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03 capnography
Capnography measures ventilation by detecting exhaled carbon dioxide (CO2) and provides a graphical waveform that can be interpreted. Pulse oximetry measures oxygenation by detecting oxygen levels in the blood. Capnography is useful for confirming endotracheal tube placement, detecting tube displacement, assessing chest compressions during CPR, and detecting return of spontaneous circulation. It also helps evaluate and monitor respiratory conditions, hypoventilation states, and low perfusion states in intubated and non-intubated patients.
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03 capnography
- 1. NON-INVASIVE C APNOGRAPHY ALS Blue In-Service Part III
- 2. Oxygenation and VentilationWhat is the difference?
- 3. Oxygenation and VentilationOxygenation (oximetry ) Cellular Metabolism Ventilation (capnography) CO 2 O 2
- 4. Oximetry and CapnographyPulse oximetry measures oxygenation Capnography measures ventilation and provides a graphical waveform available for interpretation
- 5. Oxygenation Measured bypulse oximetry (SpO 2 ) Noninvasive measurement Percentage of oxygen in red blood cells Changes in ventilation take minutes to be detected Affected by motion artifact, poor perfusion and some dysrhythmias
- 6. Oxygenation Pulse OximetrySensors Pulse Oximetry Waveform
- 7. Ventilation Measured bythe end-tidal CO 2 Partial pressure (mmHg) or volume (% vol) of CO 2 in the airway at the end of exhalation Breath-to-breath measurement provides information within seconds Not affected by motion artifact, poor perfusion or dysrhythmias
- 8. Ventilation Capnography waveformCapnography Lines
- 9. Oxygenation and VentilationOxygenation Oxygen for metabolism SpO 2 measures % of O 2 in RBC Reflects change in oxygenation within 5 minutes Ventilation Carbon dioxide from metabolism EtCO 2 measures exhaled CO 2 at point of exit Reflects change in ventilation within 10 seconds
- 10. Oxygenation versus VentilationMonitor your own SpO 2 and EtCO 2 SpO 2 waveform is in the second channel EtCO 2 waveform is in the third channel
- 11. Oxygenation versus Ventilation Now hold your breath Note what happens to the two waveforms How long did it take the EtCO 2 waveform to go flat line? How long did it take the SpO 2 to drop below 90%? SpO 2 EtCO 2
- 12. Numeric reading: HR100 Waveform:
- 13. Numeric reading: HR100 Waveform:
- 14.
- 15. Capnography in EMSLow-flow sidestream technology
- 16. Using Capnography Immediateinformation via breath-to-breath monitoring Information on the ABCs Airway Breathing Circulation Documentation
- 17. Using Capnography AirwayVerification of ET tube placement Continuous monitoring of ET tube position Circulation Check effectiveness of cardiac compressions First indicator of ROSC Monitor low perfusion states Airway Circulation
- 18. Using Capnography Breathing– Hyperventilation – Hypoventilation – Asthma – COPD
- 19. Using Capnography DocumentationWaveforms Initial assessment Changes with treatment EtCO 2 values Trends over time Waveforms Trends
- 20. Why Measure Ventilation— Intubated Patients Verify and document ET tube placement Immediately detect changes in ET tube position Assess effectiveness of chest compressions Earliest indication of ROSC Indicator of probability of successful resuscitation Optimally adjust manual ventilations in patients sensitive to changes in CO 2
- 21. A 2005 studycomparing field intubations that used capnography to confirm ETT placement vs. non-capnography use showed a 0% unrecognized misplaced ETT and 23% in the non-EtCO2 monitored group Confirm ETI with waveform capnography!!
- 22. Why Measure Ventilation— Non-Intubated Patients Objectively assess acute respiratory disorders Asthma COPD Possibly gauge response to treatment
- 23. Why Measure Ventilation—Non-intubated Patients Gauge severity of hypoventilation states Drug and ETOH intoxication Congestive heart failure Sedation and analgesia Stroke Head injury Assess perfusion status Noninvasive monitoring of patients in DKA
- 24. End-tidal CO 2 (EtCO 2 ) Ventilation Perfusion Pulmonary Blood Flow Right Ventricle Left Atrium r r O x y g e n O 2 C O 2 O 2 V e i n A t e y
- 25. a-A Gradient rr Alveolus PaCO 2 V e i n A t e y Ventilation Perfusion a rterial to A lveolar Difference for CO 2 Right Ventricle Left Atrium EtCO 2
- 26. End-tidal CO 2 (EtCO 2 ) Normal a-A gradient 2-5mmHg difference between the EtCO 2 and PaCO 2 in a patient with healthy lungs Wider differences found In abnormal perfusion and ventilation Incomplete alveolar emptying Poor sampling
- 27. End-tidal CO 2 (EtCO 2 ) Reflects changes in Ventilation - movement of air in and out of the lungs Diffusion - exchange of gases between the air-filled alveoli and the pulmonary circulation Perfusion - circulation of blood
- 28. End-tidal CO 2 (EtCO 2 ) Monitors changes in Ventilation - asthma, COPD, airway edema, foreign body, stroke Diffusion - pulmonary edema, alveolar damage, CO poisoning, smoke inhalation Perfusion - shock, pulmonary embolus, cardiac arrest, severe dysrhythmias
- 29. Physiological Factors AffectingETCO 2 Levels
- 30. Interpreting EtCO 2 and the Capnography Waveform Interpreting EtCO 2 Measuring Physiology Capnography waveform
- 31. Capnographic Waveform Normalwaveform of one respiratory cycle Similar to ECG Height shows amount of CO 2 Length depicts time
- 32. Phase 1 FirstUpstroke of the capnogram waveform Represents of gas exhaled from upper airways (I.e. anatomical dead space)
- 33. Phase 2 TransitionalPhase from upper to lower airway ventilation, and tends to depict changes in perfusion
- 34. Phase 3 Representsalveolar gas exchange, which indicates changes in gas distribution All increases of the slope of Phase 3 indicates increased maldistribution of gas delivery
- 35. Capnographic Waveform Waveformson screen and printout may differ in duration On-screen capnography waveform is condensed to provide adequate information the in 4-second view Printouts are in real-time Observe RR on device
- 36. Capnographic Waveform Capnographdetects only CO 2 from ventilation No CO 2 present during inspiration Baseline is normally zero Baseline
- 37. Capnogram Phase IDead Space Ventilation Beginning of exhalation No CO 2 present Air from trachea, posterior pharynx, mouth and nose No gas exchange occurs there Called “dead space”
- 38.
- 39. Capnogram Phase I Baseline Beginning of exhalation A B I Baseline
- 40. Capnogram Phase IIAscending Phase CO 2 from the alveoli begins to reach the upper airway and mix with the dead space air Causes a rapid rise in the amount of CO 2 CO 2 now present and detected in exhaled air
- 41. Capnogram Phase IIAscending Phase CO 2 present and increasing in exhaled air II A B C Ascending Phase Early Exhalation
- 42. Capnogram Phase IIIAlveolar Plateau CO 2 rich alveolar gas now constitutes the majority of the exhaled air Uniform concentration of CO 2 from alveoli to nose/mouth
- 43. Capnogram Phase IIIAlveolar Plateau CO 2 exhalation wave plateaus Alveolar Plateau A B C D I I I
- 44. Capnogram Phase IIIEnd-Tidal End of exhalation contains the highest concentration of CO 2 The “end-tidal CO 2 ” The number seen on your monitor Normal EtCO 2 is 35-45mmHg
- 45. Capnogram Phase IIIEnd-Tidal End of the the wave of exhalation A B C D End-tidal
- 46. Capnogram Phase IVDescending Phase Inhalation begins Oxygen fills airway CO 2 level quickly drops to zero
- 47. Capnogram Phase IVDescending Phase Inspiratory downstroke returns to baseline A B C D E I V Descending Phase Inhalation
- 48. Capnography Waveform Normalrange is 35-45mm Hg (5% vol) Normal Waveform
- 49. Capnography Waveform QuestionHow would your capnogram change if you intentionally started to breathe at a rate of 30? Frequency Duration Height Shape
- 50. Hyperventilation RR : EtCO 2 4 5 0 Normal Hyperventilation
- 51. Waveform: RegularShape, Plateau Below Normal Indicates CO 2 deficiency Hyperventilation Decreased pulmonary perfusion Hypothermia Decreased metabolism Interventions Adjust ventilation rate Evaluate for adequate sedation Evaluate anxiety Conserve body heat
- 52. Capnography Waveform QuestionHow would your capnogram change if you intentionally decreased your respiratory rate to 8? Frequency Duration Height Shape
- 53. Hypoventilation RR : EtCO 2 Normal Hypoventilation 4 5 0 4 5 0
- 54. Waveform: RegularShape, Plateau Above Normal Indicates increase in ETCO 2 Hypoventilation Respiratory depressant drugs Increased metabolism Interventions Adjust ventilation rate Decrease respiratory depressant drug dosages Maintain normal body temperature
- 55. Capnography Waveform Patterns0 4 5 Hypoventilation 4 5 0 Hyperventilation Normal
- 56. Capnography Waveform QuestionHow would the waveform shape change during an asthma attack?
- 57. Bronchospasm Waveform PatternBronchospasm hampers ventilation Alveoli unevenly filled on inspiration Empty asynchronously during expiration Asynchronous air flow on exhalation dilutes exhaled CO 2 Alters the ascending phase and plateau Slower rise in CO 2 concentration Characteristic pattern for bronchospasm “ Shark Fin” shape to waveform
- 58. Capnography Waveform Patterns Norma l Bronchospasm 4 5 0
- 59. Capnography Waveform PatternsHypoventilation Normal Bronchospasm Hyperventilation 4 5 0 4 5 0 4 5 0
- 60.
- 61. Confirm ET TubePlacement 4 5 0
- 62. Detect ET TubeDisplacement Capnography Immediately detects ET tube displacement Source: Murray I. P. et. al . 1983. Early detection of endotracheal tube accidents by monitoring CO 2 concentration in respiratory gas. Anesthesiology 344-346 4 5 0 Hypopharyngeal Dislodgement
- 63. Detect ET TubeDisplacement Only capnography provides Continuous numerical value of EtCO 2 with apnea alarm after 30 seconds Continuous graphic waveform for immediate visual recognition Source: Linko K. et. al . 1983. Capnography for detection of accidental oesophageal intubation. Acta Anesthesiol Scand 27: 199-202 4 5 0 Esophageal Dislodgement
- 64. Confirm ET TubePlacement Capnography provides Documentation of correct placement Ongoing documentation over time through the trending printout Documentation of correct position at ED arrival
- 65. Capnography in Cardiopulmonary Resuscitation Assess chest compressions Early detection of ROSC Objective data for decision to cease resuscitation
- 66. CPR: Assess ChestCompressions Use feedback from EtCO 2 to depth/rate/ force of chest compressions during CPR 4 5 0
- 67. CPR: Detect ROSCBriefly stop CPR and check for organized rhythm on ECG monitor 4 5 0
- 68. ETCO 2 & Cardiac Resuscitation Non-survivors Average ETCO 2 : 4-10 mmHg Survivors (to discharge) Average ETCO 2 : >30 mmHg
- 69. Optimize Ventilation Usecapnography to titrate EtCO 2 levels in patients sensitive to fluctuations Patients with suspected increased intracranial pressure (ICP) Head trauma Stroke Brain tumors Brain infections
- 70. Optimize Ventilation High CO 2 levels induce cerebral vasodilatation Positive: Increases CBF to counter cerebral hypoxia Negative: Increased CBF, increases ICP and may increase brain edema Hypoventilation retains CO 2 which increases levels CO 2
- 71. Optimize Ventilation Low CO 2 levels lead to cerebral vasoconstriction Positive: EtCO 2 of 25-30mmHG causes a mild cerebral vasoconstriction which may decrease ICP Negative: Decreased ICP but may cause or increase in cerebral hypoxia Hyperventilation decreases CO 2 levels CO 2
- 72. Optimize Ventilation Treatmentgoals Avoid cerebral hypoxia Monitor blood oxygen levels with pulse oximetry Maintain adequate CBF Target EtCO 2 of 35 mmHg
- 73. The Non-intubated PatientCC: “ trouble breathing”
- 74. The Non-intubated Patient CC: “trouble breathing” Asthma? Emphysema? Pneumonia? Bronchitis? CHF? PE? Cardiac ischemia?
- 75. The Non-intubated PatientCapnography Applications Identify and monitor bronchospasm Asthma COPD Assess and monitor Hypoventilation states Hyperventilation Low-perfusion states
- 76. Capnography in Bronchospastic Conditions Air trapped due to irregularities in airways Uneven emptying of alveolar gas Dilutes exhaled CO 2 Slower rise in CO 2 concentration during exhalation A l v e o l i
- 77. Capnography in Bronchospastic Diseases Uneven emptying of alveolar gas alters emptying on exhalation Produces changes in ascending phase (II) with loss of the sharp upslope Alters alveolar plateau (III) producing a “shark fin” A B C D E I I III
- 78. Capnography in BronchospasticConditions Capnogram of Asthma Source: Krauss B., et al . 2003. FEV1 in Restrictive Lung Disease Does Not Predict the Shape of the Capnogram. Oral presentation. Annual Meeting, American Thoracic Society, May, Seattle, WA Changes in dCO 2 /dt seen with increasing bronchospasm Bronchospasm Normal
- 79. Capnography in BronchospasticConditions Asthma Case Scenario Initial After therapy
- 80. Capnography in BronchospasticConditions Pathology of COPD Progressive Partially reversible Airways obstructed Hyperplasia of mucous glands and smooth muscle Excess mucous production Some hyper-responsiveness
- 81. Capnography in BronchospasticConditions Capnography in COPD Arterial CO 2 in COPD PaCO 2 increases as disease progresses Requires frequent arterial punctures for ABGs Correlating capnograph to patient status Ascending phase and plateau are altered by uneven emptying of gases
- 82. Capnography in BronchospasticConditions COPD Case Scenario Initial Capnogram A Initial Capnogram B 4 5 0
- 83. Capnography in CHFCase Scenario 88 year old male C/O: Short of breath H/O: MI X 2, on oxygen at 2 L/m Pulse 66, BP 164/86, RR 36 labored and shallow, skin cool and diaphoretic, 2+ pedal edema Initial SpO 2 69%; EtCO 2 17mmHG
- 84. Capnography in CHFCase Scenario Placed on non-rebreather mask with 100% oxygen at 15 L/m and aggressive SL nitroglycerin as per protocol Ten minutes after treatment: SpO 2 69% 99% EtCO 2 17mmHG 35 mmHG Time condensed to show changes 4 5 3 5 0 2 5
- 85. Capnography in Hypoventilation States Altered mental status Sedation Alcohol intoxication Drug Ingestion Stroke CNS infections Head injury Abnormal breathing CO 2 retention EtCO 2 >50mmHg
- 86. Capnography in Hypoventilation States EtCO 2 is above 50mmHG Box-like waveform shape is unchanged Time condensed; actual rate is slower 4 5 0
- 87. Capnography in HypoventilationStates Hypoventilation Time condensed; actual rate is slower
- 88. Capnography in HypoventilationStates Hypoventilation Hypoventilation in shallow breathing 4 5 0
- 89. Capnography in LowPerfusion Capnography reflects changes in Perfusion Pulmonary blood flow Systemic perfusion Cardiac output
- 90. Capnography in LowPerfusion Case Scenario 57 year old male Motor vehicle crash with injury to chest History of atrial fib, anticoagulant Unresponsive Pulse 100 irregular, BP 88/p Intubated on scene
- 91. Capnography in LowPerfusion Case Scenario Low EtCO 2 seen in low cardiac output Ventilation controlled
- 92. Capnography in PulmonaryEmbolus Case Scenario Strong radial pulse Low EtCO 2 seen in decreased alveolar perfusion
- 93. Capnography in RebreathingCircumstances Elevated Baseline Baseline elevation Oxygen mask Poor head and neck alignment Shallow breathing – not clearing deadspace 4 5 0
- 94. Capnography in DKACase Scenario Rapid rate, normal waveform and elevated EtCO 2 seen in early respiratory compensation in DKA Source: Flanagan, J.F., et al . 1995. Noninvasive monitoring of end-tidal carbon dioxide tension via nasal cannulas in spontaneously breathing children with profound hypocarbia. Critical Care Medicine. June; 23 (6): 1140-1142 4 5 0
- 95. Capnography Applications onNon-intubated Patients New applications now being reported Pulmonary emboli CHF DKA Bioterrorism Others? r r O x y g e n O 2 V e i n A t e y
- 96.
- 97. Sudden Loss ofWaveform Apnea Airway Obstruction Dislodged airway (esophageal) Airway disconnection Ventilator malfunction Cardiac Arrest
- 98. Increase in ETCO2 Possible causes: Decrease in respiratory rate (Hypoventilation) Decrease in tidal volume Increase in metabolic rate Rapid rise in body temperature (hyperthermia)
- 99. Esophageal Tube Anormal capnogram is the best evidence that the ETT is correctly positioned With an esophageal tube little or no CO 2 is present
- 100. Rebreathing Possible causes:Faulty expiratory valve Inadequate inspiratory flow Insufficient expiratory flow
- 101. Inadequate Seal AroundETT Possible causes: Leaky or deflated endotracheal or tracheostomy cuff Artificial airway too small for the patient
- 102. Decrease in ETCO2 Possible causes: Increase in respiratory rate (Hyperventilation) Increase in tidal volume Decrease in metabolic rate Fall in body temperature (hypothermia)
- 103. Obstruction Possible causes:Partially kinked or occluded artificial airway Presence of foreign body in the airway Obstruction in expiratory limb of the breathing circuit Bronchospasm
- 104. Muscle Relaxants “Curare Cleft”: Appears when muscle relaxants begin to subside Depth of cleft is inversely proportional to degree of drug activity
- 105. You Survived! Thanks!Questions to me via groupwise: [email_address]
Editor's Notes
- #3 Although some healthcare providers interchange the terms oxygenation and ventilation, they are two totally different physiological processes. What is the difference?
- #4 This slide illustrates the differences between oxygenation and ventilation. Inhaled air contains around 21% oxygen and less than 0.03% carbon dioxide. The oxygen diffuses into the arterial bloodstream across the membrane of the the air sacs (alveoli) that terminate the respiratory tree. Hemoglobin molecules on red blood cells (RBC) carries the O 2 atoms to the cells throughout the body. Oxygen saturation of the RBCs is measured by pulse oximetry. At the cell site, oxygen diffuses across the membrane to be used in metabolism. The primary waste product of metabolism, carbon dioxide, is then diffused out of the cell into the venous blood and circulated back to the respiratory tree. Here, the CO 2 is diffused into the alveoli and exhaled out through the airway. This gas exchange and exhalation is the ventilation process and measured by capnography.
- #5 Pulse oximetry preceded capnography and has been used for two decades. Some healthcare providers forget that pulse oximetry measures oxygenation only. Capnography measures ventilation.We will go in to the details of the differences between oxygenation and ventilation in the next section. For now, let’s look at the old and new technologies for ventilatory assessment in EMS and the new technologies that can now be used in EMS.
- #6 Oxygenation is measured noninvasively by pulse oximetry (SpO 2 ). • It detects the percentage of oxygen on red blood cells which is the percentage of oxygen-carrying hemoglobin (oxyhemoglobin) to the total hemoglobin available • Changes in ventilation take minutes to be detected by SpO 2 . Changes in ventilation become evident only when the circulating RBCs begin to become depleted - Pulse oximetry is affected by motion artifact, poor perfusion and some dysrhythmias
- #7 Here are common pulse oximeter sensors. It is placed on an extremity or ear lobe - quite a distance from the airway. This is the familiar pulse ox waveform with the pulsation pattern evident. Training note: Pulse oximetry is a very common measurement. Ask about students’ experiences such as, “has anyone had a situation where the pulse oximeter showed an “normal” oxygen saturation but your patient appeared to be in respiratory distress? This can happen because oxygenation is only half of the story.
- #8 Ventilation is the elimination of CO 2 from the body and can be measured by the end-tidal carbon dioxide. EtCO 2 is: • Expressed in the partial pressure (mm Hg) or percent volume (% vol) of CO 2 in the airway at the end of exhalation • Breath-to-breath measurement provides information within seconds • Not affected by motion artifact, poor perfusion or dysrhythmias
- #9 Capnography sensors are placed at the airway exit - the nose, mouth or ET tube hub. This is a normal capnography waveform - the “QRS” of ventilation monitoring.
- #10 A quick summary of the two physiological processes. They require different monitoring modalities which are complimentary measures of your patient’s status.
- #11 Here’s a exercise to see the important difference in monitoring your patient’s airway with EtCO 2 instead of pulse oximetry alone: Monitor your own SpO 2 and EtCO 2 . On this monitor the SpO 2 waveform is in the second channel and the EtCO 2 waveform is in the third channel. Teaching note: This is a nice classroom demonstration with students on actual devices.
- #12 Now hold your breath. Note what happens to the two waveforms. How long did it take the EtCO 2 wave form to go flat line? How long did it take the SpO 2 to drop below 90%? Teaching Note: Have someone use a stop watch to clock the time differences. Ask class members about the impact that this time difference may have on the care of a patient in respiratory distress.
- #13 Knowing the end tidal value and being able to continuously monitor that value is important in ongoing patient assessment. However, it is similar to monitoring your patient's heart rate.The heart rate number doesn’t tell you everything you may need to know. A numeric reading of 100 in your cardiac patient may be okay.
- #14 However, the waveform may indicate a completely different situation in your patient’s condition.
- #15 This is a screen with a capnography capability. Note the waveform and corresponding numeric value. The top shows the heart rate and ECG cardiac monitor. The middle is SpO 2 and pulse oximetry waveform. The lower is the EtCO 2 number (capnometry) and capnography waveform.
- #16 Here are examples of the newer low-flow sidestream cannulas and tubing. The nasal/oral cannula also delivers oxygen. The ET tube connector with the orange colored filter is easily seen here. Teaching Note: Samples of the cannulas are useful to show.
- #17 Capnography provides immediate information through breath-to-breath monitoring. It is noninvasive, yet can give you objective information on the important ABCs of your patients: Airway, Breathing, Circulation, and provide you documentation.
- #18 In the intubated patient, capnography can be used for: - Verification of ET tube placement - Continuous monitoring of ET tube position In the patient in cardiac arrest, capnography can be used: - To check effectiveness of cardiac compressions - As the first indicator of the return of spontaneous circulation, before the pulse or blood pressure - As a noninvasive measurement to monitor cardiac output in patient with low perfusion states
- #19 The exciting applications in the non-intubated patient include evaluating their breathing and differentiating. - Hyperventilation - Hypoventilation - Asthma - COPD
- #20 Documentation of this objective data on your patient includes: - Printouts of the waveforms of the initial assessment, as well as changes with treatment - Trends in the EtCO 2 values can be documented
- #21 Capnography has been used extensively in intubated patients to: • Verify and document ET tube placement • Immediately detect changes in ET tube position following correct placement • Assess effectiveness of chest compressions • Provide the earliest indication of ROSC • Determine the probability of success in a resuscitation • Optimally adjust manual ventilations in patients sensitive to changes in CO 2 Each of these applications will be discussed in detail in Part 3.
- #23 Capnography can be applied to non-intubated patients. Studies using capnography are underway to: • Objectively assess acute respiratory disorders including asthma, COPD and • Possibly gauge response to treatment These applications will be discussed in detail in Part 4.
- #24 Other new applications for capnography include: Gauging the severity of hypoventilation in: Drug and ETOH intoxication CHF Sedation and analgesia Stroke Head injury Some services use capnography in assessing a patient’s perfusion status and for noninvasive monitoring of patients in DKA.
- #25 This is a simplistic illustration of perfusion and diffusion in the pulmonary system. The pulmonary artery blood has a high concentration of CO 2 which diffuses across the alveolar membrane. Oxygen diffuses out of the alveolus into the pulmonary capillary. The process requires adequate blood flow and a healthy membrane.
- #26 The amount of of carbon dioxide in a patient's arterial blood and airway may be slightly different. This difference is called the a-A gradient.
- #27 There is a difference between the CO 2 level in the exhaled airway and the arterial system in a patient with healthy lungs. • The normal range is up to 2-5mmHg known as the “a-A gradient” • Wider differences are found - In abnormal perfusion and ventilation conditions such as pulmonary embolus - Incomplete alveolar emptying as in emphysema - Poor sampling which may be seen with a misplaced cannula or a nasal cannula on a patient who is breathing primarily through their mouth Teaching Note: This is a key point. The EtCO 2 readings often differ from the arterial blood gas done in the ED. Some ED clinicians mistake this difference as a “wrong” number in the exhaled air. A 2-5mmHg is acceptable and a wider difference should be investigated for underlying pathology.
- #28 End-tidal CO 2 reflects changes in: • Ventilation - the movement of air in and out of the lungs • Diffusion - the exchange of gases between the air-filled alveoli and the pulmonary circulation • Perfusion - circulation of blood through the pulmonary capillaries
- #29 EtCO 2 can be used to detect and monitor many of the patient problems frequently seen in EMS such as: • Ventilation - anything that interferes with the flow of air such as asthma, COPD, airway edema, foreign body, stroke • Diffusion - pathology that interferes with the delicate exchange of carbon dioxide and oxygen across through the alveolar membrane including pulmonary edema, alveolar damage, CO poisoning, smoke inhalation • Perfusion - is affected by many of the cardiovascular events you frequently encounter such as shock, pulmonary embolus, cardiac arrest, severe dysrhythmias, CHF
- #31 Now that we have covered some of the basic uses for capnography, let’s look at the values, waveform, underlying physiology and interpretations.
- #32 This is the normal waveform of one respiratory cycle - the “QRS of ventilation”. Similar to the ECG waveforms: • The x axis, or height/amplitude, shows amount of CO 2 • The y axis, or length, depicts time or duration
- #36 It is important to note that there may be quite a difference in the duration of the waveform you see on the screen and the one on the printout. Capnography waveforms on the monitor screen are condensed to provide adequate information in the 4-second view. Teaching Note: A patient with a RR of 8 would have a respiratory cycle of one breath about every 7.5 seconds. If the waveform was not condensed, you would see one full screen of a flat line, then one end of the waveform, etc. Press the PRINT button anytime you need the accurate duration .
- #37 Although other gases are present in the airway, the capnograph detects only CO 2 from ventilation. There is usually no CO 2 present during inspiration so the baseline is normally on zero.
- #38 There is no carbon dioxide at the beginning of exhalation. The air is from the trachea, mouth and nose. This upper airway area is often called “dead space” because there is no gas exchanged in the upper airway. Teaching Note: An extension of the airway such as an ET tube, expands the “dead space”.
- #40 Phase one on the capnograph is the ending of inhalation and the beginning of exhalation. This baseline is normally at zero and shows the amount of carbon dioxide in the dead space.
- #41 In phase II, or the ascending phase, CO 2 from the alveoli begins to reach the upper airway and mix with the dead space air. This causes a rapid rise in the amount of CO 2 that is now detected in exhaled air.
- #42 Phase Two, shown here between B and C, shows the rapid assent from the CO 2 present in the bronchi.
- #43 In phase three, the carbon dioxide from the alveoli has reached the airway exit. The exhaled air is now rich in CO 2 . In normal ventilation of health lungs, the concentration of CO 2 in the air is uniform.
- #44 Phase three, the alveolar plateau, is flat with a slight upward tilt toward the end. This plateau illustrates the uniform concentration of carbon dioxide in the pulmonary system.
- #45 The end of phase three is also the end of exhalation. This termination of the breath cycle contains the highest concentration of CO 2 and is labeled the “end-tidal CO 2 ”. This is the number seen on your monitor. Normal EtCO 2 is 35-45mmHg.
- #46 End of phase III illustrates the end of exhalation which called the “end-tidal CO 2 ”.
- #47 Phase four shows the beginning of the next inhalation. Oxygen fills the airway and the carbon dioxide level quickly drops to the baseline.
- #48 When inspiration does begin again, the amount of measured CO 2 quickly drops to zero. The rapid descent to baseline is shown here between D and E. The return to the baseline is called Phase IV.
- #49 A quick review of the four phases of the normal capnography waveform:. Phase I Inspiration ends and exhalation begins, dead space air is eliminated first, no CO 2 is present. Phase II Alveolar air begins to mix with dead space air, a sharp upstroke is produced. Phase III Alveolar air predominates and the CO 2 level plateaus as the exhalation continues. • The EtCO 2 is noted at the end of exhalation • Normal range is 35-45mmHg (5% vol) Phase IV Inspiration occurs, CO 2 level quickly returns to baseline. Normal baseline is at zero. The pattern repeats with each breath. Teaching note: The capnography waveform seems to be the opposite of many providers’ intuitive thinking. A helpful class exercise is to have everyone exhale on one cycle. Then walk the class through a “breath-along” with this capnography waveform strip. Have them practice inspiration at baseline, then begin exhalation in Phase II, prolong the breath slightly to emphasize the EtCO 2 , inhale on phase IV. That’s the normal pattern, let’s see how it can change.
- #50 How would your capnogram change if you intentionally started to breathe at a rate of 30? • Frequency • Duration • Height • Shape Teaching note: Have the audience respond. Key changes are: 1) Rate: increased frequency of waveforms 2) Duration: the waveform cycle shortens 3) Amount: the peak or height of the plateau will lower as the CO 2 is blown off The shape of the waveform should remain in the normal box-like pattern.
- #51 In the normal metabolic state, hyperventilation is seen as the increase in respiratory rate leads to a depletion of CO 2 . When a respiratory rate is faster than the rate of needed to maintain homeostasis, the amount of carbon dioxide in the exhaled air will decline. Teaching note: Ask when would a rapid RR not show a decline in EtCO 2 ? Answers: Metabolic states in which there is a high production of carbon dioxide such as fever, running, DKA, etc.
- #53 How would your capnogram change if you intentionally slowed your breathing down to a rate of 8? • Frequency • Duration • Height • Shape Teaching note: Have the audience respond. Two key changes are: 1) Rate: decreased frequency of waveforms 2) Duration: the waveform cycle lengthens 3) Amount: the peak or height of the plateau will higher as the CO 2 in each breath increases to compensate for the slow rate
- #54 In the normal metabolic state, hyperventilation is seen as the increase in respiratory rate leads to a depletion of CO 2 . When a respiratory rate is faster than the rate of needed to maintain homeostasis, the amount of carbon dioxide in the exhaled air will decline. Teaching note: Ask when would a slow RR not show an increase in EtCO 2 ? Answers: Slow metabolic states in which there is a lower production of carbon dioxide such as severe hypothermia.
- #56 A comparison of three common waveforms: normal, hyperventilation and hypoventilation. Teaching Note: A review of the four phases, normal range and differences is helpful to some students.
- #57 How would the waveform shape change during an asthma attack?
- #58 Bronchospasm interferes with the normally smooth flow of air as the degree and timing of spasm varies throughout the pulmonary tree. Therefore, in an asthma attack, the alveoli are unevenly filled on inspiration and empty asynchronously during expiration. This uneven emptying dilutes the carbon dioxide which results in a slower rise in CO 2 concentration during exhalation. These spasmodic alterations in air flow affect phase II (ascending phase) and phase III (the plateau) of the capnography waveform and produce a characteristic pattern often referred to as the “shark fin”.
- #59 The waveform change due to bronchospasm is easy to see when compared to the normal waveform. Just as it is now easy to spot a ventricular beat on the the ECG monitor, these capnography waveforms become readily identifiable with practice.
- #60 Quick review of common waveforms. Teaching note: Ask students to volunteer to “walk through” a waveform pattern and describe the changes .
- #61 Intubation in the field is a well-recognized challenge. From intubation to transfer of care, capnography is a new tool to assist you in caring for these critical patients.
- #62 This is a typical waveform indicating tube placement. Note the lack of CO 2 and the sudden appearance with the first exhalation.
- #63 Capnography constantly surveys the respiratory status and provides immediate feedback should the tube become displaced. Source: Murray I. P. et. al . 1983. Early detection of endotracheal tube accidents by monitoring CO 2 concentration in respiratory gas. Anesthesiology 344-346
- #64 Only capnography provides: • Continuous numerical value of EtCO 2 with apnea alarm after 30 seconds and • Continuous graphic waveform for immediate visual recognition As you can see with this waveform example, there is immediate recognition of a problem. Source: Linko K. et. al . 1983. Capnography for detection of accidental oesophageal intubation. Acta Anesthesiol Scand 27: 199-202
- #65 In addition to verifying ET tube placement and monitoring tube position, capnography provides you documentation. • Documentation of correct placement • Ongoing documentation over time with the trending printout • Documentation of correct position throughout your care until transferring your patient’s care at the ED
- #66 You can use capnography in resuscitation: • To assess chest compressions • For the earliest detection of ROSC • For objective data in the decision to cease resuscitation
- #67 Capnography provides feedback on chest compression during CPR. Use the information to determine effectiveness and monitor rescuer fatigue.
- #68 When a sudden increase in EtCO 2 is seen, briefly stop CPR and check for organized rhythm on ECG monitor and check pulses.
- #70 Use capnography to titrate EtCO 2 levels in patients sensitive to fluctuations, especially patients with suspected increased intracranial pressure (ICP). • Head trauma • Stroke • Brain tumors • Brain infections
- #71 Low CO 2 levels induce cerebral vasodilatation. Positive result is: Increased CBP to counter cerebral hypoxia. The negative is: Increased CBP, increases ICP and may increase brain edema. Hypoventilation retains CO 2 which, in turn, increases blood CO 2 levels.
- #72 Low CO 2 levels lead to cerebral vasoconstriction. • EtCO 2 levels of 25-30mmHG cause a mild cerebral vasoconstriction which may be useful in patients with high ICP • However, decrease in ICP may cause or increase cerebral hypoxia Hyperventilation decreases CO 2 levels.
- #73 Treatment goals include: Avoid cerebral hypoxia by: • Monitoring blood oxygen levels with pulse oximetry and • Maintaining adequate CBF
- #74 Neighbors called 911 when they found an elderly woman sitting in her front yard dressed in pajamas. They reported her to be “a bit confused” and complaining of “some chest or breathing problems”.
- #75 Familiar? What comes to mind?
- #76 Applications for capnography in your non-intubated patients include: Identification and monitoring of bronchospasm as in: - Asthma - COPD Assessing and monitoring: - Hypoventilation states - Hyperventilation - Low-perfusion states
- #77 Bronchospasm interferes with the normally smooth flow of air as the degree and timing of spasm varies throughout the pulmonary tree. The alveoli are unevenly ventilated on inspiration and empty asynchronously during expiration. This uneven emptying dilutes the carbon dioxide which results in a slower rise in CO 2 concentration during exhalation.
- #78 These spasmodic alterations in air flow affect phase II (ascending phase) and phase III (the plateau) of the capnography waveform and produce a characteristic pattern often referred to as the “shark fin”.
- #79 These capnograms show the changes in the dCO 2 /dt seen with increasing bronchospasm. Source: Krauss B., et al . 2003. FEV1 in Restrictive Lung Disease Does Not Predict the Shape of the Capnogram. Oral presentation. Annual Meeting, American Thoracic Society, May, Seattle, WA
- #80 Her initial capnogram is shown here with the “shark fin” on phase two. Note the change in the slope following therapy. Training Note: Ask about local protocol and what actions may be taken if the waveform changes as shown and what actions may be considered if the waveform does not change. Discuss what changes in patient symptoms and physical signs would be expected to be seen with these changes .
- #81 The COPD disease process is progressive and may be partially reversible. Airways are obstructed by: • Hyperplasia of mucous glands and smooth muscle • Excess mucous production, especially during an exacerbation • There is often some hyper-responsiveness here
- #82 Correlating capnograms to patient status would provide objective data. Arterial CO 2 in COPD patients is known to: • Increase as the disease progresses • Blood gases require frequent arterial punctures for ABGs and the procedure is not available in EMS Correlating capnograph to the COPD patient status can be helpful. As with PaCO 2 : • Ascending phase and plateau is altered by uneven emptying of gases
- #83 If his initial capnogram is similar to A. What would direction would your assessment take? If his initial capnogram is similar to B. How would your assessment change?
- #84 Here is a scenario based on a CHF report: • 78 year old male • C/O: Short of breath • H/O: COPD, MI X 2, on oxygen at 2 L/m • Pulse 66, BP 114/76/p, RR 36 labored and shallow, skin cool and diaphoretic, 2+ pedal edema • Initial SpO 2 69%; EtCO 2 17mmHG
- #85 In the initial assessment, the medics noted that his capnogram had a normal pattern and no evidence of acute bronchospasm. Based on this, they followed their medical protocol for CHF rather than COPD. He was placed on a non-rebreather mask with 100% oxygen at 15 L/m and given an IV diuretic and SL nitroglycerin. Ten minutes after treatment his SpO 2 went from 69% to 99%. The patient’s his EtCO 2 increased from 17mmHG to 35mmHG as his circulatory and respiratory status improved.
- #86 In hypoventilation, patients retain carbon dioxide with EtCO 2 >50mmHg. This can occur in an altered mental status and abnormal breathing such as in: • Sedation • Alcohol intoxication • Drug Ingestion • Postictal states • CNS infections • Head injury
- #88 This is his capnogram. Note the shape and height of the waveform.
- #89 Hypoventilation may also be exhibited differently if the patient’s breathing becomes more shallow. Shallow breathing often involves such low exhaled volumes that the gas deep inside the lung, “alveolar gas”, may not flow all the way to the mouth to be sampled. Instead, some of the gas in the trachea, called dead space gas, that does not contain CO2 may mix with the alveolar gas and dilute it. In this scenario, even though blood and alveolar CO2 are elevated, end tidal CO2 will appear to decrease. When the patient takes a deep breath, the carbon dioxide in the airway system is exhaled and the EtCO 2 level is elevated.
- #90 Capnography can also show alteration in perfusion both in the pulmonary tree and total body system. As we discussed in Part 3, it provides a noninvasive measure of cardiac output.
- #91 Let’s look at a case scenario of a patient with low perfusion. • 57 year old male • Auto crash with injury to chest • History of atrial fib, anticoagulant • Unresponsive • Pulse 100 irregular, BP 88/p • Intubated on scene
- #92 With his airway and ventilation controlled, capnography his perfusion status. The shape of the waveform is the normal rectangular box and the low EtCO 2 is an indication of his low cardiac output. Capnography provides another parameter to monitor the state of this critical patient.
- #93 In this case, the patient has a strong pulse and adequate blood pressure. Capnography indicates a low perfusion state. If the systemic circulation is adequate, the more likely reason for this reading is the diminished pulmonary perfusion. As always, this is to be added to the other information on the patient.
- #94 An elevated baseline is seen in patients who have carbon dioxide near the sampling inlet. This can be seen in patients who have - an oxygen mask over their nasal cannula. The mask traps carbon dioxide in the collection area. - poor head and neck alignment entraps carbon dioxide - shallow breathing that is not clear the upper airway and dead space.
- #95 Early stages of DKA, in which the patient’s respiratory system is correcting the acidosis, the EtCO 2 is elevated. In the ED, capnography can be used to monitor the PaCO 2 and decrease the number of arterial punctures. Capnograph can decrease the number of arterial blood draws. Source: Flanagan, J.F., et al . 1995. Noninvasive monitoring of end-tidal carbon dioxide tension via nasal cannulas in spontaneously breathing children with profound hypocarbia. Critical Care Medicine. June; 23 (6): 1140-1142
- #96 New applications for capnography are being reported as research and the use of the technology expands. These new applications include: • Pulmonary emboli • CHF • DKA • Bioterrorism • Others?