Why Do You Pass Out When You Hyperventilate?

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Hyperventilation causes too much oxygen to be taken in and carbon dioxide to be discarded too quickly, which causes fainting, as explained by WebMD. Acute hyperventilation is often triggered by anxiety or a specific phobia. Acute decreases in carbon dioxide can lower cerebral blood flow and cause neurologic symptoms such as syncope, seizure, dizziness and confusion.

WebMD recommends breathing into a paper bag in the event of hyperventilation, a home remedy which supplies an old but still applicable solution. Breathing into a paper bag forces inhalation of carbon dioxide, which slows the rate of breathing as well as regulating the acid-base balance so that the individual does not faint or enter respiratory alkalosis. Web MD also recommends diaphragmatic breathing, pinching one nostril shut, and breathing through pursed lips as other strategies to treat hyperventilation before a person reaches the point of syncope.

According to Medscape, hyperventilation can lead to syncope and in extreme cases, respiratory alkalosis. In a healthy human the acid-base balance remains relatively stable. Normal processes malfunction when pH levels climb too high (alkalosis) or drop too low (acidosis). Hyperventilation causes a loss of carbon dioxide which drives up pH levels. Hyperventilation syndrome, or acute respiratory alkalosis, is characterized by paresthesias, tingling and numbness around the mouth, chest tightness or pain, difficult breathing, and tetany.