The Fujita classification, also known as the Fujita Scale or Fujita Staging System, is a classification system used to categorize the severity of obstructive sleep apnea (OSA) based on the degree of obstruction observed during sleep.
The Fujita classification was developed by Dr. Seiji Fujita and is divided into three stages (Fujita stages) based on the anatomical site of upper airway obstruction observed during sleep:

• Fujita Stage I: This stage refers to obstruction occurring behind the soft palate (retropalatal area). The obstruction is limited to the area behind the soft palate, typically involving the uvula and the surrounding tissues. Patients with Fujita Stage I OSA experience mild to moderate airway obstruction during sleep.
• Fujita Stage II: Stage II involves obstruction at the level of the soft palate and base of the tongue (retroglossal area). The obstruction occurs further down the airway, encompassing the area behind the tongue's base. Individuals in Fujita Stage II often experience more significant airway obstruction than those in Stage I.
• Fujita Stage III: This stage represents the most severe form of obstruction, involving the complete collapse of the upper airway at multiple levels, including both retropalatal and retroglossal areas. Patients in Fujita Stage III exhibit widespread and severe airway obstruction during sleep.

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