Sinus squeeze causes are best described by which option?

• A. Inability to equalize openings of the nose
• B. Nose congestion
• C. Blocked sinus openings
• D. Nasal discharge

Answer: (C)

Sinus squeeze happens when the openings that connect the sinus cavities to the nasal passages (the sinus ostia) can’t equalize with ambient pressure during a dive. When these openings are blocked by congestion, swelling, or infection, air can’t escape or enter the sinuses as pressure changes with depth. That trapped pressure creates a differential across the sinus walls, leading to pain and potential mucosal injury—this is the core mechanism of sinus squeeze. So, blocked sinus openings best describe the cause. While nasal congestion can contribute by promoting blockage, nasal discharge is a symptom, and an inability to equalize the nose’s openings points more to ear-related pressure changes rather than the sinuses.