Oxygen Desaturation Index from Nocturnal …

1 Oxygen Desaturation Index from Nocturnal Oximetry:A Sensitive and Specific Tool to Detect Sleep- disordered Breathing in Surgical PatientsFrances Chung, FRCPC,* Pu Liao, MD,* Hisham Elsaid, MD,* Sazzadul Islam, MSc,*Colin M Shapiro, FRCPC, and Yuming Sun, MD*INTRODUCTION:It is impractical to perform polysomnography (PSG) in all surgical patientssuspected of having sleep disordered breathing (SDB). We investigated the role of nocturnaloximetry in diagnosing SDB in surgical :All patients 18 years and older who visited the preoperative clinics for scheduledinpatient surgery were approached for study participation. Patients expected to have abnormalelectroencephalographic findings were excluded. All patients underwent an overnight PSG athome with a portable device and a pulse oximeter. The PSG recordings were scored by a certifiedsleep technologist. The oximetry recordings were processed :Four hundred seventy-five patients completed the study: 217 males and 258 females,aged 60 11 years, and body mass Index 31 7 kg/m2.

2 The apnea-hypopnea Index (AHI), theaverage number of episodes of apnea and hypopnea per hour of sleep, was ( to )[median (interquartile range)] and 64% patients had AHI 5. There was a significant correlationbetween Oxygen Desaturation Index (ODI, hourly average number of Desaturation episodes) andcumulative time percentage with SpO2 90% (CT90) from Nocturnal oximetry, with the parametersmeasuring sleep breathing disorders from PSG. Compared to CT90, ODI had a stronger correlationand was a better predictor for AHI. The area under receiver operator characteristics curve for ODI topredict AHI 5, AHI 15, and AHI 30 was (CI: to ), (CI: to ),and (CI: to ), respectively. The cutoff value based on the maximal accuracy for ODIto predict AHI 5, AHI 15, and AHI 30 was ODI 5, ODI 15, and ODI 30. The accuracy was86% (CI: 83% 88%), 86% (CI: 83% 89%), and 94% (CI: 92% 96%), respectively. The ODI 10demonstrated a sensitivity of 93% and a specificity of 75% to detect moderate and severe :ODI from a high-resolution Nocturnal oximeter is a sensitive and specific tool todetect undiagnosed SDB in surgical patients.

3 (Anesth Analg 2012;114:993 1000)Obstructive sleep apnea (OSA) is one of the mostfrequent constituents of sleep disordered breathing(SDB). Growing evidence has implicated OSA as acausal pathway to the development of cardiorespiratorydiseases, diabetes mellitus and autoimmune 3 The all-cause mortality is increased in proportion with theseverity of can pose a significant challenge toanesthesiologists in the perioperative period due to thepatient s possible difficult airway, increased sensitivity tonarcotics, and postoperative upper airway been shown that OSA patients have an increasedincidence of perioperative adverse 8In the general population, OSA was found in 24% ofmen and 9% of women with apnea-hypopnea Index (AHI) 5 and in of men and of women with AHI 15as the OSA diagnostic is estimated that nearly80% of men and 93% of women with moderate to severesleep apnea are the surgicalpatient with undiagnosed OSA allows the clinician todevelop the appropriate perioperative management polysomnography (PSG)

4 Is the gold standardfor diagnosing , in-laboratory PSG is atime-consuming and costly procedure. Referring patients tosleep clinics usually results in postponing surgery. Mostportable sleep monitoring devices also require intensivetraining of patients or assistance from well-trained techni-cians, and manual scoring of recordings by certified PSGtechnologists. Lack of convenient and economical diagnos-tic tools is a major obstacle that prevents anesthesiologistsfrom diagnosing OSA and initiating treatment high resolution oximeter is a watch oximeter withhigh sampling frequency and resolution, which requireslittle training to install properly. It can detect the fluctua-tions in Oxygen saturation caused by episodes of apnea andhypopnea. In addition, the data can be automatically ana-lyzed with commercially available computer programswith an acceptable accuracy. Although oximetry has beenstudied as a screening tool in sleep clinic patients,12,13nostudy has been published to evaluate the diagnostic per-formance of oximetry for SDB in the surgical patient.

5 Theobjective of this study was to evaluate the predictiveperformance of a high-resolution oximeter in detecting SDBFrom the *Department of Anesthesia, University Health Network, Toronto,ON, Canada; Department of Anesthesia, University of Toronto, Toronto,Canada; and Department of Psychiatry, University Health Network, To-ronto, ON, for publication December 29, in part by Physicians Services Incorporated Foundation, Univer-sity Health Network Foundation, ResMed Foundation, Respironic Founda-tion, and Department of Anesthesia, University Health Network-MountSinai Hospital, and University of Toronto, Toronto, ON, authors declare no conflicts of will not be available from the correspondence to Frances Chung, FRCPC, Department of Anesthesia,University Health Network, University of Toronto, 399, Bathurst Street, To-ronto, ON, Canada M5T 2S8. Address email to 2012 International Anesthesia Research SocietyDOI: 2012 Volume 114 Number surgical patients.

6 Our hypothesis was that nocturnaloximetry is a simple alternative to PSG in diagnosing SDBin the preoperative SubjectsThe study was performed at Toronto Western Hospital ofUniversity Health Network and Mount Sinai Hospital inToronto. Approvals from the IRB of both hospitals wereobtained. Written informed consent was obtained from allstudy subjects. Patients 18 years and older were potentialcandidates for the study. Patients who were unwilling orunable to give informed consent or patients who wereexpected to have abnormal electroencephalographic (EEG)findings ( , brain tumor, epilepsy surgery, patients withdeep brain stimulator) were excluded. All eligible patientswho visited the preoperative clinics for a scheduled inpa-tient surgery were approached. The patients giving studyconsent underwent an entire night of portable PSG andsimultaneous oximetry preoperatively at the patients patients with an AHI 5, their family physicians werenotified so that the patients could be referred to sleep physi-cians for further clinical , SaO2monitoring with a high-resolutionpulse oximeter wristwatch (PULSOX-300i, Konica MinoltaSensing, Inc.)

7 , Osaka, Japan) was performed along withportable PSG (Embletta 100, Embla, Broomfield, CO).Each Oxygen probe of the oximeter and PSG were attachedto different fingers of the nondominant hand. The samplingfrequency of the oximeter PULSOX-300i is 1 Hz on memoryinterval and an averaging time of 3 seconds. The resolutionis Spo2(information provided by the manufacturer).The data were downloaded into a personal computer thefollowing morning and were processed with a specificallydesigned computer program, Profox (Profox Associates,Escondido, CA). First, the oximetry recording was visuallychecked by the technician and obvious artifacts were de-leted. The aberrant recording was then scanned and ex-cluded. Next, Oxygen Desaturation Index (ODI), cumulativetime percentage with Spo2 90% (CT90), lowest and aver-age Spo2were extracted from the oximetry data. ODI is thehourly average number of Desaturation episodes, which aredefined as at least 4% decrease in saturation from theaverage saturation in the preceding 120 seconds, andlasting 10 minimize the bias from oximetry data recorded whilethe patient was awake, only oximetry recordings obtainedbetween 00:00 hours and 6:00 hours were processed, al-though it was not known if patients were actually asleepduring this entire period.

8 Data processing was performedby a technician blinded to PSG PolysomnographyA full-night unattended portable PSG recording with Em-bletta 100 was performed at the patient s home preop-eratively. Embletta 100 is a level 2 diagnostic tool forOSA14and has been validated against laboratory PSG recording montage consisted of 2 EEG channels(C3 and C4), left or right electroculogram, chin muscleelectromyogram, nasal cannula (pressure), thoracic andabdominal respiratory effort bands, body-position sensor,and pulse oximetry. The device measures the oxyhemoglo-bin saturation at a rate of 3 samples per second. Theaveraging time is one-third of a bedtime, the device was connected to the patients bya trained PSG technician at the patients homes. Theovernight recording was unattended. The patients weretaught how to disconnect the device, which was retrievedby the same sleep technician the following morning. Pa-tients were asked to keep a sleep diary.

9 The sleep technicianretrieving the device ensured that the sleep diary wascompleted by the from the portable PSG were scored by acertified PSG technologist and reviewed by a physicianspecialized in sleep medicine. Both were blinded to theclinical information and the results of the Studio (Embla, Broomfield, CO) was theplatform used forscoring PSG. The PSG recording wasmanually scored epoch by epoch by the PSG technologist,according to the manual published by the American Acad-emy of Sleep Medicine in was defined as a 90% decrease in air flow from baseline, which lasted atleast 10 seconds. Apneas were classified as obstructiveapnea if respiratory effort was present, central apnea ifrespiratory effort was absent during the event, or mixedapnea if characteristics of both obstructive or central apneaare present. Hypopnea was defined as a 30% reduction inair flow which lasted at least 10 seconds and was associatedwith a decrease of at least 4% in arterial oxyhemoglobinsaturation.

10 The AHI was defined as the number of episodesof apnea and hypopnea per hour of Analysis and StatisticsSample Size EstimationThe calculation of sample size was performed according tothe method reported by sample sizewas calculated based on the sensitivity and specificity ofODI 10 for the prediction of AHI 5 from a previousstudy of patients suspected of having OSA18and preva-lence of ,20 When a sensitivity of , a precision , an OSA prevalence rate of 24%, a type I error of ,and a power of were used for sample size estimation,the power analysis resulted in 368 patients. Based on thespecificity of and a precision of , the sample sizewas 107 patients. To ensure sufficient power for estimationof sensitivity, a sample size of 368 patients was AnalysisData were entered into a specifically designed MicrosoftAccess database (Microsoft Corp., Redmond, WA) andchecked for possible errors. SAS for Windows (SASI nstitute, Cary, NC) was used for data analysis.