Polysomnographic profile in a sleep laboratory in Kolkata: a retrospective analysis of 714 cases

In this retrospective analysis, all patients (n=714; male=590; female=124 and female male ratio = 1: 4.76) came to Pulsar, a sleep laboratory of Kolkata, for polysomnography during ten years period were analyzed. More than half (62.46%) cases were between 41-60 years and 14.43% cases between 61-80 years age group. Fifty-two percent cases were referred by pulmonologists, followed by internist (15%), and 7% cases were self referred. Though obstructive sleep apnea was responsible for increased cardiovascular mortality and resistant hypertension, only 4% cases were referred by cardiologists. We observed hypertension as co-morbidity in 52.63% cases and ischemic heart disease in 22.83% cases. Snoring was the presenting complain in 98.88% cases, chocking was present in 48.88% cases and excessive daytime sleepiness was found in 96.64% cases. Females showed comparatively higher frequency of sleep disordered breathing than males with increasing basal metabolic rate. Nocturnal fall of SPO2 below 90% was observed in 86.97% of study population. We found abnormal respiratory disturbance index (> 5/hr of sleep) in 84.59% of our patients, normal respiratory disturbance index (< or = 5/hr of sleep) in 9.94% cases and isolated nocturnal hypoxemia in 5.46% cases (74.36% of the last category having obstructive airway disease). Snoring with respiratory disturbance index (RDI) < or = 5/hr was observed in 102 cases, of them 81.37% had simple snoring without significant arousal whereas 18.63% had multiple sleep fragmentation. We estimated that 84.06% of males, 87.10% of females and 84.59% of study population had obstructive sleep apnea. Split night polysomnography was performed in 362 cases, and of them 15.47% cases could not tolerate continuous positive airway pressure (CPAP) due to local or psychological reasons. In the present one time split-night CPAP titration study, we could not correct OSA in 19.06% subjects. Inadequate correction of hypoxemia due to co-morbid condition like COPD, asthma, obesity, hypothyroidism was the main responsible factor (49.28%). Treatment with CPAP was effective in 68.23% cases in first attempt. More than half of the cases (62.42%) required 10 cm of H20 or less CPAP.