation" is better termed "liberation" or "separation" from mechanical ventilation.

Answer 83

Seven objective criteria supporting the feasibility of withdrawing mechanical ventilation are: ( l) vital capacity > l S ml/kg (Barash states > 10 ml/kg), • (2) A-aD02 < 3SO mm-Hg while breathing 100% 0 2, (3} Pa02 > 60 mm-Hg while breathing 50% 02. ( 4} maximal negative inspiratory pressures more than 20 cm H20, (S) normal pH maintained, (6} spontaneous respiratory rate <20 breaths per minute, and (7) VD/VT < 0.6. [

Answer 84

Synchronized intermittent mandatory ventilation (SIMV) is a refinement of intermittent mandatory ventilation (IMV} in which the intermittent mandatory breaths are delivered in synchrony with, and triggered by, the patient's spontaneous efforts. SIMV can be used for full to partial support of ventilation and helps to prevent "fighting the ventilator~ and "breath stacking:'

Answer 85

Synchronized intermittent mandatory ventilation (SIMV} may be used in either pressure- or volume-cycled mode. A trigger window controls the amount of time during each expiratory cycle that the ventilator is sensitive to spontaneous breaths, by sensing negative (subatmospheric) pressure generated by the patient's diaphragm.

Answer 86

To wean a patient from synchronized intermittent mandatory ventilation (SIMV}, progressively decrease the number of breaths (by 1-2 breaths/ minute} as long as the arterial C01 tension and respiratory rate remain acceptable (generally< 45- 50 mm Hg and less than 30 breaths per minute}.

Answer 87

In assist/control (AC) ventilation, the patient is allowed to set the respiratory rate by activating the inspiratory trigger function. In volume assist/ control mode, each patient effort of sufficient magnitude will trigger the set tidal volume. In pressure assist/control, the patient again sets the frequency and the upper limit of pressure- the tidal volume varies, and consistency is sacrificed to prevent barotrauma by high pressures. As a safety measure, if no spontaneous effort occurs, the ventilator will deliver controlled breaths at a preselected backup rate. The variable used by the ventilator to cycle off the breath is time.

Answer 88

Tracheal extubation is reasonable if patients ( l} tolerate 2 hours of sponta· neous breathing during T-tube weaning, OR {2) when an SIMV (synchronized intermittent mandatory ventilation) rate of 1-2 breaths per minute is tolerated without deterioration of arterial blood gases, mental status, or cardiac functio

Answer 89

A large tidal volume (10-15 ml/kg) combined with a slow inspiratory flow rate minimizes the likelihood of turbulent flow through the airways and optimizes ventilation-perfusion matching. A slow breathing rate (6-8 breaths/min} provides sufficient time for exhalation to occur

Answer 90

Optimal size of 4-8 mesh represents a compromise between absorptive capacity and resistance to air flow through the canister

Answer 91

The advantage is increased absorptive capacity due to increased surface area. The disadvantage is that smaller granules also lead to increased resistance to gas flow due to smaller interspaces

Answer 92

A total obstruction of the circle system occurs if the clear plastic shipping wrapper is not removed from the C02 canister before use

Answer 93

Increase the fresh gas flow rate. [

Answer 94

Six early clinical signs of carbon dioxide absorbent are: ( 1) increased ETC02, (2) respiratory acidosis, (3) hyperventilation, (4) signs of sympathetic nervous system activation, (5) increased bleeding at surgical site, and (6) color of indicator. Two late clinical signs of an exhausted C02 absorbent are: (1) increase (and later a decrease) in heart rate and blood pressure, and (2) dysrhythmias.

Answer 95

About 50%. The air space occupies 48- 55% of the volume of the canister.

Answer 96

15 liters of C02 can be absorbed for each 100 g of soda lime

Answer 97

Calcium carbonate (a precipitate), sodium hydroxide, potassium hydroxide, water, and heat.

Answer 98

Ca(OH}i, CaC!i. Caso., polyvinylpyrrolidone, and water

Answer 99

Calcium hydroxide (Ca(OH)2] is the most abundant component of both soda lime and Amsorb. Soda lime has 62% Ca(OHh and Amsorb has 80% Ca(OHh. [

Answer 100

Neutralization.

Answer 101

American Society for Testing and Materials (ASTM) standards for reservoir bags require that with a bag of l.S Lor smaller with a pressure not less than 30 cm H20 or greater than SO cm H20 when the bag is expanded to four times its capacity. Latex.free bags may allow greater pressures to develop

Answer 102

l) Conservation of gases, (2) conservation of body heat, (3) conservation of moisture (H20 ), (4) minimal operating room pollution, and (5) relative constancy of inspired gas concentration.

Answer 103

The major disadvantages of a closed circle system stem from the complex design. Since there are ten or more connections, the circle system is prone to: (1) disconnects; (2) obstructions; (3) leaks; and, (4) malfunction of uni·directional valves. The larger size of a circle system (5) limits portability. Other shortcomings of a closed circle system are: (6) increased deadspace; (7) complications due to use of an absorbent; {8) difficulty predicting inspired gas concentration during low fresh gas flow; and, (9) some components are difficult to clean.

Answer 104

Although disconnections can occur anywhere in the breathing system, the most common site is between the breathing system and tracheal tube connector or heat moisture exchanger

Answer 105

Unidirectional valves ensure gas flow to and away from the patient.

Answer 106

Fresh gas enters through the common gas outlet via the fresh gas delivery hose

Answer 107

Between the Y-piece and the patien

Answer 108

The adjustable pressure limiting (APL) valve automatically relieves pressure within the semi-closed system. The APL adjusts the limit of positive pressure attained within the patient circuit and alters the amount of gas contained within the rebreathing bag. When the desired pressure in the circuit is exceeded, gas flows out of the APL valve and is vented into the scavenging system

Answer 109

A closed system exists when there is complete rebreathing of expired gas

Answer 110

The fresh gas inflow for a closed system of 150 to SOO ml 01/min satisfied the patient's oxygen requirements (150- 25O ml 02/min) during anesthesia

Answer 111

(1) Maximum humidification, (2) efficiency of gas usage, {3) less pollution of gases to atmosphere, and (4) economy

Answer 112

Inability to rapidly change the delivered concentration of anesthetic gases and 02.

Answer 113

With respect to prevention of rebreathing during spontaneous ventilation, the relative efficiency ofMapleson systems is A> DFE > CB.

Answer 114

With respect to prevention of rebreathing during controlled ventilation, the relative efficiency ofMapleson systems is DFE > BC > A.

Answer 115

The semi-closed breathing system

Answer 116

The oxygen sensor should be placed in the inspiratory limb of a circle system.

Answer 117

( l) Close APL (pop-off) valve and occlude system at patient end. (2) Fill system via 02 flush until bag is full while keeping pressure in system negligible. Set 02 flow to 5 L/min. (3) Slowly decrease O2 flow until pressure no longer rises above 20 cm H20. This approximates total leak rate, whichshould be no greater than several hundred ml/min (less for dosed circuit techniques). CAUTION: Check valves in some machines make it imperative to measure flow in step (3) when pressure just stops rising. (4) Squeeze bag to pressure of about 50 cm H20 and verify that system is tight

Answer 118

The low-pressure circuit is the most vulnerable part of the anesthesia machine because the components located within this area are the ones most subject to breakage and leaks.

Answer 119

A positive end-expiratory pressure (PEEP) valve must be placed in the expiratory side of the breathing system.

Answer 120

The ASTM standard requires that a PEEP valve be marked with an arrow indicating proper direction of gas flow or the words inlet and outlet or both.

Answer 121

The anesthesia workstation, as defined by the ASTM International (ASTM) originally known as the American Society for Testing and Materials), is a system for administering anesthetics to patients consisting of the anesthesia gas supply device (the anesthesia machine). the anesthesia ventilator, monitoring devices, and protection devices.

Answer 122

The two basic components of the anesthesia machine proper are (I) the pressure-regulating components, and (2) the gas-mixing components.

Answer 123

In order to comply with ASTM Fl850 standards, the anesthesia workstation must have: ( l) battery backup for 30 minutes; (2) alarms, grouped into high, medium, and low priority; (3) various required monitors; (4) breathing circuit pressure limited to 125 cm water ( 12.S kPa); (S) a nondetachable electrical supply cord or a cord resistant to detachment; (6) cylinder supplies; and, (7) flowmeters

Answer 124

(I) An oxygen flush, capable of 35 to 75 L/min flow that does not proceed through any vaporizers; (2) vaporizers; (3) only one common gas outlet at 22-mm outer diameter, 15-mm inner diameter, which is designed to prevent accidental disconnection; (4) pipeline gas supply; (5) a checklist must be provided (it may be electronic or performed manually by the user); and (6) a digital interface. (

Answer 125

Pipeline gas supply to the anesthesia workstation must have (or be): (I) a pipeline pressure gauge; (2) inlets for at least oxygen and nitrous oxide; (3)protected by a diameter index safety system (DISS); (4) an inline filter; and, (5) a check valve. [

Answer 126

Seven criteria for anesthesia workstation cylinder supplies are: ( l} the machine must have at least one oxygen cylinder attached; (2) the hanger yoke must be pin indexed; (3) the hanger yoke must have a damping device that resists leaks; (4) the hanger yoke must contain a filter; (5) the hanger yoke must have a check valve to prevent transfilling; (6} the hanger yoke must have a cylinder pressure gauge; and, (7) there must be cylinder pressure regulators.

Answer 127

Seven required features of anesthesia workstation flowmeters are: (I) there must be a single control for each gas; (2) each flow control must be next to a flow indicator; (3) the oxygen flow control knob must be uniquely shaped; (4) valve stops are required such that excessive rotation will not damage the flow meter; (5) the oxygen flowmeter is to the right side of the flowmeter bank; (6) oxygen enters the common manifold downstream of other gases; and, (7) an auxiliary oxygen flowmeter is strongly recommended.

Answer 128

The five tasks of oxygen in the anesthesia gas machine are: ( 1) it proceeds to the fresh gas flowmeter; (2) powers the oxygen flush, (3) activates fail-safe mechanisms; (4) activates oxygen low-pressure alarms; and, (5} compresses the bellows of mechanical ventilators

Answer 129

Components found in the low pressure system include: ( l) flowmeter tubes, (2)vaporizers, (3) check valves, and (4) the common gas outlet.

Answer 130

To perform a negative-pressure leak test, a suction bulb is attached to the common fresh gas outlet and squeezed repeatedly until the bulb is fully collapsed. The anesthesia machine is leak-free is the bulb remains collapsed for at least 10 seconds.

Answer 131

35-75 liters/min.

Answer 132

At least each day before the first case or if anesthesia providers change during the day.

Answer 133

A damaged or defective flush valve can stick in the fully open position causing barotrauma

Answer 134

The concern in this situation is the presence of trace amounts of volatile agents in the rubber and plastic components of the gas machine and in the ventilator and CO2 absorber. The following 3 actions should be taken to prepare the gas machine for the patient with a known susceptibility to malignant hyperthermia. ( l) The gas machine should be thoroughly flushed with 100% oxygen for at least 10 minutes to remove residual traces of volatile agents from rubber and plastic components in the machine. (2) The breathing circuits and C02 canister should be replaced. (3) Vaporizers should be drained, inactivated, or removed

Answer 135

The descending bellows (hanging bellows) descends during the expiratory phase.

Answer 136

If a disconnect happens, the descending bellows will continue its upward and downward movement. The drive gas pushes the bellows upward during the inspiratory phase. During the expiratory phase, room air is entrained into the breathing system at the site of disconnect because gravity acts on the weighted bellows

Answer 137

The ascending bellows is safer. The ascending bellows will not rise if disconnection occurs. The ascending bellows also permits easier detection of circuit leaks or disconnects and less chance of high airway pressures from gas entering the breathing circuit through bellow lea

Answer 138

The respirometer measures exhaled gases. Tidal volume settings of the ascending bellows, as indicated on the outside of the plastic canister, differ from respirometer readings. This is due to compression of gases, expansion of the breathing circuitry hoses during the mechanically ventilated inspiration, and the addition of humidifiers. Decreased lung compliance will also force gases that were not used by the patient through the respirometer

Answer 139

During the expiration phase of the ventilatory cycle, exhaled gases from the patient and f resh anesthetic gases flow into the bellows. (

Answer 140

Pressurized oxygen from the ventilator power outlet is found between the inside wall of the enclosure and the outside wall of the bellows. The inside of the bellows, which is an extension of the anesthesia breathing circuit, is filled with all anesthetic gases. This arrangement holds for both the ascending and descending bellows

Answer 141

The goal is to improve mobilization of secretions by increasing water content (reducing airway drying} and decreasing viscosity.

Answer 142

A nasopharyngeal airway (nasal airway, nasal trumpet) is better tolerated than an oral airway if the patient has intact airway reflexes. A nasal airway is preferable if the patient's teeth are loose or in poor condition, if there is trauma or pathology of the oral cavity and can be used when the mouth cannot be opened

Answer 143

Contraindications to a nasopharyngeal airway include (1) anticoagulation, (2) basilar skull fracture, (3) pathology, sepsis, or deformity of the nasal cavity or nasopharynx, and (4) a history of nosebleeds requiring medical treatment.

Answer 144

The length of a nasal airway can be estimated as the distance from the naresto the meatus (opening) of the ear. The length should be 2-4 cm longer than a corresponding oral airway.

Answer 145

Any airway creates an artificial, patent passage to the hypopharynx. Oral airways are used to (l) prevent the patient from biting an oral tracheal tube, (2) protect the patient from biting the tongue, (3) facilitate oropharyngeal suctioning, (4) obtain a better mask lit, and (5) provide a pathway for inserting devices into the esophagus or pharynx

Answer 146

An oral airway is indicated for an obstructed upper airway in an unconscious patient and when there is need for a bite block in an unconscious patient. An oral airway is contraindicated in the awake or lightly anesthetized patient-the patient may cough or develop laryngospasm during airway insertion iflaryngeal reflexes are intact

Answer 147

The flange projects off the left side of the laryngoscope and serves to sweep the tongue out of the way and to guide instrumentations along the laryngoscope blade

Answer 148

A lighted intubation stylet (lightwand, {flexible} lighted stylet, Trachlight-, illuminating or lighted intubating or intubation stylet) uses transillumination of the soft tissues in the anterior neck to guide the tip of the tracheal tube into the trachea or to determine the position of the tracheal tube or other airway device. During direct laryngoscopy, the lighted stylet can be used to improve the view in the hypopharynx. The lighted stylet is especially useful in situations where a liberscope is unavailable or endoscopy is difficult to perform (e.g.. • when an airway is obscured by blood or secretions or when a patient's head cannot be flexed or extended).

Answer 149

For oral intubation, an anterior T or "hockey stick" bend of approximately 75- to 90-degrees just proximal to the cuff is recommended. Sandberg recommends bending a Trachlight to an "I.:' shape. Care should be taken not to bend the stylet at the point at which the bulb meets the shaft. NB; the range of the bend for adult oral intubation is 75- to 120-degrees in the texts.

Answer 150

For nasal intubation, the shape of the lighted intubation stylet should be prepared against the patient profile.

Answer 151

To better suit and match pediatric anatomy, the Trachlight (lightwand} should be bent to 60 to 80 degrees instead of the more typical 90 degrees ("hockey stick"). Note: the range of the bend for adult oral intubation is 75 to 120 degrees in the texts.

Answer 152

An airway exchange catheter (guiding catheter, director, stylet catheter, catheter guide, elastic stylet, tracheal tube replacement obturator, tube changer or exchanger, ventilation or exchange bougie, jet-style catheter, jet stylet, intu· bation catheter, intubating introducer) can be used for a number of purposes including: tracheal tube or supraglottic device exchange, replacing and existing tube, changing a tracheal tube from oral to nasal, intubation, extubation, to provide ventilation during microlaryngeal surgery, to provide a useful guide to the trachea during flexible endoscopy. and facilitating passage of a tracheal tube over a fiberscope.

Answer 153

Airway exchange catheters have a central lumen, and rounded, atraumatic ends. The catheters are graduated from the distal end. The proximal end is fitted with either a 15-mm or a Luer-lock Rapi-Fit adapter, which can be quickly removed and replaced for ETT removal or exchange. With these adapters an oxygen source can be used to provide insufflated or jet-ventilated oxygen if the patient fails extubation and/or if reintubation over the catheter fails

Answer 154

Auscultation of bilateral breath sounds and a normal end-tidal C02 waveform ( capnography) indicate successful placement of the Combitube.

Answer 155

Nine complications of an airway exchange catheter are: (l) airway perforation, risk of is related to depth of insertion, (2) jet ventilation through an AEC may lead to barotrauma, (3) the tracheal tube may fail to pass over the AEC, (4) part of the AEC may break off and be aspirated, (5) the exchange catheter may be inadvertently removed, ( 6) the replacement tracheal tube may not end up in the trachea, (7) the channel in the AEC may become occluded by secretions, incorrectly implying placement in the esophagus, (8) the AEC may exit through the side hole in the tracheal tube, and (9) thecatheter may shear off

Answer 156

The Esophageal· Tracheal Combitube (ETC) is not intended for long-term airway management and should be removed within a few hours to decrease the risk of ischemia of the tongue and subsequent edema formation.

Answer 157

The Eschmann introducer is a 60-cm, sty/et-like device that has a 5-mm external diameter and a 35-degree bend 2.5 cm from the end that is inserted into the trachea. Its structure is designed to provide a combination • of stiffness and flexibility.

Answer 158

When providing positive-pressure ventilation with a manual resuscitator, such as a bag-valve mask, it is imperative to limit the positive pressure to 25 cm H20 to avoid inflating the stomach, which increases the risk of regurgitation

Answer 159

Transtracheal jet ventilation is a technique used to provide oxygenation from a high-pressure delivery system. More specifically, transtracheal jet ventilation is the injection of high-velocity gas into the airway through a narrow cannula, without a seal

Answer 160

If a high-pressure system is available forexample, a metered and adjustable oxygen source with a hand-controlled valve and a Luer-lock connector 15 to 30 psi of oxygen (central hospital supply or regulated cylinder) can be delivered directly through the catheter, with insutllations of l to l.5 seconds at a rate of 12 insufflations per minute. If a 16-gauge catheter has been placed, this system will deliver a tidal volume of 400 to 700 mL. At a delivered pressure of 5O psi, a 16-guage delivers 5OO mL of oxygen per second. In most instances, 25 psi is a sufficient inspiratory pressure (Nagelhout).

Answer 161

Low-pressure systems cannot provide enough flow to expand the chest adequately for oxygenation and ventilation

Answer 162

During transtracheal jet ventilation at a delivered pressure of SO psi, a 20-gauge catheter delivers approximately 400 mL of oxygen per second, a 16-gauge catheter delivers SOO mL of oxygen per second, and a 14-gauge catheter delivers 1600 mL of oxygen per second.

Answer 163

Three complications associated with transtracheal jet ventilation are: (1) barotrauma; (2) tissue emphysema; and, (3) exhalation difficulties

Answer 164

Disinfection is a process capable of destroying most microorganisms but, as ordinarily used, not bacterial spores. Sterilization is a process capable of removing or destroying all viable forms of microbial life, including bacterial spores, to an acceptable sterility assurance level.

Answer 165

The three levels of disinfection, as adopted by the Centers for Disease Control and Prevention (CDC) are as follows. (I) High-level Disinfection, Intermeidate level disinfection and Low level disinfection.

Answer 166

A procedure that kills all organisms with the exception of bacterial spores and certain species, such as the Creutzfeldt-Jakob prion. Most high-level disinfectants can produce sterilization with sufficient contact time.

Answer 167

procedure that kills vegetative bacteria, including acid-fast Mycobacterium tuberculosis, most fungi, and viruses but not bacterial spores.

Answer 168

A procedure that kills most vegetative bacteria (but not M. tuberculosis), some fungi, and viruses but no spores.

Answer 169

Pasteurization is a high-level disinfection process in which the equipment is immersed in water at an elevated temperature (but below 100 degrees C) for a specified time. A typical sequence is 30 minutes at a temperature of 70 °C.

Answer 170

The minimum time for sterilization by steam at 121 °C is 15 minutes.

Answer 171

Chemical (cold) disinfection / sterilization involves immersing an item in a solution that contains a disinfectant. This method is especially useful for heat-sensitive equipment. It can be accomplished by automated equipment, which typically provides a cycle of cleaning, rinsing, disinfection, rinsing, and sometimes drying.

Answer 172

(1) quaternary ammonium compounds (2) alcohols, (3) glutaraldehydes (Cidex•, Cetykide•, (4) hydrogen peroxide·based solutions, ( 5) formaldehyde andother aldehydes (6) phenolic compounds, and (7) chlorine (hypochlorite, bleach).

Answer 173

Only glutaraldehyde (Cidex) and hydrogen peroxide-based solutions will destroy spores.