A Protocol for Pulse Oximetry
By Mike McEvoy, Ph.D., RN, CCRN, REMT-P
New research has found that oxygen worsens certain medical conditions such as strokes and may be harmful to patients with cardiac-related problems as well. Other studies have demonstrated that up to 60% of patients given oxygen by prehospital providers do not require supplemental O2. More significantly, prehospital providers have been shown to consistently not give oxygen to 29 to 40% of patients who really require it when they rely on signs and symptoms alone.1 Enter pulse oximetry, a new assessment tool for the fire service. Having saved countless lives during surgery, in hospitals, and in emergency departments over the past two decades, oximetry is a tool to help determine when supplemental oxygen is really needed. Use of an oximeter must be guided by a solid medical protocol to achieve benefits to you and your patient.
Pulse oximeters use light-emitting diodes (LEDs) to measure and compute oxygen saturation in the bloodstream, displayed as SpO2%. Normally, SpO2 is between 95 and 100%. Oxygen is usually administered to patients with saturations below 95%. Saturations below 90% are serious because blood cells tend to hold onto oxygen molecules rather than release them to the body’s tissues at these lower levels. Current ACLS protocols suggest oxygen administration for patients with saturations below 90%. Oxygen saturations below 70% are life threatening.
An oximeter can tell you two things. First, it gives you some sense of how loaded the blood cells are with oxygen molecules. Second, it can indicate a trend in your patient’s blood oxygen saturation levels that may help you to assess the effects of your treatment. Beyond this, the signal or waveform on an oximeter can also be used as an assessment tool. An oximeter can help you to determine the presence of absence of perfusion to a fractured or otherwise injured extremity. Oximeters are also valuable adjuncts to blood pressure measurement in high-noise environments or difficult-to-hear situations, using the signal or waveform in conjunction with cuff deflation to indicate return of the distal pulse.
Finally, oximetry has been extremely valuable in firefighter rehab. Its ability to rapidly measure a pulse rate coupled with oxygen saturation significantly speeds the process of obtaining vital signs. It would be interesting to study the use of pulse oximeters as a screening criterion in firefighter rehab to identify firefighters who require further assessment, such as blood pressure and temperature measurement. Most fire departments presently take complete sets of vitals on every person in rehab despite finding that most of them are normal.
Oximetry has definite limitations as well. For a complete discussion of cautions and limits of pulse oximetry, see my September 30, 2002, fireengineering.com Web Exclusive, “Can Oxygen Hurt?”.
To gain maximal benefits for your patients and your department, oximetry must be used with a clear protocol that reflects its benefits and limitations, as well as current medical evidence based practices.
One such protocol is pictured below in Figure 1. Firefighters from the West Crescent Fire Department in Clifton Park, New York, have used this protocol to guide oxygen administration since 1997. When possible, firefighters measure a patient’s SpO2 prior to initiating oxygen therapy. Based on this reading, they select a device and flow rate, re-measuring the SpO2 every 5 minutes thereafter with adjustments to the oxygen therapy based on the SpO2. If O2 is applied prior to measuring a saturation, then adjustments are made based on readings with the O2 in place. Note that this protocol has a somewhat conservative goal of keeping every patient saturated at or above 98%. Most published studies have used a SpO2 of 95% as the cutoff point for oxygen administration, and the newest ACLS guidelines use 90%. There is very recent data suggesting that pulse oximetry readings may under or overestimate actual oxygen saturation by 2-4%, so it helps to allow some room for error in oximetry protocols.
The West Crescent Fire Department protocol has dramatically reduced oxygen costs and provided an extremely useful tool for selecting patients who require aggressive airway interventions. Firefighters have occasionally been surprised that some patients who appear well clinically actually require oxygen. Many times, the oximeter has provided lead time to initiate resuscitation before clinical signs of severe respiratory compromise became evident. Most importantly, in circumstances where oxygen could potentially cause harm, firefighters have a tool to help them decide whether supplemental oxygen is actually needed.
- Brown LH, Manring EA, Kornegay HB, Prasad H. Can prehospital personnel detect hypoxemia without aid of pulse oximeters? Am Journal of Emergency Medicine. 14(1):43-4, 1996 Jan.
WEST CRESCENT FIRE DEPARTMENT PULSE OXIMETRY PROTOCOL
- If patient requires oxygen, administer high concentration O2 by Non-Rebreather Mask (NRBM).
- If oximeter available, record SpO2% before starting O2. DO NOT DELAY ADMINISTRATION OF OXYGEN TO MEASURE SpO2.
- Measure SpO2 five minutes after starting O2 therapy.
- DO NOT adjust O2 in the following patients:
- known or suspected smoke inhalation
- known or suspected carbon monoxide poisoning
- known cigarette smoker who has smoked within the last 2 hours
- black, blue, or green nail polish under the oximeter probe
- Measure SpO2 and adjust oxygen therapy every 5 minutes (see figure below)
- Record initial oxygen device and flow rate on Prehospital Care Report (PCR) under Treatment section. Record each additional time, SpO2%, and O2 change in the Comments section.
Example: 1810 – SpO2 = 100%, O2 down to 4 L N/C
1815 – SpO2 = 99%, O2 down to 2 L N/C
1820 – SpO2 = 99%, O2 discontinued
1825 – SpO2 = 99% on room air.
WCFD Pulse Oximetry Protocol issued 2-25-97
Mike McEvoy, PhD, REMT-P, RN, CCRN – Medical Advisor
John Kelley, MD – Medical Director
Mike McEvoy, Ph.D., RN, CCRN, REMT-P, is the EMS coordinator for Saratoga County, New York. A former forensic psychologist, he now works in the Cardiac Surgical ICU at Albany Medical Center and teaches at Albany Medical College in New York. He is a paramedic for Clifton Park-Halfmoon Ambulance Corps and medical advisor for the West Crescent Fire Department. He presently serves as a member of the New York State EMS Council and the State Emergency Medical Advisory Council and is the EMS director on the board of the New York State Association of Fire Chiefs.