CLOSED-CIRCUIT HALOTHANE AND ENFLURANE USING AN IN-CIRCLE GOLDMAN VAPORIZER

A closed-circle absorber system incorporating an in-circle Goldman vaporizer was used to administer halothane or enflurane in oxygen to adult patients. The attained inspired and end-tidal concentrations of volatile agent after a period of stabilization at each vaporizer setting were measured by mass spectrometry. During spontaneous respiration under halothane the ranges of inspired concentrations at settings 1, 1½ and 2 were respectively 0.5–0.9%, 1.4–2.4% and 3.3–4.5%. Corresponding inspired enflurane concentrations at the same settings were 0.8–1.4%, 1.9–2.8% and 3.7–5.0%. IPPV to 5% end-tidal carbon dioxide, although increasing the inspired concentrations slightly, produced considerable increases in end-tidal concentrations. Minimal pre-oxygenation was used to assess the problem of nitrogen accumulation within the circuit. The maximum nitrogen concentration was 56%.