| Objective: There is limited evidence about how to choose the appropriate size of left double-lumen tube(DLT).It is widely accepted that the diameter of left main bronchus(LMB)is the determining factor to define the left DLT size.However,the left DLTs selected based on the LMB diameter often encounters obvious resistance in the subglottic area,especially in female patients.As we know,cricoid ring is the narrowest part of the trachea and it is also the only complete cartilage ring in the airway,which means that the diameter of cricoid ring may be another determining factor of the appropriate left DLT size.So far,all studies about the size of DLT have focused on the left DLT.There is no data about how to choose the size of right DLT.The aims of the study included three parts.The aim of part 1 were to measure the diameters of the cricoid ring and LMB in adult patients and to assess the accuracy of the left DLTs selected according to different methods.The aim of part 2 was to compare the accuracy of the DLT selected based on the combination of TD-C and the ED-LMB with that based on the ED-LMB alone for women.The aim of part 3 was to evaluate the feasibility of using TD-C to select right DLT for women.Methods: Part 1: The electronic medical record system of the authors’ hospital was queried from January 2015 to December 2016.A total of 181 patients who had undergone general anaesthesia for lung operations during this period were collected.On each high resolution computed tomography(HRCT)scan,a single anesthesiologist trained by the radiologist performed multiplanar reconstruction(MPR)of the upper tracheobronchial tree.All of the measurements were then performed with the correction of slant in the three dimensions.The transverse and anteroposterior diameters of LMB(TD-LMB and APD-LMB)were measured at 1 cm below the carina.The equivalent circular diameter of the LMB(ED-LMB)was calculated based on the TD-LMB and APD-LMB using perimeter formulas of ellipse and circle.The transverse and anteroposterior diameters of cricoid ring(TD-C and APD-C)were measured at the lower border of the cricoid ring.The LMB size was defined as the largest DLT size fitting the ED-LMB.The cricoid size was defined as the largest DLT size fitting the TD-C.The ideal size was defined as the largest DLT size that fits both the ED-LMB and TD-C.The accuracy of the size of left DLT selected according to different methods were assessed by comparing with the ideal size.Part 2: Eighty consecutive and blinded female patients were assigned randomly to two groups with 40 patients in each group.In the Combined group,the DLT size was selected based on the combination of the TD-C and ED-LMB.In the LMB group,the DLT size was selected based on the ED-LMB alone.The accuracy of the tracheal segment and the bronchial segment were compared between two groups.The overall accuracy of the DLT was also compared.The postoperative hoarseness and sore throat were investigated by blinded assessors.Part 3: Seventy-six female patients were divided into left intubation group(n = 38)and right intubation group(n = 38).The size of DLT in both groups were selected according to TD-C.The accuracy of the tracheal segment and the bronchial segment were compared between two groups.The overall accuracy of the DLT was also compared.The postoperative hoarseness and sore throat were investigated by blinded assessors.Results: Part 1: 1.The TD-LMB、APD-LMB 和 ED-LMB were all significantly greater in men compared with women(P < 0.001),but the shapes of LMB were not significant different.2.The TD-C 和 APD-C were all significantly greater in men compared with women(P < 0.001),and the shapes of the cricoid ring were significantly different between men and women(P < 0.001).3.In men,height was the only predictive factor for TD-C(r = 0.313).In women,ED-LMB was the only predictive factor for TD-C(r = 0.374).4.There was no predictive factor for ED-LMB in men,while height and TD-C were predictive factors for ED-LMB in women(r = 0.270 and r = 0.374).5.The ideal sizes were 39 Fr for all men.With reference to the ideal size,the rates of agreement of the cricoid size,LMB size and height size for men were 100%,100% and 94.3%,respectively.The ideal sizes for most women were 37 Fr(53.2%)and 35 Fr(39.4%),but there were seven women for whom the ideal sizes were 32 Fr(5.3%)or smaller(2.1%).With reference to the ideal size,the rates of agreement of cricoid size,LMB size and height size for women were 94.7%,63.8% and 51.1%,respectively.Part 2: 1.The accuracy of the tracheal segment was higher in the Combined group(92.5% vs 67.5%,P = 0.010).The accuracy of the bronchial segment was similar between the groups(95.0% vs 86.1%,P = 0.246).The overall accuracy of the DLT was also higher in the Combined group(87.5% vs 60.0%,P = 0.010).There was no significant difference in respiratory parameters between two groups during one-lung ventilation(OLV).The quality of lung collapse was similar between two groups at 10 minutes and 20 minutes after the initiation of OLV.The severity of hoarseness at 24 h and 48 h after the operation were similar between two groups.The severity of sore throat was higher in the LMB group at 24 h after the operation(P = 0.001).The severity of sore throat was similar between two groups at 48 h after the operation(P = 0.106).Part 3: 1.The average ED-LMB/TD-C ratio was 0.81 ± 0.07(0.65-1.01)and the average ED-RMB/TD-C ratio was 0.90 ± 0.08(0.78-1.17).2.The accuracy of the tracheal segment was similar between groups(94.7% vs 92.1%,P = 1.000).The accuracy of the bronchial segment in the right intubation group was higher than that of the left intubation group(97.4% vs 78.9%,P = 0.028).The overall accuracy of DLT in the right intubation group(89.5%)was slightly higher than that in the left intubation group(73.7%),but there was no significant difference between the two groups(P = 0.137).There was no significant difference in respiratory parameters between two groups during OLV.The quality of lung collapse was similar between two groups at 10 minutes and 20 minutes after the initiation of OLV.There was no significant difference in the severity of hoarseness between the two groups at 24 hours and 48 hours postoperatively.The severity of sore throat at 24 hours postoperatively was higher in the left intubation group(P = 0.027)The severity of sore throat at 48 hours postoperatively was not significantly different between the two groups(P = 0.237).Conclusions: 1.There were significant differences in the shape of the cricoid ring between different genders.2.The ED-LMB and TD-C could not be reliably predicted according to the height.There was weak correlation between ED-LMB and TD-C.3.For men,the size of left DLT can be accurately selected according to the height,ED-LMB or TD-C.For women,the ideal size of left DLT should be determined by the combination of ED-LMB and TD-C.The accuracy of the size of left DLT selected according to TD-C is higher than ED-LMB or height.4.The correct size of DLT for Asian women should be selected based on the combination of TD-C and ED-LMB.5.The size of right DLT for Asian women could be correctly selected based on TD-C. |
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