Respiratory volume monitoring in an obese surgical population and the prediction of postoperative respiratory depression by the STOP-bang OSA risk score.
OBJECTIVE
To 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.


METHODS
Prospective, 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.


METHODS
Pre-, intra-, and post-op patient-care areas, including the post-anesthesia care unit (PACU) in 2 academic centers with bariatric populations.


METHODS
80 patients (47±12 years), BMI of 43±7 kg/m(2) undergoing elective surgery were enrolled.


METHODS
Data collected included patient characteristics, STOP-Bang scores and RVM data from immediately preoperatively through PACU completion without effecting standard clinical care.


METHODS
Low 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.


RESULTS
In 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).


CONCLUSIONS
There 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.
Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA. Electronic address: rschumann@tuftsmedicalcenter.org.
Roman
R
Schumann
Department of Anesthesiology, University of Texas-, Houston, TX, USA.
Andrzej P
AP
Kwater
Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA.
Iwona
I
Bonney
University of West Viginia, Morgantown, WV, USA; Department of Clinical Research, Respiratory Motion, Inc., Waltham, MA, USA.
Diane
D
Ladd
Department of Surgery, Tufts Medical Center, Boston, MA, USA.
Julie
J
Kim
Department of Anesthesiology, Tufts Medical Center, Boston, MA, USA.
Anupriya
A
Gupta
Department of Anesthesiology, University of Texas-, Houston, TX, USA.
Sam D
SD
Gumbert
Department of Anesthesiology, University of Texas-, Houston, TX, USA.
Evan G
EG
Pivalizza
D000328:Adult; D001049:Apnea / Q000175:diagnosis* / Q000209:etiology; D017558:Elective Surgical Procedures / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D009765:Obesity / Q000150:complications*; D011182:Postoperative Care / Q000295:instrumentation / Q000379:methods; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology; D011184:Postoperative Period; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation; D012131:Respiratory Insufficiency / Q000175:diagnosis* / Q000209:etiology; D018570:Risk Assessment / Q000379:methods; D011795:Surveys and Questionnaires; D013990:Tidal Volume
Morbidly obese; Patient safety; Perioperative respiratory monitoring