The effects of nitrous oxide administration in the healthy elderly: N2O elimination and alveolar CO2.

Healthy young and elderly males were administered sedative concentrations of nitrous oxide/oxygen (N(2)O/O(2)) under a protocol designed to mimic that used in a dental operatory. Samples of end-tidal expired gas were taken at the end of 30-minutes inhalation of, and periodically for 70 minutes after withdrawal from, nitrous oxide/oxygen. Samples were analyzed to monitor the decline of alveolar nitrous oxide levels and any changes in alveolar carbon dioxide levels, to determine if there were any age-related differences. The fall in alveolar N(2)O following cessation of administration was rapid, and in a double-exponental manner as was expected. No age-related difference in N(2)O decline was observed. Alveolar carbon dioxide (CO(2)) levels were lower and more variable in the elderly group. Both groups exhibited elevated CO(2) levels at the end of the N(2)O period, and an unexplained rise in CO(2) at approximately 30 min post N(2)O.