12. Oxygen Therapy

Low-Flow Systems

  • Nasal cannula: 1-6 L/min, with each additional liter increasing FiO2 by 4% (i.e., 1 L delivers 24%, 2 L 28%, etc.), up to FiO2 44%. Actual FiO2 depends on minute ventilation (i.e., effective FiO2 drops as respiratory rate increases). Oxygen delivery can be increased by use of oxygen reservoir device.
  • Simple mask: delivers FiO2 35-55% at flows 5-12 L/min.
    • Flows <5 L/min should not be used to prevent rebreathing of CO2.
  • Face tent: FiO2 variable up to 50%; more comfortable than facemask.
  • Venturi mask: 1-4 L/min, FiO2 preset at 24, 28, 31, 35, 40, and 50%.
  • Non-rebreather (NRB): delivers FiO2 60-90% at flow rates of 8-15 L/min.
    • Flow rates above ventilatory demand of the patient needed to prevent reservoir from deflating, typically about 15 L/min.

High-Flow Systems

  • High-flow nasal cannula (HFNC):
    • Provides humidified, 100% oxygen.
    • Up to 40-60 L/min of flow.
    • FIO2 titratable up to 100%.
    • Higher L/min of flow provides some PEEP to the patient.
    • Benefits: decreases work of breathing, enhances CO2 washout, provision of high FiO2.
  • Noninvasive positive pressure ventilation (NIPPV): BiPAP or CPAP. See Critical Care: Noninvasive Positive Pressure Ventilation (NIPPV): BiPAP or CPAP.

Long-Term Supplemental Oxygen (Home O2)

  • For patients with chronic cardiac or pulmonary disease. Indications:
    • Chronic hypoxemia at rest:
      • PaO2 ≤55 mmHg OR SpO2 ≤88%.
      • PaO2 ≤59 mmHg OR SpO2 ≤89% IF there is evidence of cor pulmonale, right heart failure, or erythrocytosis (Hct >55%).
    • Nocturnal hypoxemia (with normal oxygenation while awake):
      • If any of the following occur during sleep:
        • PaO2 ≤55 mmHg or SpO2 ≤88%.
        • PaO2 decreased more than 100 mmHg.
        • SpO2 decreased more than 5%.
      • Note: occurs with symptoms of morning headaches, restlessness, insomnia, impaired cognitive function.
      • Note: portable oxygen would not be covered for this indication.
    • Exercise-induced hypoxemia:
      • During exercise PaO2 ≤55 mmHg or SpO2 ≤88%.

 

Burton GG, Hodgkin JE, Ward JJ. Respiratory care – a guide to clinical practice. 4th ed. Philadelphia, Lippincott-Raven Publishers, 1997; pp. 381-395.

Kory RC, Bregmann JC, Sweet RD, et al. Comparative evaluation of oxygen therapy techniques. JAMA 1962;179:123-128.