The Anesthesia Gas Machine Flashcards

Question

How does a datex -ohmeda **low-pressure alarm sound?** when does it sound?

Answer 1

* **Datex-Ohmeda: O2 supply failure** alarm **_whistles_** when the machine _turned on_ * When **the pressure _decreases to 28 psi**_ or when the machine is _**turned off,_ whistles again**

Answer 2

* sounds alarm when O2 **_supply pressure reaches 37 psi_** * Series of medium[you can silence], high [continuous] and low [pop-up] priority alarms

Answer 3

The **Hypoxic guard** (proportioning system) works on **_FLOW/ CONCENTRATION_** that the patient is getting * Designed to prevent delivery of hypoxic breathing mixtures * All link O2 and N2O so that the final breathing mixture is at least **_25% +/- 4% O2_** **_Datex-Ohmeda: Link-25 system (pneumatic/mechanical)_** Flowmeter control knobs are **linked by a chain** so that O2 is increased automatically when N2O is increased ***Consists of 29 teeth 14 teeth linkage*** _Second-stage regulators incorporated_ * O2 14psi * N2O26psi **Drager: Oxygen Ratio Monitor Controller (ORMC) or Oxygen Ratio Controller (ORC)** **Maintains at least 25% O2 by limiting N2O flow;** the flow of O2 generates pressure on a diaphragm, which is linked by ***_a rod to a second diaphragm and valve in the N2O line_***, which creates an appropriate ratio

Answer 4

**Inert gas administration (third gas such as Helium) should detect with O2 analyzer** * Most dangerous situation * Able to bypass hypoxic guard system with Drager * Machine has switch with 2 positions: N2O-O2 and All Gases * In N2O-O2 position, ORMC and alarms active * In All Gases position, ORMC and alarms inactivated and all gases (except N2O) may flow without hypoxic guard protection

Answer 5

## Footnote **Splitting ratio**

Answer 6

**Variable- Bypass (vaporizers)**

Answer 7

**Datex-Ohmeda Tec 6 (Desflurane)** * Heated, dual-circuit vaporizer * Fresh gas from the common manifold passes through the vaporizer; **_it never comes in contact with the liquid agent_** * **_NO SPLITTING RATIO_** * More vapor is delivered from the vapor circuit if either the desired volume percent setting is increased or the fresh gas flow is increased * **Heated to 39\*C**; produces **vapor pressure of 1500 mmHg** * _Desflurane near boiling at room temperature; if placed in variable-bypass vaporizer, would constitute 100% of output at first, **creating a hypoxic breathing mixture**_

Answer 8

**_Interlock system_** on anesthesia machine ensures that only one vaporizer can be on and that trace vapor output is minimal when vaporizers turned off

Answer 9

## Footnote **Desflurane Tec-6**

Answer 10

* The volume of carrier gas necessary to produce the desired agent concentration **may be determined by a computer that calculates the carrier gas flow that needs to pass through the vaporizing chamber in order to produce the desired anesthetic agent concentration** * Another type of electronic vaporizer withdraws a calculated amount of liquid agent from the agent bottle and injects that liquid into the breathing system or fresh gas flow. The amount of liquid that is injected is adjusted to achieve the desired anesthetic agent concentration

Answer 11

* I**_ncorrect agent administration:_** Must **maintain diligence** during filling * **_Tipping:_** If vaporizer tips **\> 45\*,** must **contact a service agent** ----\> Entry of liquid agent into control assembly at the top of vaporizer **can deliver unpredictable amount of agent** * **Overfilling with agent**: Prevent by filling **only to the top** etched line on the liquid level indicator glass * **Simultaneous inhaled agent administration**: place **Datex-Ohmeda vaporizers next to each other if center one removed**

Answer 12

* **Flow Rate:** The output of the vaporizer is **_generally less than the dial setting at very low (\< 200 ml/min_**) or **_very high (\> 15 L/min) flows_** * **Temperature:** Automatic temperature compensating mechanisms in bypass chambers maintain a constant vaporizer output with varying temperatures * **Back Pressure:** Intermittent back pressure (e.g. *_positive pressure ventilation causes a higher vaporizer outpu_*t than the dial setting) * **Atmospheric Pressure: Changes in atmospheric pressure affect variable bypass vaporize**r output as measured by **volume % concentration**, but not (or very little) as measured by partial pressure (lowering atmospheric pressure increases volume % concentration and vice versa) * **Carrier Gas:** Vaporizers a_**re calibrated for 100% oxygen.** Carrier gases other than this result in decreased vaporizer output._

Answer 13

* delivering O2 * eliminating CO2

Answer 14

* CO2 is eliminated by washout with adequate fresh gas flows or by absorption in soda lime

Answer 15

Resistance in a circuit minimized _by reducing circuit’s length and increasing its diameter, avoiding sharp bends, eliminating valves, and maintaining **laminar flow**_

Answer 16

* **Dead space ends at the Y-piece of the circuit** * Where the inspiratory and expiratory gases diverge

Answer 17

Bag-mask Ventilation: Valve is **_usually left partially open._** During inspiration bag is squeezed pushing gas into inspiratory limb until pressure relief is reached, opening the APL valve.

Answer 18

Only 2 common reasons for an increase in inspired CO2: **_exhaustion of absorbent granules or faulty unidirectional valves_** **_Faulty unidirectional valves: increase in inspired and expired CO2_** * Should **increase fresh gas flow to 5-8 L/min**--\> converts system to semi-open in which rebreathing of gases minimized * If this causes inspired CO2 to decrease substantially, absorbent granules are exhausted and should be replaced at end of the case * **If elevated inspired CO2 persists**, ***_valves are likely to be incompetenT_*** --\> anesthetist should * remove expiratory valve * inspect , dry and reassemble it while ventilating patient with an ambu bag

Answer 19

should be zero unless smoker

Answer 20

**LOW ETCO2 WITH GOOD PLATEAU** ## Footnote * May be the result of **hyperventilation or an increase in dead space ventilation.** Comparison of PetCO2 with PaCO2 is necessary to distinguish these two conditions.

Answer 21

**HIGH ETCO2 WITH GOOD PLATEAU** ## Footnote * May be caused by **hypoventilation or increased CO2 delivery to the lungs.**

Answer 22

## Footnote **Curare Cleft/ Spontaneous Respirations**

Answer 23

**Obstruction: Prolonged Expiratory Upstroke**

Answer 24

**BASELINE ELEVATED** * May be **c_aused by an incompetent expiratory valve or exhausted absorbent in circle system_;** insufficient fresh gas flow to Mapleson system; problems with inner tube of Bain system; deliberate addition of CO2 to fresh gas; an incompetent inspiratory valve. * May also be result of r**ebreathing under drapes in spontaneously breathing patient who is not intubated**

Answer 25

**_INCOMPETENT INSPIRATORY_ VALVE** * The waveform shows a **_prolonged plateau and a slanting inspiratory downstroke_** * The inspiratory phase is shortened, and baseline may or may not reach zero, depending on fresh gas flow * A similar pattern may be seen with suction applied to a chest tube

Answer 26

**IRREGULAR PLATEAU OR BASELINE** ## Footnote * May result from displacement of tracheal tube into upper larynx or lower pharynx with intermittent ventilation of stomach and lungs or from pressure on the chest, which causes small volumes of gas to move in and out of the lungs * maybe its mainstem

Answer 27

**Classic LEAK IN SAMPLING LINE** ## Footnote * If the patient is breathing spontaneously a falsely low end-tidal carbon dioxide reading may be seen, owing to air entrainment, but no terminal hump is seen * An upswing at the end of Phase III may also be seen in obese and pregnant patients

Answer 28

* Makes **rebreathing** of gases **possible** * **Conserves agent** and gases while **preventing respiratory acidosis** that would result from rebreathing of CO2

Answer 29

change it when its all violet!

Answer 30

THE ONLY ONE THAT DOES NOT CHANGE IN COLOR! BE VIGILANT WITH FICO2!

Answer 31

**SODA LYME** --\> strongest base **lithium product has less base**; it does not have an activator --\> water content of lithium product compared to more base products has about the same of slightly higher **higher water content helps prevents dessication** **--\> Aside from Spiralith that does not have a mesh ; its is 4-8 for the rest** **--\> Spiralith does not change color**

Answer 32

When the patient **_inspires: the inspiratory valve should go up_** When the patient **_expires: the expiratory valve should go up._**

Answer 33

**_Channeling and wall effect_** Both absorbents undergo decreases in efficiency due to channeling and the wall effect * Inside edge of canister low-resistance pathway (top and along the edges) * Exhaled gas follows this pathway through the canister, forming channels (angling along the pathway forms channels) whose capacity to absorb CO2 is exhausted before the capacity of the bulk of absorbent is used * **_wall effect and channeling produce exhaustion of absorbent before capacity reached_** * *_Prevent this by **shaking canister before place in system** to promote uniform packing throughout_*

Answer 34

**CLINICAL SIGNS OF CO2 ABSORBENT EXHAUSTION** * Increase in partial pressure of EtCO2; may also see increase in inspired CO2 * Increase (and later decrease) in HR and BP * Hyperventilation * Respiratory acidosis * Dysrhythmia * SNS activation (flushed, dysrhythmias,sweating) * Increased bleeding at the surgical site (**_surgeon says theres alot of oozing)_** * Color of indicator at end of case

Answer 35

**Production of Compound A** * Found with Sevoflurane (unstable in soda lime)in studies * Renal injury at 25-50 ppm in rats ¢ Lethal at 130-340 ppm * Theoretical concern in humans * Package insert recommends that after 2 MAC hours, increase FGF to a minimum of 2 L/min

Answer 36

**Desflurane \> Enflurane \> Isoflurane \>\> Sevoflurane and Halothane** ## Footnote * Worse in dry carbon dioxide absorbent [dessicated] * Importance of using low flows and turning off flows when done

Answer 37

* Do not change in middle of case (ideally) * Increase fresh gas flow to 1-2 times MV (\>5 L/min --\> converts to semi-open circuit) * Manufacturer recommends changing * absorbent if it is left in machine for longer than 48 hours --\> overly cautious; use clinical judgment and established practice * Dehydration and CO production are concerns with high gas flows used or flows left on overnight or during the weekend

Answer 38

**Alarms based on exhaled volume ** * Disconnect, apnea; low TV * High RR * Reverse flow * Low MV * Ascending bellows **Alarms based on pressure within breathing circuit** * High pressure * Disconnect; pressure below that expected following a mechanical breath * Continuing high pressure * Subatmospheric pressure **Alarms based on pressure within oxygen supply lines** * Low oxygen supply pressure * Alarms based on composition of gases in circuit * Low concentration of exhaled agent * Low oxygen concentration * Apnea: low or absent concentration of CO2

Answer 39

* **Gas collection assembly** --\> At APL valve and ventilator relief valve * **Transfer tubing**: 19 or 30 mm; color coded yellow sometimes * _**Scavenging interface** (most important part)_ * Gas disposal tubing * Gas disposal assembly * Active disposal (more common) or passive disposal (less common)

Answer 40

SCAVENGING SYSTEMS * Protects the breathing circuit or ventilator from excessive positive or negative pressure.

Answer 41

TYPES OF SCAVENGER INTERFACE * **_Closed interface (all Datex-Ohmeda, old Drager) _** Communicates to atmosphere only through valves * Used with passive disposal system * Must have positive pressure relief * Used with active (suction) disposal system * Must have positive and negative pressure relief

Answer 42

**Open interface (all new Drager)** ## Footnote **No valves; open to atmosphere (both negative and positive pressure relief “built in”** * Must be used only with active systems * Reservoir required **Safety** * **_Safer than closed interface for the patient; no barotrauma_** * _Less safe than closed interface for the anesthetist (if used improperly)_

Answer 43

**CAUSES OF CRITICAL INCIDENTS** ## Footnote * Underlying causes of all critical incidents Improper or reduced maintenance * Inadequate in-service education * Substandard equipment monitoring * Failure to use checklists * Lack of familiarity with equipment standards

Answer 44

**Failure to ventilate** * Disconnection * Failure to initiate ventilation initially or after an interruption * Failure to close APL (applicable to older absorber systems that lack “bag/vent”switch) * Misconnections of breathing circuit ** Occlusion or obstruction of the breathing circuit** * Kinking or plugging of ETT * Incorrect insertion of flow direction-sensitive components * PEEP valves * Cascade humidifiers * Kinking of fresh gas delivery hoses ** Leaks** * Failure or improper reassembly of bellows after cleaning * Damage to or disconnection of pressure monitoring hoses Failure of pipeline and tank oxygen supply * Driving a vent with cylinders (when pipeline is unavailable) cause rapid tank depletion ** Inadvertent application of suction to breathing circuit** * Failure of scavenger interface negative-pressure relief valve * Intubation of trachea with nasogastric tube, which is then connected to suction **Barotrauma** * Excess inflow to breathing circuit (flushing during ventilator inspiration) * Ventilator relief valve may stick closed * Control assembly problems

The Anesthesia Gas Machine Flashcards

(72 cards)