SummaryIn a randomised cross-over study, 48 anaesthetists attempted to place a Frova single-use introducer, an Eschmann multiple-use introducer and a Portex single-use introducer in the trachea of a manikin set up to simulate a grade 3 laryngoscopic view. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). Successful placement (proportion, 95% confidence interval) of either the Frova introducer (65%, 50-77%) or the Eschmann introducer (60%, 46-73%) was significantly more likely than with the Portex introducer (8%, 3-20%). There were no significant differences between the success rates for the Frova and the Eschmann introducers. A separate experiment revealed that the peak force exerted by the Frova and Portex introducers was two to three times greater than that which could be exerted by the Eschmann introducer, p < 0.0001, indicating that the single-use introducers are more likely to cause tissue trauma during placement.

SummaryIn a randomised cross-over study, 20 anaesthetists attempted to place a multiple-or single-use bougie in the trachea of a manikin, in which a grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists made two attempts at placement with each bougie and were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates for the first attempts with the multiple-and single-use bougies were 85 and 15%, respectively [mean (95% CI) difference between the two bougies 70% (40-84%); p < 0.001]. The success rates for the second attempts were similar to those for the first attempts with both bougies. There is an increased risk of failure to intubate the trachea when using a single-use bougie, and this must be weighed against the unquantified risk of cross-infection from prions when using a multiple-use bougie.

SummaryIn a randomised cross-over study, 50 anaesthetists attempted to place a multiple-use bougie in the trachea of a manikin, when holding it at either 20 cm or 30 cm from the tip. A grade 3 laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates when held at 20 and 30 cm distance from the tip were 68 and 62%, respectively (p ¼ 0.55). In a separate experiment, multiple and single-use bougies were held at four different positions and pressed onto a disc attached to a force transducer. The peak force exerted by the single-use bougies was two to three times greater than that which could be exerted by the multiple-use bougies (p < 0.0001). Holding the bougie at either 20 or 30 cm distance from the tip is unlikely to influence bougie placement. The single-use bougie is much more likely to cause trauma to tissue during placement, particularly if held close to the tip.

Thirty anaesthetists attempted to place a derived 'optimal' curve bougie or a straight bougie in the trachea of a manikin, in a randomised cross-over study. A Grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates with the curved and straight bougies were 83 and 7%, respectively, giving a difference (95% confidence interval) of 77% (54-87%) between the two bougies (p < 0.0001). On a separate occasion, under identical laboratory conditions, 30 anaesthetists attempted to place a straight coudé (angled)-tipped bougie or a straight straight-tipped bougie in the trachea of a manikin. The success rates with the coudé- and straight-tipped bougies were 43 and 0%, respectively, giving a difference (95% confidence interval) of 43% (21-61%) between the two bougies (p < 0.001). These results suggest that bougies used to facilitate difficult intubation should be curved and have a coudé tip.

SummaryThe effect of two levels of humidification on the incidence of adverse airway events was studied in 58 adult female patients during deepening of anaesthesia using up to 12% desflurane. Humidification was provided by a breathing system filter with either low moisture-conserving performance (17.2 mg.l 21 at 0.5 l tidal volume, Group L) or high moisture-conserving performance (33.5 mg.l 21 at 0.5 l tidal volume, Group H). Forty-eight per cent of patients smoked and there were more smokers in Group L than in Group H. Adverse airway events consisted of coughing and laryngospasm. For coughing, the dominant explanator was smoking. When both humidity and age were included in the analysis, there was a significant smoking±humidity interaction (p , 0.05), such that high humidity decreased the incidence of coughing in nonsmokers but not in smokers. The incidence of laryngospasm was significantly lower in Group H than in Group L (p , 0.05). We conclude that when patients inspire high concentrations of desflurane during induction of anaesthesia, increasing humidification to the levels achieved in this study decreases the incidence of coughing among nonsmokers and of laryngospasm in both smokers and nonsmokers.