Introduction: Impulse oscillometry (IOS), a simple, noninvasive method using the forced oscillation technique, requires minimal patient cooperation and is suitable for use in both children and adults. This method can be used to assess obstruction in the large and small peripheral airways. Aim: To study impulse oscillometry measurements in cases of moderate to severe sleep apnea. Materials and Methods: A study was performed in Department of Respiratory Medicine, Sri Aurobindo Institute of Medical Sciences. Thirty patients diagnosed with severe sleep apnea underwent home noninvasive ventilation therapy. Pre- and post treatment noninvasive ventilation (NIV) impulse oscillometry was given to these patients. Results: The pre-NIV spirometry showed predominant mixed pattern of disease with Impulse oscillometry showing reduced R25 and R5 levels. Post 3 months of noninvasive ventilation therapy with > 80% compliance demonstrated improvement in R25 parameters. Conclusion: Respiratory resistance and reactance measured by Impulse oscillometryare abnormal in preobese and obese obstructive sleep apnea hypopnea syndrome (OSAHS) patients, and these parameters are closely correlated with OSAHS severity. Impulse oscillometrymight be a useful screening tool for detecting OSAHS in clinic based populations.