Use of laryngeal mask airway compared to endotracheal tube with positive-pressure ventilation in anesthetized swine.

OBJECTIVE

To compare the ease of placement and ventilatory parameters of a laryngeal mask airway (LMA) with an endotracheal tube (ETT) in anesthetized swine during positive-pressure ventilation (PPV).

STUDY DESIGN

Prospective, randomized, experimental trial.

ANIMALS

Nine young domestic swine, weighing between 40 and 49 kg (mean 45.1 kg), being used for a separate terminal surgical study.

METHODS

The pigs were immobilized with tiletamine/zolazepam, 2.7-3.6 mg kg(-1), intramuscularly, followed by isoflurane in oxygen delivered by facemask. The lungs were mechanically ventilated through an ETT or an LMA, in random order, during the anesthetic period. Positive-pressure ventilation was adjusted to maintain end-tidal CO2 (Pe'CO2) between 35 and 45 mmHg, with peak inspiratory pressure (P(insp)) of 15-23 cmH2O. Buprenorphine, 0.3 mg intramuscularly, was given to each pig after instrumentation. Isoflurane vaporizer settings were adjusted to maintain a surgical plane of anesthesia. Respiratory rate (RR), tidal volume (V(T)), minute volume (V(E)), and Pe'CO2 were measured and recorded at 5-minute intervals. After the collection of 1 hour of data, the alternate airway was placed. Swine were given at least 30 minutes to stabilize and another hour of data were recorded. At the time of airway placement, the ease of placement was assessed based on time and the number of personnel required. Data were analyzed using paired Student's t-test or Wilcoxon signed rank test where appropriate.

RESULTS

Laryngeal mask airways were significantly easier to place than ETT. Values for V(T) and V(E) were not significantly different between treatments. Peak inspiratory pressures were higher in ETT-ventilated swine.

CONCLUSIONS AND CLINICAL RELEVANCE

An LMA may be used as an alternative to an ETT in mechanically-ventilated anesthetized swine. Use of an LMA may reduce time and personnel required for placement of an airway.