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20 Validation of WatchPAT 300 for pre-operative of OSA screening in patients undergoing bariatric surgery
  1. Gillian L Twigg1,
  2. Brendan Mallia-Milanes2,
  3. Alex D Miras3,
  4. Hannah Tighe1 and
  5. Graeme Wilson2
  1. 1Department of Respiratory Physiology, Imperial College Healthcare NHS Trust, London, UK
  2. 2Department of Respiratory Medicine, Imperial College Healthcare NHS Trust, London, UK
  3. 3Imperial Weight Centre, Imperial College Healthcare NHS Trust, London, UK


Introduction Undiagnosed obstructive sleep apnoea (OSA) is increasingly recognized as a serious post-operative risk with bariatric surgery, hence increasing demand for pre-operative screening and a need for simpler ways for screening than the clinical standard, respiratory polygraphy, to mitigate strain on sleep services. WatchPAT 300 (WP) is a finger-mounted sensor that uses peripheral arterial tonometry to estimate the apnoea hyponoea index (AHI). While its use is increasing it has not yet been validated in patients with a BMI >35, the target population in bariatric surgery.

Aims To validate WP against polygraphy in pre-bariatric surgery patients with clinically suspected OSA and a BMI>35 and to assess patient acceptability of WP.

Methods AHI was measured simultaneously with WP and Embletta. Outcome measures were 1) autoscored AHI from WP and 2) manually re-scored AHI from Embletta. Agreement between AHI from Embletta and WP was assessed using intra-class correlation coefficient (ICC), bland Altman and ROC plots.

Results 28 patients (22 female/6 male, mean ± SD age 44.1 ± 11.6, BMI 45.7 ± 7.5) participated. One study failed due to the patient removing the WP probe prematurely. AHI was higher in WP than Embletta (28.1± 17.9 versus 15.0 ±13.4; p<0.05). There was a strong positive correlation between WP and Embletta AHI measurements (ICC 0.876 (95% CI 0.75-0.94; figure 1)). Bland Altman plots revealed a systematic bias; differences diverging at higher AHI values. A ROC plot revealed high sensitivity and specificity for an AHI >15 (Area under the curve 0.917; p<0.05). 97% of respondents reported that WP would be acceptable to them if introduced into the bariatric surgery pathway.

Abstract 20 Figure 1

Correlation between AHI as measured by WatchPAT and Embletta

Discussion WP accurately estimates the AHI in pre bariatric surgery patients, has a low failure rate and is clinically acceptable in this group. Further larger scale studies are needed to confirm these findings before incorporating into clinical guidelines.

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