The use of overnight pulse oximetry for obstructive sleep apnoea in a resource poor setting in Sri Lanka

Abstract

Objective: To study patients with symptoms suggestive of obstructive sleep apnoea using overnight oxymetry, and describe their symptoms, risk factors and co-morbidities.

Methodology: Overnight oxymetry was carried out on consecutive patients presenting with snoring and daytime sleepiness. Daytime sleepiness was assessed with Epworth sleepiness score (ESS). Their body mass index (BMI), presence of hypertension, neck circumference, oropharyngeal Mallampathi index, thyroid status, co-morbidities, alcohol, smoking, and medication use were noted. The number of oxygen desaturations below 4% of the baseline, per hour of sleep (oxygen desaturation index: ODI) was calculated and a plot of oxygen saturation versus time was analyzed for graph morphology. Association of ODI with other clinical parameters was statistically analyzed.

Results: Forty five patients (15 females) with a mean age of 44 (±13) years underwent overnight oxymetry. Their mean BMI was 27.62 (±8.82) kg/m2, 11(24%) were obese (BMI ≥30kg/m2) and 21 (46%) were hypertensive. They complained of snoring (91%), nocturnal waking up (82%), nocturnal choking (35 %), witnessed apnoeic episodes (31%), waking up tired (16%), nocturia (31%) and waking up with headache (20%). Mean ODI was 9.32 (±9.66)/hr. Twenty six (57%) patients had an abnormal ODI above 5/hr with saw tooth appearance in oxymetry tracings and 33% of them had an ODI ≥10/hr. Hypertension, nocturia and ESS showed a significant association with ODI (P 0.05). ODI significantly correlated with ESS (P=0.02) and BMI (P=0.006).

Conclusion: Sleep apnoea is prevalent than expected, though largely unrecognized. Obesity, higher Epworth score, nocturia and hypertension indicated risk factors for OSAS. Use of widely available pulse oximetry is a practical, low cost approach to investigate sleep disordered breathing in resource poor settings.

DOI: http://dx.doi.org/10.4038/jccp.v41i2.3767  

Journal of the Ceylon College of Physicians, 2010, 41, 61-66