Anesthesia Assistant CourseModule 3

Sept 26, 2009Ashley Meister

Objectives

Case set up

Compare cases for set up

Positions, effects on patient, risks

Fluid replacement, scavenging

Suction

Ventilator set up

Patient Positioning

Indications, precautions, complications and procedure for each of the following patient positions:

Supine

Prone

Lithotomy

Beach chair

Lateral decubitus

Supine/ fracture table

General Concepts in positioning

sedated/ anesthetized patients should not be placed in positionsthey are not comfortable in when they are awake

Compromise between what patient can tolerate structurally and physiologically, and what is required for surgical access

Physiologic instability may be magnified by rapidly moving seriously ill patients

Positioning

Bony prominences can produce ischemic necrosis of overlying tissue unless proper padding is required

Enhanced by hypothermia and hypotension

Caution particularly with ulnar nerve

Supine

Lying horizontally

Arm pressure points padded and either tucked to side or abducted

Abduct less than 90 degrees

Extend hands ventrally

Ensure perfusion to the hand, no skin to metal contact and no stretch on brachial neurovascular bundle

No compression in the axilla

Bony contacts at occiput, elbows & heals padded

Supine

Horizontal supine, minimal changes to vascular system

If tipped into trendelenburg or reverse trendelenburg, effects of gravity on blood flow significant.

Pressures change 2mmHg for each 2.5cm above or below level of the heart

Supine

Reverse trendelenburg

Blood pools in legs, decreasing effective circulating volume

Decreased cardiac output

Decreased systemic perfusion

Perfusion pressure in brain correspondingly decreased compared to if measured at level of the heart

Ventilation dynamics are enhanced

Supine

Trendelenburg

Increased pressure in cerebral veins

Can increase ICP

Congestion around eyes and airway

Negative impact on ventilation

Supine

Respiratory “Zones of West” shift

Diaphragm is pushed cephalad

Decreased FRC

Supine

Pregnant uterus rests on great vessels of the abdomen

Aortocaval compression- therefore tilt into Left lateral decubitus position/ left uterine displacement

Supine

Excessive flexion or extension of the spine in anesthetized patients who are placed in unique surgical positions may contribute to spinal cord ischemia and catastrophic neurological damage

Considerations with Prone positioning?

Prone

Venous pooling in legs, decreased preload and decreased cardiac output

If pressure is on abdominal viscera, transmitted to veins in spinal canal, causes increased bleeding in spine procedures

Extensive spine procedures in the prone position is associated with post operative visual loss (associated with blood loss, anemia & hypotension)

Prone

Importance of secure airway

Always have stretcher outside room in case airway is lost

Congestion of face and airway

Check eyes & ears carefully

Ensure arms not extended > 90 degrees, and well padded

What would you do?

A/W is lost when prone

Key point- prevention

Lithotomy

Gynecologic and urologic procedures

Supine, arms crossed on trunk or extended laterally on arm boards

Flex lower extremities at hip and knee

Both limbs simultaneously elevated and separated

Nerve injury possible if hips flexed greater than 90 degrees

Lithotomy

Ensure padding over lower extremities if pressure points exist

Can get hypotension if legs lowered quickly or decreased effective circulating blood volume

Decreases diaphragmatic excursion and impairs ventilation

Caution with hands and watch BP when leveling table back to neutral

Lithotomy

Elevated lower extremity positions may reduce perfusion pressure in the elevated extremities

conditions for developing compartment syndromes, especially when extremities are elevated for prolonged periods

Maintain perfusion pressure to extremities

Beach Chair

Often intubated as access to airway is difficult

Ensure ETT well secured and stays in place while moving patient and bed

Caution with elevating head of table with venous pooling and hypotension

Case reports with decreased cerebral perfusion

Lateral Decubitus

Turned onto one side

(left side down = left lateral decubitus position)

Place an axillary roll just under chest to take pressure off axillary neurovascular bundle

V/Q mismatch may occur, particularly with co-existing pulmonary disease

Caution with pressure to eyes & ears

Fracture Table

For repair of fractured femur

Pelvis is retained in place by a vertical pole at perineum with the foot of the injured extremity fixed to a mobile rest

Traction is applied between the foot and pelvis

Perineal crush injury possible

Setting up the case

Assist with surgical draping, while maintaining the integrity ofthe sterile field

Avoid walking between or crossing over sterile fields

Setting up the case

Prepare, in consultation with the anaesthesiologist, medication needs for general and regional anesthesia

Emergency Drugs

Selection and preparation of medications, checked and labelled for usage as appropriate

For every case:

Succinylcholine 20 mg/ml 10mL syringe

Atropine 0.4mg/ml- 0.6 mg/ml vials, 1mL syringe

Ephedrine 5mg/ml (50mg vial/ 10cc)

Phenylephrine 100mcg/ml (10mg/100cc)

Equipment to Prepare

Local

Sedation

Regional

Neuraxial – spinal/ epidural/ CSE

General

CAS monitors

Required:

Pulse oximeter

Apparatus to measure blood pressure, either directly or noninvasively

Electrocardiography

Capnography, when endotracheal tubes or laryngeal masks are inserted.

Agent-specific anesthetic gas monitor, when inhalation anesthetic agents are used.

CAS monitors

Exclusively available for each patient:

Apparatus to measure temperature

Peripheral nerve stimulator, when neuromuscular blocking drugs are used

Stethoscope - either precordial, esophageal or paratracheal

Appropriate lighting to visualize an exposed portion of the patient.

CAS monitors

Immediately available:

Spirometer for measurement of tidal volume.

Preparation for Local/ standby

Standard CAS standard monitors in use

Anesthesia available to provide sedation

Local anesthetic as per surgeon (watch doses)

Have emergency drugs available

Preparation for Sedation

CAS monitors

Emergency drugs available, IV, oxygen

Useful to monitor capnography

Many drugs can be used to provide sedation

Midazolam

Fentanyl

Remifentanil

Ketamine

Preparation for Regional

CAS monitors

Emergency Drugs available, iv, oxygen

Again, variety of drugs may be used

Midazolam

Fentanyl

ketamine

Titrate to effect

Preparation for Regional

Neuromuscular stimulator, electrodes - ultrasound available

Surface electrode - dressing if catheter

Skin prep - local anesthetic for skin

Local anesthetic for skin infiltration - gloves

Local anesthetic for nerve block

Nerve stimulating needle for block

Regional Setup

Preparing for Spinal/Epidural

CAS monitors, iv, oxygen may be required

Emergency drugs available - skin prep

Prepackaged trays - trays

Local anesthetic/ opiod for injection - local anesthetic

Ready to assist with patient positioning

Preparing for General Anesthesia

CAS monitors

iv fluids

Machine checked

Other lines as necessary

Emergency drugs ready

( Drugs for case ready )

Any other lines, procedures, equipment ready if anticipated

Preparing for General Anesthesia

Suction

Oxygen

Laryngoscope

ETT

Stylet

Consider Airway and location of A/W backup equipment

How to manage emergencies

Anaphylaxis

Emergency Situation- Anaphylaxis

ABC’s

Fluid resuscitation

Large bore iv access available

Epinephrine titrated to response

start at 10 mcg, escalate dose as required,

50-100mcg if hypotensive,

1mg ACLS dose

Emergency Situation- Anaphylaxis

H1 blocker

Benadryl 50mg

Corticosteroid

Hydrocortisone 50-100mg

Stop inciting allergen exposure

How to manage emergencies

Cardiovascular collapse

Emergency Situations- Cardiovascular Events

ABC’s

ACLS protocols

Responses dictated by clinical scenario

Crash cart available

Ensure CPR started

How to manage emergencies

Increased ICP

Emergency Situations- Increased ICP

Head of bed 30 degrees elevated

Ensure adequate cerebral venous drainage

General goals:

Avoid hypoxemia

Avoid hypotension/ maintain cerebral perfusion

CPP= MAP - ICP

Avoid abrupt hypertension

Emergency Situations- Increased ICP

Pharmacologic measures to lower ICP

Moderate hyperventilation pCO2 30-35, (short term)

Mannitol 0.5-1g/kg through 50 micron filter

Lasix 0.5mg/kg

How to manage emergencies

Malignant Hyperthermia

How to manage emergencies

Malignant hyperthermia

Hypermetabolic disorder of skeletal muscle

Intracellular hypercalcemia in muscle activates metabolic pathways

Energy depletion, acidosis, membrane destruction, cell death

Heritable component, not invariably present by family history

Hallmark- hypercarbia, tachycardia, tachypnea, hyperthermia, rigidity, arrhythmias, hyperkalemia, renal failure, DIC, death

Emergency Situations- Malignant Hyperthermia

ABC’s

Ensure MH crisis issued - MH cart

Stop triggering agents - hyperventilate, 100% O2,

Finish case ASAP high flows

Dantrolene 2.5mg/kg, repeat q5min prn until 10mg/kg

(20mg mix with 60ml sterile H2O

Emergency Situations- Malignant Hyperthermia

Arterial line- blood work and blood gasses

Begin cooling patient

Treat supportively

Patient will need ongoing treatment in ICU

Determine case requirements for suction; such as:Airway suctionGastric suctionThoracic suctionSurgical suctionPost-surgical wound drainage

Suction

Airway

Have suction ready as part of any induction

Attached to bronchoscopy port

Gastric

Bowel obstructions- low intermittent suction

Cell Saver

Cell saver

Intraoperative blood salvage

Anticoagulate salvaged blood as it leaves the surgical field

Separates rbc’s from other components and debris

Washes the rbc’s for return to patient

Cell Saver

Useful for procedures with anticipated significant blood loss

Reduce the use of autologous rbc transfusion

Contraindications:

infection - malignant cells

Contamination with urine, bowel contents, amniotic fluid

Cell saver

Complications

Dilutional coagulopathy

Reinfusion of contaminants- fat, leukocytes, red blood cell stroma, air, free hemoglobin, heparin, bacteria, debris from surgical field

The Anesthesia MachineHigh Intermediate Low Pressure Circuit

Anesthesia Workstation

High pressure circuit

Cylinders including N2O, O2 & Air

O2 2200psi -> 50 psi

N20 750 psi -> 50 psi

Decreased through pressure regulators

High Pressure SystemReceives gasses from the high pressure E cylinders attached to the back of the anesthesia machine (2200 psig for O2, 745 psig for N2O)

Consists of:Hanger Yolk (reserve gas cylinder holder)Check valve (prevent reverse flow of gas)Cylinder Pressure Indicator (Gauge)Pressure Reducing Device (Regulator)

Usually not used, unless pipeline gas supply is off

E Size Compressed Gas Cylinders

Cylinder Cylinder CharacteristicsCharacteristics

OxygenOxygen Nitrous OxideNitrous Oxide Carbon DioxideCarbon Dioxide AirAir

ColorColor White White (green)(green)

BlueBlue GrayGray Black/White Black/White (yellow)(yellow)

StateState GasGas Liquid and gasLiquid and gas Liquid and gasLiquid and gas GasGas

Contents (L)Contents (L) 625625 15901590 15901590 625625

Empty Weight Empty Weight (kg)(kg)

5.905.90 5.905.90 5.905.90 5.905.90

Full Weight (kg)Full Weight (kg) 6.766.76 8.808.80 8.908.90

Pressure Full Pressure Full (psig)(psig)

20002000 750750 838838 18001800

Hanger Yolkorients and supports the cylinder, providing a gas-tight seal and ensuring a unidirectional gas flow into the machine

Index pins: Pin Index Safety System (PISS) is gas specific prevents accidental rearrangement of cylinders (e.g.. switching O2 and N2O)

Anesthesia Workstation

Intermediate pressure circuit

Includes pipeline O2 and N20 at 50-55psi

Extends to flow control valves

Intermediate Pressure SystemReceives gasses from the regulator or the hospital pipeline at pressures of 40-55 psig

Consists of:Pipeline inlet connectionsPipeline pressure indicatorsPipingGas power outletMaster switchOxygen pressure failure devicesOxygen flushAdditional reducing devicesFlow control valves

Pipeline Inlet ConnectionsN2O and O2, usually have air and suction too

Inlets are non-interchangeable due to specific threading as per the Diameter Index Safety System (DISS)

Each inlet must contain a check valve to prevent reverse flow (similar to the cylinder yolk)

Low Pressure System

Extends from the flow control valves to the common gas outlet

Consists of:Flow metersVaporizer mounting deviceCheck valveCommon gas outlet

Anesthesia Workstation

Cylinder supply source is back-up if pipeline supply fails

Fail-safe valve located downstream from N2O supply sources

Interface between O2 & N20 with proportioning system

Prevent delivery of hypoxic gas mixtures

Anesthesia Workstation

High priority alarm- if O2 supply pressure is less than a critical pressure (<30psi)

Regulated flow enters low pressure circuit with adjustments in flowmeters

Gas mixture travels through a common manifold directed to vaporizer

Precise amounts of inhaled anesthetics added, controlled by dial flow

Anesthesia Workstation

Fresh gas flow with added anesthetic vapor travel to common gas outlet

Datex-Ohmeda have one-way check valves between vaporizer and common gas outlet

Prevent back flow into the vaporizer during PPV

Minimize effects of downstream intermittent pressure fluctuations on inhaled anesthetic concentrations

One-way check valve influences preoperative leak test

Pipeline Supply Source

Critical errors have occurred if incorrect supply attached to machines

Pipeline inlet fittings are gas specific with threaded fittings

Diameter Index Safety System (DISS)

If pipeline crossover suspected: turn on back-up O2 cylinder

Pipeline supply must then be disconnected

Cylinder Supply Source

E cylinders

Pin Index Safety System

Pressure reducing valve downstream

If not turned off, will be preferentially used

Volume of gas remaining in the cylinder is proportional to cylinder pressure

Oxygen supply pressure failure safety device

Designed to not allow hypoxic mixture delivery

Alarm sounds if oxygen pressure falls

O2 linked with delivery of other gasses to be oxygen dependent

If O2 pressure falls, other gas delivery falls

Flowmeters

Indicator float position is where upward force from gas flow equals downward force on float from gravity

O2 flow knob physically different from other gas knobs

N2O and O2 interfaced mechanically/ pneumatically, maximum 3:1 ratio

Oxygen flowmeter located downstream from other flowmeters in case of a leak

Limitations of Proportioning Systems

Machines equipped with proportioning systems can still deliver a hypoxic mixture under the following conditions:

Wrong supply gasDefective pneumatics or mechanics (e.g.. The Link-25 depends on a properly functioning second stage regulator)Leak downstream (e.g.. Broken oxygen flow tube)Inert gas administration: Proportioning systems generally link only N2O and O2

In general, an oxygen analyzer is the only machine safety device that can detect these problems (gas sampling done at the Y-piece of the patient circuit)

Oxygen Flush Valve

Direct communication with high pressure and low pressure circuit

Enters circuit downstream from vaporizers and from machine outlet check valve

100% O2 at 35-75 L/min (50 psi)

Potential problems: barotrauma, decreasing volatile anesthetic concentration, awareness

Oxygen Flush Valve (O2+)Receives O2 from pipeline inlet or cylinder reducing device and directs high, unmetered flow directly to the common gas outlet (downstream of the vaporizer)

Machine standard requires that the flow be between 35 and 75 L/min

The ability to provide jet ventilationvia the O2 flush valve is presence of a check valve between the vaporizer and the O2 flush valve (otherwise some flow would be wasted retrograde)

Vaporizers

Instrument designed to change a liquid anesthetic agent into its vapor and add a controlled amount of this vapor to the fresh gas flow

Important that each volatile anesthetic is in type specific vaporizer

Physical properties of volatile anesthetics

If incorrectly filled with inappropriate anesthetic, resulting output drastically changes

Vaporizers

Variable bypass- regulating anesthetic agent output

Concentration control dial determines ratio of flow through the bypass chamber and enters the vaporizer inlet

Gas channeled through the vaporizing chamber flows over the liquid anesthetic and becomes saturated with vapor

Flow over- method of vaporization

Vaporizers

Temperature compensated- maintains a constant vaporizer output over a wide range of operating temperatures

Agent specific

If vaporizer is overfilled or tilted, liquid anesthetic can spill into the bypass chamber

Final concentration of inhaled anesthetic is the ratio of the flow of the inhaled anesthetic to the total gas flow

Generic Bypass VaporizerFlow from the flowmeters enters the inlet of the vaporizer

The function of the concentration control valve is to regulate the amount of flow through the bypass and vaporizing chambers

Splitting Ratio = flow though vaporizing chamber/flow through bypass chamber

Examples include the Tec 3, Tec 4, Tec 5 and the Drager 19.1

Vaporizers- safety features

Agent- specific, keyed filling devices

Overfilling minimized because the filler port is located at the maximum safe liquid level

Firmly secured to a vaporizer manifold

Interlock system to prevent administration of >1 anesthetic agent

Desflurane’s Tec 6 Vaporizer

Because of physical properties of Desflurane, supplying it in a conventional vaporizer would lead to excessive cooling of the vaporizer

Vapor pressure is much higher than other volatile anesthetics

Much less potent (higher MAC)

Would vaporize many more volumes of Desflurane than other agents

Tec 6 electrically heated and vaporized

Tec-6 VaporizerElectronically heated and pressurized to achieve controlled vaporization of desflurane

2 independent circuits (fresh gas and vaporizer)

Vaporizer output is controlled by adjusting the concentration control valve (R2)

Pressure in the two limbs is equalized by the pressure regulating valve

Desflurane’s Tec 6 Vaporizer

Essentially a dual gas blender

By controlling the dial, the operator controls a variable restrictor valve

The Circuit: Circle SystemSo-called because the components are arranged in a circular manner

Arrangement is variable, but to prevent re-breathing of CO2, the following rules must be followed:

Unidirectional valves between the patient and the reservoir bagFresh-gas-flow cannot enter the circuit between the expiratory valve and the patientAdjustable pressure-limiting valve (APL) cannot be located between the patient and the inspiratory valve

Circle Breathing System

Prevents rebreathing of CO2 by use of CO2 absorbents

Allows partial rebreathing of other exhaled gasses

Components:

Fresh gas inflow source - CO2 absorbent

Inspiratory and expiratory unidirectional valves - reservoir bag

Adjustable Pressure Limiting (APL) valve - Y-piece connector

Circle Breathing System

Unidirectional flow

Maintenance of relatively stabile inspired gas concentrations

Conservation of respiratory moisture and heat

Prevention of OR pollution

Disadvantage is- many possible sites for misconnections and leaks

The Adjustable Pressure Limiting (APL) Valve

User adjustable valve that releases gases to the scavenging system and is intended to provide control of the pressure in the breathing system

Increased pressure in the breathing system (from patient) pushes the diaphragm off its seat venting the excess gas into the scavenging system

The control knob controls the position of the diaphragm

Bag-mask Ventilation: Valve is usually left partially open. During inspiration the bag is squeezed pushing gas into the inspiratory limb until the pressure relief is reached, opening the APL valve. At this point the additional volume the patient receives is determined by the relative resistances to flow exerted by the patient and the APL valve

Mechanical Ventilation: The APL valve is excluded from the circuit when the selector switch is changed from manual to automatic ventilation

CO2 absorber

2 clear plastic canisters arranged in series

Soda lime, Baralyme and calcium hydroxide lime

Soda lime- calcium hydroxide, water, sodium hydroxide and potassium hydroxide, silica

CO2 + H2O <-> H2CO3

H2CO3 + 2NaOH (KOH) <-> Na2CO3 (K2CO3)+2H20 + heat

Na2CO3 (K2CO3) + Ca(OH)2 <->CaCO3 +2NaOH (KOH)

CO2 Absorber

pH indicator added to assess absorbent

Changes to violet color when pH of the absorbent decreases as a result of CO2 absorption

Indicates absorptive capacity of material has been consumed

Scavenging System

Collection and subsequent removal of waste anesthetic gases from the operating room

Minimizes OR pollution by removing excess gasses

National Institute for Occupational Safety and Health (NIOSH) standards

2ppm for halogenated agent alone

25 ppm for N2O

Halogenated with N20 0.5 ppm

Scavenging SystemsScavenging Interface: Protects the breathing circuit or ventilator from excessive positive or negative pressure. There are 2 kinds of scavenging interfaces:

Open: Contains no valves and is open to the atmosphere allowing both positive and negative pressure reliefClosed: Communicates with the atmosphere through valves

Gas Disposal Assembly: This assembly ultimately eliminates the waste gas. There are 2 kinds of gas disposal assemblies:

Passive: Uses the pressure of the waste gas itself to produce flow through the systemActive: Uses a central vacuum to induce flow in the system, moving the waste gas along. A negative pressure relief valve is mandatory (in addition to positive pressure relief)

Scavenging System

Adds to OR pollution:

Failure to turn off gas flow at end of case

Poorly fitting masks, flushing the circuit

Filling vaporizers

Other circuit types which are difficult to scavenge

Scavenging System

Active or passive

Active- uses central evacuation system to eliminate waste gases

Passive- pressure of waste gas itself produces flow

Waste anesthetic gases are vented through the APL valve or through the ventilator relief valve

Scavenging System

Potential problems:

Obstruction- excessive positive pressure in the breathing circuit and barotrauma

Excessive vacuum- negative pressures within the breathing circuit

Generic Ascending Bellows VentilatorBellows physically separates the driving gas circuit from the patient gas circuit

During the inspiratory phase the driving gas enters the bellow chamber resulting in:

Compression of bellows delivering the anesthetic gases within the bellows to the patientClosure of the overflow valve, preventing anesthetic gas from escaping into the scavenging system

During the expiratory phase the driving gas exits the bellows chamber.

Exhaled gas fills the bellowsExcess gas opens the overflow valve (PEEP of 2-3 cmH2O) allowing scavenging of excess gases to occur

Machine CheckAnesthesia Apparatus Checkout Recommendations, FDA. 1993.

Categories of check:

• Emergency ventilation equipment - high pressure system

• Low-Pressure system - low pressure system

• Scavenging system - breathing system

• Monitors - final position

• Manual and automatic ventilation system

• Final Position

Checking Anesthesia Machines

Preoperative Checklist- High Pressure System

Check O2 cylinder supply

-open cylinder and verify at least ½ full

-close cylinder

Check central Pipeline Supplies- check connections and pipeline gages

Preoperative Checklist- Low Pressure System

Check initial status of low pressure system- close flow control valves and turn vaporizers off- check fill level and tighten vaporizer’s filler cap

• Perform Leak Check - machine master switch and flow control valves OFF- attach suction bulb to common gas outlet- squeeze bulb until fully collapsed- verify bulb fully collapsed > 10 seconds- check same for each vaporizer

Low Pressure Circuit Leak Test

Checks the integrity of the anesthesia machine from the flow control valves to the common outlet (e.g. leaks at flow tubes, O-rings, vaporizer)

Two types of leak test (depending on presence or absence of check valve)

Oxygen Flush Positive-Pressure Leak Test: Only used in machines withoutcheck valves; basically just pressurize the low pressure circuit using the O2+ flush valve and look for leakNegative Pressure Leak Test: Used in machines with or without check valves (i.e. Ohmeda). Attach suction bulb to common gas outlet, squeeze repeatedly until fully collapsed and ensure that it remains collapsed for 10 seconds. Will detect leaks as small as 30 ml/min.

Preoperative Checklist- Low Pressure System

Turn on Machine Master Switch

Test flowmeters

- adjust flow off all gasses checking for smooth operation of floats and undamaged flow tubes

- attempt to create a hypoxic N2O/O2 mixture and verify correct changes in flow

Preoperative Checklist- Scavenging System

Adjust and check scavenging system

- ensure proper connections between scavenging system and APL valve and ventilator relief valve

- adjust waste gas vacuum

- fully open APL valve and occlude Y-piece

Preoperative Checklist- Scavenging System

- with minimum flow, allow scavenger reservoir bag to collapse completely and verify that absorber pressure gauge reads zero

- with O2 flush activated, allow scavenger reservoir bag to distend full, and verify that absorber pressure gauge reads <10 cm H2O

Preoperative Checklist- Breathing System

Calibrate O2 monitor

- ensure monitor reads 21% on room air

- verify low O2 alarm is enabled and functioning

- reinstall sensor in circuit and flush breathing system with O2

- verify that monitor now reads > 90%

Preoperative Checklist- Breathing System

Check Initial Status of Breathing System

- set switch to “bag” mode

- check that circuit is complete, undamaged and unobstructed

- verify that CO2 absorbent is adequate

- install breathing circuit accessory equipment to be used during case (HME)

Preoperative Checklist- Breathing System

Perform Leak Check of the Breathing System

- Set all gas flows to zero- Close APL valve and occlude Y-piece- Pressurize breathing system to 30 cmH2O with

O2 flush- Ensure that pressure remains fixed > 10seconds- Open APL valve and ensure pressure decreases

Preoperative Checklist- Manual and Automatic Ventilation Systems

Test Ventilation systems and unidirectional valves

-place a second breathing bag on Y-piece

-switch on automatic ventilation

-turn ventilator on and fill bellows and breathing bag with O2 flush

-set O2 flow to minimum, other gasses off

Preoperative Checklist- Manual and Automatic Ventilation Systems

- verify that during inspiration bellows deliver appropriate TV and that during expiration bellows fill completely- set fresh gas flow to approximately 5 L/min

-Verify ventilator bellows and simulated lungs fill and empty appropriately without sustained pressure and end expiration

-Check for proper functioning of unidirectional valves

Preoperative Checklist- Manual and Automatic Ventilation Systems

-switch to bag/APL mode- Ventilate manually and assure inflation

and deflation of artificial lungs and appropriate feel of system resistance and compliance

- Remove second breathing bag from Y-piece

Preoperative Checklist- Monitors

Check, calibrate and/or set alarm limits of all monitors- Capnometry- O2 analyzer- Pressure monitor with high and low A/W

pressure alarms- Pulse oximeter- Respiratory volume monitor

Preoperative Checklist- Final Position of Machine

Check final status of machine- vaporizers off- APL valve open- selector switch to “bag”- all flowmeters to zero/minimum- patient suction level adequate- breathing system ready to use

Oxygen Analyzer Calibration

only machine safety device that evaluates the integrity of the the low-pressure circuit continuously

Other machine safety devices are upstream from flow control valves

Expose O2 concentration sensing element to room air for calibration to 21%

The Virtual Anesthesia Machine

http://vam.anest.ufl.edu/