Capnography and interpretations

Capnography and interpretations

1. Capnography and Interpretations Presenter- Dr. Suresh Pradhan Moderator- Dr. Nabin Regmi

2. Respiration

3. Capnography depicts respiration

4. Terminology Capnography: Recording of CO 2 concentration versus time and also its graphic display as a function of time or volume Capnograph : Machine that generates waveform Capnometry : Measurement of CO 2 in gas mixture and display in numeric form only Capnometer : Device that measures and displays readings Capnogram : Actual waveform

5. Capnography is synonymous with patient safety during anesthesia and sedation, and a boon during CPR Since the introduction of the first infrared CO 2  measuring and recording apparatus by Luft in 1943, capnography has evolved into an essential component of standard anesthesia monitoring armamentarium

6. the primary goal of anesthesiologists is to prevent hypoxia, and capnography helps to identify situations that can lead to hypoxia if uncorrected also helps in the swift differential diagnosis of hypoxia before hypoxia leads to irreversible brain damage

7. Because of these advantages, the utility of capnography has recently been extended outside of the operating room arena to- emergency rooms endoscopic suites x-ray rooms on-site emergency and trauma fields Sedation in all areas CPR Intensive Care Units Postoperative patients receiving narcotics Prehospital transport Interdepartmental transport

8. the American Society of Anesthesiologists (ASA) and Association of Anaesthetists of Great Britain and Ireland (AAGBI) require capnography to be used to monitor ventilation during moderate to heavy sedation the American Heart Association (AHA) recommends using capnography to judge the effectiveness of chest compression during CPR

9. Capnography helps to assess anesthesia equipment, circuits, ventilation perfusion mismatching in the lungs, cardiac output, and metabolism

10. CO 2 waveform during CPR chest compression for effective CPR should be optimized so that PETCO 2 values are between 10 and 20 mm Hg (>20 mm Hg) if PETCO 2 values, measured after initiation of ACLS, are less than 10 mm Hg, it is associated with a poor outcome

11. An abrupt increase in PETCO2 may indicate a return of spontaneous circulation(ROSC) Increase in pulmonary circulation brings more CO 2 into lungs for elimination

12. Capnography – The Past The first CO 2 analyzer ( Godart Capnograph medical CO 2 analyzer) in the Central Military Hospital, Utrecht, The Netherlands (1962) • Prof. Bob Smalhout

13. Capnogram

14. Arterial to end-tidal CO2 gradient Under normal physiologic conditions, the difference between arterial PCO 2 (from ABG) and alveolar PCO 2 (EtCO2 from capnograph ) is 2 to 5 mmHg This difference is termed the PaCO 2 —PEtCO 2 gradient and can be increased in: COPD (causing incomplete alveolar emptying) ARDS (causing V/Q mismatch) A leak in the sampling system or around the ET tube

15. CO2 measurement techniques Various configurations and measurement techniques are currently available in devices that measure CO2, some of them are: Infrared (IR) absorption Colorimetric detectors mass spectrometry Raman scattering gas chromatography

16. Infrared (IR) absorption has endured and evolved in the clinical setting for more than two decades the most popular and versatile technique today Principle is based on the fact that CO 2 molecules absorb infrared light energy of specific wavelengths the amount of energy absorbed being directly related to the CO 2 concentration

17. when an IR light beam is passed through a gas sample containing CO 2 , the electronic signal from a photodetector can be obtained this signal is then compared to the energy of the IR source, and calibrated to accurately reflect CO 2 concentration in the sample to calibrate, the photodetector’s response to a known concentration of CO 2 is stored in the monitor’s memory

18. Solid State vs. Chopper Wheel since the intensity of the IR light source must be known for a CO 2 measurement to be made, some method must be employed to obtain a signal which makes that correlation this can be done with or without moving parts Solid state CO 2 sensors CO 2 sensors that are not solid state

19. Solid state CO2 sensors use a beam splitter to simultaneously measure the IR light at two wavelengths: one that is absorbed by CO 2 (data) and one that is not (reference) also, the IR light source is electronically pulsed in order to eliminate effects of changes in electronic components the major advantage of solid state electronics is durability

20. CO2 sensors that are not solid state employ a spinning disk known as a chopper wheel, which can periodically switch among the following to be measured by the photodetector: The gas sample to be measured (data) The sample plus a sealed gas cell with a known CO2 concentration (reference) No light at all due to the moving parts, this type of arrangement tends to be fragile

21. Mainstream vs. Sidestream sampling Mainstream and sidestream sampling refer to the two basic configurations of CO2 monitors,regarding the position of the actual measurement device relative to the source of the gas being sampled Mainstream sampling Sidestream sampling

22. Mainstream mainstream CO 2 sensors allow the inspired and expired gas to pass directly across the IR light path state-of-the-art technology allows this configuration to be durable, small, lightweight and virtually hasslefree the major advantages of mainstream sensors are fast response time and elimination of water traps

23. Mainstream

24. Sidestream are located away from the airway, requiring the gas sample to be continuously aspirated from the breathing circuit and transported to the sensor by means of a pump

25. Sidestream

26. Colorimetric CO 2 Detectors Principle- Colorimetric CO 2 detectors rely on a modified form of litmus paper, which changes color relative to the hydrogen ion concentration (pH) present it actually measures the pH of the carbonic acid that is formed as a product of the reaction between carbon dioxide and water (present as vapor in exhaled breath)

27. exhaled and inhaled gas is allowed to pass across the surface of the paper and the clinician can then match the color to the color ranges printed on the device it is usually recommended to wait six breaths before making a determination

28. Value of the Capnogram is an extremely valuable clinical tool that can be used in many applications, including, but by no means limited to: Validation of reported end-tidal CO 2 value Assessment of patient airway integrity Assessment of ventilator, breathing circuit and gas sampling integrity Verification of proper endotracheal tube placement

29. Capnography examples and Interpretations

30. THANK YOU!!!