Inspiratory flow-volume curve in snoring patients with and without obstructive sleep apnea

ABSTRACT

We analyzed the flow-volume curves of 50 patients with complaints of snoring and daytime sleepiness in treatment at the Pneumology Unit of the University Hospital of Brasília. The total group was divided into snorers without obstructive sleep apnea (OSA) (N = 19) and snorers with OSA (N = 31); the patients with OSA were subdivided into two groups according to the apnea/hypopnea index (AHI) AHI<20/h (N = 14) and AHI>20/h (N = 17). The control group (N = 10) consisted of nonsmoking subjects without complaints of snoring, daytime sleepiness or pulmonary diseases. The population studied (control and patients) consisted of males of similar age, height and body mass index (BMI); spirometric data were also similar in the four groups. There was no significative difference in the ratio of forced expiratory and inspiratory flows (FEF50 per cent/FIF50 per cent) in any group control, 0.89; snorers, 1.11; snorers with OSA (AHI<20/h), 1.42, and snorers with OSA (AHI>20/h), 1.64. The FIF at 50 per cent of vital capacity (FIF50 per cent) of snoring patients with or without OSA was lower than the FIF50 per cent of the control group (P<0.05) snorers 4.30 l/s; snorers with OSA (AHI>20/h) 3.69 l/s; snorers with OSA (AHI>20/h) 3.17 l/s and control group 5.48 l/s. The FIF50 per cent of patients with severe OSA (AHI>20/h) was lower than the FIF50 per cent of snorers without OSA (P<0.05) 3.17 l/s and 4.30 l/s, respectively. We conclude that 1) the FEF50 per cent/FIF50 per cent ratio is not useful for predicting OSA, and 2) FIF50 per cent is decreased in snoring patients with and without OSA, suggesting that these patients have increased upper airway resistance (UAR).