To the Editor:
We read with interest the study by Monsel et al.1 on the relationship between tapered-cuff tracheal tube and early postoperative pneumonia. The authors should be congratulated for the excellent work they did.
They found no significant difference in the postoperative pneumonia rate or in the microaspiration of gastric contents and oropharyngeal secretions between patients intubated with tapered tracheal tubes and those intubated with standard tracheal tubes. They recorded cuff pressure (Pcuff) for 5 h and reported that the percentage of time spent with overinflation of tracheal cuff (Pcuff more than 30 cm H2O) was significantly higher in the tapered compared with the standard groups. They suggested that the higher variations in Pcuff might have been related to the tapered-cuff shape and could explain the negative results of their study. However, in our opinion, the cause-to-effect relationship between the tapered-cuff shape and overinflation of the tracheal cuff is unlikely. First, the percentage of time spent with underinflation was low and not significantly different between the two groups, which is against this hypothesis. Second, Pcuff is tightly correlated to airway pressure (Paw). Therefore, no valuable conclusion could be drawn without information on Paw in the two study groups. The significantly higher positive end-expiratory pressure reported in the tapered compared with the standard groups suggests that Paw might have been also higher in the intervention group. Have the authors recorded Paw during Pcuff recording? If not, could they at least provide the data usually recorded by nurses every 2 to 4 h regarding Paw?
Two previous prospective studies including a large number of patients in which Pcuff and Paw were continuously recorded for 24 h did not find any impact of tapered-cuff shape on time spent with overinflation, underinflation, or Pcuff variations.2,3
The authors concluded that tapered shape had no significant impact on microaspiration of gastric contents or oropharyngeal secretions. However, pepsin and α-amylase were only measured at two time points (once per day, during two consecutive days). It is well known that microaspiration is not a constant phenomenon, and to evaluate it accurately, one must measure it in consecutive tracheal aspirates during at least 24 to 48 h.4 Measuring these markers at several time points allows identification of those patients with abundant microaspiration, i.e., the presence of pepsin or α-amylase at significant concentrations in more than 30% of tracheal aspirates, and a higher risk of ventilator-associated pneumonia. Microaspiration is very common in intubated critically ill patients, but only a few patients develop subsequent ventilator-associated pneumonia. Previous animal studies clearly showed that a higher concentration of bacteria in the lower respiratory tract was associated with an increased risk of pneumonia.5 One could argue that microaspiration could not be completely prevented in intubated patients but only reduced using different preventive measures. Therefore, accurate quantification of microaspiration in intubated critically ill patients is a key point in evaluating the efficiency of preventive measures aiming at reducing microaspiration.6
Our group performed a large randomized controlled multicenter study to evaluate the impact of tapered-cuff shape on microaspiration of gastric content.7 Pepsin and α-amylase were quantitatively measured in all tracheal aspirates during 48 h. The results of the BestCuff study will be helpful to determine the efficiency of tapered-cuff shape in reducing microaspiration.
Dr. Nseir received funding (lecture) from Medtronic (Dublin, Ireland). The other authors declare no competing interests.