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Capnography

Capnography. Riding the wave of ventilation. “Technology, you can either embrace it or run from it…”. The Science. ETCO 2 Monitoring. Review of Pulmonary Anatomy & Physiology The primary function of the respiratory system is to exchange carbon dioxide for oxygen.

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Capnography

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  1. Capnography Riding the wave of ventilation....

  2. “Technology, you can either embrace it or run from it…”

  3. The Science

  4. ETCO2 Monitoring Review of Pulmonary Anatomy & Physiology • The primary function of the respiratory system is to exchange carbon dioxide for oxygen. • During inspiration, air enters the upper airway via the nose where it is heated, humidified and filtered. • The inspired air flows through the trachea and bronchial tree to enter the pulmonary alveoli where the oxygen diffuses across the alveolar capillary membrane into the blood.

  5. “CO2 is the smoke from the flames of metabolism.” - Ray Fowler MD

  6. History

  7. The unintentional and unrecognized esophageal intubation was identified as early as 1938 as a cause of mortality associated with anesthesia. The incidence was much lower than that of death from regurgitation/aspiration, which at the time was among the leading causes of perioperative death (Edwards 1938, Edwards et al, 1956, Maleck et al. 2001).

  8. In 1979 a review of anaesthetic accidents forwarded to the Medical Defence Union of the United Kingdom between 1970 and 1977 found unrecognized esophageal intubation to be the most common cause of death and brain damage. The authors recommended NOT to rely on movements of the reservoir bag and the chest to identify the endotracheal tube (ETT) position and coined the well-known phrase "when indoubt, take it out" (Utting et al, 1979).

  9. The capnogram has been described in text and picture as early as 1949. Both infrared (Luft, 1943; Fowler 1949) and mass spectrography devices (Kydd & Hitchcock, 1949) were already used at that time.

  10. The application of capnometry for the detection of esophageal tube malposition was first proposed in 1981 and formally studied in 1983 (Ionescu, 1981; Kalenda & van der Vliest, 1982; Linko et al 1983; Murray & Modell, 1983; Klein & Moyes, 1984).

  11. While by the mid 80's capnometry was rightly seen as the "gold standard" in checking the ETT position in hospital, this had little relevance for the out-of-hospital setting; no portable devices existed at that time. Also, at least in the English speaking countries which used (and use) paramedic based emergency medical systems, prehospital intubations were rare in the 1980s.

  12. Definitions • Capnography: The measurement of Carbon Dioxide (CO2)in exhaled breath. • End Tidal CO2 (ETCO2 or PetCO2): The level of (partial pressure of) Carbon Dioxide released at end expiration.

  13. ETCO2 detector types • Colorimetric: Positive color change in the presence of CO2. • Capnometer: The numeric measurement of CO2. • Capnogram: The expired wave form in addition to a numeric value.

  14. The Past

  15. The MiniCap III Gave an audible ‘beep’ in the presence of CO2

  16. Colorimetric

  17. Colorimetric • pH sensitive, chemically impregnated paper encased in a plastic chamber that’s placed between the ETT and ventilation device • Color change is reversible • On the spontaneous breathing patient it will be purple on inhalation, yellow on exhalation

  18. Pros Very accurate Inexpensive (~$10-15) Changes color when CO2 is present Continues to work up to two hours Disposable Cons Secretions Don’t detect hypo-or hypercarbia Increased deadspace Changes color when CO2 is present False positives Hard to read at night Colorimetric

  19. Capnometry

  20. Pros First generation of CO2 monitors Portable Given at least a numeric value Able to monitor a trend (?) Cheaper than capnography Cons Numeric value only Only found on eBay(?) Outdated Bulky adapter Treating the machine Capnometry

  21. Capnography

  22. “End Tidal CO2 reading without a waveform is like a heart rate without an ECG recording.” - Bob Page

  23. ICU Cousins

  24. Pros Numeric value plus expiratory waveform Able to monitor a trend Ability to assess perfusion Very accurate Cons Expensive Fragile Warm-up time (?) Secretions Temperature sensitive (?) Capnography

  25. All in one

  26. Types of Technology • Infrared (IR) Spectroscopy • Side stream sampling • Main stream sampling • Microstream Technology

  27. Infrared Spectroscopy • Technology most often used • Infrared light is used to expose the sample • Infrared sensors detect the absorbed light and calculate a value

  28. Sidestream • “First generation” devices • Sample of exhaled gas is aspirated from the patients airway interface into the monitor which houses the sensor • Can be used in nonintubated patients • Secretions/moisture

  29. Mainstream • “Second generation” • Sensor attaches directly to the airway • During exhalation, exhaled gas passes directly over the sensor • Primarily for intubated patients • Secretions • FRAGILE!

  30. Microstream Technology • Samples 1/20th the volume • Vapor permeable tubing • Sub micron-multi-surface tubing • Expensive parts are protected • Microbeam IR sensor is CO2 specific • Can be used for adult and pediatrics

  31. For the non-intubated patient

  32. The Normal Capnogram • Phase I: Respiratory baseline • Phase II: Expiratory upstroke • Phase III: Expiratory plateau • ETCO2: Peak ETCO2 level • Phase IV: Inspiratory downstroke III II IV I

  33. Normal Capnography

  34. Hyperventilation • Narrow waveform • Decrease in CO2 • Hyperventilation syndrome • Overzealous bagging (CHI) • Pulmonary emboli • DKA

  35. Hypoventilation • Narcotic overdose • CNS dysfunction • Heavy sedation

  36. Before Narcan After Narcan

  37. Apnea • Dislodged ET tube • Total obstruction of the ET tube • Respiratory arrest in the non-intubated patient • Equipment malfunction (if the patient is still breathing) check all connections and collecting chamber

  38. Loss of Alveolar Plateau • Incomplete or obstructed exhalation • Asthma • COPD • Tube kinked or partially obstructed

  39. on arrival after start of neb treatment after two A&A nebs

  40. Elevated baseline • Air trapping (asthma or COPD) • CO2 rebreathing (ventilator circuit problem)

  41. Capnography and CPR

  42. Poor perfusion (CPR) change • The capnogram can indicate perfusion during CPR and effectiveness of resuscitation efforts • The trough is when the rescuers switched • The fatigue of the first rescuer was demonstrated when the second rescuer took over compressions rescuer

  43. ROSC

  44. Shocked ROSC ROSC ROSC ROSC

  45. Other Uses

  46. Rapid Triage

  47. Sedation

  48. Search & Rescue/Terrorism

  49. Field Applications for Capnography -Closed head injury -Obstructive pulmonary disease -Tube confirmation -Perfusion

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