Background and Goal of Study: Single-limb ventilatory circuits are suggested to be more thermally efficient than conventional two-limb circuits (1). The aim of this study was to compare the effect on the airway climate of these two types of circuit in patients undergoing short peripheral surgery under low-flow anesthesia.
Materials and Methods: After IRB approval and informed consent, 24 ASA I/II patients undergoing thyroidectomy or rhinoseptoplasty were prospectively included (50 ± 16yr, 62 ± 16 kg) and randomized into 2 groups: doublelimb (Europe Medical®) and single-limb circuit (Vital Signs®). The mean inspiratory values of the temperature, relative (RH) and absolute (AH) humidities were measured between the breathing filter (Clear-Guard Mid, Intersurgical®) and the catheter mount. Data were obtained using the Gibeck Humidity Sensor System (Gibeck®) inserted between the filter and the catheter mount. An oesophageal probe was inserted to assess the central core temperature of each patient. The circuit was closed immediately after tracheal intubation (T0) (Fresh gaz flow: 1 L/min, 50% air/50% oxygen mixture, RR: 12 cycles/min, PEEP: 0 cmH2O). The tidal volume was adjusted to maintain ETCO2 at 35mmHg. Sevoflurane (0.8 MAC) and remifentanil (0.15-0.20 μg/kg/min) were used for maintenance of anaesthesia. Data were obtained at T0, T5 and then every 15 minutes until the end of the procedure.
Results and Discussions:
Conclusion(s): Single limb circuits allowed higher inspiratory temperatures and reduced the patient temperature drop during anaesthesia.
1 Branson RD, Campbell RS, Davis K et al. Anesth. Intensive Care