Quiz - 15 - Diving Knowledge Workbook - Diving Physiology

[Pedro Burrito]

From the Diving Physiology Section of the PADI Diving Knowledge Workbook Version 2.02 © PADI 2009:

Objective 2.5 - Explain the physiological mechanism that causes a "carotid-sinus reflex" and how this affects the diver.

Question 2

The carotid-sinus reflex is caused by an excessively tight

a. exposure suit or boots that constrict the feet.

b. exposure suit that constricts the thorax.

c. exposure suit or hood that constricts the neck.

d. mask strap that constricts the head. ​

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[Pedro Burrito]

Spoiler: Answer

c. exposure suit or hood that constricts the neck.

Because the receptors are in the carotid arteries (neck), anything constricting that area could cause the reflex to occur. Dry suit neck seals are particularly noted for this.

This happened to me on my first dry suit dive using a rented suit with a too tight neck seal. I barely got into the water, my instructor and his assistant gave the thumbs down signal and I called the dive. I went back to the parking lot, changed into my 3/2mm wet suit and spent that dive doing other activities shivering the whole time in 10°C water. My instructor wanted to stress the importance of checking your gear before you get in the water.