There's a huge, mostly unmet, market requirement for low acuity patient monitoring. Much of this is driven by JCAHO's recent focus on pain management. A lot of hospitals were receiving poor patient evaluations regarding pain management on general nusing units. In response, hospitals have increased their administration of pain meds; but when you increase therapies you need to increase surveillance to ensure patient safety. Unfortunately in today's staffing environment (legally mandated nursing ratios aside) hospitals are not in a position to add more nurses to provide that additional surveillance. As a consequence there have been numerous sentinel and adverse events as a result of a failure to rescue.

Some hospitals have wisely decided that increased patient monitoring is the best way to increase surveillance for patients on some pain meds. And some of those hospitals want to provide this monitoring using SpO2. Unfortunately, current standalone SpO2 monitoring systems are not up to the challenge. Most devices offer no connectivity at all – just standalone devices with local alarms. Vendors with networked solutions, like Nellcor, have wired solutions that don't work well outside critical care areas where patients are moving in bed, going to the bathroom and walking around the units. Masimo has responded to this need by OEMing the MicroPaq and Acuity central station from Welch Allyn.

When hospitals think SpO2-only monitoring they're thinking “lower cost” and “easier to use” when compared to telemetry and patient worn monitors. They are wrong – currently available networked SpO2 systems with central stations are not significantly less expensive that ECG/SpO2 solutions. The resulting proliferation of different device workflows and duplicate central stations is a great example of what's wrong with proprietary end-to-end monitoring systems – a topic that we will have to save for another time.

On the Biomed listserv Douglas Back of Medical Concepts posted a comment about a wireless SpO2 R&D project that a vendor told him about. He was not impressed:

I see a lot of wireless system these days. I spoke to an OEM who builds Spo2 monitors and they informed me sometime next year you might see a wireless Spo2 monitor with Adult probes on the market. I can see many of these ending up missing of course like the telemetry units. Good for the vendor bad for the hospital. I don't think this is a good idea.

Here's my reply:

When SpO2 monitors are used outside of critical care areas, alarm notification and ambulatory patients become big issues. Local device alarms in private rooms (or at the end of long hallways) are easy to miss – not to mention a real hassle for caregivers.

SpO2 monitors that plug into a wired network are fine for gorked out patients, but a hassle for patients on a med/surg unit. And what do you do when they ambulate? They can carry the monitor and rely on the local alarm, or more likely go off monitor until they return to bed – neither is an ideal solution.

When these devices go wireless, there are a couple of things to look for. First and foremost are all those false/positive alarms that many SpO2 monitors generate. Managing this problem is not really that tough, but it will add to the cost of a wireless solution, so look for some (most) vendors to “round corners” here. The other issue will be workflow – will the overall system (plus other devices on your units, and current policies and procedures) actually improve patient safety and caregiver productivity? This is a less simple requirement to meet, and must be understood and built into the system from the ground up.

Douglas, your concerns are not unfounded. Historically, the first generation of wireless devices is pretty lousy. However, I do expect to see good things from Masimo. [No, they're not a client – but they do have some key people who know what they're doing, and a load of cash from Nellcor.]

Douglas' response:

Yes as long as you have something to attach the Spo2 probe to. I was talking about a Spo2 probe with the transmitter built in. Very small!!!

A reusable Spo2 probe with a cable attached will run average $ 250.00 each and a disposable Spo2 probe will run $ 6.00 each. You can replace it. If you had a probe with a built in transmitter you could be looking at a higher unit cost if you had to replace it. They would have to be dedicated to each monitor. You would have to keep spares. It is not like just replacing a Spo2 probe to a telemetry box.

This is the technology they are talking about releasing.

And my reply…

A wireless sensor, like this vendor described to you, would need a patient located gateway to receive sensor signals and relay them to the wireless LAN. (Power constraints in a sensor preclude communications directly with the WLAN.) Gateways can also provide front end signal processing, data storage and analysis to help keep the sensor small (and cheap). Done right, an SpO2 probe with an appropriate radio should not cost much more than a current probe and cable combo.

I would expect most first generation wireless SpO2 to have a WiFi radio in the monitor (with a cable attached sensor) that talks directly to the network – sort of like a patient worn monitor. The earlier telemetry/SpO2 example is like this, only smaller because SpO2 vendors don't do ECG (although maybe they should). Then all of your existing sensors would plug into the new monitor. Not having to rev the sensor assembly keeps the R&D project scope reasonable too.

Very few medical device vendors understand the importance of establishing patient context (let alone how to do it) in networked devices. If you add the complexity of associating one or more patient-connected sensors to a gateway (that could be in proximity with other gateway/sensors on other patients) the complexity goes up exponentially.

Most early efforts from medical device vendors who design world class “black box” embedded systems will have two likely outcomes. First, in an effort to minimize R&D cost and complexity, they will push tasks onto the user that should be done by the system – this will result in poor workflow. The other likely outcome is a tortured implementation of some poor off the shelf technology – tortured in that there will be little or no regard for a complete implementation of the technology that facilitates systems integration with your hospital IT infrastructure. An example of this might be network connectivity that can't be routed – thus requiring all devices connect to the same subnet or dedicated VLAN.

Most vendors don't realize that once they connect their products to a general purpose local area network they aren't in the “embedded systems” business anymore. Sadly, this is as much a problem for you guys as it is the hapless vendor who tries to support you.

Wireless sensors are the next big thing in patient monitoring – I've got a category of posts on my blog for wireless sensors. Here are two academic projects that have developed systems using wireless sensors:, the CodeBlue project at Harvard, and Aid-N at Johns Hopkins.

Pictured right is an old school Masimo SpO2 monitoring system.