Prevalence and characteristics of OSA patients with sawtooth sign in spirometry

<bold>Introduction:</bold> The sawtooth sign observed in spirometry was first identified by Sanders et al(1) in patients with obstructive sleep apnea (OSA), suggesting it as a potential indicator of extrathoracic central airway obstruction. However, there is ongoing debate regarding its prevalence among individuals with OSA. This study aims to determine the prevalence of the sawtooth sign in OSA patients and explore the characteristics of this subgroup (OSA patients with sawtooth sign). <bold>Methods:</bold> Retrospective study conducted at the clinical physiology department of Constantine university hospital , patients with confirmed obstructive sleep apnea (OSA) by polysomnography (AHI>5) undergoing spirometry on the same day. <bold>Results:</bold> A total of 106 patients (52 womens) diagnosed with obstructive sleep apnea were enrolled in this study. The mean age was 54±13 years, and the mean Body Mass Index (BMI) was 37±7 kg/m². The average Apnea-Hypopnea Index (AHI) was 38 events/hour. Among the patients, the sawtooth sign in spirometry was detected in 18 patients (5 womens) representing 17% of our population. In comparison with a control group (OSA patients without the sawtooth sign), the subgroup of OSA patients with the sawtooth sign have a significantly higher AHI (p=0.042), increased neck circumference (p=0.009), and a higher index of microarousals (p=0.003). No statistically significant differences were observed between the two groups in terms of other polysomnographic parameters. <bold>Conclusion:</bold> The subgroup of OSA patients with sawtooth sign in spirometry appears to be relatively common, and it is characterized by severe OSA, increased neck circumference, and fragmented sleep.