Choosing the appropriate double-lumen tube: a glimmer of science comes to a dark art

Choosing the correct-sized adult double-lumen tube: Quest for the holy grail

Appropriate size selection of double-lumen tubes (DLTs) for one-lung ventilation (OLV) in adults is still a humongous task. Several important factors are to be considered like patient height, gender, tracheal diameter, left main bronchial diameter, and cricoid cartilage transverse diameter. In addition to radiological assessment of the airway diameters, the manufacturing details of the particular DLT being used also play a significant role in size selection. Optimal positioning of the appropriately sized DLT is indispensable to avoid complications like airway trauma, cuff rupture, hypoxemia, and tube displacement. It is imperative to know whether the one-size-fits-all dictum holds for DLT size selection as claimed by certain studies. Further randomized studies are required for crystallizing standard protocols ascertaining the correct DLT size. This systematic review article highlights the various parameters employed for DLT size selection and explores the newer DLTs used for adult OLV.

Comparisons of the segments of left-sided double-lumen tracheobronchial tubes as industrial products

BACKGROUND

Although there are at least seven manufacturers producing left-sided double-lumen tubes (DLTs), there have been few reports comparing the segments of these DLTs. In this study, we compared various segments of left-sided DLTs further.

MATERIALS AND METHODS

We examined five manufacturers' left-sided DLTs: Mallinckrodt, Portex, Rüsch, Sheridan, and Daiken-medical. We conducted the following six trials or measurements, and three supplemental trials or measurements: First, we tried to pass various sizes of steel balls down each lumen in order from the smallest (3 mm) to largest (4.5 mm). If the ball passed on the first attempt, we tried just once; otherwise, we made a second attempt. Second, we measured the external diameter of tracheal and bronchial cuff using a profile projector. Third, we measured the length of the cuff and tip of the bronchial segment of the tubes using the profile projector. Fourth, we measured various lengths of the tubes. Fifth, we measured the external diameter of both lumens and the tubules for tracheal and bronchial cuff inflation. Finally, we measured various cross-sectional areas including the tracheal lumen, bronchial lumen, and tubules for cuff inflation. We also conducted three supplemental studies. First, we measured air volume in the cuff when intracuff pressure equaled 2 or 3 kPa. Second, we defined the configuration of the tracheal and bronchial cuffs. Third, we defined the presence or absence of bevels and also measured the angle of the bevels using the profile projector.

RESULTS

We performed nine trials and measurements and found large disparities between each manufacturer's tubes.

CONCLUSIONS

The large disparities found between the measurements of the five manufacturers' tubes may be due to different lots or changes in specifications made by each manufacturer. We found tubes exhibiting lower quality, such as deformations, and non-universal and inconsistent sizing, in the comparison of the manufacturers' tubes. Practitioners should be aware of the features and aspects of these tubes.

Comparison between computerized tomography-guided bronchial width measurement versus conventional method for selection of adequate double lumen tube size

Background:

Selection of adequate size double lumen tube (DLT) is complicated by marked inter-individual variability in morphology and dimensions of tracheobronchial tree. Computerized tomography (CT)-guided left bronchus width measurement has been used to predict adequate size DLT in European and Singapore population; however, no such data exist for Indian population who are racially different. We compared the effect of DLT size selection based on CT-guided bronchial width measurement to the conventional method of DLT selection on the adequacy of both lungs isolation and on the safety margin of right-sided DLT.

Methods:

Fifty-five adults scheduled to undergo thoracotomy were enrolled in this prospective observational study. An appropriate size left- or right-sided DLT with outer diameter 0.5–1 mm smaller than the CT-measured bronchial width was selected for the isolation of lungs. Adequacy of separation was checked using fiberoptic bronchoscope. The safety margin of selected right-sided DLT size was calculated from CT-measured right upper lobe bronchus width and diameter of right upper lobe ventilation slot of the DLT.

Results:

Adequate separation of lungs was achieved in 92.7% of studied population, 90.9% in males, and 95.4% in females. Among these, 54.9% patients required different sized DLT as compared to conventional method. Overall safety of margin of right-sided DLTs was comparable between two methods of DLT selection (median [IQR] 4.8 (3.5–6.8) vs. 6.59 (3.5–7.8), P = 0.317). DLT size with adequate isolation of lung correlated with height, tracheal width (TW) on chest X-ray, and age of the patients. A formula to calculate DLT size based on these variable was derived.

Conclusion:

CT-measured bronchial width predicts the appropriate DLT size better than conventional method. In the absence of CT scan facility, patient height, age, and chest X-ray TW may be used to predict DLT size with reasonable accuracy.

Dimensional Variations of Left-Sided Double-Lumen Endobronchial Tubes

Background

Tube size selection is critical in ventilating patients' lungs using double-lumen endobronchial tubes (DLTs). Little information about relevant parameters is readily available from manufacturers. The aim of this study is to provide reference data for relevant dimensions of conventionally available DLTs.

Methods

In this study in a benchmark in vitro setup, several dimensional parameters of four sizes of left-sided double-lumen endobronchial tubes from six different manufacturers were assessed, such as distances and diameters of tube shaft, cuff lengths, and diameters as well the angle at the tip.

Results

Endobronchial tubes of ostensibly the same size revealed wide variation in measured parameters between brands from different manufacturers. In some parameters, there was an overlap between different sizes from the same manufacturer, i.e., diameters and distances did not increase with increasing nominal endobronchial tube size. The information about dimensions of endobronchial tubes provided by manufacturers' leaflets is insufficient.

Conclusions

Endobronchial tube size selection carries unnecessary uncertainty because clinically relevant parameters are unknown and vary considerably between different manufacturers.

[Risk factors for intraoperative hypoxemia during monopulmonary ventilation: an observational study]

BACKGROUND

Left double-lumen endotracheal tubes have been widely used in thoracic, esophageal, vascular, and mediastinal procedures to provide lung separation. Lacking clear objective guidelines, anesthesiologists usually select appropriately sized double-lumen endotracheal tubes based on their experience with 35 and 37Fr double-lumen endotracheal tubes, which are the most commonly used. We hypothesized the patients with a left main bronchus of shorter length (<40mm) had a greater chance of experiencing desaturation during one lung ventilation, due to obstruction in the orifice of the left upper lobe with the bronchial tube.

METHODS

We included 360 patients with a left double-lumen intubated between September 2014 and August 2015. The patient's age, sex, height, weight, and underlying disease were recorded along with type of surgical procedure and the desaturation episodes. In addition, the width of the trachea and the width and length of the left bronchus were measured using computed tomography.

RESULT

Patients with a left main bronchus length of less than 40mm who underwent intubation with a left double-lumen endotracheal tubes had significantly higher incidence of desaturation (Odds Ratio (OR: 8.087)) during one-lung ventilation. Other related factors of patients identified to be at risk of developing hypoxia were diabetes mellitus (OR: 5.368), right side collapse surgery (OR: 4.933), and BMI (OR: 1.105).

CONCLUSIONS

We identified that patients with a left main bronchus length of less than 40mm have a great chance of desaturation, especially if other desaturation risk factors are present.

Risk factors for intraoperative hypoxemia during monopulmonary ventilation: an observational study

Background

Left double-lumen endotracheal tubes have been widely used in thoracic, esophageal, vascular, and mediastinal procedures to provide lung separation. Lacking clear objective guidelines, anesthesiologists usually select appropriately sized double-lumen endotracheal tubes based on their experience with 35 and 37 Fr double-lumen endotracheal tubes, which are the most commonly used. We hypothesized the patients with a left main bronchus of shorter length (<40 mm) had a greater chance of experiencing desaturation during one lung ventilation, due to obstruction in the orifice of the left upper lobe with the bronchial tube.

Methods

We included 360 patients with a left double-lumen intubated between September 2014 and August 2015. The patient's age, sex, height, weight, and underlying disease were recorded along with type of surgical procedure and the desaturation episodes. In addition, the width of the trachea and the width and length of the left bronchus were measured using computed tomography.

Result

Patients with a left main bronchus length of less than 40 mm who underwent intubation with a left double-lumen endotracheal tubes had significantly higher incidence of desaturation (Odds Ratio (OR: 8.087)) during one-lung ventilation. Other related factors of patients identified to be at risk of developing hypoxia were diabetes mellitus (OR: 5.368), right side collapse surgery (OR: 4.933), and BMI (OR: 1.105).

Conclusions

We identified that patients with a left main bronchus length of less than 40 mm have a great chance of desaturation, especially if other desaturation risk factors are present.

Automated measurement of tracheal and main bronchial diameters: a feasibility study

BACKGROUND

A thoracic computed tomography scan is rarely used to help choose the appropriate double-lumen tube. Nowadays, bronchial measurements can be automated using dedicated software. The aim of this prospective monocentric study was to compare manual and automated measurements of the diameter of the trachea and both main bronchi in adult patients free from a history of lung surgery or disease.

METHODS

Diameters of the trachea and of the main stem bronchi were measured by trained physicians or automatically using Thoracic Volume Computer Assisted Reading software (GE Healthcare, Chicago, IL, USA). Manual measurements were considered as the goal standard.

RESULTS

Two hundred and forty-three patients were assessed for eligibility, 216 were allocated to intervention and 173 analyzed: 102 males and 71 females (61.4±13.9 years, 169.7±9.4 cm, 73.3±16.8 kg). Reliability between the two investigators was poor (20.8±9.0% of measurements with a difference >10%). Intraclass correlation coefficient (ICC) and its confidence interval at 95% (ICC [95% CI]) was 0.97 [0.96; 0.98] for the maximal diameter and 0.94 [0.92; 0.95] for the minimal diameter of the trachea (P<0.01 for both). ICC [95% CI] was 0.97 [0.94; 0.98] for the maximal diameter and 0.93 [0.90; 0.95] for the minimal diameter of the right main bronchus (P<0.01 for both). ICC [95% CI] was 0.96 [0.95; 0.97] for the maximal diameter and 0.93 [0.90; 0.95] for the minimal diameter of the left main bronchus (P<0.01 for both).

CONCLUSIONS

This feasibility study has mixed results since automated measurements were not feasible in around 20% of the cases.

A New Technique to Determine the Size of Double-lumen Endobronchial Tubes by the Two Perpendicularly Measured Bronchial Diameters

The cross-section of the mainstem bronchi is not completely round. For preoperative selection of a double-lumen endobronchial tube size, it may be necessary to measure the mediolateral and the anteroposterior bronchial diameters, which can be measured respectively on chest radiograph and computed tomography. With Internal Review Board approval and patients’ informed consent, 105 elective thoracic surgical patients who needed left-sided double-lumen tubes were enrolled. Double-lumen tube size was selected depending on the arithmetic mean of the mediolateral and anteroposterior bronchial diameters. Moreover, the outer diameters of the bronchial tube should be smaller than both mediolateral and anteroposterior diameters. The recommended bronchial diameter for each double-lumen tube size was chosen so that the mean of the two bronchial diameters was 0 to 2.0 mm larger than the upper limit of 95% confidence interval of the averaged outer diameter of the bronchial tube of the selected double-lumen tube. In no case was the predicted double-lumen tube size inappropriate. Generally, anteroposterior bronchial diameters appeared to be different from mediolateral diameters (P=0.001). The double-lumen tube size to be selected based on only one bronchial diameter was different from the one selected based on two perpendicularly measured bronchial diameters in 54.3% of patients (57/105). Preoperative selection of the double-lumen tube size based on the anteroposterior, mediolateral and mean bronchial diameters seems to be useful in that this may obviate the need to change an inappropriately sized double-lumen tube and may be helpful in reducing the related complications.

Physiology of One-Lung Ventilation

The understanding of the physiology and management of one-lung ventilation (OLV) has advanced over the last two decades. OLV induces an obligatory shunt through the nonventilated lung that causes varying degrees of arterial hypoxemia. Shunt may also occur in the venti lated lung. The optimal mode of ventilation of the dependent lung has not been well defined. The optimal tidal volume, respiratory rate, inspired oxygen concen tration, and positive end-expiratory pressure (PEEP) during OLV are not known. Functional residual capacity (FRC) of the ventilated lung can be lower than during two-lung ventilation, causing atelectasis and arterial hypoxemia. Patients who desaturate might be expected to show improvement in oxygenation with dependent lung PEEP, because of increased FRC and reduced V/Q mismatch. Not all patients have low lung volumes, and not all patients who have low lung volumes will desatu rate. Therefore, prophylactic PEEP is not usually neces sary or appropriate. Because the predominant cause of hypoxemia during OLV is shunt in the nondependent lung, therapies to improve arterial oxygenation during OLV should be primarily directed toward the nondepen dent lung. Partial reinflation of the nondependent lung with O2will reduce the physiological shunt fraction of the lung. Continuous positive airways pressure (CPAP) is an effective prophylactic and therapeutic treatment for hypoxemia. All studies examining CPAP have found it to be effective, provided it is preceded by lung reinflation.

Cricoid and left bronchial diameter in the pediatric population

BACKGROUND

Lung isolation in the pediatric population can be problematic. The diameter and length of the right and left mainstem bronchi are not well described in young children. Information regarding these measurements may help determine the appropriate size of endotracheal tubes for endobronchial intubation as well as the development of lung isolation devices for the pediatric population. The present study is based on computed tomography (CT) measurements to evaluate airway dimensions. The goal of this study was to define the relationship between the diameters of the left mainstem bronchus (LMSB) and the cricoid ring, and to study the effect of age, weight, and height on these dimensions.

METHODS

The two-dimensional CT images of 102 children, ranging in age from 1 month to 10 years, undergoing radiological evaluation unrelated to airway symptomatology were examined. The cricoid dimensions (anteroposterior and transverse diameters) were measured using transverse plane images. The LMSB diameter was measured below the carina along the long axis of left main bronchus. Univariate regression analysis was used to determine whether one or more of the variables (age, gender, height, weight) had a predictable relationship with the cricoid and the LMSB diameters.

RESULTS

The cricoid as well as the LMSB diameters increase with age, height, and weight. The relationship between the cricoid diameter and the LMSB diameter remains constant across all ages with a ratio of 0.78 ± 0.14. This ratio was slightly larger for girls than boys (0.81 ± 0.16 vs 0.77 ± 0.13).

CONCLUSION

The cricoid to LMSB ratio (relationship) remains constant with respect to age, height, and weight.

The effect of gel lubrication on cuff leakage of double lumen tubes during thoracic surgery*

High-volume, low-pressure tracheal cuffs of disposable double lumen tubes may offer limited protection to the dependent lung if fluid leaks through folds in the inflated cuffs. This study was undertaken to determine the incidence of fluid leakage past the tracheal cuff and whether gel lubrication reduces the incidence. Fifty-five patients were randomly assigned to receive a double lumen tube with or without gel lubrication. The dependent lung was intubated. With the patient in the lateral position, methylthionium chloride was administered above the tracheal cuff via a pre-attached catheter. Fibreoptic bronchoscopy was performed to determine if dye had passed the tracheal cuff. Three patients were excluded. Dye leakage was seen in 12/27 and 3/25 patients in the unlubricated and lubricated group, respectively (p = 0.014). Gel lubrication significantly reduces fluid leakage past the tracheal cuff of a double lumen tube and should be considered for all thoracic surgical patients requiring one-lung ventilation.

Tracheal width and left double-lumen tube size: a formula to estimate left-bronchial width

STUDY OBJECTIVE

To determine which patient parameters best predict left bronchial width (LBW) when selecting the correct size double-lumen tube (DLT). If LBW is known, a DLT that will fit that bronchus can be chosen.

DESIGN

Prospective study.

SETTING

University medical center.

PATIENTS

Three hundred twenty-one consecutive patients scheduled for thoracic surgery and for whom there was a chest radiograph and for whom tracheal width (TW) and LBW could be measured.

MEASUREMENTS

Tracheal width and LBW were directly measured from the chest radiograph. Patient demographic data were recorded and then analyzed to see which factor(s) best predicted LBW. Parameters often used for DLT selection (age, sex, height, and weight) as well as TW were compared by univariate and multivariate statistical analysis to see which factor(s) most accurately predicted LBW.

MAIN RESULTS

There were weak but significant correlations between age and height and LBW in men, and height and LBW in women. Multivariate statistical analysis showed that, for both men and women, TW was the best predictor of LBW. Sex, height, and weight did not improve predictability over TW alone. The equation that best predicts LBW for both sexes is: LBWmm = (0.50)(TWmm) + 3.7 mm. This model explains 46% of the variance in LBW. As structures measured from a chest radiograph are magnified by 10%, the formula to predict LBW, which normalizes for this magnification factor, is: LBWmm = (0.45)(TWmm(CXR)) + 3.3 mm.

CONCLUSIONS

Direct airway measurement is the most accurate way to select an appropriate DLT. However, when direct measurement of LBW cannot be performed, estimating LBW from TW is a better predictor of LBW than either sex, height, or weight.

Dimensions of double-lumen tracheobronchial tubes

The diameter of the left main bronchus is the determining dimension when selecting the size of a left tracheobronchial (double-lumen) tube for lung separation. However, this information is not given by any manufacturer, either on the tube or in the package insert. This paper describes the lengths and diameters of the deflated bronchial cuff segment of left tracheobronchial tubes in common use. One hundred and seventy-one left tracheobronchial tubes ranging in size from 28 to 41 nominal French gauge from four manufacturers were measured. There was wide variation between tubes of the same nominal size from the same manufacturer. For tubes of the same size from the same manufacturer, the diameter of the segment with the deflated bronchial cuff varied by more than 1 mm in diameter in some instances. The diameter of the bronchial cuff segment did not consistently decrease as the nominal size decreased even for the same manufacturer. There was major overlap in diameters of the bronchial segments between Fr 41, Fr 39, and Fr 37 tubes from most manufacturers, so that some of the Fr 39 tubes have a bronchial cuff segment diameter as much as 0.5 mm larger than the Fr 41 tube. It is concluded that the current French gauge markings on left tracheobronchial tubes are of very limited value in determining the appropriate size to be selected for a patient. More accurate and consistent dimensions of tracheobronchial tubes are required to improve clinical selection.

Predicting the size of a double-lumen endobronchial tube using computed tomographic scan measurements of the left main bronchus diameter

We investigated the use of chest computer tomographic (CT) scan measurement of the left mainstem bronchial diameter to predict the correct left-sided double-lumen endobronchial tube (DLT) size in Asian patients who may require smaller DLT sizes. Fifty consecutive Asian adults aged 17-80 yr with preoperative chest CT scans undergoing elective thoracic surgery were entered into the study. The measurements of the left main bronchus diameter were made by using the electronic calipers of the spiral scanner to the nearest millimeter. The sizes of DLT selected were 32F, 35F, 37F, 39F, and 41F for left main bronchus diameters of <10 mm, 10 mm, 11 mm, 12 mm, and >12 mm, respectively. All DLT placements were confirmed and positioned by using fiberoptic bronchoscopy. The tracheas of all patients were successfully intubated with the predicted DLT sizes. Thirty-four patients (68%) were predicted to require smaller DLTs (37F or smaller). Six patients were correctly predicted to receive 32F DLTs. Twelve patients (24%) received an oversized DLT, but none received an undersized DLT. The overall positive predictive value for the male and female patients was 84.4% and 61.1%, respectively. Our study showed that CT scan measurements of the diameter of the left bronchus were especially useful in choosing smaller DLTs.

IMPLICATIONS

We used computer tomographic scans to measure the diameter of the left mainstem bronchus, then selected the size of the left-sided double-lumen endobronchial tube (DLT) accordingly. We found that we could predict the sizes of the DLT fairly accurately, especially the smaller DLTs.

Predicting the size of a double-lumen endobronchial tube based on tracheal diameter

We assessed whether using the tracheal diameter to predict the correct size of the left double-lumen endobronchial tube (DLT) could be used for our generally smaller sized Asian patients. Sixty-six consecutive adult patients under anesthesia for elective surgery requiring the use of a DLT were studied. The size of the left-sided DLT used was based on the width of patients' trachea measured from the preoperative posterior-anterior chest radiograph. The placement of the DLT was standardized and confirmed with fiberoptic bronchoscopy. The correct size of the DLT was the largest size tube inserted into the left bronchus with a small air leak detectable when the endobronchial cuff was deflated but not exceeding the recommended resting volume when inflated for lung isolation. Using this method of choosing our DLT, we found that an oversized DLT was often chosen especially among our female Asian patients. The overall positive predictive values for the male and female patients were 77.3% and 45.5%, respectively. We postulate that this could be due to our criteria for correct DLT size or that our local Asian patients, especially the females, were smaller and shorter.

IMPLICATIONS

This study assessed whether the correct double-lumen endobronchial tube size could be predicted from tracheal diameter measurements taken from the chest radiograph. We found that this method of choosing the double-lumen endobronchial tubes was not always reliable.

Evaluation of an approach to choosing a left double-lumen tube size based on chest computed tomographic scan measurement of left mainstem bronchial diameter

OBJECTIVE

Evaluation of an approach to choosing left double-lumen tube size based on chest computed tomographic (CT) scan measurement of left bronchial diameter.

DESIGN

Prospective.

SETTING

The operating rooms of a university hospital.

PARTICIPANTS

Patients scheduled for elective thoracic surgery.

INTERVENTIONS

Patients had their left bronchial diameter measured on the preoperative chest CT scan. Left double-lumen tube size for the individual patient was chosen from a protocol based on left bronchial diameter.

MEASUREMENTS AND MAIN RESULTS

The double-lumen tube size was considered appropriate for the patient if some air leak was detected when the bronchial cuff was deflated and if airtight seal of the left bronchus was obtained with a bronchial cuff volume of 2 mL or less. In 17 of 20 patients, the double-lumen tube size fulfilled both criteria. In 3 women with left bronchi measuring 10 mm or less, the bronchus was sealed without any air in the bronchial cuff of size 35 Fr left double-lumen tubes. In 1 patient, who was excluded from the study, the double-lumen tube size was chosen based on measurement of the left bronchial diameter on chest radiograph because of motion artifact on the chest CT scan.

CONCLUSIONS

Chest CT scan measurement of left bronchial diameter can successfully guide the choice of left double-lumen tube size for an individual patient. In individuals with a small left bronchus measuring less than 10.0 mm in diameter, currently available adult double-lumen tube sizes will tightly wedge in their bronchus.