10 May 09

Screening for obstructive sleep apnea before surgery: why is it important?

Posted in Obstructive sleep apnea, Pre-operatie evaluation at 18:46 by Laci

By F Chung, H Elsaid

Current Opinion in Anaesthesiology 2009;22:405-411

The purpose of this article is to review the screening tools available in the preoperative clinic for patients at risk of obstructive sleep apnea.

Recent findings
Obstructive sleep apnea (OSA) is the most prevalent sleep disorder. An estimated 82% of men and 92% of women with moderate-to-severe sleep apnea have not been diagnosed. Patients with undiagnosed OSA may have increased perioperative complications. The perioperative risk of patients with OSA may be reduced by appropriate screening to detect undiagnosed OSA in patients. The snoring (S), tiredness (T) during daytime, observed apnea (O), and high blood pressure (P) (STOP) questionnaire is a concise and easy-to-use screening tool to identify patients with a high risk of OSA. It has been validated in surgical patients at preoperative clinics as a screening tool. Incorporating BMI, age, neck size and gender into the STOP questionnaire (STOP-Bang), will further increase the sensitivity and negative predictive value (NPV), especially for patients with moderate-to-severe OSA.

The STOP questionnaire is short and can be easily incorporated into routine screening of general or surgical patients.

18 Oct 08

STOP Questionnaire: A tool to screen patients for obstructive sleep apnea

Posted in Obstructive sleep apnea at 13:50 by Laci

By F Chung, B Yegneswaran, P Liao, S Chung, S Vairavanathan, S Islam, A Khajehdehi, C Shapiro

Anesthesiology 2008;108:812-821

Obstructive sleep apnea (OSA) is a major risk factor for perioperative adverse events. However, no screening tool for OSA has been validated in surgical patients. This study was conducted to develop and validate a concise and easy-to-use questionnaire for OSA screening in surgical patients.

After hospital ethics approval, preoperative patients aged 18 yr or older and without previously diagnosed OSA were recruited. After a factor analysis, reliability check, and pilot study; four yes/no questions were used to develop this screening tool. The four questions were respectively related to snoring, tiredness during daytime, observed apnea, and high blood pressure (STOP). For validation, the score from the STOP questionnaire was evaluated versus the apnea-hypopnea index from monitored polysomnography.

The STOP questionnaire was given to 2,467 patients, 27.5% classified as being at high risk of OSA. Two hundred eleven patients underwent polysomnography, 34 for the pilot test and 177 for validation. In the validation group, the apnea-hypopnea index was 20 ± 6. The sensitivities of the STOP questionnaire with apnea-hypopnea index greater than 5, greater than 15, and greater than 30 as cutoffs were 65.6, 74.3, and 79.5%, respectively. When incorporating body mass index, age, neck circumference, and gender into the STOP questionnaire, sensitivities were increased to 83.6, 92.9, and 100% with the same apnea-hypopnea index cutoffs.

The STOP questionnaire is a concise and easy-to-use screening tool for OSA. It has been developed and validated in surgical patients at preoperative clinics. Combined with body mass index, age, neck size, and gender, it had a high sensitivity, especially for patients with moderate to severe OSA.

17 Aug 08

Diagnosis and initial management of obstructive sleep apnea without polysomnography

Posted in Obstructive sleep apnea at 11:20 by Laci

By A T Mulgrew, N Fox, N T Ayas and C F Ryan

Ann Intern Med 2007;146:157-166

Polysomnography (PSG), despite limited availability and high cost, is currently recommended for diagnosis of obstructive sleep apnea and titration of effective continuous positive airway pressure (CPAP).

To test the utility of a diagnostic algorithm in conjunction with ambulatory CPAP titration in initial management of obstructive sleep apnea.

A randomized, controlled, open-label trial that compared standard PSG with ambulatory CPAP titration in high-risk patients identified by a diagnostic algorithm.

A tertiary referral sleep disorders program in Vancouver, British Columbia, Canada.

68 patients with a high pretest probability of moderate to severe obstructive sleep apnea (apnea–hypopnea index [AHI] >15 episodes/h) identified by sequential application of the Epworth Sleepiness Scale (ESS) score, Sleep Apnea Clinical Score, and overnight oximetry.


Patients were randomly assigned to PSG or ambulatory titration by using a combination of auto-CPAP and overnight oximetry. They were observed for 3 months.

Apnea–hypopnea index on CPAP, ESS score, quality of life, and CPAP adherence.

The PSG and ambulatory groups had similar median BMI (38 kg/m2), age (55 years), ESS score (14 points), and respiratory disturbance index (31 episodes of respiratory disturbance/h). Each episode is determined by a computer algorithm based on analysis of oxygen saturation measured by pulse oximetry. After 3 months, there were no differences in the primary outcome, AHI on CPAP (median, 3.2 vs. 2.5; difference, 0.8/h [95% CI, –0.9 to 2.3]) (P = 0.31), between the PSG and ambulatory groups, or in the secondary outcomes, ESS score, Sleep Apnea Quality of Life Index, and CPAP. Adherence to CPAP therapy was better in the ambulatory group than in the PSG group (median, 5.4 vs. 6.0; difference, –1.12 h/night [CI, –2.0 to 0.2]) (P = 0.021).

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