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RESPIRATORY CYCLE:
     • Oxygenation: oxygen is inhaled into the lungs and carried into the blood
     • Ventilation: C02 is transported back from the blood to the lungs & exhaled
         •Relationship between C02 & respiratory rate (RR):
             Increased RR = decreased C02 = HYPERventilation (ETC02 < 35) - resp. alkalosis
             Decreased RR = increased C02 = HYPOventilation (ETC02 > 45) - resp. acidosis

 

CAPNOGRAPHY = “The VENTILATION VITAL SIGN”:

 

INTUBATED APPLICATIONS:
• Verification of ETT placement
• ETT surveillance during transport
• CPR: compression efficacy, early sign of ROSC (return of spontaneous circulation), survival predictor

NON-INTUBATED APPLICATIONS:
• Bronchospasm: asthma, COPD, anaphylaxis
• Hypoventilation: drugs, stroke, CHF, post-dictal
• Shock & circulatory compromise
• Hyperventilation syndrome: biofeedback monitor

NORMAL RANGE of ETC02: 35 – 45 mm Hg

3 Questions to ask every time capnography is used:

  1. IS THE ET TUBE IN THE TRACHEA (rise and fall of detectable C02)?

  2. WHAT IS THE ETC02 VALUE (height of the waveform)?

  3. WHAT IS THE SHAPE OF THE WAVEFORM?

 

 

 

CAPNOGRAPHY WAVEFORM ANALYSIS:

 

NORMAL: “Square box” waveform; baseline C02 = 0;
ETC02 = 35-45 mm Hg
Management: Monitor

DISLODGED ETT: Loss of waveform, Loss of ETC02 reading
Management: Replace ETT

ESOPHAGEAL INTUBATION: Absence of waveform, Absence of detectable ETC02.
Management: Re-intubate

CPR: “Square box” waveform; baseline C02 = 0; ETC02 = 10-15 mm Hg (possibly higher) with adequate CPR
Management: Change rescuers if ETC02 drops < 10

“ SHARKFIN” with/without prolonged expiration = Bronchospasm (asthma, COPD, allergic rxn):
Management: Bronchodilators (Albuterol, Atrovent, or epinephrine)

ROSC (return of spontaneous circulation): As in CPR, but ETC02 rises above 10-15 mm Hg
Management: Check for pulse

RISING BASELINE = Patient is rebreathing C02:
Management: Check equipment for adequate oxygen inflow

Allow intubated patient more time to exhale

HYPOVENTILATION: ? RR; Prolonged waveform; baseline C02 = 0; ETC02 > 45 mm Hg
Management: Assist ventilations or intubate, if needed

HYPERVENTILATION: ? RR; shortened waveform; baseline ETC02 = 0; ETC02 < 35 mm Hg Management: Biofeedback if conscious, decrease assisted ventilation rate if unconscious/intubated
**Important exceptions: Severe metabolic acidosis (DKA, sepsis, salicylate poisoning, acute renal failure, methanol ingestion, tricyclic overdose) will cause tachypnea (?? RR), but ETC02 will be HIGH.
**In other words, if RR is high, but ETC02 is also high, consider the above diagnoses. This is NOT normal!

PATIENT BREATHING AROUND ET TUBE: angled, sloping downstroke on waveform
Adult: Broken cuff or tube is too small
Pediatric: tube is too small
Management: Assess patient, oxygenation, ventilation; may need to reintubate

 

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