ABSTRACT
Exhaled volumes were measured in 8 children during uptake and elimination of 3 percent and 75 percent N2O, using a volume-controlled ventilator. Absorption of 75 percent N2O during induction reduced the exhaled minute volume, which fell a mean of 16 percent in the 1st or 2nd minute and returned to normal by 15 to 20 minutes. Elimination was the mirror image of uptake; the mean increase in the exhaled minute volume was 13 percent. The concentration effect during uptake was measured (3 percent versus 75 percent N2O) and the data were used to calculate a fall in alveolar volume of at least 8 percent by the 2nd minute of uptake. The type of ventilation (volume-limited, pressure-limited, or spontaneous) was seen to have a modifying role on the respiratory pattern caused by the absorbed and excreted volume of N2O.
Subject(s)
Anesthesia, Inhalation , Lung/metabolism , Nitrous Oxide/metabolism , Child , Child, Preschool , Clinical Trials as Topic , Dose-Response Relationship, Drug , Humans , Infant , Lung Volume Measurements , Respiration/drug effectsABSTRACT
An in-vitro experiment demonstrated the concentration effect of N2O (3% versus 75%) during elimination and during uptake. Other pulmonary absorption-excretion phenomena also occur simultaneously, as paired events during uptake and then during elimination:diffusion hyperoxia and diffusion anoxia; alveolar concentration of CO2, and alveolar dilution of CO2. These clinical phenomena, as well as the second gas effect, are all related, and the pulmonary absorption-excretion volume is found to depend in part on the type of ventilation:volume controlled, pressure controlled, or spontaneous respiration.
