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Capnography

Capnography. Mike McEvoy, PhD, NRP, RN, CCRN EMS Coordinator – Saratoga County, NY EMS Editor – Fire Engineering magazine Cardiac Surgical ICU RN & Chair Resuscitation Committee – Albany Medical Center. Mike McEvoy: www.mikemcevoy.com. Outline:. Carbon dioxide

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Capnography

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  1. Capnography Mike McEvoy, PhD, NRP, RN, CCRN EMS Coordinator – Saratoga County, NY EMS Editor – Fire Engineering magazine Cardiac Surgical ICU RN & Chair Resuscitation Committee – Albany Medical Center

  2. Mike McEvoy: www.mikemcevoy.com

  3. Outline: • Carbon dioxide • Capnography – what, where, why? • Oxygenation • Ventilation • EtCO2 equipment • Waveforms • Uses • Cases

  4. Carbon Dioxide = CO2 • 2 oxygen atoms + 1 carbon atom • Trace gas on earth (0.036-0.039%) • CO2 produced by: • Coal combustion (hydrocarbons) • Fermentation of beer • Respiration of living organisms • Plants: sunlight + CO2 + water O2

  5. Carbon Dioxide = CO2 • Human body produces 2.3 # per day • Solid form = dry ice • Gas = fire extinguishers, carbonated drinks…

  6. CO2 (Carbon Dioxide) Greenhouse gas (heavier than air) • Global warming • Ocean acidification (carbonic acid)

  7. Physiology of Metabolism Oxygen Lungs  alveoli  blood Oxygen Breath CO2 Muscles + Organs Lungs Oxygen CO2 Cells ENERGY Blood Oxygen + Glucose CO2

  8. Carbon Dioxide • Oxygen (O2) enters the body through the lungs and is used to produce energy • This process is called metabolism • Carbon Dioxide (CO2) is the waste product of metabolism

  9. Typical Gas Percentages Normal Exhaled CO2 = 35 – 45 mmHg

  10. CO2 In the Blood • CO2 is your drive to breathe •  CO2causes air hunger • Goal is to maintain PaCO2 at 40 • Body adjusts respiratory rate & depth • Oxygen does notaffect respirations

  11. Question: What would happen if you injected CO2 into the blood? Respiratory rate and depth would 

  12. Question: Why do swimmers who hyperventilate loose consciousness underwater?  CO2 eliminates the drive to breathe

  13. Measuring Exhaled CO2 Colorimetric Capnometry Capnography Turns yellow when CO2 is detected

  14. Pros Accurate Cheap (~$10-15) Changes color when CO2present Work for 2+ hours Disposable Cons Secretions Not quantitative Adds dead space False positives Hard to read at night Colorimetric

  15. Measuring Exhaled CO2 Colorimetric Capnometry Capnography

  16. Cons No waveform Does not trend Bulky adapter/unit Pros Numeric value + RR Portable Cheaper than waveform capnography Capnometry PHASEIN EMMA™ (Masimo)

  17. Measuring Exhaled CO2 Colorimetric Capnometry Capnography

  18. Pros Numeric value + RR Waveform Trending Very accurate Cons Expensive Fragile Warm-up time (some units) Secretions Temperature sensitive (some) Capnography

  19. Infrared Spectroscopy • CO2 absorbs 4.26 µm wavelength • Infrared light aimed at sample • Infrared sensors detect absorption and calculate CO2

  20. Capnography Technologies • Sidestream (1st generation) • Sensor in remote location • Samples gas from circuit (150-250 mL/min) • Mainstream (2nd generation) • Sensor in the airway

  21. Capnography Technologies • Microstream® (next generation) • Sensor in remote location • Samples only 50 mL/min from circuit

  22. SpO2 versus EtCO2

  23. Oxygenation (Pulse Ox) O2 for metabolism SpO2 measures % of O2 in RBCs Reflects changes in oxygenation within 5 minutes Ventilation (Capnography) CO2 from metabolism EtCO2 measures exhaled CO2 at point of exit Reflects changes in ventilation within 10 seconds Oxygenation and Ventilation

  24. Physiology of Metabolism Oxygen Lungs  alveoli  blood Oxygen Breath CO2 Muscles + Organs Lungs Oxygen CO2 Cells ENERGY Blood Oxygen + Glucose CO2

  25. Pulse Oximetry Problems: • Accuracy • Motion & artifact • Dyshemoglobins • Perfusion

  26. Pulse Oximetry

  27. Pulse Oximetry

  28. ACVariable light absorption due pulsatile volume of arterial blood DCConstant light absorption due to non-pulsatile arterial blood. DCConstant light absorption due to venous blood. DCConstant light absorption due to tissue, bone, ... Absorption Time Model of Light Absorption At Measurement Site Without Motion

  29. ACVariable light absorption due pulsatile volume of arterial blood DCConstant light absorption due to non-pulsatile arterial blood. ACVariable light absorption due to moving venous blood DCConstant light absorption due to venous blood. DCConstant light absorption due to tissue, bone ... Absorption Time Model of Light Absorption At Measurement Site With Motion

  30. Influence of Perfusion on Accuracy of Conventional Pulse Oximetry During Motion Good Perfusion (Conventional PO) SpaO2=98 SpO2=93 SpvO2=88 Poor Perfusion (Conventional PO) SpaO2=98 SpO2=74 SpvO2=50

  31. MEASUREMENTT R/IR CONFIDENCE Post Processor % Saturation % Saturation Conventional Pulse Oximetry Algorithm Digitized, Filtered & Normalized R & IR 3 options during motion or low perfusion: • Freeze last good value • Lengthen averaging cycle • Zero out

  32. Next Generation Pulse Oximetry

  33. Next Generation Pulse Oximetry

  34. MEASUREMENT R/IR(Conventional Pulse Oximetry) CONFIDENCE MEASUREMENT DSTTM CONFIDENCE Post Processor Confidence Based Arbitrator % Saturation Digitized, Filtered & Normalized MEASUREMENT R & IR FSTTM CONFIDENCE DST SET – 97% MEASUREMENT SSTTM CONFIDENCE 0 50% 66% 97% 100% SpO2% MEASUREMENT Proprietary Algorithm 4 CONFIDENCE Masimo SET: Signal Extraction Technology SET “Parallel Engines”

  35. Variable Constant Variable Constant Averaging - inaccurate Separating - accurate 0 50% 66% 86% 97% 100% 0 50% 66% 86% 97% 100% SpO2% SpO2% Measure Through Motion Pulse Oximetry Discrete Saturation Transform (DST) SET separates the venous and arterial saturation values (conventional oximetry averages the values to produce a reading) Conventional Pulse Oximetry

  36. Carbon Monoxide (CO) Gas: • Colorless • Odorless • Tasteless • Nonirritating Physical Properties: • Vapor Density = 0.97 • LEL/UEL = 12.5 – 74% • IDLH = 1200 ppm

  37. Limitations of Pulse Oximetry Conventional pulse oximetry can not distinguish between COHb and O2Hb From Conventional Pulse Oximeter SpCO-SpO2 Gap: The fractional difference between actual SaO2 and display of SpO2 (2 wavelength oximetry) in presence of carboxyhemoglobin From invasive CO-Oximeter Blood Sample Barker SJ, Tremper KK. The Effect of Carbon Monoxide Inhalation on Pulse Oximetry and Transcutaneous PO2. Anesthesiology 1987; 66:677-679

  38. Pulse CO-oximetry

  39. Pulse CO-oximetry • Uses multiple wavelengths of light • Differentiates CO from O2

  40. Hgb Signatures: Physics of O2 Pathways

  41. SpCO User Concerns • Multiple wavelengths of light (8+) = Probe Placement: • Probe fits the finger • Centered over nail bed • Visible spectrum light = Protect from ambient light • Sunlight, strobes, etc.

  42. Know Your Equipment

  43. Back to CO2… What does exhaled CO2 tell us? • Ventilation • Perfusion • Metabolism

  44. Endotracheal Intubation

  45. What Should Happen Lungs (Good) $tomach (Bad, Very Bad)

  46. Anesthesia Litigation

  47. Respiratory Damaging Events Capnography Introduced American Society for Anesthesiologists: Closed Claims Project Database, 2010

  48. #1 Capnography Use for EMS:

  49. Guidelines 2005 EtCO2 recommended to confirm ET tube placement

  50. Intubated Patient • Airway adapter plugs into LifePak® • Be sure adapter is tightly attached • If not seated, waveform may flatten

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