Authors (including presenting author) :
chiang LK (1), Kam CW (1), Ng L (1)
Affiliation :
(1) KWH General Outpatient Clinic, Department of Family Medicine and General Outpatient Clinics, KCC
Introduction :
Cardiovascular, metabolic and neuropsychological morbidities, and increased risk of motor vehicle accidents have been demonstrated in untreated obstructive sleep apnea (OSA). Overnight full-channel polysomnography (PSG) performed in a sleep laboratory remains the gold standard diagnostic test for OSA. However, PSG is time consuming, costly and requires expertise involvement for interpretation. Young et al reported that 82% of men and 93% of women with moderate to severe sleep apnea have not been diagnosed. The prevalence of OSA in primary care setting is higher than in the community. Due to limitation of clinical assessment and lack of diagnostic test, the usual practice for primary care physicians is referring all those patients to respiratory physician or sleep center for confirmation test. Oximetry alone is often used as the first screening tool for obstructive sleep apnea.
Objectives :
The program aims to study prevalence of OSA among at risk adult patients in primary care setting; to test the OSA screening performance of portable overnight pulse oximetry, thirdly to test the feasibility and outcomes of OSA screening program.
Methodology :
KWH GOPC implemented OSA screening program by using overnight pulse oximetry since year 2011. All adult Chinese patients with risk factors for obstructive sleep apnea were indicated for OSA screening. The oximeter was loaned to indicated patients to completed overnight pulse oximetry at home. If the oximetry suggested the patient having moderate or severe OSA, they will be referred to sleep service for further confirmation and management.Demographics and screening outcomes of all indicated patients were summarized and analyzed.
Result & Outcome :
From year 2011 to 2017, 505 (59.8%) male and 339 (42.9%) female patients were involved in OSA screening with overnight pulse oximetry. Their mean (SD) age was 54.1 (13.5) years old, mean (SD) BMI was 27.0 (4.7) kg/m2, mean (SD) neck circumference was 37.8 (2.9) centimeters, and the mean (SD) Epworth Sleepiness Scale (ESS) score was 9.8 (5.5). Snoring (47.7%) and excessive daytime sleepiness (16%) were the top two presenting symptoms. Three of commonest comorbidities were hypertension (44.9%), obesity (44.3%) and hyperlipidaemia (20.2%). 524 patients (62.1%) were screened positive to have OSA. The mild, moderate and severe OSA based on oxygen desaturation index of 4% (ODI_4) determination were 57.1%, 29.0% and 13.9% respectively. Among 147 patients had performed PSG, the ODI_4 and apnoea hypopnea index (AHI) had Pearson correlation coefficient, r = 0.73 (95% CI 0.59 – 0.81, P < 0.001). Using case designation criteria of ODI_4 5 events/hr, the sensitivity and specificity for OSA diagnosis are 94% and 79% respectively. About one third of patients (263/844) had referred to specialty for further management. Ninety two patients had performed at home PSG in the community sleep service. Their reports were seen by primary care physician for further risk categorization and management. On conclusion,the prevalence of OSA is 62.1% among a selected adult primary care population who are at risk for OSA. Overnight pulse oximetry shows good performance as a screening tool for the screening of OSA. A reliable and valid screening tool can avoid unnecessary referrals to the pre-existing overloaded respiratory specialist service in the public health sector and it can also expedite early management of OSA patients.
