Nasal ventilation is more effective than combined oral-nasal ventilation during induction of general anesthesia in adult subjects.

BACKGROUND The authors hypothesized that nasal mask ventilation may be more effective than combined oral-nasal mask ventilation during induction of general anesthesia. They tested this hypothesis by comparing the volume of carbon dioxide removed per breath with nasal versus combined oral-nasal mask ventilation in nonparalyzed, apneic, adult subjects during induction of general anesthesia. METHODS Fifteen adult subjects receiving general anesthesia were ventilated first with a combined oral-nasal mask and then with only a nasal mask. The patient's head was maintained in a neutral position, without head extension or lower jaw thrust. Respiratory parameters were recorded simultaneously from both the nasal and oral masks regardless of ventilation approach. RESULTS The volume of carbon dioxide removed per breath during nasal mask ventilation (median, 5.0 ml; interquartile range, 3.4-8.8 ml) was significantly larger than that during combined oral-nasal mask ventilation (median, 0.0 ml; interquartile range, 0.0-0.4 ml; P = 0.001); even the peak inspiratory airway pressure during nasal ventilation (16.7 +/- 2.7 cm H2O) was lower than that during combined oral-nasal ventilation (24.5 +/- 4.7 cm H2O; P = 0.002). The expiratory tidal volume during nasal ventilation (259.8 +/- 134.2 ml) was also larger than that during combined oral-nasal ventilation (98.9 +/- 103.4 ml; P = 0.003). CONCLUSIONS Nasal mask ventilation was more effective than combined oral-nasal mask ventilation in apneic, nonparalyzed, adult subjects during induction of general anesthesia. The authors suggest that nasal mask ventilation, rather than full facemask ventilation, be considered during induction of anesthesia.