Tehran University of Medical Sciences Journal of Sleep Sciences 2476-2938 2 1-2 2018 02 13 1 6 EN Abolhasan Halvani Department of Internal Medicine, School of Medicine, Yazd Medical Science Branch, Islamic Azad University, Yazd, Iran Shahrzad Sabzevari Department of Internal Medicine, School of Medicine, Yazd Medical Science Branch, Islamic Azad University, Yazd, Iran Mehrdad Mostaghaci Department of Occupational and Environmental Medicine, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Amir Houshang Mehrparvar Department of Occupational Medicine, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mohammad Javad Zare Sakhvidi Department of Occupational Health, School of Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Raziyeh Soltani Gerdfaramarzi Department of Occupational Medicine, School of Medicine, Industrial Diseases Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran 2016 12 19 2017 02 12 Background and Objective: Previous studies have reported abnormal changes in spirometric parameters and flow-volume curves in patients with obstructive sleep apnea syndrome (OSAS) during sleep. This study aimed to evaluate the lung function capacities and flow-volume curves in these patients. Materials and Methods:This was a cross-sectional study. A total of 120 adults aged 18-65 years with suspected OSAS were selected. A full record of demographic characteristics and history of chronic diseases, as well as the results of spirometry and polysomnography were obtained. Spirometric indices and flow-volume curves in OSAS patients and normal subjects were compared. Results:The mean body mass index was 30.85 ± 6.18 kg/m2. Average neck and abdominal circumferences were 41.68 ± 3.53 and 108.56 ± 14.34 (cm); respectively. The subjects were divided into three groups based on their AHI. The sawtooth signal was observed in a flow-volume curve in 20.2% and 2.8% of patients with and without OSAS; respectively. Significant differences were seen in sawtooth appearance signs and forced expiratory flow (FEF) 50/forced inspiratory flow (FIF) 50 (P > 0.001), but these parameters were not significantly different in AHI subgroups of sleep apnea. Conclusion:Sawtooth sign and FEF50/FIF50 ≥ 1 could be useful in diagnosis of OSAS, although it cannot be used to predict the severity. Despite a significant difference in a sawtooth sign and FEF50/FIF50 between OSAS patients and nor-mal subjects, no significant differences in lung functions were observed between OSAS patients and normal subjects. https://jss.tums.ac.ir/index.php/jss/article/view/59