09 pre hospital capnography

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09 pre hospital capnography

  1. 1. Pre-Hospital Capnography Dr Nick Foster EMICS
  2. 2. Early Warning: When do you want the patient’s parachute to open? Capnography 4-10 minutes Pulse Oximetry Pulse Oximetry 30-60 seconds ECG ECG 10 seconds No monitor = free fall!
  3. 3. Physiology Carbon dioxide <ul><li>A Capnograph will show you second by second where you are with the patient by showing you </li></ul><ul><ul><li>The CO2 reading </li></ul></ul><ul><ul><li>The CO2 waveform </li></ul></ul><ul><ul><li>The Respiratory rate </li></ul></ul><ul><ul><li>The Oxygen saturation </li></ul></ul><ul><ul><li>The pulse rate </li></ul></ul><ul><li>Metabolism/Perfusion/Ventilation </li></ul>
  4. 4. Capnography An EtCO 2 value of e.g..38mm/Hg with a trace i s as diagnostic as an ECG T i m e 5 0 4 0 3 0 2 0 1 0 0
  5. 5. ► Application in clinical practice Objectives ► How it works ► The physiology involved
  6. 6. ► How it works
  7. 7. ► CO 2 monitoring technology <ul><li>Capnometry: the measurement and numerical display of the CO 2 level appearing in the airway </li></ul><ul><li>Capnograpahy: the measurement and graphical display of the CO 2 level appearing in the airway </li></ul>
  8. 8. ► CO 2 monitoring technology Compares the amount of infrared light absorbed by a sample of expired CO 2 to a chamber with no CO 2 Infrared spectroscopy
  9. 9. ► CO 2 monitoring technology Respiratory gases are continuously aspirated by a side port tube connection from the patients airway Sidestream sampling <ul><li>Advantages </li></ul><ul><li>Able to monitor intubated and non-intubated patients </li></ul><ul><li>Uses thin tubing therefore less dead space </li></ul><ul><li>Less likely to become contaminated with moisture because it is away from the airway </li></ul><ul><li>Uses a zero reference to keep the monitoring calibration </li></ul>
  10. 10. ► CO 2 monitoring technology Sidestream sampling <ul><li>Disadvantages </li></ul><ul><li>There is a lag time between sampling and measurement Advances: faster response time </li></ul><ul><li>If the patient is breathing rapidly, there may be contamination of the inhaled and exhaled gases and give a falsely low CO2 reading. Advances: Lower sample rates now used </li></ul><ul><li>The tubing can get obstructed by water and mucus </li></ul><ul><li>Pre-hospital use is in its infancy </li></ul>
  11. 11. ► The physiology involved Physiology of Respiration Physiology of Metabolism
  12. 12. Physiology of metabolism <ul><li>An acidoisis makes the pH more acidic than usual </li></ul><ul><li>An alkalosis makes the pH more alkaline than usual </li></ul>Metabolism Homeostasis. The body tries to maintain a state of equilibrium despite everything we throw at it. Body pH range 71.-7.8, homeostasis is about 7.3 -7.4 A body pH of 7.2 called acidaemia A body pH of 7.5 called alkalaemia
  13. 13. Physiology of metabolism <ul><li>There are a number of acids in the body </li></ul><ul><ul><ul><ul><ul><li>CO2 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Lactic acid from cell activity if starved of oxygen. </li></ul></ul></ul></ul></ul>Complex chemical interactions that keep these in balance. <ul><li>These dangerous acids need to be removed </li></ul><ul><ul><li>Buffers: immediate </li></ul></ul><ul><ul><li>CO2 production: minutes </li></ul></ul><ul><ul><li>Renal excretion/Liver breakdown: days </li></ul></ul>
  14. 14. Physiology of metabolism <ul><li>A balance exists </li></ul><ul><li>ACID CO2 </li></ul><ul><li>Tissues Lungs </li></ul>By looking at what goes into the body via the lungs (Oxygen) and what comes out (Carbon dioxide) you get a picture as to how damaged or ill the body is
  15. 15. Physiology of respiration <ul><li>a natural waste product of cellular activity </li></ul>Carbon dioxide
  16. 16. Oxygen -> lungs -> alveoli -> blood muscles + organs Oxygen cells Oxygen Oxygen + Glucose energy CO 2 blood lungs CO 2 breath CO 2 Physiology of respiration Oxygen/Carbon dioxide interaction: Metabolism CO2 produced by cellular metabolism diffuses across the cell membrane into the circulating blood. 5-10% carried in solution 20-30% bound to haemoglobin 60-70% carried as bicarbonate in the red blood cell
  17. 17. O 2 CO 2 O 2 CO 2 CO 2 Physiology of respiration Oxygen/Carbon dioxide interaction: Perfusion and Ventilation Ventilation Perfusion
  18. 18. <ul><li>Oxygenation = oxygen -> lungs -> alveoli -> blood </li></ul><ul><li>Metabolism = oxygen is converted to energy + CO 2 </li></ul><ul><li>CO 2 elimination = CO 2 -> blood -> lungs -> exhalation </li></ul>Physiology of respiration Ventilation Perfusion
  19. 19. METABOLISM PERFUSION VENTILATION So CO 2 levels provide evidence of three parameters going on the body Physiology What's happening at the cellular level How well the circulation is performing How well the lungs are working
  20. 20. METABOLISM PERFUSION VENTILATION Physiology If metabolism fails, acid forms (metabolic acid). With severe shock, the patient becomes very “acidic” and very ill Metabolic acidosis This may be tolerated if circulation and oxygenation are maintained. The acid is converted to CO2 and this is blown off by the lungs
  21. 21. METABOLISM PERFUSION VENTILATION Physiology If the circulation is failing, this “acid” cannot be transported to the lungs and the patient becomes iller Metabolic acidosis CO2 cannot be removed from the lungs as it cannot get there. Your only hope is to get the circulation working more effectively
  22. 22. METABOLISM PERFUSION VENTILATION Physiology Carbon dioxide If the breathing is inadequate, CO2 accumulates in the blood and is converted to acid Respiratory acidosis By ventilating the patient, we can get rid of the excessive CO2 and thereby reduce the damage the “acid” in the blood is doing to the tissues
  23. 23. Physiology <ul><li>Metabolic acidosis </li></ul><ul><li>Acid builds up (anaerobic metabolism) </li></ul><ul><li>Tissue hypoxia (anaemia, shock, severe infection, diabetic ketoacidosis) </li></ul><ul><li>Renal failure </li></ul><ul><li>Loss of body salts (severe diarrhoea) </li></ul><ul><li>Respiratory acidosis </li></ul><ul><li>Hypoventilation: CO2 builds up </li></ul><ul><li>Airway obstruction </li></ul><ul><li>Central neuro : brain injury, stroke, opiates </li></ul><ul><li>Periph neuro : spinal cord, MND </li></ul><ul><li>Chest wall disease (muscle, flail chest, trauma, pneumothorax </li></ul><ul><li>COPD </li></ul><ul><li>Pneumonia , </li></ul><ul><li>Respiratory alkalosis </li></ul><ul><li>Hyperventilation: CO2 blown off </li></ul><ul><li>Anxiety states </li></ul><ul><li>Asthma - low O2, low CO2 </li></ul><ul><li>PE - low O2, low CO2 </li></ul><ul><li>BUT as exhaustion sets in </li></ul><ul><li>-low O2 with rising CO2 </li></ul><ul><li>Metabolic alkalosis </li></ul><ul><li>Acid is lost </li></ul><ul><li>Severe vomiting (acid lost from stomach) </li></ul>
  24. 24. Capnography measurements
  25. 25. Normal waveform: Capnography measurements The waveform I just want you to look at the display first for a minute and then I will break the wave down into its constituent parts
  26. 26. Capnography measurements The waveform The lungs are composed of tissue involved in gas exchange (alveoli) and tubes connecting them to the outside world (bronchi, trachea). These tubes ARE NOT involved in gas exchange and is called dead space.
  27. 27. Capnography measurements The waveform Phase I Represents the CO2-free gas from the airways (anatomical and apparatus dead space).
  28. 28. Capnography measurements The waveform Phase II Consists of a rapid upswing on the tracing (due to mixing of dead space gas with alveolar gas).
  29. 29. Capnography measurements The waveform Phase III Consists of an alveolar plateau representing CO2-rich gas from the alveoli. It almost always has a positive slope, indicating a rising PCO2
  30. 30. Capnography measurements The waveform Phase 0 Is the inspiratory phase where normal air is breathed in. There is only 0.36mmHg of CO2 in the air compared to 40mmHg in expired air
  31. 31. Capnography measurements The waveform
  32. 32. Normal waveform: Capnography measurements The waveform
  33. 33. Causes for a rise in end tidal CO 2 Fever Hypercatabolic states Increased cardiac output Increased blood pressure Hypoventilation by patient Bronchial intubation (reduces the dead space) Rebreathing Inadequate fresh gas flows Poor ventilation by Dr Faulty valves Technical errors Machine faults Reduced Alveolar Ventilation Increased Pulmonary perfusion Increased CO2 output
  34. 34. Causes for a fall in end tidal CO 2 Hypothermia Hypocatabolic state (eg gross myxoedema) <ul><li>Reduced cardiac output </li></ul><ul><li>Hypotension </li></ul><ul><li>Hypovolaemia </li></ul><ul><li>Pulmonary embolism </li></ul><ul><li>Cardiac arrest </li></ul>Hyperventilation Apnoea Airway blocked: obstruction, ET tube extubated Circuit disconnection Sampling tube leak Technical errors Machine faults Increased Alveolar Ventilation Reduced Pulmonary perfusion Reduced CO2 output
  35. 35. <ul><li>Look for five characteristics of the waves, </li></ul><ul><li>Height (normal = 38mmHg. Tall = high CO2, small = low CO2) </li></ul><ul><li>Rate </li></ul><ul><li>Rhythm (regular, getting bigger (or smaller) </li></ul><ul><li>Base line (how wide it is) </li></ul><ul><li>Shape of the wave </li></ul>Waveform analysis
  36. 36. Waveform analysis Hypoventilation Base line at zero, but height is increased gradually Hyperventilation Baseline at zero, but height is reduced gradually
  37. 37. Clinical applications
  38. 38. Intubated patients Applications
  39. 39. <ul><li>Intubation </li></ul><ul><li>Verification of tube placement and monitoring ET placement during transport AND its dynamic (cf to a CO2 disc) </li></ul><ul><li>5-20% of tubes are misplaced either at the time of intubation or during transfer. </li></ul>Applications Intubated patients
  40. 40. <ul><li>Cardiac arrest </li></ul><ul><li>CO2 is a a measure of cardiac output. Because CO2 tracks cardiac output, capnography can show you how effective CPR is. </li></ul><ul><li>It is the earliest sign of a returning circulation. It is even more effective than a pulse check </li></ul><ul><li>PEA – an ECG with no endtidal CO2. </li></ul>Applications Intubated patients
  41. 41. <ul><li>Cardiac arrest and CPR </li></ul>Applications Intubated patients
  42. 42. Non-intubated patients Applications
  43. 43. <ul><li>Chest pain: MI or not an MI </li></ul><ul><li>Chest pain + tachyarrhythmia with normal capnogrpahy: Pt stable </li></ul><ul><li>Chest pain + tachyarrhytmia with CO2 at 10mmHg is about to have a cardiac arrest on you </li></ul>Applications Non-intubated patients
  44. 44. <ul><li>3 patients who are short of breath </li></ul><ul><li>Who has asthma, who has COPD and who has CCF? </li></ul>Applications
  45. 45. <ul><li>Waveform diagnostic of asthma/COPD. It indicates bronchospasm/airway obstruction </li></ul>Applications 3 patients short of breath Asthma The reason for the shark fin shape is due to the increased dead space present Bronchospasm/Airway Obstruction Normal
  46. 46. <ul><li>Asthma </li></ul>Applications The shape is a shark fin Width of the shape gets smaller as the patient gets worse
  47. 47. Applications Worsening asthma This patient needs ventilatory assistance Note the narrow base and tachypnoea and rising CO2 3 patients short of breath Asthma
  48. 48. Applications Response to treatment with Terbutaline. Indices return to normal. This patient has asthma: Diagnosis . 3 patients short of breath Asthma
  49. 49. Applications COPD Shark fin shaped waveform appearance showing airway obstruction. Wide base (cf asthma which was narrow) Elevated ETCO2 level 50mmHg Pt has COPD In contrast with asthma 3 patients short of breath
  50. 50. Applications CCF <ul><li>The low waveform height shows a low CO2 level. </li></ul><ul><li>It is not shark fin in shape so not COPD/asthma. </li></ul><ul><li>The low CO2 level indicates poor perfusion. </li></ul><ul><li>This is a poor circulation that could go with CCF. The heart is not pumping as well as it should </li></ul>3 patients short of breath
  51. 51. <ul><li>Chest infection </li></ul>Applications
  52. 52. <ul><li>Chest infection </li></ul><ul><li>Fever causes the CO2 level to go up and the pulse rate to go up </li></ul><ul><li>The pneumonia causes the SpO2 level to go down </li></ul>Applications
  53. 53. <ul><li>Another patient with a chest infection </li></ul>Applications Endtidal CO2 27% SpO2 91 RR 30 Pulse 120 Seen by GP 5 days before and diagnosed flu. Fever for 6 days. Temp 104F, Left side chest sign, creps ++, increased breathsounds, Whisp pect, Diagnosis left pneumonia in fact Legionella developed empyema 4 days later.
  54. 54. <ul><li>Patient with pleuritic chest pain </li></ul>Applications Endtidal CO2 38 SpO2 99 on air RR 14 Pulse 80 Chest pain, pleuritic. 4 hours. ECG normal. Chest examination normal, normal percussion, normal breath sounds. Tender chest wall. Calves normal and no tenderness
  55. 55. <ul><li>RTA – M1 Car fire following RTA </li></ul>Applications Endtidal CO2 22 SpO2 – on 99% oxygen RR 23 Pulse 98 24 year old male, driver RTA car fire. Had to be pulled from the car by passers by. Airway open, no carbonaceous material around mouth, nares clear. Breathing spontaneous, good A/E. Cap refill <2 radial pulse 110/80 GCS 14/15. No focal neurology. No obvious fracture
  56. 56. <ul><li>The unconscious patient </li></ul>Applications
  57. 57. Applications The unconscious patient Look for hypoventilation i.e. a high endtidal CO2 reading And a low respiratory rate
  58. 58. Applications The unconscious patient <ul><li>Sedation: </li></ul><ul><li>Alcohol: a drunk with a normal CO2 is stable. A drunk who is hypoventilating is at risk </li></ul><ul><li>Drug ingestion: </li></ul>
  59. 59. <ul><li>Metabolic states </li></ul>Applications
  60. 60. Applications Metabolic states With acidosis, the respiratory rate increases (e.g. diabetic ketoacidosis)
  61. 61. METABOLISM PERFUSION VENTILATION Physiology reminder If the circulation is failing, this “acid” cannot be transported to the lungs and the patient becomes iller Metabolic acidosis CO2 cannot be removed from the lungs as it cannot get there. Your only hope is to get the circulation working more effectively
  62. 62. Applications Metabolic states: a tale of two patient both with diabetic ketoacidosis Who is the sickest of the two? Patient A Endtidal CO2 30mmHg SpO2 100 RR 30 Pulse 120 Patient B Endtidal CO2 30mmHg SpO2 99 RR 10 Pulse 120
  63. 63. Applications Metabolic states A diabetic with a normal ETCO2 is not sick A diabetic with a low ETCO2 is a sick person. An ETCO2 of 6mmHg is bordering on a cardiac arrest
  64. 64. Applications Metabolic states 55 year old male collapsed at home Endtidal CO2 24 SpO2 92 RR 10 Pulse 80 Alcoholic, Myxoedema ( had not taken thyroxine for two years) very pale (Hb 2.4) BP 80/-, hepatic encephalopathy, jaundice, hypotensive. He died 3 days later This patient is very ill.
  65. 65. <ul><li>The head injured patient </li></ul>Applications
  66. 66. <ul><li>The head injured patient </li></ul><ul><li>Midazolam light anaesthesia </li></ul><ul><li>capnography </li></ul><ul><li>and assisted ventilation to maintain homeostasis </li></ul>Applications
  67. 67. Why is Pre-Hospital Capnography important
  68. 68. Why is Pre-Hospital Capnography important <ul><li>We cannot do anything about those who are going to die whatever we do. (Triage) </li></ul><ul><li>However we should be able to recognise and prevent those who would otherwise die needlessly </li></ul>
  69. 69. Why is Pre-Hospital Capnography important <ul><li>Preventable needless deaths occur </li></ul><ul><ul><li>Immediately at the time of injury </li></ul></ul><ul><ul><ul><li>Hypoxia and Airway obstruction </li></ul></ul></ul><ul><ul><li>Later following their injury </li></ul></ul><ul><ul><ul><li>Hypercarbia (too much CO 2 ) </li></ul></ul></ul><ul><ul><ul><ul><li>Acidaemia </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Cerebral vasodilation </li></ul></ul></ul></ul><ul><ul><ul><li>Hypoxia (not enough O 2 ) </li></ul></ul></ul><ul><ul><ul><ul><li>Hypoxic encephalopathy </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Cardiac arrest </li></ul></ul></ul></ul>
  70. 70. Why is Pre-Hospital Capnography important <ul><li>Time is important. For every minute of “no pre-hospital resuscitation”, the risk of dying increases by 4.3% </li></ul>
  71. 71. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Breathing </li></ul><ul><li>Circulation </li></ul>Scene Management The only thing about ABC is that it occurs at the beginning of the alphabet but it ain’t very practical and doesn't really help
  72. 72. <ul><li>Ilkeston 2330hrs head on RTA – four casualties three unconscious, one conscious but with a fractured L3 spine </li></ul><ul><li>female </li></ul><ul><li>GCS 7 </li></ul><ul><li>SpO2 100 </li></ul><ul><li>Pulse 120 </li></ul>Applications Real life incidents <ul><li>RR 10 </li></ul><ul><li>End tidal CO2 72mmHg </li></ul>The ABC had been followed But as I arrived, she had her first fit capnography
  73. 73. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Breathing </li></ul><ul><li>Circulation </li></ul>Scene Management Just because they are BREATHING, does NOT mean they are oxygenating and ventilating properly
  74. 74. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Breathing </li></ul><ul><li>Circulation </li></ul>Scene Management and just because they have a CIRCULATION doesn’t mean the blood’s going to the right places or may even be going in the wrong direction.
  75. 75. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Breathing </li></ul><ul><li>Circulation </li></ul>Scene Management So having caused you all to have sleepless nights, I would like to suggest an alternative concept
  76. 76. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Breathing </li></ul><ul><li>Circulation </li></ul>Scene Management Ventilation Perfusion Capnography
  77. 77. Why is Pre-Hospital Capnography important <ul><li>Airway </li></ul><ul><li>Ventilation </li></ul><ul><li>Haemorrhage control </li></ul><ul><li>Assisting the circulation </li></ul><ul><li>Procedural sedation </li></ul><ul><ul><ul><ul><ul><li>To facilitate extrication </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>To facilitate manipulation </li></ul></ul></ul></ul></ul><ul><li>Pre-hospital anaesthesia </li></ul>Severe trauma management is not ABC Perfusion Ventilation Airway
  78. 78. <ul><li>Beware……………….. </li></ul><ul><li>The patient with the low CO2 and the low respiratory rate </li></ul><ul><li>They could be about to die on you </li></ul>Take home tip
  79. 79. When do you want the parachute to open? Capnography 4-10 minutes Pulse Oximetry Pulse Oximetry 30-60 seconds ECG ECG 10 seconds No monitor = free fall!

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