TechTool Thursday 044 Pulse Oximeter

TechTool review Pulse Oximeter by digiDoc on iOS

digiDoc Pulse Oximeter is a fabulous concept. It uses your iPhone to take saturations and HR measurements. However the developers mike it clear that it cannot be marketed as a clinical tool and can only be used for fitness and recreation.

Website: – iTunes – Website


  • Pulse Oximeter is a nicely designed app, simple and enjoyable to use.  The colour scheme and designs are eye catching and the developers have clearly worked hard on the graphics. It is designed to be used on iOS7 in particular the dual flash iPhone 5S.
  • The first time using the app is a bit tricky but once you get the hang of it, it’s easy to use and simple to explain to others. It has never crashed on me.

Clinical Content

  • The function of the app is simple: hold your fingers over the flash and the camera and wait for it to complete and give you your sats and HR results.

digiDoc Pulse Oximeter

Practical evidence

  • However, the application is only useful if it produces regular, reliable results. So, we put it to the test.
  • The LITFL team analysed the data from 38 different subjects. In a completely non-validated study, we selected 38 of our colleagues and compared their sats and heart rates from the app against our ED/ICU standard machines.
  • The results were statistically analysed using Pearson’s correlation coefficient and the outcome was, well, disappointing.
  • For oxygen saturation, r=0.57 and for heart rate, r=0.37. (with r=1 being a perfect positive correlation). In other words, from this brief and low power analysis oxygen saturations show a moderate positive relationship and heart rate shows only a weak positive relationship.
  • In short, comparing the Pulse Oximeter application to our gold standard measurements we found that the application not to be valid.
  • Read the formal Bland-Altman analysis of the first version of the application


  • $6.49 – would be great, if it was a valid measurement


  • It would be completely awesome to have a pulse oximeter application. It could be used in community setting, rural locations, by transport teams and potentially by patients themselves.
  • …and this application does look great. However, it only counts for anything if the results it produces are accurate and valid.
  • The developers have stated that the app cannot be used as a clinical tool, which makes it seems rather redundant, and when comparing this app with our hospital standard for oxygen saturations and heart rate measurements, we were unable to find a good correlation.
  • In short, in its current form it is not accurate, so for now we will have to save it for showing off to our friends.


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  1. KC See says

    Perform paired measurements of SpO2 using the App and a reference pulse oximeter, on patients with a wide range of SpO2. One will need to specially recruit stable patients with low SpO2 such as those with congenital cyanotic heart disease. Then do Bland-Altman analysis for SpO2. Repeat for HR on patients with a wide range of HR.