Simply stated, a pulse oximeter non-invasively monitors oxygen saturation levels in a patient's blood. It does this by measuring the difference in light absorption between oxygenated and deoxygenated hemoglobin molecules. And, as opposed to blood pressure's intermittent cycles, it does this in continuous real time.

Since the safe administration of anesthesia relies on providing adequate oxygenation and ventilation, pulse oximetry is key to determining that the patient is getting sufficient oxygen into their blood during surgery. If you're considering equipping your providers with new pulse oximeters, here are some insights.

Unit and technology
Pulse oximetry is a relatively mature field and you won't have to break the bank to get a good system. The monitoring products that are currently on the market tend to be reliable across the board.

While a standalone pulse oximetry unit may not be a necessity for every surgical facility, certain post-operative situations, such as 23-hour observation holds or sleep apnea monitoring, see benefits from a device dedicated to checking a patient's oxygen saturation levels.

Similarly, following the administration of spinal narcotics for post-op pain management procedures, the continuous monitoring of oxygenation and respiration is vital to patient safety.

Every pulse oximeter includes a patient sensor to measure light absorption in the capillaries of local tissue, which correlates with arterial oxygen content for the purposes of monitoring. In terms of sensor placement, the extremities are the most commonly used sites: fingers, toes, and occasionally the earlobe or nose. While some models offer forehead sensors, this option may not be necessary unless you're dealing with infant patients.

The most cost-effective sensors will be reusable clips, but each monitor should also have the ability to use flexible, disposable sensors to accommodate patients with anatomical or procedural variations. If your surgery center sees a lot of pediatric patients, make sure to look into obtaining special sensor probes that fit children's and infants' fingers.

The information that an oximeter gives an anesthesia provider is a number, a saturation rate. Most healthy, awake patients will register at 96 percent or higher when breathing room air. Patients suffering from respiratory issues such as chronic obstructive pulmonary disease, asthma, sleep apnea and the co-morbidities of obesity, as well as children who have higher metabolic rates, may show lower numbers and run the risk of becoming hypoxic at dangerous levels more quickly.

It's strongly recommended that a pulse oximeter give providers the ability to view a waveform as well as a numeric representation of the patient's oxygen saturation. The importance of seeing a waveform as well as a number is to verify that the number you're receiving is accurate. If the waveform shows the appropriate pulsation, for instance, an abnormal number means that something may be wrong with the patient's oxygenation, requiring immediate evaluation.

It's also advisable to seek out an oximeter that you can interface with an electronic medical records system for digital storage of anesthesia data. Even if your facility doesn't use electronic records, it won't hurt to prepare for future connectivity. (See "Connecting Anesthesia Monitors to EMRs," February 2007.)

A monitor's alarms are a touchy subject in the OR. Some personnel are exquisitely sensitive to alerts that signal significant changes. There's not much leeway here, since both the American Society of Anesthesiologists and the Joint Commission mandate that physiological monitors' alarms should always be set for appropriate clinical values and be attended to during surgery.

Monitors that let clinicians customize or adjust their alerts are helpful, though. All models include both visual and auditory signals that report saturation values. Then clinicians can react quickly if the value changes without having to look at the screen, since the monitor sounds an immediate shift in tone to indicate changes in a sensing trend and you can easily hear even a one-percent change.

Hands on
The surest way to determine which pulse oximeter is best for your facility is to bring in trial models that anesthesia providers can evaluate during their procedures, that nurses can learn how to set up and that are tested for reliability on actual patients.

A hands-on trial is important because providers need to be comfortable with the equipment they'll be using in your OR — even if they're not on regular staff. Standardized equipment allows everyone to adapt quickly. The people who drive patient care need to have a say in equipment purchases, and any manager worth her salt knows that it pays to listen to that valuable input.

Cardinal Health
Alaris SpO2 Module
(800) 854-7128
www.cardinalhealth.com/alaris
List price: not disclosed
FYI: Cardinal's Alaris SpO2 Module provides continuous, non-invasive monitoring of blood oxygen level and pulse rate in adult, pediatric and neonatal patients. Its common user interface, which reduces training time and programming complexity, includes a tabular trend display with icons to indicate alarm history, provides customizable alarm limits and connects to the nurse call system to transmit alarm states.

Covidien
Nellcor OxiMax Pulse Oximetry System
(800) 635-5267
www.nellcor.com
List price: not disclosed
FYI: Clinicians can more effectively monitor a broader range of patients with the Nellcor OxiMax Pulse Oximetry System. This oximetry platform includes a variety of handheld and standalone monitors that deliver accurate, reliable readings even during low perfusion, patient motion and other signal interferences, says the company.

Criticare Systems
503DX MiniSpo2t
(262) 798-8282
www.csiusa.com
List price: not disclosed
FYI: Criticare's 503DX MiniSpo2t handheld oximeter uses the company's DOX digital technology to evaluate oxygen saturation and heart rate in a broad range of patients. The completely digital instrument creates a benchmark for higher performance in low perfusion situations with artifact and ambient noise rejection, says the company. Small, lightweight and easy to use, the MiniSpo2t oximeter is ideal for spot-checking and transport monitoring, says Criticare.

Masimo
Radical-7 Pulse CO-Oximeter
(800) 326-4890
www.masimo.com
List price: not disclosed
FYI: Masimo's Radical-7 is a bedside, handheld and transport oximeter featuring the company's Rainbow SET technology, the first and only upgradable platform that continuously and non-invasively measures hemoglobin and oxygen content, carboxyhemoglobin, methemoglobin, oxyhemoglobin, perfusion index and pulse rate, says the company. Additional measurements can be added with a simple software upgrade.

Mindray
PM-60 Pulse Oximeter
(888) 816-8188
www.mindray.com
List price: $550
FYI: Mindray's PM-60 pulse oximeter, suitable for adult, pediatric and neonatal patients, features a high-resolution 2.4-inch color LCD display; spot-check and continuous monitoring modes; adjustable audible and visual alarms; real-time data transfer via infrared technology; a 36-hour continuous battery life; a protective cover and a carrying case for portable monitoring, says the company.

Smiths Medical PM
Digit Finger Pulse Oximeter
(800) 558-2345
www.smiths-medical.com
List price: $199
FYI: Smiths' Digit Finger Pulse Oximeter delivers fast, reliable oximetry in an extremely handy, pocket-sized solution by combining the monitor and sensor into one unit, says the company. While small in size, Smiths says Digit is big on performance, providing SpO2, pulse rate and pulse strength measurements on patients from pediatric to adult.