Breathing is a process which intakes oxygen into the body and delivers out carbon dioxide. In medical terms, normal breathing is termed as eupnoea whereas a brief pause in breathing is termed as Apnea. These long stops are usually normal in his or her way of breathing and are also caused by other sleep-related problems. The respiration muscles are idle and movement doesn't happen when it is in apnea stage. Also the lung's volume does not change during the initial moment. The cellular respiration and the exchange of gas between the lungs have no chance to get affected depending on its openness of airways. This disorder can be achieved voluntarily by holding the breath, by inducing drug, by inducing mechanically. They are also referred to strangulation and explicate as a result of trauma or any neurological disorders.

'Apnea' word comes from a Greek origin which means "without air". People are not well equipped to identify the difference between snoring and apnea. Although all human beings have their breathing pauses in a normal condition, this apnea turns out to be a problem when the breathing count stops about 20 seconds or even longer. As oxygen cannot be stored much in the human body under normal circumstances, apnea causes lack of oxygen severely in blood circulation. It may even cause complete brain damage as minimum to three minutes or if the ventilation is not restored within a few minutes after it, death occurs inevitably. Longer duration of apnea might be tolerated with no severe consequences in special cases like hypothermia, apneic oxygenation, hyperbaric oxygenation or extracorporeal membrane oxygenation.

Humans who are not trained with voluntary apnea cannot withstand more than a couple of minutes. The fact behind this is that, the breathing rate and the breath volumes are forcibly regulated to uphold steady values of Carbon dioxide and the acidity or alkanity solution of blood technically specified as the pH.  Carbon dioxide mounts up in the blood during apnea and it is not extracted via the lungs. The drop in pH and the increase in Carbon dioxide tension consequently cannot be conquered voluntarily, as the brain's respiratory centre results in stimulation. Longer tolerance of apnea comes out naturally even in untrained humans when they are immersed in water and when their body causes physiological variations. Also in free-diving, an ancient method of practice requires to hold breath. Experts in it hold their breaths for a longer duration - say about nine minutes or even more underwater holding a depth of 214 meters.

A test for apnea could also be done to identify when there exists a breathing problem in an unaided manner for some period or if someone is brain dead. If the breathing doesn't have support from the life systems, the test for apnea turns out positive and results in the confirmation of brain death.

When normal breathing becomes a problem, routine life of a human being gets affected and causes various disorders. Even though pauses in breathing could be serious, most of apnea cases can be well managed or treated with medications, surgery or monitoring instruments. Also many of the apnea cases go on its own way.