Acapnic is a medical term that refers to the state of low or absent carbon dioxide levels in the blood. There are several synonyms for this term, including hypocapnia, hypocarbia, and respiratory alkalosis. These terms are often used interchangeably in medical contexts to describe the same condition of reduced CO2 levels in the bloodstream. Other related terms for acapnia include hyperventilation, which can cause a decrease in carbon dioxide levels due to increased breathing rate, and alkalosis, which refers to a more general state of increased blood pH (or decreased acidity). While acapnia can occur naturally, it is often associated with medical conditions such as anxiety or pulmonary disease.