If the Boy Scout manual included an aviation edition, pulse oximeters would surely be on the required list of field equipment. Theyre a terrific idea, but above a certain price, theyre a gadget most of us will do without. Based on Nonins success with its clever FlightStat, we would guess that price barrier to be about $300, a price point that appears to have sustained a market for at least four years. (Nonin has outlasted other products in the niche aviation market.)
At Oshkosh in July, we were handed a new contender called the Check Mate.Its being pitched by SPO Medical to the sports and aviation markets as practically a throw-away device at $199. We recently obtained a sample Check Mate and flew it alongside the Nonin FlightStat weve had for a couple of years and found that it performed acceptably, although for $100 less than the Nonin, we werent expecting the Mercedes Benz of oximeters. (And thats not what we got, either.)
How They Work
Pulse oximeters are creations of the digital age and have grown ever smaller and cheaper. They work by shining light at two wavelengths through a finger or toe with a sensor that measures how much light is partially absorbed by hemoglobin in the bloodstream. By calculating the difference in light absorption, the device can determine oxygen saturation or %SPO2. This is displayed as a numerical value along with measured pulse rate. Hospital-type oximeters are typically taped to a toe or finger while the portables-so-called fingertip oximeters-are designed for easy finger insertion. The Check Mate uses a reflective method rather than shine-through, as in the Nonin, but the principle is the same. SPO says the reflective method is more motion tolerant, but the calculation takes a little longer because its an average of several readings.
The benefits of oximetry to pilots are obvious. At any altitude, monitoring %SPO2 puts solid numbers on the otherwise fuzzy issue of hypoxia.If you spend a lot of time in the teens or flight levels breathing oxygen, an oximeter will measure how well the equipment is working and how effective your breathing is. How you breathe definitely affects oxygenation. You can keep the oximeter handy for spot checks or leave it clamped around a finger for continuous readings. (One company, Aerox, sells a panel-mount oximeter system that offers continuous monitoring. It also includes a carbon monoxide monitor. See www.aerox.com.)
Hardware-wise, the Nonin FlightStat consists of two vise-like halves joined by a single bail spring. You simply insert your finger, the device turns on and in a few seconds, you have your %SPO2 and pulse rate. A few seconds after your finger is removed, it shuts off. The display is a bright red seven-segment LED for both oxygenation and pulse rate. Pulse also includes a flashing green indicator. The FlightStat is powered by a pair of AAA batteries good for 18 hours of continuous use or 1600 spot checks, according to Nonin.
The made-in-Israel Check Mate has a silicone elastic thimble into which a finger is inserted, after which a small button is pushed to activate the device. The button also turns on a green backlight to illuminate the Check Mates LCD display. Although readable in sunlight, the LCD viewing angle is limited and not nearly as crisp as the Nonin. The Check Mate uses a single lithium battery which is supposed to last for 1000 hours of continuous use.
Before flying with the oximeters, we had to ship our two-year-old Nonin off for repairs, for which the company charges a princely $150 flat fee.According to the repair report, a battery contact was corroded. Frankly, a $150 flat-rate repair on a $300 device makes this product a non-starter for us. Were not opposed to flat-fee repairs, but in our view, Nonins 50 percent of cost is unreasonable. By the way, although our batteries had not leaked, we think its a good idea to store this device with batteries removed. Thats a bit of hassle with the Nonin, because the battery access door is poorly designed, in our view, and difficult to seat correctly. It has a captured plastic slot screw for the battery cap but really should have a thumbscrew.
In use, the Nonin has two advantages over the Check Mate: The display is easier to read in all light conditions and the Check Mates thimble-although a good idea-is just too tight to accommodate anything but a pinky or an otherwise small finger. While the finger doesnt have to be fully inserted, we think the thimble should be a bit larger. The Nonin, on the other hand, will easily accommodate any finger, including a thumb.
We found readings between the two devices to be comparable, although the Check Mate consistently read 3 to 4 percent lower than the Nonin. (Both oximeters came to us freshly calibrated.) In checking with two oximeter experts not connected to either company, we were told that a small disparity between readings should be expected. Oximeters have about a 2 percent error margin so our findings appeared to be at the outside limits of that tolerance.
In our view, neither of these devices are ideal, but either is acceptable.If youre seriously interested in oxygen monitoring, we think a more expensive medical-grade instrument is worth considering, such as the Nonin PalmSat ($679) sold by prescription through www.aeromedixrx.com. Of the two devices tested here, we lean toward the Check Mate because it does essentially what the Nonin does for $100 less. It has a one-year warranty but its too new to judge its durability. SPO hasnt established repair costs.But given the cost of a single Nonin repair, you could buy two Check Mates and still be $50 ahead. We were disappointed with the Nonin in this regard.This is, after all, not life-saving technology, but a safety enhancer.Theres not much enhancement if its priced out of the market.
Also With This Article
Aeromedix.com (FlightStat), 888-362-7123, www.aeromedix.com
Aircraft Spruce and Specialty (Check Mate), 877-477-7823, www.aircraftspruce.com
Nonin Medical, www.nonin.com
SPO Medical, www.spomedical.com