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بسم الله الرحمن الرحيم

بسم الله الرحمن الرحيم. Dr .Gihan A Tarabih . MD, ASS.Prof. of Anethesia And SICU, Mansoura Faculty of Medicine. Respiratory Monitoring= Rapid progress with greater safety in Anesthesia field and better ICU outcome. Oximetry.

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بسم الله الرحمن الرحيم

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  1. بسم الله الرحمن الرحيم Dr .Gihan A Tarabih . MD, ASS.Prof. of Anethesia And SICU, Mansoura Faculty of Medicine.

  2. Respiratory Monitoring= Rapid progress with greater safety in Anesthesia field and better ICU outcome. Oximetry

  3. Early Warning: When do you want the patient’s parachute to open? Capnography( 4-10 minutes) capnography Pulse Oximetry (30-60 seconds) Pulse Oximetry ECG( 10 seconds) ECG No monitor = free fall!

  4. ASA Standard Care • During all anesthesia care the following parameters will be continually monitored: 1-oxygenation 2-ventilation 3-circulation 4-temperature

  5. CAPNOGRAPHY-OXIMETRY Why use them?

  6. Main Anesthesia Enemies Cardiac arrest Pulmonary embolism Hypoxia Hypoventilation Severe hypotension

  7. Objectives ► The physiology involved ► Application in clinical practice ► How it works Indications ►

  8. Physiology of respiration Oxygen/Carbon dioxide interaction: Perfusion and Ventilation Ventilation O2 CO2 CO2 O2 CO2 Perfusion

  9. Physiology of respiration Oxygen/Carbon dioxide interaction: Metabolism Oxygen -> lungs -> alveoli -> blood Oxygen breath CO2 produced by cellular metabolism diffuses across the cell membrane into the circulating blood. CO2 muscles + organs lungs 5-10% carried in solution 20-30% bound to haemoglobin 60-70% carried as bicarbonate in the red blood cell Oxygen CO2 cells energy blood Oxygen + Glucose CO2

  10. Oxygenation • Objective: ensure adequate oxygen concentration in inspired gas and blood • Montoring: 1-inspired gas oxygen analyzer with alarms (GA) 2-Arterial oxygen saturation(Spo2). 3-Arterial oxygen tension(Po2).

  11. Pulse Oximetry How does it really work? Why should I care?

  12. Oximetry History • Became standard of care in the 1980’s • 1935 Carl Matthes • first oximeter • 1940 J.R. Squires • self calibrating oximeter

  13. Oximetry History (Cont’d) • 1940’s Glen Milliken • aviation ear –oximeter for use in avitation research to investigate high altitude hypoxic problems. • -1964 Robert Shaw(surgeon) built a self caliberating ear oximeter Which was marketed by Hewlett Packard in 1970 for use in physiology and cardiac cathterization laboratories

  14. Terminology Review • SpO2 : Non invasive oxygen saturation • SaO2 : Arterial (invasive)Oxygen Saturation (oxygen bound to the hemoglobin molecules) • PaO2 : Arterial Partial Pressure, oxygen dissolved in the plasma (only about 3% of total content) or PO2 • CaO2: Total amount of oxygen in the blood or the (SaO2 + PaO2).

  15. Oxygen Saturation • Percentage of hemoglobin saturated with oxygen • Normal SpO2 is 95-98% • Suspect cellular perfusion compromise if less than 92% SpO2 • Insure adequate airway • Provide supplemental oxygen • Monitor carefully for further changes and intervene appropriately

  16. PULSE OXIMETRY: WHAT DOES IT DO? • MEASURES/DISPLAYS • - O2 SAT OF HbG • - PULSE RATE • - INDICATES PERFUSION • - PULSATE FLOW

  17. Various forms of pulse ox’s

  18. What are the Normal? • 97-100% sat :Good gas exchange . • 90-95% sat : Mild hypoxia • <90% sat : Severe hypoxia • Not all patients are the same • - COPD • - Anemia

  19. Pros of Pulse Oximeters PROS • Non-invasive • Allows continuous measurement in real time • Easy to use

  20. Cons of Pulse Oximetry CONS • Measures Hb saturation rather than the actual level of Hb. Only measures oxygenation status. • Does not detect carbon dioxide levels in the blood. CO2 determines the ventilation status. • Measurements are not always accurate. Inaccuracy may occur due to nail polish, light interference, poor peripheral perfusion, intravenous dyes, the presence of carboxyhemoglobin and hemoglobinopathies.

  21. PROS Accurate The gold standard for measuring respiratory status CONS Invasive Not easy to perform on a patient Does not reflect measurements in real time status Pros/Cons of an arterial blood gas

  22. Objectives • Understand how a pulse oximetry works (technology) • Define normal and abnormal pulse oximetry readings. • State the indications and limitations when using a pulse oximetry in anesthesia ,POCU and ICU.

  23. Indications for Pulse Oximetry • Uses of Pulse Oximetry generally fall into two categories • Real Time Indicator of hypoxemia • End point for titration of therapeutic interventions.

  24. Technology • The pulse oximeter has Light-emitting diodes (LEDs) that produce red and infrared light • LEDs and the detector are on opposite sides of the sensor • Sensor must be place so light passes through a capillary bed • Requires physiological pulsatile waves to measure saturation • Requires a pulse or a pulse wave (Adequate CPR)

  25. Pulse Oximetry • Principle of operation -1

  26. Pulse Oximetry • Optical plethysmography detects pulsatile changes in blood volume • Spectrophotometry measures pulsatile hemoglobin saturation • Assumptions all pulsation is arterial light passes through pulsatile beds

  27. DEFINITIONS • WAVE LENGTH - DISTANCE FROM ONE PEAK TO THE NEXT. (NANOMETERS) • INTENSITY - # OF ENERGY “PACKETS” GENERATED IN 1 SECOND. (HEIGHT OF THE WAVE). (LUX) • CYCLE- ACTIVITY FROM ONE PEAK TO THE NEXT. (CYCLES/SEC = HERTZ) • FREQUENCY - # WAVES PER SECOND. (CYCLES/SEC)

  28. DEFINITIONS(cont...) • LIGHT EXTINCTION/ABSORPTION - THE ABILITY OF A SUBSTANCE TO ABSORB SPECIFIC PORTIONS OF THE LIGHT SPECTRUM. • WAVE THEORY - LIGHT IS A CONTINUOUS STREAM OF ENERGY WHICH VARIES IN AMPLITUDE AT SPECIFIC FREQUENCIES. • PACKET THEORY- LIGHT IS ‘BUNDLES’ OF ENERGY MOVING AT SPECIFIC FREQUENCIES.

  29. BEER-LAMBERT LAWASSUMPTIONS: • LIGHT PASSES AS ACOHERENTBEAM - DOES NOT SCATTER. • SOLUTIONS AREHOMOGENEOUS - TISSUE DENSITY IS CONSTANT. • OPTICAL PATH LENGTH ISCONSTANT.

  30. Beer - Lambert Law Incident light Transmitted light

  31. Physics (Beer-Lambert law) • * Beer s law: • The concentration of a liquid is exponentially related to the intensityof light that will pass through it. • * Lambert s Low: • The distanceof light travelled through the liquid is exponentially related to the intensity of light that will pass through it. • Oxygenated hemoglobin absorbs a different wavelength of light than does deoxygenated blood

  32. Beer-Lambert Law

  33. Beer-Lambert Law • I trans = I inc . A • A = DCE • Where: • I trans = intensity of transmitted light . • I inc = intensity of incident light. • ِِِA = fraction of light absorption. • D = distance light transmitted throught the liquid (path length). • C = concentration of solute(hemoglobin). • E = extinction coefficient of the solute (a constant for a given solute at spcified wavelenght).

  34. Spectrophotometry • Beer-Lambert Law:

  35. eo[HbO2] + er [Hb] L = A1 BEER-LAMBERT LAW Iin1 Iout1 Homogenous Solution L Iout1 = A1 = e[HbO2] L Iin1 Iin1 Iout1 Non-Homogenous Solutions L

  36. Beer’s –Lambert Law for Spo2 SPO2 Reading More light is absorbed

  37. Photospectrometry Photospectrometry is a method of using light emission or absorption to determine the composition of substances. It generally involves the use of light emitters and receptors coupled with signal analyzers.

  38. WHERE DO WE USE PHOTOSPECROMETRY? • Pulse OXIMETRY • Capnography • Capnometry • Co-OXIMETRY • Mass Spectrometry • Serum Glucose (glycolated Hb 2Ac) • ?

  39. PULSE OXIMETRY: HOW DOES IT WORK? • I.R. PHOTOSPECTROMETRY: - HEMOGLOBIN ABSORBS LIGHT. • - THE ABSORBED LIGHT VARIES WITH: * OXYGEN SATURATION * TYPE OF HEMOGLOBIN * LENGTH OF THE OPTICAL PATH.

  40. PULSE OXIMETRY: HOW DOES IT WORK? (cont.) • ABSORBENCE CAN BE CALCULATED * EXTINCTION CO-EFFICIENTS * OPTICAL DENSITY EQUATIONS * BEERS-LAMBERT EQUATION

  41. Concept of Pulse Oximetry

  42. Pulse Oximetry principles Two main principles: • First Principle of operation – 1 • Infrared absorption by oxygenated and de-oxygenated haemoglobin at 2 different wavelengths

  43. RBC’s & Hemoglobin

  44. Oxygenated blood and deoxygenated blood absorb different light sources • Oxyhemoglobin absorbs more infrared light • Reduced hemoglobin absorbs more red light • Pulse oximetry reveals arterial saturation my measuring the difference.

  45. Pulse Oximetry • First principle of SPo2: two wavelengths (660 and 960 nm) calculates functional saturation (physiologic saturation)

  46. Pulse Oximetry • First Principle of operation - Wavelength of red and infrared light emitted by the 2 LEDs

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