Spontaneous ventilation with halothane in children : a comparative study between endotracheal tube and laryngeal mask airway

It has been reported that, in children breathing spontaneously via an endotracheal tube, halothane depresses ventilation with paradoxic inspiratory movement. Endotracheal tubes have a higher airflow resistance than do laryngeal mask airways (LMAs). Therefore, the aim of this study was to compare spontaneous ventilation via the LMA with that via the endotracheal tube in children anesthetized with halothane. The authors studied two groups of 6-24-month-old children with no cardiorespiratory and neurologic disorders, undergoing elective minor surgery with halothane anesthesia: one group breathing via LMA (n = 10) and one group breathing via endotracheal tube (n = 10). They measured tidal volume, respiratory rate, minute ventilation, and end-tidal CO2. They assessed paradoxic inspiratory movement using amplitude index and phase delay index. Age and weight were similar in both groups. Mean +/- SD tidal volume (7.5 +/- 1.9 ml/kg in the LMA group vs. 5.3 +/- 1.1 ml/kg in the endotracheal tube group; P < 0.05) and minute ventilation (325 +/- 105 ml.min-1.kg-1 in the LMA group vs. 246 +/- 38 ml.min-1.kg-1 in the endotracheal tube group; P < 0.05) were lower in the endotracheal tube group. The phase delay index (18 +/- 11% in the LMA group vs. 41 +/- 19% in the endotracheal tube group; P < 0.05) and the amplitude index (25 +/- 43% in the LMA group vs. 74 +/- 72% in the endotracheal tube group; P < 0.05) were significantly smaller with the LMA than with the endotracheal tube. In 6-24-month-old children anesthetized with halothane, paradoxic inspiratory movement is less when breathing through an LMA than through an endotracheal tube.