Hi everyone, I would like to measure length, depth and area under the curve of SpO2 desaturation curves recorded overnight in patients with obstructive sleep apnoeas. Do you know if there is a software available that allows such data extrapolation from graphic records? Is there a method to automatize the process? To avoid the need to automatize the calculation, I might use the following formula ((desaturation length * deaturation depth)/2)*AHI, but then I would need to find a standardizing method that allows me to choose a proper search window for each patient. Thank you in advance.
EDIT: I managed to find a formula for integrating the area under threshold of the SpO2% desaturation curve. The problem is that I am able to use it only with a fixed threshold (e.g. 90%), and this does not allow to take into account registration artifacts (e.g. sometimes the patient moves and the sensor reads 89% rather than 90%, and, with a fixed threshold of 90%, this would count as desaturation). Any suggestions?
As I understand your question, there are two problems, a. to extract the digital information from graphical output, and b. to perform the integration and other operations on this digital output.
a. There are quite a few digitizer apps on the net, these can turn the paper based graph (or better its scan) into something like .csv (comma separated values) or .xls(x) format file containing the digitised chart. You can find an overview of (some of) the available digitisers here http://connectedresearchers.com/graph-digitizer-comparison-16-ways-to-digitize-your-data/ and one I've used a few times https://www.digitizeit.de/ (a moderately priced pro solution with 21d period to try for free). If none of these satisfies your needs, you might wish to continue Googling along the keywords you find in the above links.
b. Once you have the digital data, most any statistical SW or a dedicated Matlab/R add-on might help you to evaluate the requested parameters. Alternatively, you may wish to create a spreadsheet in Excel, OfficeLibre, whatever table think, or to write (have written for you) a simple app in whatever programming language you (or your friends) feel proficient in. Even the good old Basic would do.
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