GUide 2-Anesthesia Machine

How does anesthesia work?

Glossary

Anesthesia: Is a way to control pain during a surgery or procedure by using medicine called anesthetics. It can help control your breathing, blood pressure, blood flow, and heart rate and rhythm. Other medicines may be used along with anesthesia, such as ones to help you relax or to reverse the effects of anesthesia.

Canister: Contains soda lime which absorbs the carbon dioxide and water vapour expired by the patient.

Soda Lime: Is used in breathing systems to absorb expired CO2 during anaesthesia. It can be incorporated in a Mapleson C system or a circle system.

Vapor: It refers to gas phase at a temperature where the same substance can also exist in liquid or solid.

Vaporizer: Anesthetic agent delivery system or vapor delivery system. A vaporizer is a device that changes a liquid anesthetic agent into its vapor and adds a controlled amount of that vapor to the fresh gas flow or the breathing system.

Anesthesia machine simulator

Ventilation modes

1. Automatic ventilation (IPPV) and pressure-controlled ventilation (PCV).

Parameters for IPPV:

- Maximum pressure (Pmax). Normally 10-15 cm H2O.

- Running volume (or Tidal, VT): 10 ml / kg.

- Frequency: 6 - 20 resp / min.

- Inspiration - expiration ratio: 1: 1.5-2.

- Ti / Tip or speed in reaching the average pressure in the airways: 10-30%.

- End-tidal pressure (PEEP) PEEP: 35 cmH2O.

- The final goal is to maintain a capnometry of 35-45 mmHg.

In this modality, the level of inspiratory pressure that one wishes to use, the respiratory rate and the duration of inspiration are adjusted, and circulating volume and flow are variable. For this reason, it is common to associate the use of controlled ventilation under pressure with the inverted I: E ratio, since the prolongation of inspiratory time can somehow prevent hypoventilation. Parametros para PCV:

- Maximum pressure (Pmax). Initially at 8-10 cmH2O.

- Frequency. Initially at 12-20 resp / min. A smaller size greater frequency.

- Inspiration - expiration ratio: 1:1,5-2.

- Ti / Tip or speed in reaching the average pressure in airways: 10-30%.

- PEEP: 3-5 cmH2O.

- Normocapnia or maintenance at 35-45 mmHg the CO2 pressure in exhaled gas.

2. Manual ventilation (MAN).

In this ventilation mode the valve should only be placed in manual mode to ventilate the patient. If the circuit used is a circuit without reinhalation, this should be placed in the existing outlet in the upper right corner of the block of the machine, metal tube of 1.3 cm in diameter.

3. Spontaneus ventilation (SPONT).

The requirements to use spontaneous ventilation are:

-That the patient has indemnity in the respiratory center at the level of the brainstem.

-Adequate level of sedation.

-Hemodynamic stability.

Spontaneous ventilation should not be used in patients in whom it is required to reduce their maximum respiratory work and their metabolic rate is reduced, for example in patients with severe cerebral embolism.

The following measured values are displayed:

1. Peak pressure, mean pressure, plateau pressure and PEE.

2. Expiratory minute ventilation Tidal volume VT Breathing rate Patient compliance.

3. Inspiratory and expiratory concentration of O2, N2O, anaesthetic gas and CO2.

4. Functional oxygen saturation (SpO2) and pulse rate.

The following parameters are displayed as curves:

1. Airway pressure.

2. Expiratory flow.

3. Inspiratory and expiratory concentration of O2, CO2 and anaesthetic gas.

Display

On the screen we will find three main parts:

1. Fresh gas delivery.

2. Ventilation.

3. Monitoring.

The main functions for anaesthesia, e.g. selection of N2O or AIR, or selection of ventilation modes, can be selected directly by keys with permanently defined functions.

The softkeys are used to set the fresh gas delivery parameters and ventilation parameters.

1. Bloque izquierdo: las teclas para configurar la concentración de O2 y el flujo de gas nuevo.

2. Bloque derecho: las teclas para configurar los parámetros para el modo de ventilación relevante.

3. The "turn-and-push" rotary knob is the main operating control of the apparatus and has the following functions in all setting operations:

-Select = turn.

-Confirm = press.

SCREEN LAYOUT

1. The status field shows the actual operating mode.

2. The graphics fields show both curve and bar graphs.

3. Alarms will display warnings with their respective priority.

4. Numerical value field.

5. Lower softkeys.

6. For user guidance the prompt field.

7. For ventilation parameters the lower softkeys.

8. Right-hand soft keys for monitoring.

Preparation of the equipment

1. Screw the central gas supply pressure hoses for O2, AIR and N2O.

2. The two ports on the front are reserved for back-up gas cylinders.

3. Vacuum supply block (VAC) is available as an option for aspiration of secretions.

4. Three manometers are in a green area. pag 23

Sensor in te anesthesia machine

Maintenance: The workstation and its components must be cleaned and disinfected before every maintenance operation - even when returning for repair!

Water separator: Replace when dirty or when the message CO2 line?! is displayed (if the sample line is correctly installed and free of any blockage). Can be disposed of as domestic waste.

Replacing the water separator:

– When soiled or when the message CO2 line? ! is displayed (if the sample line is correctly installed and free of any blockage).

● Grip the water separator by its sides and pull it out.

● Push the new water separator into the holder as far as possible.

● The old water separator can be disposed of as domestic waste.

Removing water trap container

● Pull the container of the water trap down and off, and empty it.

● Prepare the container of the water trap for disinfection and cleaning in a washing machine.

Replacing the "Waterlock" water trap:

● See separate Instructions for Use.

O2 sensor: Calibration of the O2 sensor is every24 hours. Replace when calibration is no longer possible or when the message FIO2 INOP! is displayed.

Replacing the O2 sensor:

– When the message FIO2 INOP! is displayed or when the sensor can no longer be calibrated.

1 Remove the screw.

2 Remove the spent O2 sensor from the screw and insert a new O2 sensor in the screw. 1 Refit the screw.

Disposing of batteries and O2 sensors

Batteries and O2 sensors:

● must not be incinerated or thrown into a fire – risk of explosion!

● must not be opened forcibly – danger of chemical burns!

● must not be recharged. Batteries must be handled as special waste:

● They must be disposed of in conformity with the local waste disposal regulations.

Spent O2 sensors can also be returned to campany of fabircation.

Flow sensor: The flow sensor is automatically calibrated as soon as a CO2 signal is detected by the gas measuring system. Device takes account of the relevant gas mixture when calculating the volumetric concentrations. Replace when calibration is no longer possible or when the message FLOW INOP! is displayed.

For Removing the flow sensor:

1 Unscrew the expiration port.

2 Remove the flow sensor.

The flow sensor cannot be disinfected / cleaned in a washing machine, nor can it be sterilized in hightemperature steam.

● The flow sensor must be disinfected in 70 % ethanol solution for approx. 1 hour. Leave the sensor to dry in air for at least 30 minutes, otherwise the remaining alcohol can damage the sensor when calibrated.

● The flow sensor can be reused as long as it can be calibrated successfully.

● The flow sensor must be disposed of as infectious special waste. It can be incinerated with little pollution at temperatures of more than 800 °C.

Bacterial filter for secretion aspiration: Replace after two weeks. Must be disposed of as infectious special waste. Can be incinerated with little pollution at temperatures of more than 800 °C.

Bacterial filter for measured gas recirculation: Replace every six months. Can be incinerated with little pollution at temperatures of more than 800 °C.

Microbial filter:

● Wipe the surface with a disposable cloth. Do not clean with solvents such as naphtha, alcohol or ether.

Do not clean the filter in cleaning and disinfecting machines.

Do not immerse the filter in disinfectant solution.

● Sterilize the filter at max. 134 °C in a hot steam sterilizer. Do not use ethylene oxide sterilization! Do not sterilize when connected!

● Mark each sterilization in the corresponding field on the filter housing (e.g. with a water-resistant pen). The filter can be sterilized up to 24 times.

Cooling air filter (set of 3): Should be cleaned and thoroughly dried or replaced every month. Must be replaced after one year at the latest. Can be disposed of as domestic waste.

Lithium battery for data backup (set of 2): Must be replaced by professionals after two years. Must be disposed of in accordance with local waste disposal regulation.

Lead gel battery in power pack (set of 2): The device should be used in battery mode without a patient at least every 4 weeks. A fully charged battery should keep the workstation operating for at least 30 minutes. If not, get lead gel battery (set of 2) replaced by professionals. Must be replaced by professionals after 2 years. Must be disposed of in accordance with local waste disposal regulations.

Optical measuring set for determining the anaesthetic gas concentration: Must be checked by professionals every six months.

Time-keeper RAM : Must be replaced by professionals after three years. Must be disposed of in accordance with the local waste disposal regulations.

Inspection and maintenance : Must be carried out by professionals every six months.

Cleaning the cooling air filters :

– clean filters monthly.

1 Remove all three cooling air filters from their mount.

● Clean in warm water to which a detergent has been added; dry thoroughly.

● Insert the cooling air filters in their mount without creasing.

● Replace the cooling air filters after not more than one year. The filters can be disposed of as domestic waste.

Questionnaire

How does the vaporizer work?

The purpose of a vaporizer is to add anaesthetic vapor into the fresh gas flow in a way  that the output of the vaporiser delivers the set concentration of anaesthetic agent accurately.

Fresh gas enters the inlet of the vaporizer and is divided into two flow pathways.  The splitting valve, depending on the setting of  the control dial, adjusts how much goes through each of the pathways.  The fresh gas that is sent along the “by pass” pathway doesn’t come into contact with any vapor.  On the other hand, the fresh gas that is sent to the vaporising chamber becomes fully saturated with vapuor.

 At the exit end of the vaporizer, the by pass gas meets the chamber gas and the two mix.  The resultant output depends on how much of fresh gas went though each of the pathways.

When you dial a high anaesthetic concentration requirement, the splitting valve sends more fresh gas via the vaporising chamber.

Finally, when you set the dial to zero to make vaporiser deliver no anaesthetic vapuor, the splitting valve sends all the fresh gas via the by pass pathway and nothing through the vaporising chamber.

You have seen that the anaesthetic concentration that is output by the vaporizer is determined by the ratio of fresh gas flow that goes through the vaporising chamber and the fresh gas flow that goes through the bypass pathway. This ratio is called the ‘splitting ratio’.

Why the different valves inside of the machine are important for the system?

The control valves of the flow meters are of special importance in the operation of the anesthesia machine, they separate the medium pressure circuit from the low pressure circuit. The operator regulates the flow that enters the low pressure circuit by adjusting said valves. The total flow moves through a central manifold, located at the top of the flow meters, which is communicated to the vaporizers. Specific amounts of halogenated anesthetic can be added to the gases depending on the position of the dial in the vaporizer. The final mixture flows makes the common exit of gases.

How does the breathing circuit operate? What is a flush valve and when the system needs it?

Non-rebreathing circuits

• With these, the patient breathes in from the reservoir and out to atmosphere. The gases are not re‑used.

• However in practical sense, this terminology is incorrect because some rebreathing of exhaled gases occurs in most of these systems, especially with lower recommended flow rates.

• Satisfactory elimination of CO2 is dependent on adequate gas flow, and on minimal dead space in the circuit.

• Examples: Bain, Ayre’s T piece, Magill, Lack.

Rebreathing circuits

• Here the same gases are re‑used, and CO2 is removed by passage of the gas through soda lime.

• Examples: Circle, To and Fro, Universal-F

A circle rebreathing circuit is composed of:

• Carbon dioxide absorbing canister

• Y-piece

• Inhalation and exhalation breathing tubes

• Inhalation and exhalation unidirectional (one way) valves

• Fresh gas inlet

• Pressure manometer

• pop-off valve

• A reservoir bag

What is a flush valve and when the system needs it?

The oxygen flush valve, dilutes anesthetic gas in breathing circuit. Its purpouse is allow 100% oxygen to bypass the vaporizer and go directly to the patient. The oxygen flush valve only use with a rebreathing system, because the resistence in the system keeps the preassure from entering the lungs.

Bibliography

[1]"Anesthesia Vaporizer for PG students", ISA KAKINADA Education Portal, 2018. [Online].

[2] F. Cold, E. Health, H. Disease, P. Management, S. Conditions, S. Problems, S. Disorders, S. Checker, E. Interviews, M. Boards, Q. Answers, I. Guide, F. Doctor, M. Medications, P. Identifier, C. Interactions, C. Drugs, T. Pregnant, D. Management, W. Obesity, F. Recipes, F. Exercise, H. Beauty, H. Balance, S. Relationships, O. Care, W. Health, M. Health, A. Well, H. Teens, F. Kids, G. Pregnant, F. Trimester, S. Trimester, T. Trimester, N. Baby, C. Health, C. Vaccines, R. Kids, H. Cats, H. Dogs, M. Records, S. Memory, W. Gluten-Free, C. Tumors, M. Korea, M. Boards, E. Blogs, N. Center and P. Management, "Anesthesia-Topic Overview", WebMD, 2018.

[3]"Anesthetic Machine Parts and Functions Flashcards | Quizlet", Quizlet, 2018.

[4]"Anaesthesia UK : Soda lime", Frca.co.uk, 2018.

[5]Dräger Medizintechnik GmbH, Julian Anaesthetic Workstation Instructions for Use Software 2.n, 1st ed. Germany, 1998, pp. 116-118.

[6]"How anaesthesia vaporisers work explained simply.", HowEquipmentWorks.com, 2018.

[7]C. Gurudatt, "The basic anaesthesia machine", 2018.