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O2 Related Outcomes

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eyl407 edited this page Dec 15, 2022 · 4 revisions

O2 Modes

O2 Modes refers to the way in which patients receive supplemental oxygen:

  • RA = room air
  • NC = nasal cannula
  • HFNC = high-flow nasal cannula
  • CPAP = continuous positive airway pressure, a form of non-invasive mechanical ventilation
  • BIPAP = bilevel positive airway pressure, a form of non-invasive mechanical ventilation
  • ETT = endotracheal tube, a form of invasive mechanical ventilation. Includes the following O2 Modes values from flowsheet data
    • LMA
    • Oral Tracheal Tube
    • Nasal Tracheal Tube
    • ET Tube
    • Endotracheal Tube
  • TRACH = tracheostomy, patients may or may not be mechanically ventilated at the same time. Includes the following O2 Modes values from flowsheet data
    • Tracheal Tube
    • Tracheal Collar
    • Tracheal Mask
    • Tracheostomy
  • Uncategorized Values:
    • Humidified Air, Manual Ventilation, Invasive Ventilation, NIV, BVM, Other, Blow By, Ambu Bag, Whiskers, Oxygen Hood, Hi-flow (does not reliably indicate HFNC), T-Piece, TOT-HUT, HME
    • Face Mask, Aerosol Mask, Venti Mask, NR FM, Large Volume Nebulizer, Face Tent, Partial Rebreather Mask

FiO2 (Fraction of inspired oxygen)

FiO2 refers to the %age of oxygen in the air that the patient breathes. FiO2 values can be obtained from multiple sources

  • Lab results
  • Flowsheet measurements
  • Estimated values based on O2 Mode and O2 flow rate

Estimated FiO2

  • FiO2 values of patients on Room Air (RA) are estimated at 21%.
  • FiO2 values of patients assisted via high flow nasal cannula (HFNC) or nasal cannula (NC) are estimated with the following formula:

    FiO2 = 0.21 + (0.03 * [O2 liters/min])

  • Note that this equation should only be used when O2 flow rate <= 15 LPM.

If both estimated and measured FiO2 values are present for a given timestamp, FiO2 measured values will take precedence over estimated values.

AA Gradient (Alveolar–arterial gradient)

AA gradient refers to the difference in O2 concentration between a patient's alveoli and arteries. A higher AA gradient indicates that oxygen is not being transferred to the blood adequately.

The AA gradient is calculated from the following formula:

AA gradient = (FiO2*(P_atm - P_H2O) - PaCO2/0.8) - PaO2

  • PaO2 = arterial PO2 (measured in arterial blood)
  • PaCO2 = partial pressure of CO2 in arterial blood; currently only using PaCO2 values measured from same sample as PaO2
  • FiO2 = closest FiO2 prior to PaO2 and PaCO2 measurements
  • P_atm = at sea level = 760 mmHg
  • P_H2O = assuming 100% humidity in the alveoli = 47 mmHg
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