evaluation of obstructive sleep apnea in a pregnant population and its correlation with maternal airway
Abstract Number: 199
Abstract Type: Original Research
Obstructive sleep apnea (OSA) occurs in approximately 5% of women aged 30-49(1). OSA is characterised by upper airway obstruction and nocturnal hypoxemia during sleep. In pregnancy, OSA is associated with IUGR, fetal death (2). Physiological changes in pregnancy can contribute to the severity of OSA in pregnancy due to alterations in fat distribution in the airway and pharyngeal edema. Polysomnography is the gold standard for diagnosing OSA however it is costly, time consuming and not a suitable screening tool. The STOP questionnaire consists of 4 questions and was validated in a trial of over 2400 non-pregnant patients. The STOP questionnaire is easy to use and has a high sensitivity especially for moderate to severe OSA. The four questions in the STOP questionnaire relate to Snoring, daytime Tiredness, Observed apnea and high blood Pressure. With the addition of BMI, Age, Neck circumference and Gender it is even more sensitive, (STOP-Bang scoring model).(3) OSA symptoms are associated with difficult tracheal intubation. In one study high Mallampati scores were a risk factor for OSA .Our study uses the STOP-Bang questionnaire to determine the prevalence of OSA in pregnancy and whether there is improvement postpartum. The study will also look at the association between OSA symptoms and a possible difficult intubation as determined by airway assessment.
Following REB approval and written consent, eligible women in their third trimester are administered the STOP- Bang scoring model. Photographs are taken of the airway for determination of modified Mallampati score by an independent researcher. As well, standard airway measurements are done by an investigator. Data collected include BMI, neck circumference, gestational and maternal age, modified Mallampati score, thyromental distance and blood pressure. A telephone interview using the STOP questionnaire will be repeated two months postpartum to see whether there is a change in the incidence of OSA.
To date 25 subjects have been recruited. Interim analysis indicates that 16% have OSA using the STOP- Bang questionnaire in third trimester pregnancy . There is an association between OSA and airway assessment that may predict a difficult intubation. The study is ongoing with an aim to recruit 300 subjects.
There are limited studies of OSA in pregnancy and none which associate OSA symptoms with airway assessment. The simplicity of the STOP questionnaire would make it an easy tool to predict OSA in the pregnant population. If the association of OSA with a potentially difficult airway using standard airway assessment is confirmed it would be useful to the OB anesthesiologist
1 Young TB, N Eng J Med 1993 ;328; 1230-1238
2 Leung PL, BJOG Nov 2005;112;1568-1571
3 Chung F, Anesthesiology 2008; 108;812-21