New insights on the pathophysiology of inspiratory flow limitation during sleep.

INTRODUCTION: Inspiratory flow limitation (IFL) is defined as a "flattened shape" of inspiratory airflow contour detected by nasal cannula pressure during sleep and can indicate increased upper airway resistance especially in mild sleep-related breathing disorders (SRBD). The objective of this study was to investigate the association between upper airway abnormalities and IFL in patients with mild SRBD. METHODS: This study was derived from a general population study consisting of selected individuals with apnea-hypopnea index (AHI) below 5 events/h of sleep, ("no obstructive sleep apnea" group) and individuals with AHI between 5 and 15 events/h ("mild obstructive sleep apnea" group). A total of 754 individuals were divided into four groups: group 1: AHI <5/h and <30 % of total sleep time (TST) with IFL (515 individuals), group 2: AHI <5/h and >30 % of TST with IFL (46 individuals), group 3: AHI: 5-15/h and <30 % of TST with IFL (168 individuals), and group 4: AHI: 5-15/h and >30 % of TST with IFL (25 individuals). RESULTS: Individuals with complains of oral breathing demonstrated a risk 2.7-fold larger of being group 4 compared with group 3. Abnormal nasal structure increased the chances of being in group 4 3.2-fold in comparison to group 1. Individuals with voluminous lateral wall demonstrated a risk 4.2-fold larger of being group 4 compared with group 3. CONCLUSION: More than 30 % of TST with IFL detected in sleep studies was associated with nasal and palatal anatomical abnormalities in mild SRBD patients.

Impact of thyroidectomy on the control of obstructive sleep apnea syndrome in patients with large goiters.

PURPOSE: A large goiter can cause a series of compressive symptoms such as dyspnea and dysphagia, and previous case reports have indicated the coexistence of obstructive sleep apnea syndrome (OSAS) in these patients. The aim of this study was to evaluate the impact of thyroidectomy on the control of OSAS in patients with large goiters. METHODS: Twenty-four patients with euthyroid goiters larger than 100 ml were consecutively selected. Of these, 17 (70.8%) presented OSAS and formed the research group. The protocol consisted of sleep questionnaires, physical examination, and polysomnography in baseline and after 3 months of surgery. RESULTS: The average age of the patients was 58.3±9.9 years, and there were 5 (29.4%) males and 12 (70.6%) females. The significant findings in the postoperative period included a reduced neck circumference (p=0.041), reduced Epworth sleepiness score (p=0.025), decreased percentage of high-risk OSAS cases according to the Berlin questionnaire (p<0.001), and a tendency for a significant reduction in snoring (p=0.052). However, polysomnographic respiratory parameters showed no significant improvement after surgery. CONCLUSION: Despite the high prevalence of OSAS in patients with large goiters and the improvement of OSAS symptoms, thyroidectomy showed no significant impact on the polysomnographic parameters.