• Roman Schumann, Andrzej P Kwater, Iwona Bonney, Diane Ladd, Julie Kim, Anupriya Gupta, Sam D Gumbert, and Evan G Pivalizza.
• Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA. Electronic address: rschumann@tuftsmedicalcenter.org.
• J Clin Anesth. 2016 Nov 1; 34: 295-301.

Study ObjectiveTo evaluate use of a respiratory volume monitor (RVM; ExSpiron, Respiratory Motion, Inc., Waltham, MA, USA) that provides minute ventilation (MV), tidal volume (TV) and respiratory rate (RR) measurements in obese surgical patients, hitherto undescribed.DesignProspective, IRB-approved observational study of RVM parameter accuracy in obese surgical patients, designed to test the ability of the RVM to detect predefined postoperative respiratory depression (PORD) and apneic events (POA) and to correlate STOP-Bang scores with PORD and POA.SettingPre-, intra-, and post-op patient-care areas, including the post-anesthesia care unit (PACU) in 2 academic centers with bariatric populations.Patients80 patients (47±12 years), BMI of 43±7 kg/m(2) undergoing elective surgery were enrolled.InterventionsData collected included patient characteristics, STOP-Bang scores and RVM data from immediately preoperatively through PACU completion without effecting standard clinical care.MeasurementsLow minute ventilation (LMV) was defined as 40% of predicted MV, and PORD was defined as sustained LMV for 5 minutes. Appropriate parametric and non-parametric statistical analyses were performed, P<.05 considered significant.Main ResultsIn 56 patients with complete intraoperative ventilator data, correlation between RVM and ventilator MV measurements was r=0.89 (measurement bias 1.5%, accuracy 11%). Measurement error was 0.13 L/min (95% confidence interval-0.93 L/min - 1.20 L/min). In PACU, 16.3% and 31% of patients had PORD and POA respectively. There were no significant differences in the incidence of PORD and POA in 3 STOP-Bang risk categories (P>.2).ConclusionsThere was excellent correlation and accuracy between the RVM and ventilator volumes in obese surgical patients. A considerable number of patients exhibited PORD and POA in the PACU. The STOP-Bang risk scores correlated poorly with PORD and POA which suggests that obese surgical patients remain at risk for early post-operative respiratory events irrespective of the STOP-Bang score.Copyright © 2016 Elsevier Inc. All rights reserved.

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