Maybe you missed this tip in your travel magazine about those horse collar neck gaskets? (keeps your head off of your shoulders when you snooze upright in your airline seat) The brand that inflates to a pillow could expand and damage the tissue causing trauma injury or death. If the aircraft cabin were to suddenly depressurize the neck doughnut would become a very large very hard balloon. Testing is incomplete and it is undetermined that this balloon pops before the circulation to your head is constricted. Important safety tip 🙂