• C Keller, H J Sparr, T J Luger, and J Brimacombe.
• Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University, Innsbruck, Austria.
• Can J Anaesth. 1998 Jun 1;45(6):564-7.

PurposeTo compare patient outcomes for positive pressure ventilation (PPV) and spontaneous ventilation (SV) in non-paralysed patients with the LMA using either isoflurane or sevoflurane anaesthesia.MethodsOne hundred and sixty four adult patients were studied. Anaesthesia was with fentanyl/propofol and N2O 66% in O2 with 0.75 MAC isoflurane or sevoflurane and either PPV or SV. Positive pressure ventilation was with tidal volumes of 6-8 ml.kg-1. Peak airway pressures were < 15 cm H2O. Patients were evaluated for airway problems, cardiorespiratory effects, and anaesthesia emergence times.ResultsThere were no failed episodes of PPV or SV. Gastric insufflation was not detected by epigastric auscultation. Airway problems and cardiovascular effects were similar among groups. During maintenance: SpO2 was greater in the PPV group than in the SV group (98.4 vs 97%, P < 0.001); also, (PETCO2) (34 vs 43 mmHg) and the respiratory rate (RR) (15 vs 19 min-1) were higher and the minute ventilation (MV) (5.7 vs 7.2 L) were lower in the SV groups (P < 0.0001). Shorter times to LMA removal and orientation were observed in the sevoflurane groups (P < 0.0001).ConclusionsPatient outcome is similar for SV and PPV in non-paralysed adult patients with the LMA. Isoflurane and sevoflurane at 0.75 MAC provide suitable conditions for maintenance and emergence, but emergence is more rapid with sevoflurane.

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