Participating interns developed mask ventilation skills faster than orotracheal intubation skills, and there was more variability in the rate at which intubation skills developed. A median of 29 procedures was required to achieve an 80% orotracheal intubation success rate.

A dvantages of muscle relaxants for face-mask ventilation have been suggested in recent studies. But their direct effects are unclear because those studies did not control mechanical factors that influence ventilation. A hypothesis was tested that muscle relaxants, either rocuronium or succinylcholine, improve mask ventilation. Tidal volumes during face-mask ventilation were measured in anesthetized adult patients with a normal upper airway anatomy while maintaining the neutral head and mandible position and the airway pressures of a ventilator before and during muscle paralysis was induced by either rocuronium (n = 14) or succinylcholine (n = 17). Tidal volumes of oral and nasal airway routes were separately measured by Fleisch no. 2 pneumotachographs (4719; Hans Rudolph, Kansas City, Mo) using a custommade oronasal positioning full face mask. The behavior of the oral airway was observed by an endoscope (FB10X; Pentax, Tokyo, Japan; 3-mm outer diameter) in 6 other patients receiving succinylcholine. Total oral and nasal tidal volumes did not markedly change at complete muscle paralysis with rocuronium. By contrast, succinylcholine markedly increased total tidal volume after being administered (mean, 4.2 [SD, 2.1] vs 5.4 [SD, 2.6] mL/kg) because of increases in ventilation through both airway routes. Abrupt tidal volume increased more through the oral airway route than the nasal. Dilation of the space at the isthmus of the fauces was endoscopically seen during pharyngeal fasciculation in all 6 patients. It was concluded that rocuronium did not cause facemask ventilation to deteriorate, and it improved it after succinylcholine administration combined with airway dilation during pharyngeal fasciculation, an effect that continued to a lesser degree after resolution of the fasciculation. COMMENTThis elegant and important study by the Japanese investigators who previously greatly advanced our understanding of the airway anatomy and dynamics involved in obstructive sleep apnea has now explored the effects of face-mask positivepressure ventilation (FMV) in adults at low risk for difficult mask ventilation (DMV). Recently, some investigators reported that muscle relaxants improve FMV. These studies, however, did not control for changes in head and mandible position, nor did they measure the contribution of oral and nasal ventilation. The current investigators studied 31 subjects with normal upper airway anatomy and held the head and mandible in fixed neutral position during pressure-controlled ventilation with the oral aperture stented open via a 15-mm mouthpiece. They found that administration of rocuronium had no effect, but succinylcholine transiently improved FMV by 30% during the fasciculation period, with a greater airflow augmentation noted through the oral route compared with the nasal route. The opening force produced by pharyngeal fasciculation was impressive and may explain the reversal of DMV after succinylcholine injection in the study by Amanthieu and colleagues. 1 Should we discard the traditional anesthet...

Background: Recent studies suggest advantages of muscle relaxants for facemask ventilation. However, direct effects of muscle relaxants on mask ventilation remain unclear because these studies did not control mechanical factors influencing ventilation. We tested a hypothesis that muscle relaxants, either rocuronium or succinylcholine, improve mask ventilation. Methods: In anesthetized adult persons with normal upper airway anatomy, tidal volumes during facemask ventilation were measured while maintaining the neutral head and mandible positions and the airway pressures of a ventilator before and during muscle paralysis induced by either rocuronium (n ϭ 14) or succinylcholine (n ϭ 17). Tidal volumes of oral and nasal airway routes were separately measured with a custom-made oronasal portioning full facemask. Behavior of the oral airway was observed by an endoscope in six additional subjects receiving succinylcholine. Results: Total, oral, and nasal tidal volumes did not significantly change at complete muscle paralysis with rocuronium. In contrast, succinylcholine significantly increased total tidal volumes at 60 s after its administration (mean Ϯ SD; 4.2 Ϯ 2.1 vs. 5.4 Ϯ 2.6 ml/kg, P ϭ 0.02) because of increases of ventilation through both airway routes. Abrupt tidal volume increase occurred more through oral airway route than nasal route. Dila-

Dyspnea and pain have a number of similarities. Recent brain imaging experiments showed that similar cortical regions are activated by the perceptions of dyspnea and pain. We tested the hypothesis that an individual's pain sensitivity might parallel the individual's dyspnea sensitivity. Studies were carried out in 52 young healthy subjects. Each subject experienced experimentally induced pain and dyspnea. Pain was induced by a cold-pressor test and dyspnea was induced by breathholding while the unpleasant experience of pain and dyspnea was assessed by using a Visual Analogue Scale (VAS). The times from the start of cold stimulation and breathholding to the onset of uncomfortable sensation (pain threshold time and the period of no respiratory sensation, respectively) and to the limit of tolerance (pain endurance time and total breathholding time, respectively) were also measured. In response to cold pain stimulation, a behavioral dichotomy (pain-tolerant and pain-sensitive) was observed. The period of no respiratory sensation was significantly shorter in the PS (pain-sensitive) group than in the PT (pain-tolerant) group (16.9+/-3.8 vs. 19.6+/-5.3 s: P<0.05), whereas no significant difference in the total breathholding time was found between the PT and PS groups. A significant correlation was observed between the pain threshold time and the period of no respiratory sensation in both the PT and PS groups. However, no significant association was observed between pain and dyspnea tolerance in both groups. In conclusion, an individual's pain threshold is correlated to the individual's dyspnea threshold, but the individual's pain tolerance is not consistently correlated to the individual's dyspnea tolerance.

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