Fainting, or syncope, is a sudden and temporary loss of consciousness. This usually occurs due to a lack of oxygen reaching the brain.
Many things can cause oxygen deprivation to the brain, including low blood pressure.
Fainting is not usually serious. However, sometimes it can indicate a serious medical issue. People should treat every case of fainting as a medical emergency until they have uncovered the cause and treated the symptoms.
In this article, we look at why fainting occurs and when to seek medical treatment.
Fainting usually results from a lack of oxygen to the brain, such as from problems with the lungs or blood circulation or carbon monoxide poisoning.
Fainting is a survival mechanism. If blood and oxygen levels in the brain drop too low, the body immediately starts shutting down nonvital parts to direct resources to vital organs.
When the brain detects lower levels of oxygen, breathing will speed up to increase the levels.
The heart rate will also increase, so that more oxygen reaches the brain. This reduces blood pressure in other parts of the body. The brain then receives extra blood at the expense of other body areas.
Hyperventilation plus hypotension may result in short term loss of consciousness, muscle weakening, and fainting.
Different underlying causes can cause a person to faint. We discuss some of them in detail below:
Neurocardiogenic syncope
Neurocardiogenic syncope develops due to a short term malfunction of the autonomous nervous system (ANS). Some people call it neurally mediated syncope (NMS).
The ANS controls automatic body functions, including heart rate, digestion, and respiration rate.
In NMS, a drop in blood pressure slows the heartbeat and pulse rate. This temporarily interrupts the brain’s blood and oxygen supply.
Possible triggers of neurocardiogenic syncope include:
- an unpleasant or shocking image, such as seeing blood
- sudden exposure to an unpleasant sight or experience
- abrupt emotional upset, such as after receiving tragic news
- extreme embarrassment
- standing still for a long time
- being in a hot and stuffy environment for a long time
Occupational syncope
Occupation, or situational, syncope is a type of neurocardiogenic syncope with physical rather than emotional, mental, or abstract triggers. Triggers include:
- laughing or swallowing
- passing stools or urine
- coughing or sneezing
- strenuous physical activities, such as lifting a heavy weight