In this study, the PFT tube caused significantly less trauma and bleeding compared with a standard-tip tube during nasal intubation. The PFT tube seemed to glide rather than scrape over mucosal surfaces and surface irregularities such as the tracheal rings, and it was this property to which the observed differences were attributed. It was evident when reviewing the videos that the curved and slightly elevated tip of the PFT tube allows it to “surf” or “ski” along irregular surfaces and mucosal membranes, leading to less catching on the upper airway anatomical structures as viewed on the following links to our videos:
It was also noted that the path of travel of the PFT tube would alter more readily than the standard-tip tube. When the tube encountered resistance, the PFT tube tip would bend and redirect the tube, while the standard tube seemed to wedge against and bruise the involved mucosa. Sometimes the standard tube would tear the mucosa covering harder structures protruding into its path. This difference in flexibility was also evident as the tube passed the arytenoid cartilages. It was frequently noted that the PFT tube would glide over the cartilages and through the glottic opening, while the standard-tip tube would more frequently get caught against the cartilage structures, and then with added pressure or rotation of the tube, abruptly pass the cartilage structure. It should be noted, however, that in many cases both types of tubes, when advanced slowly under fiber-optic supervision, passed through the airway with very little or no trauma or bleeding.
VASs have been used successfully and reliably for many years for the assessment of patient subjective findings such as pain. The authors undertook the study assuming that a VAS might also be a useful tool to assess bleeding and trauma, encouraged by the opinions of other authors and their experiences using VASs for subjective yet quantifiable data collection. Marsh-Richard et al have summarized some satisfactory uses of both the VAS and DVAS (discrete visual analogue scale). Both their and our search of PubMed confirm that indeed the VAS has been used and validated in its use for the assessment of quantifiable yet subjective observations in a number of areas dealing with parameters other than pain. These observations included health, self-perception, physician rapport, and assessment of symptoms and side-effects after pharmacological manipulations.17
The conduct of this study and our subsequent findings provided no indication that the use of a VAS suffered any obvious limitations during this study; indeed, it seemed to be a useful and easily interpreted tool for our researchers to use. The primary ANOVA analysis did show a difference between the 2 groups in both bleeding and trauma. However, it is hard to give clinical meaning to a difference of 8.7 mm and 9.1 mm, respectively. When we organized our data categorically, so that patients had either evidence of bleeding or no bleeding and either signs of trauma or no signs of trauma, a very clear difference was seen. The probability of having bleeding or trauma when using the Parker tube was significantly less, P
.0001 and P
.007, respectively ( and ).
With regard to the time required for intubation, our study failed to show a significant difference between the 2 tubes. Since all the intubations were deliberately conducted slowly to facilitate accurate fiber-optic observation and recording, this was not a surprising finding. It would be interesting to see how differences in tip designs might affect the success and speed of blind nasal intubations, since that technique is still commonly used in outpatient centers, in urgent situations in the hospital, and in the field by emergency medical services personnel. The tip design directed a more centrally orientated passage of the PFT tube along the airway, and it may offer a clinical advantage over other designs for improving the success rate and speed of blind nasal intubation.
It was impossible to eliminate all bias in the current study. The distal end of both tubes could be visualized during intubation, thus permitting identification of the tube being used. We attempted to reduce or eliminate bias in the study by including one reviewer, a dental assistant, with little, if any, knowledge of intubation or the identification of the tubes used, as well as others with significant intubation experience. We were surprised by the correlation between the interclass and intraclass coefficients. Despite the variations in experience, understanding of the airway, and the process of intubation, all evaluators produced results very similar to each other.
Assessment of hard-to-quantify parameters, such as trauma, have plagued many studies. In an attempt to reduce the variability that often occurs when recording measurements having a subjective element to them, ten of the original videos were presented to the evaluators at a later date and in a different sequence, with the goal of estimating intra- and interrater reliability. We found that what was rated as moderate trauma or bleeding by an evaluator at one time was likely to be rated at the same level of trauma and bleeding by the same rater at a later date. In addition, a high degree of interrater reliability was demonstrated. What 1 rater described as moderate trauma was highly likely to be described in the same way by the other 2 evaluators. This interrater consistency not only strengthened the observational evidence that the PFT caused less trauma and bleeding during intubation, but also encouraged us to include this investigational structure in future projects of this nature.