A man with severe OSA (AHI: 56.7; Epworth Sleeping Scale: 11/24) underwent expansion sphincter pharyngoplasty (ESP) proved effective in controlling apnea and hypopnea and daytime sleepiness (AHI: 5.5; Epworth Sleeping Scale: 0/24) at six months after surgery. Otherwise, the nasal cannula inspiratory flow contour signal for almost of the 7 hours of recording time showed Inspiratory Flow Limitation (IFL), an indicator of a residual pharyngeal collapsibility when exposed to negative inspiratory pressure. The IFL seems to be associated with significant physiological changes, such as an increase in end-tidal CO2, esophageal pressure or inspiratory time. To date, clinical studies are warranted to elucidate the clinical role of these physiological changes and guide the best management of these patients. Our case report has a significant educational and clinical value. In fact, the instrumental and clinical resolution of the OSA may hide a residual effect, the collapsibility of upper airway, that has been associated with potential detrimental effect on the health of the subject with OSA. We suggest that in case of residual and persistent IFL it should be necessary to provide a structured management to prevent the occurrence of comorbidities and for an early diagnosis of a possible recurrence of OSA.