article_snippet: But it's only when this pressure cannot be released, such as due to blockage from a cold, for example, that the passenger will really be made aware of the change.
article_snippet: Luckily, alleviating the pressure in most cases is relatively easy - simply by swallowing, chewing or yawning.
article_snippet: This could cause light-headedness, shallow breathing or difficulty concentrating.
article_snippet: Occasionally, it may lead to complications such as pulmonary embolism, which is when a piece of blood clot breaks off into the bloodstream and blocks one of the blood vessels in the lungs.