Inhalation

Nitrous oxide ("laughing gas") has been used recreationally since 1899 for its ability to induce euphoria, hallucinogenic states and relaxation, and is legal in some countries.

Helium can be inhaled to give the voice a reedy, duck-like quality, but this can be dangerous as the gas is an asphyxiant and displaces the oxygen needed for normal respiration.

Gases and other drugs used in anaesthesia include oxygen, nitrous oxide, helium, xenon, volatile anaesthetic agents.

Then takes place the onset of contraction of the thoracic diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's law.

It may occur in partial obstruction of a large airway, as in e.g. congenital lobar emphysema, bronchial atresia and mucus plugs in asthma.