Nitrous oxide administration in the presence of subcutaneous emphysema: an experimental model.

Adverse effects may occur when patients with air in the pleural space or in the cerebral ventricles breathe nitrous oxide. We developed an animal model to learn whether similar adverse effects are associated with the inhalation of nitrous oxide when air is present in the subcutaneous space. We induced extensive subcutaneous emphysema in swine and measured oxygen and carbon dioxide tensions in systemic arterial and mixed venous blood; cardiac output; intravascular, airway, and pre-sternal subcutaneous pressures; total pulmonary-thoracic static compliance; and thoracic girth before and after a 45 minute period of breathing 75 per cent nitrous oxide in oxygen. Cardiac output decreased from 3.13 +/- 0.51 l/min to 2.40 +/- 0.62 l/min (p less than 0.05); no other values changed significantly. No significant adverse cardiorespiratory effects resulted from the transfer of inhaled nitrous oxide to the subcutaneous space in this animal model.