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A reply
- John E. Smith, Jeff L. Tong (22 November 2008)
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Are pathways of the endotracheal tube true causes for difference in complications of nasal intubatio
- Fushan Xue, Xu Liao, Yanming Zhang (9 May 2008)
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John E. Smith , Jeff L. Tong
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Editor - We thank Professor Xue and colleagues for their interest1 in our article, but it is unfortunate that only the first paragraph of their 1,400 word letter was relevant to the focus of our manuscript.2 The purpose of our investigation was to determine the frequency with which endotracheal tubes traversed the upper nasal pathway, because when they traverse this pathway, there is a far greater chance of damage to the middle turbinate,3, 4 than if they traverse the lower nasal pathway. The observation that intubation of the upper nasal pathway caused significantly more epistaxes was an unanticipated bonus, but it was not the reason for our study. We reported this significant event in our paper and added the other non-significant epistaxis data for completeness. We did not claim to have proved or to have disproved any epistaxis hypothesis, but merely indicated when our data was consistent with other work.5 Overall, there was a significant difference between epistaxis in upper and lower pathway cannulation, but as we indicated in the paper, the number of preformed and thermosoftened preformed tubes passing though the lower pathway were too small (16.7% and 20% respectively) for meaningful statistical analysis on their own. However, when reinforced tubes were considered, there was a significant difference between epistaxis in upper and lower pathway cannulation (Table 2, second comparison). Hence the statement by Dr Hue et al that “we consider that the differences in incidence of epistaxis …. should be contributed to the differences in texture, tip shape and flexibility between the tubes, rather than the differences in anatomical structures…..” is patently incorrect. In a randomized controlled trial, sample size is based on the primary focus of the investigation and not on secondary factors, particularly when the investigators are not aware of the existence of a particular secondary factor. Hence the possibility of a Beta error with regard to the epistaxis data is irrelevant here, and the more astute question to ask is whether or not an alpha error has occurred, i.e. a significant result when the null hypothesis is in fact true. It is well recognised that stiffening of the tube recurs rapidly as the tube cools. We therefore assumed it would be obvious to readers that following thermosoftening, intubation would be performed promptly and without delay. Details of the thermosoftening process used are described in paragraph 4 of our Methods. The laryngeal view, the alignment of the tip of the tube to the glottis, the times required for intubation, auxiliary manoeuvres like the use of Magils forceps, external laryngeal manipulation and adjustment of head/neck position to facilitate entry of the tube into the larynx were all completely irrelevant to our study which was concerned with the nasal pathway taken by the tube. The size of tubes used (7 mm and 6 mm tubes, for males and females respectively) are perfectly satisfactory for routine nasal intubation. There is seldom any need to resort to 7.5 mm tubes, which are more likely to cause nasal damage.6 We discussed the fact that the external diameter of the reinforced tube is greater than that of the preformed tube in the first paragraph of Discussion. All patients received normal post-operative care. Following routine enquires and appropriate clinical examination, the clinical data were recorded in the patients’ notes, as normal, but were not recorded as part of the clinical investigation, as this information was not relevant to the study in hand. We certainly did not perform nasal endoscopy as part of our post-operative care since we consider that it is unethical to subject patients to unnecessary interventions. The nasendoscopy findings following nasal intubation have been well documented in a widely quoted paper7 and we do not believe that our repeating this study would have added any useful information to our study, which aimed to identify the nasal pathway was taken by the tube. When reading a scientific paper, it is important to recognize the precise nature of the research question being asked and to differentiate this from other research questions that are not of direct concern to this key question. References 1. Xue F, Liao X, Zhang Y. Are pathways of the endotracheal tube true causes for difference in complications of nasal intubation. http://bja.oxfordjournals.org/cgi/eletters/100/2/269. May 2008. 2. Ahmed-Nusrath A, Tong JL, Smith JE. Pathways for nasal intubation: A comparison of three endotracheal tubes. Br J Anaesth 2008; 100: 269-74. 3. Patir S, Ho EC, Herdman RC. Partial middle turbinectomy by nasotracheal intubation. Ear Nose Throat J 2006; 85: 382–3. 4. Hall CEJ, Shutt LE. Nasotracheal intubation for head and neck surgery. Anaesthesia 2003; 58: 249–56. 5. Coe TR, Human M. The peri-operative complications of nasal intubation: a comparison of nostril side. Anaesthesia 2001; 56: 447–50. 6. Tong JL. Smaller is better through the nose. Anesthesia and Analgesia 2008; 106: 1925. 7. O’Connell, Stevenson PS, Stokes MA. Pathological changes associated with short-term nasal intubation. Anaesthesia 1996; 51: 347-50 Conflict of Interest:None declared |
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Fushan Xue, Anaesthesiology Professor, Xu Liao, Yanming Zhang
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Are pathways of the endotracheal tube true causes for difference in complications of nasal intubation? Editor—We read with interest the paper of Ahmed-Nusrath et al.1 In this randomised study, they compared the frequency with which the preformed, reinforced, and thermosoftened preformed tubes pass through upper and lower pathways in nasal intubation, and concluded that the endotracheal tubes, particularly preformed tubes, frequently took the less favourable pathway, in spite of specific attempts to avoid this. However, several issues of study design merit further comment. The MallinckrodtTM preformed nasal tube is a cuffed PVC tube with a stiff texture and requires the thermosoftening treatment before intubation to decrease the incidence of epistaxis and nasal damage.2 However, it must be emphasized that the tube will cool to the ambient temperature of the room very quickly and consequently, become stiffer. Accordingly, if the intubation is to be delayed for a long time because of a difficult manipulation, the positive effects of the thermosoftening tube will be negated by the time taken to attempt reintubation.3 This may be a reason for no significant differences in all observed variables between the preformed and thermosoftened preformed tubes. The details regarding the thermosoftening treatment of the preformed tube were not, unfortunately, provided. Of the PVC tubes available, the Portex Ivory preformed cuffed tube has been shown to be the most malleable for the nasal passage and yet retain the overall curve that is required for ease of laryngeal nasal intubation.4 George demonstrated that the incidence of minor epistaxis only was 1% when size 6 or 7 mm heat-softened Ivory preformed cuffed tubes were used. The Portex preformed latex cuffed tube is another suitable selection for the nasal intubation due to a soft texture and a good malleable.5 If these tubes were used as the control, the results obtained in this study might have greater clinical values. We are also very interested in selection methods of the nasal tube size which sizes 7 and 6 mm tubes were used for male and female patients, respectively. They seemed to have selected smaller tube sizes for the adult patients with a mean weight of > 70 kg compared with those used in other previous studies.3,6-9 In the vast majority of adults, sizes 7 to 7.5 mm nasal tube can smoothly pass the nares. At same size, moreover, the external diameter of the MallinckrodtTM reinforced tube is slightly larger than that of preformed nasal tube. These factors could arguably influence the passage of the tube through the nasal meatus and the occurrence of nasal trauma. In this study, the authors used the two steps to overcome resistance in advancement of nasal tube. A slight rotation of the tube is another simple measure to solve this difficulty.2,9 The resistance for the passage of the tube (slight or moderate) and severity of epistaxis were not clearly defined. The authors did not also describe the laryngeal views obtained, alignment of the nasal tube tip with the glottis, times required for successful intubation and auxiliary maneuvers adopted (such as use of the Magill forceps, left or right rotation of the nasal tube at the external naris, external laryngeal manipulation, adjustment of head-neck position and etc) during the nasal intubation.9 After extubation, nature of the nasal damage (none, bruise, crust, and tearing of mucosa) should be examined with the nasal endoscopy by the independent investigators who were blind to study scheme. Immediately after surgery, nasal patency, bleeding and pain were also required to be blindly checked.3 The postoperative fellow-up of the nasal complications was important, but was evidently ignored in this study. Based on the assumption that a 50% reduction in the tubes passing the upper pathway would be a clinically important difference between the groups, a sample size of 30 patients each group was selected to detect this difference with a power of 80% and a P value of 0.05. However, the power of the study is not sufficient to detect a statistically significant in the incidence of epistaxis between groups, though number of epistaxes caused by passing tubes were apparently greater in the use of the preformed tubes than in the use of the reinforced and thermosoftened preformed tubes. In this study, when the preformed, reinforced and thermosoftened preformed tubes were used, the incidences of epistaxis were 60% (18/30), 40% (12/30) and 36.7% (11/30), respectively. Assuming that this difference is actual index in the whole population, 96 patients per group would be required to have an 80% chance of finding a difference. Likewise, the small sample size of studied population might also have prevented authors from excluding a type II error when comparing the incidences of epistaxis between left and right nostril intubations, and evaluating the proportions of the preformed and thermosoftened preformed tubes causing epistaxis between upper and lower pathways. Therefore, we do not agree the conclusion of this study that the two nostrils have a similar incidence of epistaxis, when the tube is passed through either nostril with the bevel facing to the left. In the study of Coe et al.,10 use of Portex Ivory preformed cuffed tubes with the soft texture and a selection of small tube sizes for the adult patients might have decreased the nasal trauma caused by passing tubes and excluded the differences in incidence of epistaxis between the intubations through two nostrils. Standard teaching of nasal intubation recommends that when the tube is introduced through the nostril, its bevel should face the turbinates to reduce damage to them by the sharper tube tip, especially when a stiff PVC nasal tube is used.2 The authors stated that tubes passing through the upper pathway caused significantly more epistaxis than tubes passing through the lower pathway. In this study, 83.3% of preformed tubes and 80% of thermosoftened preformed tubes passed through the upper pathway compared with 43.3% of reinforced tubes. Therefore, we consider that the differences in incidences of epistaxis between upper and lower pathways should be contributed to the differences in the texture, tip shape and flexibility between the tubes, rather than the differences in anatomical structures between two pathways. The preformed tube has a stiffer texture, a stronger shearing tip and a lower flexibility compared with the reinforced tube. Additionally, the soft tip of the reinforced tube also helps to reduce epistaxis and nasal damage.9 In this study, a high incidence of (62/90) of the tubes passing along upper pathway following the standardized insertion technique may mainly be related to a selection of smaller tube sizes for adult patients. It is generally believed that the causes of epistaxis during nasal intubation are multiple factors.3,6,8 A significant weakness of this study is not to identify the reciprocal effects of the tube types, thermosoftening treatment of the nasal tube, pathways of the tubes and ease of the tube insertion on incidence of epistaxis. The authors did also not attempt o identify the independent risk factors for epistaxis using stepwise selection multiple logistic regression analysis. The volume and page number of reference 5 are incorrect. F. S. Xue X. Liao Y. M. Zhang Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing, People’s Republic of China. E-mail: fruitxue@yahoo.com.cn or profxuefushan@xxmu.edu.cn References 1. Ahmed-Nusrath A, Tong JL, Smith JE. Pathways through the nose for nasal intubation: a comparison of three endotracheal tubes. Br J Anaesth 2008; 100:269-74. 2. Berry JM. Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single-lumen tube). In: Hagberg CA, Benumof’s Airway Management: Principles and Practice, 2ed. St Louis, MO: Mosby, 2007; 390- 1. 3. Kim YC, Lee SH, Noh GJ, et al. Thermosoftening treatment of the nasotracheal tube before intubation can reduce epistaxis and nasal damage. Anesth Analg 2000; 91:698-701. 4. Hall CEJ, Shutt LE. Nasotracheal intubation for head and neck surgery. Anaesthesia 2003, 58: 249-56. 5. Xue F, Zhang G, Liu J, Li X, Sun H, Wang X, Li C, Liu K, Xu Y, Liu Y. A clinical assessment of the Glidescope videolaryngoscope in nasotracheal intubation with general anesthesia. J Clin Anesth 2006; 18:611-5. 6. O'Hanlon J, Harper KW. Epistaxis and nasotracheal intubation–prevention with vasoconstrictor spray. Ir J Med Sci 1994; 163:58-60. 7. O'Connell JE, Stevenson DS, Stokes MA. Pathological changes associated with short-term nasal intubation. Anaesthesia 1996; 52: 347-50. 8. Sim WS, Chung IS, Chin JU, Park YS, Cha KJ, Lee SC, Kim YC. Risk factors for epistaxis during nasotracheal intubation. Anaesth Intensive Care 2002;30:449-52. 9. Kihara S, Komatsuzaki T, Brimacombe JR, Yaguchi Y, Taguchi N, Watanabe S. A silicone-based wire-reinforced tracheal tube with a hemispherical bevel reduces nasal morbidity for nasotracheal intubation. Anesth Analg 2003; 97:1488-91. 10. Coe TR, Human M. The perioperative complications of nasal intubation: a comparison of nostril side. Anaesthesia 2001; 56: 447-50. Conflict of Interest:None declared |
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