Pulse ox in the clinical setting

As patient status can change rapidly during anesthesia, a qualified anesthesia provider should be present continuously to monitor the patient and provide anesthetic care. The American Society of Anesthesiologists has determined standards for basic anesthetic monitoring, which state that “during all anesthetics, the patient’s oxygenation, ventilation, circulation and temperature shall be continually evaluated.” 

Regarding blood oxygenation and SpO2 measurement during anesthesia, ASA standards state that “a quantitative method of assessing oxygenation such as pulse oximetry” should be used at all times. It is important that the volume, pitch, and low threshold alarm noises be audible to the anesthesia care team personnel throughout the duration of anesthesia.

References: ASA Monitoring Requirements

Keywords: anesthesia, monitoring, frequency

Monitoring SpO2 is a critical part of managing patients with respiratory failure. The frequency of monitoring should take into consideration the severity of the patient’s illness and be tailored to the individual patient at the provider’s discretion. Here are some considerations:

• For patients with mild disease, SpO2 should be checked on initial assessment.
• For patients with moderate disease, SpO2 should be monitored intermittently (about every four hours).
• For patients with severe or critical disease, SpO2 should be monitored continuously or as frequently as possible.

For more information on routine monitoring and patient care, use this Charting Tool from the OpenCriticalCare.org project. 

References: Charting Tool Templates for COVID19 Care

Keywords: monitoring SpO2, respiratory failure, COVID

While SpO2 can be useful in many cases, there are certain situations where an arterial blood gas (ABG) should be drawn and analyzed. If the pulse oximeter shows a tracing that is dampened or erratic, or low PI or signal quality indicator, this may indicate that the SpO2 readings are unreliable and an ABG is warranted. Also, if there are any other factors present that might reduce the pulse oximeter’s accuracy (such as poor perfusion, low body temperature, etc.), an ABG should be obtained. 

Other reasons to get an arterial blood gas include if there is a clinical suspicion of Met-Hb, CO-Hb, S-Hb, or other hemoglobin types. Additionally, pulse oximetry does not provide information about ventilation or acid-base status, so an ABG is needed in situations where this information is also needed.

Keywords: ABG, arterial, blood gas

Pulse oximeters can be used to measure many different clinically important values. Some (but not all) pulse oximeters can measure the following:

• Respiratory rate
• Perfusion
• Carboxyhemoglobin
• Methemoglobin
• Hemoglobin concentration
• Pulsatility variation

Keywords: measurement, respiratory rate, pulsatility variation

The optimal SpO2 for patients with respiratory failure has not been well established and is still being evaluated. The World Health Organization (WHO) guidance for patients with hypoxemic respiratory failure due to COVID-19 recommends the following targets: Initial SpO2 of >94% for stabilization, then >90% for stable patients who are not pregnant or 92-95% for stable patients who are pregnant. It is important not to make SpO2 goals too high, as this can cause oxygen toxicity and will deplete the oxygen supply more quickly. For more discussion on optimal SpO2 goals in patients with respiratory failure, please read more here.

References: WHO SARI Toolkit 

Keywords: target SpO2, goal, respiratory failure, COVID-19