Generally, there are two ways to carry out hypoventilation: at high lung volume or at low lung volume. At high lung volume, breath holdings are performed with the lungs full of air (inhalation then breath hold). Conversely, during hypoventilation at low lung volume, breath holdings are performed with the lung half full of air. To do so, one has to first exhale normally, without forcing, then hold one's breath. This is called the exhale-hold technique.