|Year : 2021 | Volume
| Issue : 11 | Page : 1609-1615
Comparison of anthropometric and conic beam computed tomography measurements of patients with and without difficult intubation risk according to modified mallampati score: New markers for difficult intubation
D Senol1, D Ozbag2, N Dedeoglu3, F Cevirgen2, S Toy4, M Ogeturk5, E Kose2
1 Department of Anatomy, Faculty of Medicine, Düzce University, Düzce, Turkey
2 Department of Anatomy, Faculty of Medicine, İnönü University, Malatya, Turkey
3 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Inönü University, Malatya, Turkey
4 Department of Anatomy, Faculty of Medicine, Karabük University, Karabük, Turkey
5 Department of Anatomy, Faculty of Medicine, Fırat University, Elazığ, Turkey
|Date of Submission||23-Dec-2020|
|Date of Acceptance||27-Feb-2021|
|Date of Web Publication||15-Nov-2021|
Dr. D Senol
Department of Anatomy, Duzce University, Faculty of Medicine, Duzce
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: The aim of this study was to compare the anthropometric and cone beam computed tomography (CBCT) measurements taken from risk-free and risky groups by using the modified Mallampati score (MMS). Patients and Methods: A total of 176 volunteers between the ages of 18 and 65 in four different MMS classes were included in the study. The patients in classes MMS I and MMS II were accepted as risk-free and the patients in classes MMS III and MMS IV were accepted as risky for intubation. The Mann–Whitney U test was performed on the data to compare the anthropometric and radiological measurements taken from the risk-free and risky groups. A receiver operating characteristic (ROC) analysis was applied to the parameters that had a statistically significant difference. Results: According to the analysis results, statistically significant differences were found in the neck circumference (NC), maximum interincisal distance (MID), thyromental distance (TMD) and sternomental distance (SMD) of the anthropometric measurements of men and women between the risk-free and risky groups (P < 0.05). In terms of CBCT measurements, the thickness of the tongue (TT), distance between the uvula and posterior wall of pharynx (U-Ph), distance between posterior nasal spine and nasopharynx (Snp-Nph) and length of the epiglottis (LE) were found to have statistically significant differences between the risk-free and risky groups of men and women (P < 0.05). Conclusion: The NC, MID, TMD and SMD anthropometric measurements and TT, U-Ph, Snp-Nph and LE radiologic measurements were found to support MMS, which is one of the most widely used bedside intubation prediction tests. In addition to the inclusion of CBCT for intubation prediction, U-Ph and Snp-Nph radiologic measurements were added as difficult intubation markers.
Keywords: Airway, anthropometry, cone beam computed tomography, intubation, Mallampati
|How to cite this article:|
Senol D, Ozbag D, Dedeoglu N, Cevirgen F, Toy S, Ogeturk M, Kose E. Comparison of anthropometric and conic beam computed tomography measurements of patients with and without difficult intubation risk according to modified mallampati score: New markers for difficult intubation. Niger J Clin Pract 2021;24:1609-15
|How to cite this URL:|
Senol D, Ozbag D, Dedeoglu N, Cevirgen F, Toy S, Ogeturk M, Kose E. Comparison of anthropometric and conic beam computed tomography measurements of patients with and without difficult intubation risk according to modified mallampati score: New markers for difficult intubation. Niger J Clin Pract [serial online] 2021 [cited 2021 Nov 28];24:1609-15. Available from: https://www.njcponline.com/text.asp?2021/24/11/1609/330479
| Background|| |
Airway patency should be provided and maintained for the continuity of vital functions., It is known that the endotracheal intubation method is the safest while maintaining anesthesia in the operation room and supporting the respiration of a patient, or delivering artificial respiration to a patient who stops breathing in intensive care or emergency unit., However, sometimes, successful intubation is not possible due to various difficult anatomic features of patients and their existing systemic diseases. Hypoxia-induced brain damage, airway trauma, myocardial damage and even risk of death are only a few of the barriers that can be encountered during airway clearance., It is reported that the most important cause of unsuccessful airway management is poor and inadequate evaluation; therefore, predictive tests, evaluation methods and anthropometric measurements are vital.,
The modified Mallampati score (MMS) is the most frequently used simple, repeatable, common and rapidly applicable test in terms of evaluating the size of the tongue and pharyngeal structures and predicting difficult intubation.,
Prediction of a difficult airway can decrease the risk of complications., However, studies conducted have reported that no preoperative test alone offers a superior prediction. Since there is still no known bedside imaging method, the combination of simple bedside evaluations and radiological measurements show successful results in predicting difficult intubation.,,
Airway assessment became more reliable with the technological advancement of three-dimensional recording techniques, such as cone beam computed tomography (CBCT). CBCT airway measurements can be used for orthodontic and surgical diagnoses and treatment plans. In addition, CBCT was preferred in this study since it is low cost; it can show the craniofacial area in more details and it exposes the patients to less radiation.
Although there is a limited number of study in literature concerning difficult intubation parameters and anthropometric measurements taken from the head and neck, no studies were found that associated images of CBCT and anthropometric measurements from the head, neck and mandible with difficult intubation. In recent years, it has been reported that airway assessment has become safer with the technological advancement of three-dimensional recording techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and recently CBCT.,, CBCT is distinguished by its compact size and high image accuracy when determining soft tissues and boundaries of empty spaces, and when compared with CT, its association with a decrease in exposure to radiation and cost, increases its importance in diagnosis.,
The aim of this study was to examine the differences between groups by comparing the anthropometric and CBCT measurements taken from risk-free and risky groups according to MMS, which is used in the determination of difficult intubation and to show the changes that can be seen in the cut-off, sensitivity, specificity and area under the curve (AUC) values.
| Materials and Methods|| |
The study was conducted at Inönü University Faculty of Medicine Department of Anatomy and Faculty of Dentistry Department of Oral and Maxillofacial Radiology after 2017/65 coded approval of Malatya Clinical Research Ethics Board was taken 10-May-2017. A total of 176 patients (88 males and 88 females) between the ages of 18 and 65 were included in the study, and [Figure 1] summarizes the flow chart of the study, all patients read and signed the informed consent form. For the measurements, the patients who were included in the American Society of Anesthesiology (ASA) I-II classification were included in the study. Ethics committee approval number is 2017/65 Ethics committee approval date is 10-May-2017.
Determination of risk-free and risky groups
Risk was determined based on the scoring of pharyngeal structures by the patient opening their mouth as much as possible and pulling the tongue forward, under the instruction of the evaluator, while in a sitting position and looking at the examiner. The patients in classes MMS I and MMS II were accepted as risk free for intubation (easy intubation); those in MMS III and MMS IV were accepted as risky for intubation (difficult intubation).,,,,
The maximum interincisal distance (MID), thyromental distance (TMD) and sternomental distance (SMD) measurements were measured using a Harpenden anthropometric set (Holtain Ltd., Crymych, Dyfed, Wales, UK), while the neck circumference (NC) was measured with a tape measure.
1. NC: Perimeter length passing through the laryngeal prominence level was measured with a tape measure while the subject was seated with their waist and back stretched upwards and looking forward while facing parallel to the ground.,
2. MID: After the subject was asked to open his/her mouth, the distance between the upper and lower incisors in the midline of the oral cavity was measured with an anthropometric set.,
3. TMD: The length between the laryngeal prominence and gnathion was measured with an anthropometric set while the incisors were closed and the head was in a fully extended position.,
4. SMD: The distance between sternal and gnathion landmarks was measured with an anthropometric set while the head was in a fully extended position.,
The study was carried out using axial sections, which were obtained by scanning with the device, the gantry angle of which was perpendicular to the ground, with the patient in a supine position, teeth in centric relation, hard palate parallel to the gantry and positioned perpendicular to the ground. The radiological images used in the study were obtained using NewTom 5G (Verona, Italy) CBCT. The gantry of the CBCT device from which the images were obtained was perpendicular to the ground and at a fixed angle. The patient scanning time of the device was 18 or 24 seconds and it scans with 1-20 mA and standard 110 kVp. The images obtained as a result of CBCT scanning were evaluated with an NNT software program. Axial section thickness and voxel values of the evaluated images were 0.2, 0.25 and 0.3 mm.
1. Length of the mandible (LM): The distance between the condylion and gnathion was measured from the left side of the tomography image [Figure 2].,,
|Figure 2: Measurements taken from the mandible; 1: length of the mandible (LM), 2: gonial angle (GA)|
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2. Gonial angle (GA): The distance between the ramus of the mandible and the corpus of the mandible was measured from the left side of the tomography image [Figure 2].,
3. Length of the tongue (LT): The distance between the tip of the tongue closest to the anterior incisors and the anterior point of the epiglottis base was measured on the sagittal plane [Figure 3].
|Figure 3: 3: Length of the tongue (LT), 4: Thickness of the tongue (TT), 5: Length of the uvula (LU), 6: Thickness of the uvula (TU), 7: Distance between uvula and posterior wall of pharynx (U-Ph), 8: Distance between posterior nasal spine and nasopharynx (Snp-Nph), 9: Distance between epiglottis base and pharynx posterior wall (EgB-Ph), 10: Length of the epiglottis (LE)|
Click here to view
4. Thickness of the tongue (TT): The distance between the highest point of the tongue on the sagittal plane and the line of the tongue connecting the anterior incisors and anterior point of the epiglottis base was measured to calculate the thickness of the tongue [Figure 3].,
5. Length of the uvula (LU): The distance between the posterior nasal spine and the tip of the uvula was measured on the sagittal plane [Figure 3].,
6. Thickness of the uvula (TU): The distance where the uvula was the thickest on the sagittal plane was measured [Figure 3].
7. Distance between uvula and posterior wall of pharynx (U-Ph): The distance between the lower end point of the uvula and the posterior pharyngeal wall was measured on the sagittal plane [Figure 3].,
8. Distance between posterior nasal spine and nasopharynx (Snp-Nph): On the section taken from the tomography image, the line connecting the posterior nasal spine to the anterior surface of the posterior pharyngeal wall and the distance connecting the nasopharynx roof to this line was measured [Figure 3].
9. Distance between epiglottis base and posterior pharyngeal wall (EgB-Ph): On the section taken on the sagittal plane from the tomography image, the distance between the base of epiglottis and the anterior of the posterior pharyngeal wall was measured [Figure 3].
10. Length of the epiglottis (LE): The distance between the peak point and base point of the epiglottis was measured on the sagittal plane [Figure 3].
Normality distribution of the data was tested using the Kolmogorov–Smirnov test. Results were presented as median, minimum (min) and maximum (max) values were given for the data that were not normally distributed. The Mann–Whitney U test was applied to the data to compare risk-free and risky groups in terms of difficult intubation, and a P value of < 0.05 was considered as statistically significant. The IBM SPSS Statistics 22.0 program was used in the analyses. The receiver operating characteristic (ROC) curve method was applied to the data to find the cut-off, sensitivity, specificity and the area under the ROC curve (AUC) values of the statistically significant results of the patients in the risk-free and risky groups; MedCalc software (trial version 17.9) was used for the ROC analysis.
| Results|| |
[Table 1] shows the median values of age (year), height (cm), weight (kg) and BMI (body mass index = kg/m2) of the risk-free and risky groups in terms of intubation.
|Table 1: Median (min-max) values of age, height, weight and BMI of males and females|
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[Table 2] shows the results of the Mann–Whitney U test that was conducted to compare the median values of the anthropometric and radiological measurements taken from the male risk-free and risky groups in terms of MMS. According to the results of the analysis, a statistically significant difference was found between the risk-free and risky groups in terms of anthropometric (NC, MID, TMD and SMD) and CBCT measurements (TT, U-Ph, Snp-Nph, LE) (P < 0.05).
|Table 2: Median (min-max) values and Mann–Whitney U test results of the measurements taken from males patients in risk-free and risky groups|
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[Table 3] shows the results of Mann–Whitney U test conducted to compare the median (min-max) values of anthropometric and radiological measurements taken from risk-free and risky female groups in terms of MMS. According to the results of the analysis, statistically significant difference was found between risk-free and risky groups in terms of anthropometric (NC, MID, TMD and SMD) and CBCT measurements (TT, U-Ph, Snp-Nph, LE) (P < 0.05).
|Table 3: Median (min-max) values and Mann–Whitney U test results of the measurements taken from females patients in risk-free and risky groups|
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According to the Mann–Whitney U test, results of the patients in the risk-free and risky groups shown in [Table 2] and [Table 3], the ROC analysis was conducted on the data to determine cut-off, sensitivity, specificity and AUC values of the variables that were found to be statistically significant [Table 4]. The accuracy rate of the parameters in female patients was 63-74%, and the accuracy rate in male patients was between 65 and 71%. Sensitivity of TT for female patients was 45.82, for male patients 47.73, sensitivity of U-Ph was 60.09 in female patients, 59.09 for male patients, sensitivity of Snp-Nph for female patients 63.64, for male patients 68.18, men, sensitivity of LE for female patients was 74.5, for male patients 67.5.
|Table 4: ROC analysis results of male and female patients in risk-free and risky groups|
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| Discussion|| |
According to the results of the study, it was concluded that anthropometric measurements NC, MID, TMD and SMD and CBCT measurements TT, U-Ph, Snp-Nph and LE) taken from the risk-free and risky groups could be significant prediction measurements for difficult intubation. It was found that anthropometric measurements NC, MID, TMD and SMD had shorter measurements in the risky group compared with the non-risky group. And it was found that CBCT measurements Snp-Nph and LE also had shorter measurements in the risky group when compared with the non-risky group.
A literature review reported the probability of encountering difficult intubation between 1 and 18%, while the rate of unsuccessful intubation varied between 0.05 and 0.35%., It has been shown that up to 30% of morbidity and mortality attributed to anesthesia is related to airway management, which makes it the most frequent cause of anesthetic complications.
It has been reported that difficult intubation is a multifactorial problem; a prediction test alone cannot be expected to give accurate results and a combination of these tests should be used for effective prediction. MMS is a simple and repeatable technique used to evaluate tongue size and pharyngeal size, and it is the most commonly used method as a tool in evaluating the risk of difficult intubation.,
Large NC is considered to be one of the indicators of a difficult airway. Existing literature shows a statistically significant difference in NC measurements of those in the risk-free and risky groups in terms of MMS.,, In this study, the variable of NC gave statistically significant results in both the risk-free and risky groups. According to the ROC analysis results, NC measurements had higher values than in the study by Acer et al. (2011). In other words, they were found to have a high significance in determining difficult intubation. MID is one of the predictive tests that does not show a consensus in literature. There are studies that report that there is no significant association between MID and intubation difficulty., However, it is also reported that MID shows temporomandibular joint mobility and a limited MID can make the larynx visibility more difficult. In addition to the studies showing that a patient's intubation will be difficult in cases of a MID of <5 cm, there are also studies that accept a MID ≤3.8 cm criteria as the anthropometric measurement limit of difficult intubation. In this study, MID was found to be a variable to distinguish between risk-free and risky groups in males and females. The reason for the disagreement in literature can be the fact that MID is generally evaluated with the three-finger rule in clinic and that this method does not give objective results. It is reported that TMD can be a good indicator in the evaluation of the mandibular opening and there are a large number of studies in literature which report that decreased TMD can cause difficult intubation and should be evaluated in the risky group. Kandemir et al. (2015) reported that combined use of MMS and TMD is the most effective test in determining difficult intubation. In parallel with the literature, the TMD measurement results of this study showed a statistically significant difference between the risk-free and risky groups in males and females (P < 0.05).
SMD is accepted as an indicator of mobility in the head and neck area, and it is known to be one of the leading tests used in the determination of intubation difficulty. There are even studies suggesting the use of SMD as the single objective indicator of intubation difficulty. Aktas et al. (2015) found the sensitivity of SMD to be 76%. However, in this study, SMD sensitivity was found to be 95.4%, and a statistically significant difference was found between the risk-free and risky groups in males and females. significant difference was found between the risk-free and risky groups in females (P < 0.05).
In the studies that evaluated the association between TT and difficult intubation with ultrasound, a significant positive association was found between the two. As a result of the CBCT measurements in this study, TT was found to show a statistically significant difference between the risk-free and risky groups in patients (P < 0.05). In addition to affecting normal breathing, pharyngeal contraction becomes important in airway evaluation due to the increase in obstructive sleep apnea syndrome. It can be seen that the effects of U-Ph and Snp-Nph measurements of the contraction in the posterior airway have been examined in literature but they have not been included in the evaluation in predictive tests conducted to determine difficult intubation. For this reason, no studies were found that had compared the measurements. According to the results of this study, it is believed that U-Ph and Snp-Nph can be indicators of difficult intubation in the risk-free and risky patients, and this shows that they can add to the existing literature since they are the first measurements made. The decision for difficult intubation can be made by examining the U-Ph and Snp-Nph parameters determined by CT of the patients in the risky group according to MMS. In their study, Randell et al. (1998) found that the LE and intubation difficulty have a positive correlation. According to the results of this study, LE can be an indicator of difficult intubation for risk-free and risky groups of both males and females.
This study had some limitations. More participants could be included in future studies; however, for patients who come to the Oral and Maxillofacial Radiology department, tomography is mostly performed on implant patients. The presence of missing teeth affects the position of the tongue and the fact that such patients were not included in the study limited the number of participants. Another limitation of the study was that the patients who came to the Department of Oral and Maxillofacial Radiology were patients who did not need to be intubated. It would be more useful to evaluate these parameters in patients undergoing general anesthesia, however, ethical problems could be encountered at this point.
| Conclusions|| |
The present results from the preoperative tests show that information regarding easy or difficult intubation will allow clinicians to make easier interventions and will also make them aware of any difficulties that need to be overcome. Supporting the use of MMS to determine difficult intubation with anthropometric and CBCT measurements, and using the results in pre-intubation evaluations, is thought to be important. Measurements taken from CBCT images to predict difficult intubation were conducted in the present study for the first time and supporting predictive tests with objective methods will contribute to a decrease in morbidity and mortality rates associated with intubation. From this study, it is believed that these results provide significant data for the anesthesia staff regarding the prediction of intubation difficulty and providing airway safety and surgical branch areas related to anatomic structures affecting the MMS.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
This research was supported by İnönü University BAP unit with project number TDK-2017-828.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]