For data downloaded before November 23, 2020:
We have found a discrepancy in the processing of certain breathing metrics: MV adjusted (minute ventilation adjusted) and TV adjusted (tidal volume adjusted). Please note the error only affects these metrics and not the processed data files themselves (minute_ventilation_adjusted.wav and tidal_volume_adjusted.wav).
This issue was present in the following locations:
1) the record/activity summary table (Dashboard)
2) the charts section (Dashboard)
3) the statistics.csv file (when using the "Download Binary file" option)
The calculation error affected the following respiratory metrics:
- MV Adjusted Avg
- MV Adjusted Max
- MV Adjusted Min
- TV Adjusted Avg
- TV Adjusted Max
- TV Adjusted Min
As of November 23rd, 2020 these metrics will be automatically corrected on our server for each record/activity. If you had already downloaded some records/activities, you can look in the info.json file; the problematic algorithm was respiration: 2.1.0, the corrected algorithm is now respiration: 2.2.0.
For records exported before November 23rd, 2020, the easiest solution would be to re-download the data. Any MV_adjusted(Avg, Min, or Max) or TV_adjusted(Avg, Min, or Max) taken from the summary table of a record/activity or the statistics.csv file prior to this date should also be discarded and replaced with the corrected values.
Alternatively, you can manually recalculate the correct metrics using the respiration 2.2.0 formula:
MV_Adjusted_(Avg, Min or Max) = MV(Avg, Min or Max) * weight_in_kg / 65
TV_Adjusted_(Avg, Min or Max) = TV(Avg, Min or Max) * weight_in_kg / 65
How do calibrate breathing measurements:
If you wish to obtain absolute values for the respiration metrics, you can do a calibration using a spirometer. To do the calibration step, you need a spirometer. We suggest using a spirometer to measure a forced expiration that will be measured simultaneously with the Hexoskin, then calculate the amplitude of the expiration curve from the Hexoskin respiratory raw data. The volume measured with the spirometer will correspond to the amplitude of the expiratory curve. You will then be able to calculate the factor of conversion to change in volume measured by Hexoskin into an absolute value. However, it is important to know that ventilation measurements with Hexoskin are precise but accuracy varies from one person to the other. Thus, the algorithm needs calibration to provide accuracy, a calibration step needs to be done for every user and each time the user puts on the Hexoskin Shirt.
For any questions, contact us at firstname.lastname@example.org.
Keywords: error, out of range, aberrant, abnormal, minuteventilation, tidalvolume, lung volume, lung measurements, respiratory metric