A reply

Abstract

We felt that it was ethically necessary to state specifically in the protocol that ‘No undue force was used during laryngoscopy to avoid possible damage to the teeth or the oropharynx’. We had no intention to imply that less than adequate force was used, or are Drs Dravid and Popat implying that we should have used undue force? They state that our study was biased since manoeuvring of the metal handle of the intubating laryngeal mask was allowed, whereas cricoid pressure was not allowed for laryngoscopy. Cricoid pressure could indeed have increased the success rate of tracheal intubation in the laryngoscope group, but one can then argue that other methods, such as the use of BURP (backward, upward and rightward pressure on the thyroid cartilage) [1], the McCoy laryngoscope or a lighted stylet could also have increased the success rate. We considered that manoeuvring the handle in the laryngeal mask group was balanced by the use of the gum elastic bougie in the laryngoscopy group. Had any additional procedure (e.g. cricoid pressure) been added to the laryngoscope group, couldn't one have argued that the study was biased toward the laryngoscopy group? We decided to allow manoeuvring of the handle of the laryngeal mask, since the procedure is a useful feature of the device – otherwise, isn't it akin to prohibiting the rotation of the bougie to adjust the direction of the angled tip or prohibiting leverage of the blade tip of the McCoy laryngoscope? We did not show time and VAS for tracheal intubation through the laryngeal mask for the patients in whom tracheal intubation using a laryngoscope and bougie had failed, since this part was not the main interest of the study. Nevertheless, time (median = 34 s; 95% CI for the median: 19–45 s) and the ease (median VAS = 23 mm; 95% CI = 13–100 mm) in this group of patients were similar to those who were originally allocated to the use of the laryngeal mask (median time = 32 s; 95% CI = 25–50 s; median VAS = 18 mm; 95% CI = 12–40 mm) [2]. The same type and size of tracheal tube was used in the two groups; the same investigator carried out all the intubations in both groups. We cannot define the level of our experience, but one may acknowledge that we are at least not inexperienced by seeing the number of our studies published in this field. Is there any situation where the VAS for ease of tracheal intubation is in the middle (e.g. slightly easy, moderately difficult) after failed intubation? In this setting, the score should automatically be the maximum if it was impossible to intubate. We calculated the required number of patients based on the standard deviation, since the data in our preliminary study were normally distributed [2]. However, a nonparametric test was used for comparison, since the data in the formal study were not normally distributed. Drs Dravid and Popat did not suggest an alternative method of power calculation (which must be calculated before the start of the formal study, when it is uncertain if the data in the formal study are normally distributed). Interestingly, in a recent study they themselves did power analysis based on the mean and standard deviation and yet compared median values [3]. We do not recommend routine use of the intubating laryngeal mask for tracheal intubation. We feel that one should take several other factors into consideration. For example, the device may not always be available, it may be contraindicated, or its running cost may be high. We believe that it is up to each clinician to decide if there is a value of the method described in our article.