Noninvasive CO2 Monitoring Technology & Clinical Applications

1. Noninvasive CO2 MonitoringTechnology & Clinical Applications Lonnie Martinez Director of Respiratory Care Swedish Medical Center

2. Objectives • Definitions and Parameters • Descriptors and Overview • Interpretation – Especially Waveform • Bedside Application • Conscious Sedation

3. Capnography • Respiration - The Big Picture 1 Cellular Metabolism of food into energy - O2 consumption & CO2 Production Transport of O2 & CO2 between cells and pulmonary capillaries, & diffusion from/into alveoli. Ventilation between alveoli & atmosphere 2 3

4. MTV Metabolism (CO2 Production) Monitoring CO2 Elimination => Patient response to changes in Transport PaCO2 Circulation Ventilation CO2 Elimination (VCO2) Diffusion Ventilation

5. Capnography Depicts Respiration Capnography Metabolism Transport Ventilation CO2 CO2 CO2

6. Capnography Technical Aspects of Capnography

7. Capnography vs. Capnometry Capnography Capnography • Measurement & display of ETCO2 and the (CO2 waveform) • Measured by a capnograph Capnometry • Measurement & display of the ETCO2 value (no waveform) • Measured by a capnometer

8. Capnography • Mainstream Technology • Sensor placed in ventilator circuit • Measurement made at the patient’s airway • Fast response time • No water traps or tubing needed - hassle free • Non-intubated patient may use Capno Masks Sensor

9. Capnography • Sidestream Technology • Sensor located away from the airway • Gas moved to sensor by pump inside the monitor • Use with cannula or adapt for ventilator airway • Water traps, filters, or dehumidification tubing may be required

10. Quantitative vs. Qualitative ETCO2 Capnography Quantitative ETCO2 • Provides actual numeric value • Found in capnographs and capnometers Qualitative ETCO2 • Only provides range of values • Colorimetric CO2 detectors

11. 50 25 0 Beginning of expiration = anatomical deadspace with no measurable CO2 Normal Capnogram - Phase I CO2 mmHg B A

12. Anatomical Dead Space • Anatomical Dead Space • Internal volume of the upper airways • Nose • Pharynx • Trachea • Bronchi Anatomical Deadspace Conducting Airway - No Gas Exchange

13. 50 25 0 Normal Capnogram - Phase II CO2 mmHg C B Mixed CO2, rapid rise in CO2 concentration

14. Phase II - Transitional Gas CO2 mmHg Exhaled Volume

15. 50 Alveolar Plateau, all exhaled gas took part in gas exchange 25 End Tidal CO2 value 0 Normal Capnogram - Phase III CO2 mmHg D C Time

16. 50 25 0 Normal Capnogram - Phase IV Inspiration starts, CO2 drops off rapidly CO2 mmHg D E

17. Capnography Physiologic Factors Affecting ETCO2 Levels Increase in ETCO2 Decrease in ETCO2 • Decreased muscular activity (muscle relaxants) • Hypothermia • Decreased cardiac output (cardiac arrest) • Pulmonary embolism • Bronchospasm • Increased minute ventilation • Increased muscular activity (shivering) • Malignant hyperthermia • Increased cardiac output • Bicarbonate infusion • Tourniquet release • Effective drug therapy for bronchospasm • Decreased minute ventilation

18. Arterial CO2 (PaCO2) From Arterial Blood Gas Sample (ABG) ETCO2 from Capnograph Capnography Normal Arterial & ETCO2 Values Normal PaCO2 Values: (at sea level) Normal ETCO2 Values: 35- 45 mmHg 30- 43 mmHg 4.0-5.7 kPa 4.0-5.6%

19. Understanding why ETCO2 doesn’t match the ABG is important, if you don’t understand why it doesn’t match, it erodes confidence in all of the values!!! You may throw the baby out with the bath water!!

20. Arterial - End Tidal CO2 Gradient Capnography In healthy lungs the normal a-ETCO2 gradient is 2-5 mmHg In diseased lungs, the gradient will increase due to ventilation/perfusion mismatch. Decreased cardiac function will also reduce the ETCO2 value, due to decreased pulmonary blood flow

21. Capnography • Deadspace • Ventilated areas which do not participate in gas exchange Total Deadspace + + Anatomic Deadspace (airways leading to the alveoli Alveolar Deadspace (ventilated areas in the lungs) Mechanical Deadspace (artificial airways including ventilator circuits)

22. CO2 O2 Normal V/Q . . ETCO2 / PaCO2 Gradient = 2 to 5 mmHg

23. Shunt Perfusion – Low V/Q . . ETCO2 / PaCO2 Gradient = 4 to 10 mmHg No exchange of O2 or CO2

24. Dead Space Ventilation . . High V/Q ETCO2 / PaCO2 Gradient is large May exceed 60 torr Ventilation is not the problem! Perfusion is the problem No exchange of O2 or CO2 occurs

25. 53 53 0 53 0 0 0 0 0 0 Dead Space Ventilation ETCO2 = 33 mmHg PaCO2 = 53 mmHg Alveoli that do not take part in gas exchange will still have no CO2 – Therefore they will dilute the CO2 from the alveoli that were perfused The result is a widened ETCO2 to PaCO2 Gradient

26. Capnography Clinical Application of Capnography

27. Capnography • Value of the CO2 Waveform • Provides validation of ETCO2 value • Visual assessment of patient airway integrity • Verification of proper ET tube placement • ASA, JCAHO guidelines • Recent CMS recommendation • Assessment of ventilator, breathing circuit integrity

28. Alveolar Plateau established No Alveolar Plateau Capnogram – Valuable Tool CO2 (mmHg) 50 25 0

29. Abnormal CO2 Waveforms

30. Capnography Endotracheal Tube in Esophagus Possible Causes: • Missed Intubation • A normal capnogram is the best evidence that the ET tube is correctly positioned. • When the ET tube is in the esophagus, little or no CO2 is present

31. Capnography Inadequate Seal Around ET Tube Possible Causes: • Leaky of deflated endotracheal or tracheostomy cuff • Artificial airway that is too small for patient • Tube could be at the vocal cords

32. Capnography Obstruction in Airway or Breathing Circuit Possible Causes: • Partially kinked or occluded artificial airway • Presence of foreign body in the airway • Obstruction in expiratory limb of breathing circuit • Bronchospasm

33. CO2 Day 1 Day 5 Exhaled Volume Patient with Asthma

34. Capnography Hypoventilation - Increase in ETCO2 Possible Causes: • Decrease in respiratory rate • Decrease in tidal volume • Increase in metabolic rate • Rapid rise in body temperature (hyperthermia)

35. Capnography Hyperventilation - Decrease in ETCO2 Possible Causes: • Increase in respiratory rate • Increase in tidal volume • Decrease in metabolic rate • Fall in body temperature

36. CAPNO2 Mask O2 Delivery/CO2 Mainstream Mask • Based on simple O2 delivery style mask • Allows measurement of EtCO2 and delivery of O2 on non-intubated patients • Effective Capnogram to verify data • Excellent Choice for Conscious Sedation

37. Cannula O2 Delivery/ CO2 Sidestream

38. Procedural Sedation • Capnography is the logical device to monitor ventilation during procedural sedation • Why? • Airway problems are primary causes of morbidity associated with sedation/analgesia • Drug induced respiratory depression • Airway obstruction

39. Procedural Sedation with O2 • Capnography is a valuable monitoring tool to to detect respiratory events that could culminate in hypoxia • Why? • Patients in the ED are often on supplemental oxygen • Increased FIO2 may mask the decrease in ventilation early on if you are only observing pulse oximetry

40. Procedural Sedation • Capnography offers a safety net • A decrease in ventilation during procedural sedation almost always precedes a drop in saturation • The decrease in ETCO2, or a change in the shape of the capnogram will indicate a change in ventilation or airway integrity • This safety net can facilitate early intervention and avoid subsequent hypoxemia

41. CPR

42. A cool story…Ventilator Dyssynchrony

43. Conclusion • Improved Patient Monitoring • It’s not just about the Number • Waveform Interpretation • Helps with Differential DX • Clinical Application