Breathing brings oxygen into the lungs. From there, oxygen travels to the rest of the body via the hemoglobin in blood. Maintaining adequate oxygen delivery throughout the body is vital to healthy body function.
Oxygen saturation, or SpO2, is a measure of the percentage of oxygen-carrying hemoglobin in the blood. Without oxygen delivery, hypoxemia (low blood oxygen) and hypoxia (lack of oxygen in tissue) can occur—both of which can be life threatening and cause irreversible harm if not acted upon quickly. That’s why measuring SpO2 can be important when assembling a full picture of a patient’s status and assessing their care needs.
Pulse oximetry is commonly used to measure SpO2 levels; It’s accurate, noninvasive and easy to use. Pulse oximeters can either provide continuous monitoring or spot-checking. Both types of measurement are useful, although continuous monitoring offers additional benefits that may help inform clinical assessments.
Know the Difference
Here are some different approaches to monitoring SpO2 levels. Knowing which is preferable helps detrmine which technology to use.
Spot-checking SpO2 provides caregivers with a snapshot of a patient’s blood oxygen status at the precise moment the measurement is made. This can be more convenient in situations where a patient may not need continuous surveillance, such as with stable, low-acuity or ambulatory patients. Many spot-check devices are portable and handheld, making them convenient for use on the go. However, through recent innovations, continuous monitoring is now available in wireless and tetherless forms that allow patients to move about freely while still being monitored—offering the best of both worlds.
With more data comes the potential for more effective clinical assessment. Continuous monitoring offers trended data and configurable alarms, helping caregivers stay aware of patient progress and providing early indications that further intervention may be needed. Timely warnings or notifications about patient status are key to early intervention, which helps support better patient outcomes. For example, a high-risk, chronic care patient taking one or more medications can experience unexpected adverse events. With continuous monitoring, caretakers have greater visibility into their patient’s condition and—with the aid of continuous, high-fidelity data—can make effective clinical judgements and care decisions.
Remote continuous SpO2 monitoring is also growing in popularity. The COVID-19 pandemic and the need for telemedicine solutions have driven increased demand for SpO2 monitoring that conveys trended data from patients convalescing at home to clinicians off site. Remote monitoring solutions combine continuous SpO2 measurements with a secure patient surveillance platform, allowing physicians to review a patient’s trended data remotely and communicate with them through a secure application in the event a return to the hospital is necessary.
Recommending the Right Pulse Oximeter
When monitoring patients at home, it’s important to use a pulse oximetry solution that is light, comfortable, easy to use, durable and portable—keeping in mind that, as mentioned above, technological advancements have now made it possible to provide the benefits of continuous monitoring in a device that promotes patient comfort and allows freedom of movement as readily as fingertip spot-check devices.
But even when narrowing your selection to pulse oximeters with these physical attributes, there are many technological differences that separate good pulse oximeters from bad and reliable from unreliable. Be wary of inexpensive, unproven, nonhospital-grade devices that trade a low price for a lack of accuracy and reliability. Also avoid smartwatches and other fitness-focused devices that may claim to measure SpO2 but aren’t actually medical devices.
Instead, consider these criteria when recommending a pulse oximeter:
- Has it received Food and Drug Administration clearance for reading (accurately measuring) through challenging conditions such as patient motion and low perfusion (decreases in arterial blood flow)? This is especially important for neonatal patients, who are often prone to involuntary movement. Low perfusion is also common, for example in elderly patients with vascular or cardiac conditions. Many of the cheap fingertip devices found readily online do not have such capabilities, lacking the advanced algorithms and signal processing that allow more sophisticated devices to separate noise from true arterial signal. Unreliable SpO2 readings under these common conditions can lead to excessive false alarms and inaccurate data, delayed notifications, and an inability to obtain timely information about high-acuity patients.
- Has the technology been validated by a substantive body of clinical evidence drawn from objective, peer-reviewed studies?
- Has the device had its performance proven in hospital environments and been used on the sickest of patients, such as those in the intensive care unit or neonatal intensive care unit?
- Does it have validated accuracy specifications of 2% or less, even in challenging conditions?
- Was the technology developed and has it been shown to measure accurately on a variety of skin pigmentations? Because pulse oximeters depend on the passage of light through the skin, older technologies and those not developed or tested on a variety of pigmentations are often unable to accurately measure the SpO2 of patients with darker skin tones.
To sum up, it’s important to seek out a pulse oximeter that can perform even when the patient is in motion, has cold hands and has darker skin or is in bright sunlight.
It’s important to remember that the less direct clinician involvement in a patient’s care—that is, the less time a patient spends being actively supervised—the more the patient and caregiver are reliant on the pulse oximeter to do its job accurately and reliably, with timely notifications and alarms when it matters most.
Keys to Success When Measuring SpO2
Proper patient preparation and sensor application are crucial for obtaining accurate readings. The ideal monitoring site is selected based on the perfusion of the digit or extremity. Perfusion readings are available on some pulse oximeters to help select a site with a strong signal. Before applying a sensor, prepare the monitoring site by making sure the skin is clean and dry.
Pulse oximetry sensors use an emitter to shine light through the application site and measure light that passes through the site using a detector. Upon sensor application, ensure that the optical components (the emitter and the detector) are aligned. Misapplied sensors or sensors that are not securely placed or have gaps where extraneous light might enter can lead to inaccurate readings and, in some cases, false alarms. Also, because sensors are designed for specific application sites and patient populations (e.g., adult versus pediatric), ensure that the appropriate sensor is being used. Proper application can also vary depending on the type of sensor being used; for example, when using a neonatal wrap sensor, it should be spiral-wrapped down the digit rather than wrapped around itself to help prevent pressure necrosis and ensure adequate blood flow.
Sensor sites should also be checked periodically, or per clinical protocol, to ensure adequate adhesion and circulation, skin integrity and correct optical alignment. Remember to be especially cautious in the case of poor perfusion; skin erosion and pressure necrosis can result if a sensor is not moved or readjusted regularly. To maximize sensor life, replacement tapes that replace only the adhesive components of the sensor can be extremely convenient and make rechecking and readjusting sensor sites relatively simple.