Review 1.6

• "Figure 8" waveform on the Pressure-Volume Loop

  Indicates to increase flow
• Capnography


  NIV method to monitor ventilation (CO2) by measuring the exhaled CO2 pressure (Waveform)
• Capnometry


  Refers to measurement and display of exhaled CO2 concentration in numerical values (#s)
• PETCO2


  End tidal PCO2 (ETCO2)
• Normal PETCO2 range is 35-45 mmHg
• Uses of Capnography


  • Detects changes in CO2- hypoventilation or hyperventilation
  • Assess changes in pulmonary blood flow- PE, cardiac arrest, severe hypotension
  • Used for verification of ETT placement- CO2 detection, infrared absorption or mass spectrometry
  • Useful for assessing effectiveness of resuscitation efforts following cardiac arrest
• Reasons for PETCO2 to increase

  • Decreased alveolar ventilation
  • Increased CO2 production
  • Rebreathing exhaled gas
  • Fever
  • Sepsis
  • Seizures
  • Bicarbonate admin
  • Leaks in vent resulting in hypoventilation
• Reasons for PETCO2 to decrease


  • Increased alveolar ventilation
  • Decreased co2 production
  • Ventilators disconnect
  • Esophageal intubation
  • Complete airway obstruction
  • Leaks around the ETT cuff
  • Hypothermia
  • Cardiac arrest
  • Hypotension
  • Low pulmonary perfusion- PE
• Relationship between PETCO2 and PaCO2

  PETCO2 is slightly lower than PaCO2, generally difference is 1 to 5 mmHg
• Low cardiac output


  Reduces PETCO2
• During cardiac arrest


  PETCO2 will cease
• Patient's pulse has returned after a code blue

  There will be immediate increase in the capnography reading
• Should not be used as a substitute for ABG, but there are NO specific contraindications to using capnograph/capnometry
• Mainstream capnography


  • Attached directly to the ETT to get instant PETCO2 reading, but devices are affected by accumulation of moisture, debris and secretions
• Sidestream capnography


  • Typically used, cheaper than mainstream but have a slower response to PETCO2 reading, can be used on intubated pts by using a small bore that is attached to monitor or on non-intubated patients that use a NC with a chamber for capnography
• Phase I of the capnograph

  Initial exhalation of dead space gas with no CO2 present, CO2 lvl should be 0 bc the beginning of exhalation is coming from the airways that did not participate in gas exchange
• Phase II of the capnograph

  Continuation of exhalation with significant increase in CO2 from both terminal airways and alveoli. During this phase gas from the conducting airways mixes with gas from proximal alveoli and the CO2 lvls begin to rise rapidly
• Phase III of the capnograph

  AKA plateau pressure, CO2 lvl essentially plateaus representing the exhalation of alveolar gas rich in CO2. VERY END OF PPLAT REPRESENTS ETCO2 MEASURMENT
• Inspiration phase on the capnograph

  Inspiration happens right after phase 3, inspiration begins the CO2 lvl abruptly drops back to 0
• Be familiar with ALL the abnormal capnograph waveforms