Sub-category: Physics and Principles of Measurement Topic: Monitoring anesthetic gases and vapours Date: January 15-17, 2016 Language: English

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Course n : Course 3 Title: RESPIRATORY PHYSIOLOGY, PHYSICS AND PATHOLOGY IN RELATION TO ANAESTHESIA AND INTENSIVE CARE Sub-category: Physics and Principles of

1 Course n : Course 3 Title: RESPIRATORY PHYSIOLOGY, PHYSICS AND PATHOLOGY IN RELATION TO ANAESTHESIA AND INTENSIVE CARE Sub-category: Physics and Principles of Measurement Topic: Monitoring anesthetic gases and vapours Date: January 15-17, 2016 Language: English City: Karachi Country: Pakistan Speaker: Prof. Fauzia Anis Khan

2 TYPES OF MONITORS Side Stream Monitors A pump aspirates a gas sample into sampling tube Mainstream Monitors A sensor is located within the gas stream

3 MONITORING IN ANAESTHESIA GASES Oxygen Nitrous oxide Carbon dioxide INHALATIONAL AGENTS

4 WHY DO WE REQUIRE O 2 MEASUREMENT DURING ANAESTHESIA To detect hypoxia To detect hyperoxia To detect disconnection To detect adequacy of pre oxygenation

5 METHODS O 2 analyzers 1.Paramagnetic analysis 2.Electrochemical analysis

6 O 2 analyzers What is a paramagnetic substance? A substance which when introduced in a magnetic field will locate itself in the strongest part of the field Oxygen is the only paramagnetic gas

7 O 2 analyzers Paramagnetic analyzer Physical principle Oxygen is introduced in an active magnetic field A pressure wave is generated that is proportional to its partial pressure

8 O 2 analyzers Paramagnetic Analyzer Physical Principles (continued) A reference gas is needed (air) Both reference gas and oxygen are pumped in an electromagnetic field Two gas paths are joined by a differential pressure or flow sensor Difference is detected by a transducer Difference is converted to an electrical signal

9 Paramagnetic Analyzer

10 O 2 analyzers Paramagnetic Analysis Signal display Oxygen partial pressure (mm Hg) Oxygen volume percent (%)

11 Electrochemical analysis Sensor components cathode anode electrolyte solution membrane permeable to gases Analyzer box Electronic circuitry Display monitor Alarms

12 Electrochemical analysis Physical principles Galvanic cell / Fuel cell Polarographic electrodes

13 Electrochemical analysis 1. Fuel cell Cathode: O H 2 O + 4e - 4OH - Anode: 4OH + 2Pb 2 PbO + 2H 2 O + 4e - Electron flow (current) generated between anode and cathode equal to partial pressure of gas Current operates a meter and scale marked in %

14 Electrochemical analysis 2. Polarographic electrode / Clarks electrode

15 O 2 analyzers Comparison of different methods Of oxygen analysis

16 O 2 analyzers HOW OFTEN SHOULD THE CALIBRATION BE CHECKED For electrochemical analysis Daily before use Subsequently 8 hourly

17 HOW TO CHECK THE MONITOR Calibrate: Expose to room air (21%) Set alarms Low O 2 above 21% High O 2 below 21% O 2 analyzers Activate visual and available signals. The alarms should sound

18 ANALYSIS OF CARBON DIOXIDE,NITROUS OXIDE,AND VOLATILE AGENTS Infra red absorption spectroscopy Photoacustic spectroscopy Silicone rubber and piezoelectric absorption Refractrometry Raman scattering Mass spectrometry

19 CARBON DIOXIDE Infra red analysis (Accuracy + 0.2%) Chemical analysis

20 CO2 analyzers INFRA RED ANALYSIS Used for gases with 2 dissimilar atoms 2 types 1. Blackbody radiation technology 2.Micro stream technology

21 CO2 analyzers 1.Micro Stream Technology Glass discharge lamp coupled with a infrared transmitting window Electrons generated by radiofrequency voltage CO 2 molecules excited by already excited nitrogen molecules Excited CO 2 molecules deexite and emit wave length of CO 2 Emission is split Emission passes via gas sampling chamber and a reference cell Detected

22 CO2 analyzers 2. Black body radiation Heated element Filters black radiation outside range Individual filters used for different agents so that absorption of selected agent is maximized at its peak wavelength Sensor detects the transmitted infra red rays Electrical signal produced Amplified and displayed

24 CO2 analyzers Chemical Methods (colorometric) Consists of a ph sensitive indicator in a housing On exposure to carbonic acid it changes color 2 types Hygroscopic Hydrophobic

25 NITROUS OXIDE (N 2 O) Measurement of nitrous oxide concentration Infra red analysis Accuracy + 2% for 0-100% conc

26 WHY MONITOR N 2 O Monitoring function of flow meters Avoiding diffusion hypoxia

27 WHY MONITOR THE CONCENTRATION OF INHALATIONAL ANAESTHETICS 1. To measure vaporizer output 2. Measurement of anaesthetic depth 3. Teaching uptake and elimination

28 INHALATIONAL ANAESTHETICS 1. Infra red analyzers 2. Refractometry 3. Piezoelectric analysis

29 Inhalational anaesthetics 1.Infra Red Analysis Physical principle Substances absorb infra red rays When molecules of a substance rotate asymmetrically strong infrared absorption occurs, this results in a change Anaesthetic gases have unique bands of absorption at certain wavelengths

30 Inhalational anaesthetics Infra red analyzer Physical principle Optical filters Gas from patient Infrared optical path beam Signal processor Infrared source Gas sampler Detector

31 Infra Red Analysis Relationship between gas absorption and concentration C = [-1n (1-Pa)]/ D Lambert Beer Law C = molar gas concentration Pa = absorbed energy fraction = absorption co-efficient D = Distance of beam travel through gas

32 Inhalational anaesthetics 2. Refractometry Maily used for vaporizer caliberation A light beam is split One portion passes via a chamber which contains sample gas Second portion passes via an identical chamber containing air Pattern compared to a scale

33 Inhalational anaesthetics 3.Piezoelectric crystal adsorption Vibrating quartz crystal coated with lipids On exposure vapor absorbed on lipids Alternation of vibration frequency Electrical signal proportional to concentration is generated

34 Inhalational anaesthetics 5.Raman Scattering Can analyze multiple agents When monochromatic light interacts with a gas molecule some light energy is absorbed leading to a shift Scattered light passed to a detector and a signal processor

35 4.Mass Spectrometry Inhalational anaesthetics Can analyze multiple agents Mostly utilized in research A low pressure sample chamber is attached to a vacum chamber Molecules of gas are ionized and accelerated by a cathode plate and are seperated by mass Filtered and detected

36 AAGBI Recommendations for Standards of Monitoring during Anaesthesia and Recovery Oxygen analyser with an audible alarm Carbon dioxide analyser Inhalational agents /vapour analyser Ambient anaesthetic agent concentration

37 SUMMARY Oxygen - paramagnetic and electrochemical analyzers Nitrous oxide infra red analyzers Carbon dioxide Infra red and chemical analyzers Inhalational agents Infra red, refractometry and piezoelectric analysis

38 Following is a paramagnetic gas a)nitrous oxide b)oxygen c)carbon dioxide d)nitrogen e)helium

39 Following is a paramagnetic gas a)nitrous oxide b)oxygen c)carbon dioxide d)nitrogen e)helium

40 The following physical method is used in measuring oxygen concentration a) Paramagnetic analyzer b) Blackbody radiation infrared analysis c) Micro stream technology infrared analysis d) Refractrometry e) Piezoelectric crystal

41 The following physical method is used in measuring oxygen concentration a) Paramagnetic analyzer b) Blackbody radiation infrared analysis c) Micro stream technology infrared analysis d) Refractrometry e) Piezoelectric crystal

42 The following analyzer is based on Lambert Beers law a) Paramagnetic analyzer b) Electrochemical analyzer c) Infrared analyzer d) Refractrometer e) Piezoelectric crystal

43 The following analyzer is based on Lambert Beers law a) Paramagnetic analyzer b) Electrochemical analyzer c) Infrared analyzer d) Refractrometer e) Piezoelectric crystal

44 The following is true regarding a side stream monitor a) The sensor is housed near the patient b) It increases the dead space c) It has a faster response time than a mainstream monitor d) Calibration is required with air and a standard gas e) A water trap is not needed

45 The following is true regarding a side stream monitor a) The sensor is housed near the patient b) It increases the dead space c) It has a faster response time than a mainstream monitor d) Calibration is required with air and a standard gas e) A water trap is not needed

46 An infrared analyzer will not measure the following a)carbon dioxide b)nitrous oxide c)oxygen d)halothane e)isoflurane

47 An infrared analyzer will not measure the following a)carbon dioxide b)nitrous oxide c)oxygen d)halothane e)isoflurane Key C Infrared analysis only measures gases/agents with dissimilar atoms

Anaesthesia Gas Monitoring Štefan Trenkler

Anaesthesia Gas Monitoring Štefan Trenkler Department of Anesthesiology and Intensive Medicine P.J.Šafárik University Medical faculty Košice Košice CEEA 2015 Why anaesthesia gas monitoring The ability