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  1. Oxygen

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In this lesson, we'll cover oxygen therapy and all of its clinical effects, including its mechanism of action, indications, precautions, contraindications, and adult dosages.

Oxygen, an atmospheric gas, increases the saturation of hemoglobin oxygen. When used at therapeutic concentrations, it serves to aid the oxygenation of body tissues.

Oxygen Indications

The primary indications for the use of oxygen in ACLS are for any suspected cardiac or respiratory emergency, particularly when there are concerns of shortness of breath or suspected ischemic pain. Look to the following clinical guidelines:

  • Acute Coronary Syndrome (ACS): Consider oxygen until the patient is stable. Continue oxygen therapy if there is clinical evidence of pulmonary congestion, ongoing ischemia, or if the oxygen saturation drops below 90%.
  • Suspected Stroke: Oxygen is only indicated for patients presenting with hypoxemia where the arterial oxygen saturation is below 94%. It may also be considered if the saturation level is unknown or if the patient displays a poor clinical presentation.
  • Active Cardiac Arrest: Provide 100% oxygen to maximize oxygen delivery during low-flow states.
  • Post-Cardiac Arrest (ROSC): Once the patient achieves ROSC, the goal shifts to using the minimal amount of oxygen needed to maintain an oxyhemoglobin saturation between 90% and 98%.

A Warning About Over-Oxygenation

We are extremely cautious with over-oxygenation in all patients due to the clinical concern of hyperoxia. Hyperoxia can trigger harmful hemodynamic effects and has been shown to cause direct vasoconstriction across multiple organ beds, including a significant decrease in blood flow to both the heart and the brain.

Oxygen Precautions and Contraindications

There are few if any known contraindications for oxygen use in the true hypoxic patient. However, since giving oxygen to everyone is not appropriate, healthcare provider precautions should focus on specific assessment findings that could lead us to withhold or misapply treatment:

Pro Tip #1: Carbon Monoxide Exposure: If a patient was exposed to carbon monoxide, they might present with a pulse oximetry reading near 100%. Because CO replaces oxygen on the hemoglobin molecules, this patient is still severely hypoxic and requires immediate high-flow oxygen regardless of the electronic reading.

Pro Tip #2: COPD History: If a patient has a known history of COPD, it is appropriate to titrate oxygen back to their normal baseline O2 saturation, which is usually between 88% and 92%. Attempting to achieve higher standard saturation levels may be harmful to their respiratory drive.

Inaccurate Pulse Oximetry Readings

Be aware that your technical pulse oximetry reading itself might be incorrect or misleading due to the following physiological factors:

  • Low Peripheral Blood Flow: Seen in patients who are in shock, or simply individuals with cold hands that shunt blood flow away from the fingers.
  • Anemia: The patient has overall low hemoglobin levels but may still show a normal hemoglobin saturation percentage on the monitor. Always treat the patient's signs and symptoms rather than relying solely on electronic monitoring systems.

Adult Dosage and Delivery of Oxygen

Oxygen has several different delivery methods, and the percentage of oxygenation is regulated by both the flow rate per minute and the specific delivery adjunct used:

  • Nasal Cannula: If a nasal cannula is indicated, deliver oxygen at a flow rate of 2 to 6 liters per minute.
  • Nonrebreather Mask: If a nonrebreather mask is used, increase the oxygen flow rate to 12 to 15 liters per minute.
  • Positive Pressure Device (e.g., Bag-Valve Mask): For patients who are respiratory depressed or completely apneic, deliver oxygenated ventilations via a positive pressure device with the oxygen flow set at 15 liters per minute.

Pro Tip #3: Always remember that a restricted airway will severely affect the therapeutic response of your oxygenation treatment. The prompt use of a basic or advanced airway adjunct may be required to open or maintain a patent airway and treat your patient effectively.