I'd say a combination of the hot tub and the sinuses could cause you to do this but it's scary! Have you ever tried a neti pot? My husband swears by them for his blocked sinuses. The steam from the hot tub seems good for trying to unclog the sinuses but I've gotten light headed from being in a hot tub too long and the heat. Call your doctor if the issue continues (pain and then dizziness or passing out!). good luck and let me know how it goes!