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October 18, 2009
10:00 AM - 11:30 AM
Room Room 356
Nocturnal Oximeter: A Sensitive and Specific Tool To Detect the Surgical Patients with OSA
  **   Frances Chung, M.D., F.R.C.P.C., Pu Liao, M.D., Frank Sun, M.D., Colin Shapiro, M.D., F.R.C.P.C., Hisham Elsaid, M.D.
Anesthesia, University Health Network, University of Toronto, Toronto, Ontario, Canada
Introduction: Undiagnosed obstructive sleep apnea (OSA) is associated with increased occurrence of perioperative adverse events. It is impractical to do polysomnography (PSG) in all patients at high risk of OSA before surgery. The objective of the study is to explore the capacity of nocturnal oximeter in detecting the undiagnosed OSA in the surgical patients.

Method: Following REB approval, the surgical patients who gave consent at preoperative clinic underwent a 8-hour sleep study at home with a portable PSG device (Embletta X100) and a simultaneously SaO2 monitoring with pulse oximeter wristwatch (PULSOX-300i). Embletta X100 has 10 channels: 2 electroencephalography, electrooculography, electromyography, snoring, nasal flow, abdominal and thoracic movement, oximetry and position. The devices were installed by well trained technicians. The PSG recordings were scored by a certified sleep technologist. The oximetry recordings between 00:00h and 6:00h were processed with software Profox. Oxygen desaturation index (ODI) was defined as hourly number of episodes of desaturation with ≥4% and lasting ≥10s. Patients with Apnea Hyponea Index (AHI) > 5 were considered having OSA. The data were analyzed with SAS 9.1 .

Result: 371 patients completed the study:174 male and 197 female. Age was 61 ± 12 and BMI 30 ± 7. Number of patients diagnosed by PSG to have obstructive sleep apnea (AHI >5) were 248 (67%) and the number of patients without OSA were 123 (33 %). Of the patients diagnosed with OSA, 117 (32 %) had mild OSA (AHI> 5∼15), 74 (20%) had moderate OSA (AHI>15∼30), and 57 (15 %) had severe OSA(AHI>30). There was a strong correlation between parameters from oximeter and PSG: AHI and ODI (r=0.829, p<0.01), AHI-REM and ODI (r=0.644, p<0.01), AHI-NREM and ODI (r=0.820, p<0.01), respiratory arousal index and ODI (r=0.805, p<0.01). The sensitivity for ODI > 5 to predict OSA patients (AHI>5) was 95% (95% CI: 93-98%), specificity: 67%(CI:58-75%) and accuracy:86 %. The sensitivity for ODI >15 to predict moderate and severe OSA (AHI>15) was 76% (CI: 69-83%), specificity: 93 % (CI: 90-96%) and accuracy: 87 %. The sensitivity for ODI >30 to predict severe OSA (AHI>30) was 75% (CI: 64-87%), specificity: 97 % (CI: 95-99%) and accuracy: 94 %.

Conclusion: There was a strong correlation between Oxygen Desaturation Index (ODI) from nocturnal oximetry and Apnea Hyponea Index (AHI) from PSG. ODI>5, ODI>15 and ODI>30 were sensitive and specific predictors for the surgical patients with AHI>5, AHI>15 or AHI>30 respectively.

From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists.