Need a needle in an artery? Move over, doc, there's an app for that

Research published in the Canadian Medical Association Journal (CMAJ) has shown a smartphone application is superior to traditional physical examination for spotting when it is safe to stick a needle into an artery.

Researchers used an elderly iPhone 4S running the Instant Heart Rate application by Azumio to check the patient's circulation and compared it to results from the Modified Allen test, the traditional way to assess how well arteries are working prior to inserting a needle.

The test involves a patient making a fist, and the attending medic watching for when colour returns to the hand. Less than five seconds is good, less than 10 is less good and anything more will leave doctors reluctant to go anywhere near the artery with a sharp implement.

Unfortunately, the Modified Allen test has its limitations (PDF) and can exclude patients that might otherwise qualify for surgery under other, more complicated and expensive non-invasive procedures such as Colour Doppler ultrasonography.

With the smartphone, researchers apply radial artery compression and then simply hold the camera over the patient's index finger. The pulse trace can then be monitored on the screen.

Researchers devised a randomised controlled trial to compare the Modified Allen test with the smartphone assessment and enrolled 438 patients between July 2015 and March 2016.

Things went well for the smartphone. The app was 10.1 per cent more accurate than a human attempting the Modified Allen test. In terms of false positives, 15 patients (6.8 per cent) would have been incorrectly excluded from treatment by the smartphone compared to 37 (16.9 per cent) from the Modified Allen test group.

Unfortunately, since the iPhone 4S could charitably be described as "obsolete" and the app in question has moved far beyond the version 4.5.0 used in the trial, further work will be needed before a normal smartphone is wielded at the bedside by a medical professional.

The authors of the paper observe: "Given the differences in software and hardware specifications, these results are not necessarily generalizable to all smartphone platforms nor to different photoplethysmographic applications."

So fanbois of all varieties can put their phones away for the time being.

However, the paper concludes optimistically. "Although this application is not certified at present for use in health care by any regulatory body, our study highlights the potential for smartphone-based diagnostics to aid in clinical decision-making at the patient's bedside." ®