Lung isolation using double-lumen tubes (DLTs) is widely used to facilitate optimal conduct of thoracic surgery.1,2 Accurate positioning of DLTs is crucial to ensure adequate gas exchange during one-lung ventilation (OLV).3,4 There are several methods for proper placement and positioning of DLTs.2,5–11 These methods include the conventional blind technique,2 estimations based on patient height,5 preoperative chest radiographs,6 change in endobronchial cuff pressure7 or volume,8 external measurements,9 and the fiberoptic-guided technique.10,11 The latter is the most reliable method that ensures proper positioning of DLTs.10,11 Insertion of DLTs with a carinal hook, such as Carlens tubes,12 was associated with a frequent incidence of proper positioning,13 but technical problems with insertion and potentially life-threatening hazards have discouraged their use.14,15 In this study, we fashioned a carinal hook to facilitate correct initial DLT placement. However, we made this carinal hook retractable to avoid insertion difficulty and complications. The aim of this study was to determine whether this design could improve the success rate and duration of correct DLT positioning, compared with the conventional method.
After local research committee approval and informed patient consent, 40 ASA I–III adult patients, undergoing elective thoracic surgery requiring OLV with a left-sided DLT, were enrolled in this study. Patients who had severe spinal scoliosis, kyphosis, obvious tracheal deviation, or those with apparent difficult intubation were excluded. Patients were randomly allocated using an online research randomizer (http://www.randomizer.org) into two groups (20 patients each); the conventional group in which the DLT was inserted using the conventional blind technique and the hook group in which the modified blind technique with a retractable carinal hook was used.
In both groups, after administration of oxygen, anesthesia was induced with fentanyl IV (2 μg/kg) and propofol (2.5 mg/kg). DLT insertion was facilitated with rocuronium IV (0.8 mg/kg). Anesthesia was maintained with sevoflurane and a mixture of air and oxygen. Continuous electrocardiogram, noninvasive arterial blood pressure, plethysmographic oxygen saturation, and end-tidal carbon dioxide were monitored using an S/5 anesthesia monitor (Datex-Ohmeda, Finland). Following the recommendations of Brodsky et al.,16 DLT size was based on the tracheal diameter as measured directly from the chest radiograph. Sher-I-Bronch™ (Sheridan, Argyle, NY) DLTs were used and the same anesthesiologist performed tube insertion in all cases.
In the conventional group patients, after direct laryngoscopy, the left-sided DLT with a stylet was passed through the larynx with distal curvature concave anteriorly. The stylet was removed when the bronchial cuff had passed the vocal cords. The tube was then rotated 90° and with the head rotated slightly to the right, the tube was advanced blindly until slight resistance was felt.
In the hook group, a sterile well-lubricated retractable carinal hook was used to assist with placing the left-sided DLT. The retractable carinal hook is a modified gum elastic bougie17 (Eschmann tracheal tube introducer, Portex, Kent, UK) (Fig. 1A). The bougie was retracted inside the tracheal lumen of the DLT during tube insertion and then was advanced 15 mm during advancement of the DLT toward the carina (Fig. 1B). The bougie was shortened at its proximal end and fitted with a 15-mm adaptor. Fitting this adaptor to the tracheal connector of the DLT ensures proper length and direction of the carinal hook (Fig. 1C). The DLT was blindly advanced with the patient's head rotated slightly to the right until an obvious resistance was felt assuming engagement of the hook with the carina. All DLT insertions were made by the same senior anesthesiologist who was experienced in thoracic anesthesia.
In both groups, after DLT insertion, the tracheal cuff was inflated and clinical assessment of correct tube placement was performed by observing chest wall expansion, checking lung compliance, and auscultation of both lungs. To assess the ability to isolate each lung, the endobronchial cuff was inflated (with 2 mL air), and correct DLT position was assessed by auscultation after selective clamping of the bronchial and tracheal limbs.
Immediately after this procedure, a second anesthesiologist, who was unaware of the insertion technique or the initial clinical assessment, performed all fiberoptic bronchoscopies (FOBs), made the final assessment of DLT placement, and corrected any tube malposition in the supine position. Bronchoscopic criteria for correct DLT position were defined as follows: unobstructed view into the left upper and lower lobe bronchus through the endobronchial lumen, visualization of the bronchial cuff immediately below the carina, absence of herniation of the bronchial cuff over the carinal surface, and unobstructed view down to the nonintubated bronchus through the tracheal lumen.18 The following variables were measured: number of malpositions after initial tube placement noted by FOB, time from laryngoscopy until the end of clinical assessment, and the time for fiberoptic confirmation and tube adjustment. Any relevant complication to DLT placement was recorded in both groups.
Values were expressed as the mean ± sd or percentages as appropriate. Data were tested for normal distribution using the Kolmogorov-Smirnov test. Comparison of nonparametric data, such as gender or the incidence of tube malposition, was performed using Fisher's exact test. Parametric data such as patient age, weight, height, and the time for clinical placement and final FOB confirmation were analyzed using unpaired t-test. A P value <0.05 was considered significant. Analysis was performed using Statistica software version 7.0 for windows (Statsoft, Tulsa, OK).
There were no significant differences between the two groups with regard to age, weight, height, and gender (Table 1). After intubation and initial DLT placement, clinical finding alone detected a comparable incidence of tube malposition in the two groups (3 of 20 patients [15%] in the conventional group and 1 of 20 patients [5%] in the hook group; P = 0.6). Subsequent FOB assessment revealed DLT malposition in six additional patients in the conventional group and one additional patient in the hook group. Therefore, total malpositions in the conventional group were nine patients, who were diagnosed as follows: six patients with distal displacement, two patients with proximal malposition, and one patient with bronchial cuff herniation. In the hook group, distal displacement was detected in two patients. Therefore, a significantly lower incidence of total tube malposition was found in the hook group (2 of 20, 10%) than in the conventional group (9 of 20, 45%) (P = 0.03).
The mean time for clinical placement and verification of DLT position was similar in both groups (113.9 ± 24.2 s and 117.5 ± 21.1 s, P = 0.62, in the conventional and hook groups, respectively). The mean time for bronchoscopic confirmation and adjustment was significantly shorter in the hook group (88.9 ± 35.7 s) compared with the conventional group (152.3 ± 40.3 s) (P < 0.0001). There were no recorded complications related to DLT insertion in both groups.
Our study showed that the modified method using a retractable carinal hook for left-sided DLT placement was associated with a higher rate of correct tube positioning compared with the conventional method. In addition, a shorter time was required for bronchoscopic confirmation and adjustment of tube position using our new design.
To allow easier placement, and improve the utility, performance, and safety criteria of DLTs, several modifications in the design, configuration, material, and manufacturing technology have been added to the old generation tubes.19 DLTs with fixed carinal hooks19 facilitated proper placement and minimized further tube advancement during positioning.20,21 However, potential problems and complications were associated with carinal hooks. These included a higher incidence of insertion difficulty, laryngeal trauma, amputation of the hook during placement, and possible impedance of lung resection.22,23 Therefore, contemporary DLTs are manufactured without carinal hooks. We modified a gum elastic bougie and used its distal curve as a carinal hook. However, this carinal hook can be retracted during insertion and rotation and completely removed after correct placement of the DLT, and therefore, it avoids the problems associated with fixed hooks. This retractable hook could be used with both left and right-sided DLTs, although we studied only left-sided DLTs.
In our study, the incidence of malpositions with DLTs was higher in the conventional group (9 of 20, 45%) than after using the retractable carinal hook (2 of 20, 10%). Malpositions in the conventional method patients were comparable with previous studies.6,13,24 Malpositions in the hook group were due to distal displacement of the endobronchial tube that could be explained by the use of unnecessary force while advancing the tube down the trachea. This cause of malposition could possibly be avoided by using a firmer introducer, with a fixed distal curve of the retractile hook specific for each tube. In addition, operator familiarity and experience with this method could increase the likelihood of success.
The mean time required for fiberoptic assessment and correction in the hook group was significantly shorter than in the conventional group. This could be explained by a lower incidence of tube malposition reducing the time and effort of subsequent bronchoscopic adjustment. This finding suggested that the use of a retractable carinal hook could facilitate quick lung isolation, particularly in some life-threatening situations. Boucek et al.25 showed that the directed bronchoscopic approach of DLT placement required an average of 181 s, whereas the blind technique required only 88 s, which is comparable with this study.
Although the occurrence of major complications related to DLTs are rare, they can be life-threatening.14,15 Minor airway injuries including sore throat, vocal cord lesions, and bronchial injury occur in a large percentage of patients after DLT administration.26 In this study, no relevant complications were reported in either group. Further larger studies are required to identify the incidence and severity of these complications with the new design.
One limitation of this study is that the study protocol terminated before patient positioning and initiation of OLV. Further studies are required to determine if the significant increase in the initial success rate of DLT placement is due to the incidence of DLT malposition after repositioning of the patient to the lateral position. However, we suggest that this design could be valuable when OLV is indicated in thoracic procedures requiring supine positions, some emergency conditions, and in situations of FOB unavailability, inapplicability, or limited experience. A second limitation was our inability to conduct a completely blinded study, because the carinal hook was easily recognized during insertion in the first phase of the study. However, the second phase of the study was blind because a single anesthesiologist who was unaware of study plan and was not present during the placement of DLTs performed all FOBs.
In conclusion, this preliminary study reported the use of retractable carinal hook to facilitate correct initial DLT placement. The technique appears to be simple and takes less time than the conventional method. Tube manufacture using a specifically designed retractable carinal hook may improve the reliability of the technique. This technique, however, is not an alternative to bronchoscopic confirmation of DLT final position, which is considered the standard of care. A further larger study is required to confirm the clinical merits of this design and verify its safety and reliability.
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