WatchPAT™200 System
52
Operation Manual
Snoring and Body Position Accuracy
This section gives statistical performance measure for Itamar Medical’s SBP sensor, when
used with the WatchPAT™ device.
I.
Body Position
The body position measured by the WatchPAT™ device with Itamar SBP sensor, was
compared to the gold standard, manual scoring of the video recording of 31 patients, in
1 minute’s epochs (total of 7111 epochs) during sleep.
The Agreement between the device and the video recording was 90%.
Simple Kappa agreement value was 0.8185 (95% confidence level of 0.8059 and
0.8311).
II.
Snoring
The snoring level measured by the WatchPAT™ device with Itamar SBP sensor, was
compared to a gold standard PSG dB-meter placed 1 meter from patient’s head. The
study included 26 patients, and the analysis was done in 30sec epochs.
The correlation coefficient was calculated using Pearson method, assuming a linear
relation between the results of the two devices. A statistically significant correlation
was calculated between the two devices: r=0.65 p value<0.0001.
The next figure shows a scatter plot of sleep disturbance Index produced by the
WatchPAT™ device and dB-meter, with linear regression line.
An estimation of the error in each snoring level was calculated by looking at the
WatchPAT™ device measurement cut by the results of dB-meter in intervals of 1 dB
in the range of above 40dB (below 40 dB was considered not clinically significant
being background noise). A high correlation was observed between the results of the
two devices for the range of 40-70dB (where sufficient data points were gathered),
meaning the resemblance in the results uniformly existed for all the snore levels
measured.
