Noninvasive Oxygen Therapy

Noninvasive Oxygen Therapy is a topic covered in the Washington Manual of Medical Therapeutics.

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General Principles

  • Nasal cannulas: Most commonly used, but the exact FIO2 delivered is unknown because it is influenced by peak inspiratory flow demand. Each additional liter of flow increases FIO2 by approximately 4% (e.g., 2 L/min delivers ∼28%). Flow rates should generally be limited to ≤6 L/min. An oxygen reservoir device can increase oxygen delivery.
  • Simple facemask: Delivers oxygen at FIO2 of 35%–55% using flows of 5–12 L/min (lower flow rates should be avoided to prevent breathing in expired CO2).
  • Venturi masks: Allow the precise administration of oxygen via a Venturi facemask. Usual FIO2 values delivered are 24%, 28%, 31%, 35%, 40%, and 50%.
  • Nonrebreathing masks: Use a reservoir bag to achieve higher oxygen concentrations (up to 80%). Flow rates are generally at least 8–15 L/min. A one-way valve prevents exhaled gases from entering the reservoir bag, maximizing the FIO2 that is inspired.
  • Heated humidified high-flow nasal cannula (HFNC): Delivers heated and humidified oxygen at high flows and concentrations such that it flushes out a significant amount of nonoxygenated air from the upper airway. The system can be titrated up to 60 L/min and 100% FIO2 and may provide a small amount of PEEP at high flow rates.
    • The use of HFNC devices has increased recently with some studies showing encouraging benefits. In one open-label trial, patients with hypoxemic nonhypercapnic respiratory failure were randomly assigned to HFNC versus standard oxygen therapy or noninvasive positive-pressure ventilation (NPPV). Intubation rates were similar between groups; however, there was a significant improvement in 90-day mortality in patients who received HFNC as compared with other modalities.1
    • The role of HFNC following extubation is discussed in the mechanical ventilation section below.
  • NPPV: Delivers respiratory support with positive airway pressure via a sealed facemask, nasal mask, or helmet device. NPPV includes continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) ventilation. NPPV can be delivered by home devices or ventilators.
    • CPAP: Delivers continuous positive airway pressure throughout the respiratory cycle and prevents alveolar collapse during expiration. CPAP is often used in the treatment of obstructive sleep apnea and pulmonary edema. Initially, 5 cm H2O of pressure should be applied, and if hypoxemia persists, the level should be increased by 3–5 cm H2O up to a level of 10–15 cm H2O.
    • BiPAP: Delivers two different airway pressures during inspiration and expiration to decrease the work of breathing. BiPAP is often used for COPD exacerbations, weaning, and neuromuscular weakness. An inspiratory pressure of 5–10 cm H2O and an expiratory pressure of 5 cm H2O are reasonable starting points. Ventilation is determined by the difference between inspiratory and expiratory pressures (i.e., “drive pressure”), and inspiratory pressures can be uptitrated to achieve adequate tidal volumes and minute ventilation.
    • Benefits of NPPV: NPPV decreases the need for mechanical ventilation in appropriately selected patients.2 The benefits of NPPV are particularly strong in patients with neuromuscular disease, COPD, pulmonary edema, and postoperative respiratory insufficiency.3 A recent single-center trial found that NPPV delivered via a transparent helmet device covering the entire head reduced the need for intubation and improved survival in patients with ARDS.4
    • Potential harms of NPPV: NPPV is generally safe but can cause skin damage, eye irritation, claustrophobia, and aerophagia and be difficult to tolerate for some patients. Use should be limited to patients who are conscious, are cooperative, able to protect their airway, and are hemodynamically stable.5 NPPV use should be limited to those with an anticipated short duration of respiratory failure. Close monitoring is required during its use.

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General Principles

  • Nasal cannulas: Most commonly used, but the exact FIO2 delivered is unknown because it is influenced by peak inspiratory flow demand. Each additional liter of flow increases FIO2 by approximately 4% (e.g., 2 L/min delivers ∼28%). Flow rates should generally be limited to ≤6 L/min. An oxygen reservoir device can increase oxygen delivery.
  • Simple facemask: Delivers oxygen at FIO2 of 35%–55% using flows of 5–12 L/min (lower flow rates should be avoided to prevent breathing in expired CO2).
  • Venturi masks: Allow the precise administration of oxygen via a Venturi facemask. Usual FIO2 values delivered are 24%, 28%, 31%, 35%, 40%, and 50%.
  • Nonrebreathing masks: Use a reservoir bag to achieve higher oxygen concentrations (up to 80%). Flow rates are generally at least 8–15 L/min. A one-way valve prevents exhaled gases from entering the reservoir bag, maximizing the FIO2 that is inspired.
  • Heated humidified high-flow nasal cannula (HFNC): Delivers heated and humidified oxygen at high flows and concentrations such that it flushes out a significant amount of nonoxygenated air from the upper airway. The system can be titrated up to 60 L/min and 100% FIO2 and may provide a small amount of PEEP at high flow rates.
    • The use of HFNC devices has increased recently with some studies showing encouraging benefits. In one open-label trial, patients with hypoxemic nonhypercapnic respiratory failure were randomly assigned to HFNC versus standard oxygen therapy or noninvasive positive-pressure ventilation (NPPV). Intubation rates were similar between groups; however, there was a significant improvement in 90-day mortality in patients who received HFNC as compared with other modalities.1
    • The role of HFNC following extubation is discussed in the mechanical ventilation section below.
  • NPPV: Delivers respiratory support with positive airway pressure via a sealed facemask, nasal mask, or helmet device. NPPV includes continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) ventilation. NPPV can be delivered by home devices or ventilators.
    • CPAP: Delivers continuous positive airway pressure throughout the respiratory cycle and prevents alveolar collapse during expiration. CPAP is often used in the treatment of obstructive sleep apnea and pulmonary edema. Initially, 5 cm H2O of pressure should be applied, and if hypoxemia persists, the level should be increased by 3–5 cm H2O up to a level of 10–15 cm H2O.
    • BiPAP: Delivers two different airway pressures during inspiration and expiration to decrease the work of breathing. BiPAP is often used for COPD exacerbations, weaning, and neuromuscular weakness. An inspiratory pressure of 5–10 cm H2O and an expiratory pressure of 5 cm H2O are reasonable starting points. Ventilation is determined by the difference between inspiratory and expiratory pressures (i.e., “drive pressure”), and inspiratory pressures can be uptitrated to achieve adequate tidal volumes and minute ventilation.
    • Benefits of NPPV: NPPV decreases the need for mechanical ventilation in appropriately selected patients.2 The benefits of NPPV are particularly strong in patients with neuromuscular disease, COPD, pulmonary edema, and postoperative respiratory insufficiency.3 A recent single-center trial found that NPPV delivered via a transparent helmet device covering the entire head reduced the need for intubation and improved survival in patients with ARDS.4
    • Potential harms of NPPV: NPPV is generally safe but can cause skin damage, eye irritation, claustrophobia, and aerophagia and be difficult to tolerate for some patients. Use should be limited to patients who are conscious, are cooperative, able to protect their airway, and are hemodynamically stable.5 NPPV use should be limited to those with an anticipated short duration of respiratory failure. Close monitoring is required during its use.

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