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Clinical experience with a new right-sided endobronchial tube in left main bronchus surgery
Clinical Experience With a New Right-Sided Endobronchial Tube in Left Main Bronchus Surgery Rinaldo Trazzi, MD and Stefano Nazari, MD Clinical experience during one-lung anesthesia using a new right-sided endobronchial tube (Portex Ltd, Hythe, Kent, UK) is reported in 148 patients with cancer of the left lung. The method allowed a reliable airtight separation of the lungs as well as right upper lobe ventilation in all cases. The new tube also allowed proper upper lobe ventilation in cases with anatomical variations of the length of the right main
bronchus. The intubation technique was greatly simplified when compared with commercially available double-lumen tubes. Airway pressures and arterial blood gases were similar to those obtained with standard double-lumen tubes during one-lung ventilation. There w e r e no complications due to the new tube system. © 1989 by W.B. Saunders Company.
NE-LUNG ANESTHESIA is commonly used during thoracic surgery. Its major aims are to prevent down-lung flooding by blood or secretions from the upper lung; to guarantee proper ventilation when the bronchus is open; and to make the surgical procedure easier by collapsing or inflating the lung in the operative field. 1 Although many methods for one-lung anesthesia have been used in the past, 1-3 doublelumen endobronchial tubes are now most frequently used in clinical practice. 4 However, use of these tubes is quite complex; the major problem is proper tube positioning. The left-sided tubes, Carlens (Rusch, Waiblingen, FRG) and Robertshaw (Hallinckrodt GmbH, Hennef/Sieg 1, FRG), 2 are routinely used in most centers. 4 Fiberoptic bronchoscopy is usually used to obtain the proper position. 5 However, major problems still arise with intubation of the right mainstem bronchus, which is often used when left-sided surgery is planned. 1 The right main bronchus is shorter than the left, and right upper lobar bronchial obstruction by the tube or cuff and/or incomplete lung separation often result. 1 Right-sided double-lumen tubes fitted with a lateral opening in the cuff have been used to try to prevent these complications (Fig 1). Nevertheless, extreme precision in positioning these tubes is required in order to achieve correct alignment of the upper lobar bronchus with the lateral opening of the tube. This problem is worse in cases with abnormalities in the length of the right main bronchus. In these cases, the presence of the carinal hook on a White tube (Rusch) may stop the tube tip in an incorrect position, and incomplete separation of the lungs may result
(Fig 1). Thus, although this and other techniques (ie, Robertshaw) enable right bronchus intubation, the anatomy of the right mainstem bronchus and its variations frequently limit their practical clinical use. The purpose of this article is to report on a large clinical experience using a new right-sided endobronchial tube.
O
MATERIALS A N D METHODS
The right-sided single-lumen endobronchial tube used in this series of patients consisted of a longer-than-normal (5to 6-mm inner diameter) cuffed tube. At its distal end, the tube is fitted with a side branch arm originating immediately after the cuff, which forms a 45 ° angle with the major axis (Fig 2). Separate lung ventilation is achieved by positioning the tip of the endobronchial tube into the right main bronchus after passing through a standard endotracheal tube (Fig 2). The two tubes assembled in this way define two independent channels, each in communication with one lung. Coupling the endobronchial tube size with the suitable size of the endotraeheal tube (Table 1), the two resulting channels have similar air resistances allowing similar tidal volumes to the two lungs when both lumens are ventilated.7 The endobronchial tube can be positioned in several ways, even during surgery in the lateral decubitus position. However, the following technique is recommended. A standard endotracheal tube is positioned with the usual technique at 20 to 22 cm from the dental arch and the patient is ventilated. The inner surface of the endotracheal tube as well
From the Department of Surgery, Division Patologia Chirurgica, University of Pavia, Pavia, Italy, and H Cattedra di Anestesia e Rianimazione, Universita di Milano, Milan, Italy. Address reprint requests to Professor Rinaldo Trazzi, Direttore della II Cattedra di Anestesia e Rianimazione dell'Universita di Milano, Padiglione Zonda, Via Francesco Sforza, Milan, Italy. © 1989 by W..B. Saunders Company. 0888-6296/89/0304-0013503.00/0
Journal of Cardiothoracic Anesthesia, Vol 3, No 4 (August), 1989: pp 461-464
461
462
TRAZZl AND NAZARI Table 1. Possible Combinations of Trachael and Bronchial Tubes
Tracheal tube (mm) Inner diameter Outer diameter Bronchial tube (mm) Inner diameter Outer diameter Cross-sectional area (mm 2) Bronchial channel Tracheal channel
A
Set1
~t2
~t3
11 15
10 13.6
9 12.2
6 6.2
5.5 7.4
5 6.8
28.3 42.2
23.7 35.5
19.6 27.3
The bronchial tubes are available upon special request from Portex, Ltd.
Fig 1. The right-sided double-lumen tubes commercially available (White and Robertshaw} are fitted with a lateral opening in order to prevent right upper lobar bronchus obstruction by the cuff. (A) However, extreme accuracy is required in positioning these tubes to obtain proper alignment of the lateral opening of the tube with the upper lobar bronchus origin. (B) In cases of even minor variation of the length of the right main bronchus, the proper alignment of the lateral opening with the upper lobar bronchus may not be achievable; this may result in incomplete lung separation (arrow).
As a general rule, the largest possible endotracheal tube is inserted, coupled with the corresponding bronchial tube size (Table 1) to obtain two lumens with minimal resistance. However, when exact division of the tidal volume between the two lungs is not mandatory, ie, one-lung anesthesia, any combination of the tracheal and bronchial tubes can be used. From January 1985 through August 1987, 148 patients (122 men, 26 women; mean age, 54 _+9 years) underwent one-lung anesthesia with the new right-sided endobronchial tube for left lung cancer surgery. Thirty-five patients underwent pneumonectomy, 102 upper or lower lobectomy, and 11 left main bronchus plastic procedures, alone or in association with upper lobectomy and/or sleeve resections. In 10 patients, airway pressure andblood gases during one-lung anesthesia were recorded.
as the outer surface of the bronchial tube must be lubricated before insertion with suitable material (Silkospray, Rusch). Then the right bronchial tube is inserted and pushed down into the endotracheal tube. A longitudinal blue line on the anterior surface of the tube provides a reference for proper orientation during insertion. An external mark on the bronchial tube indicates when the distal end of the tube with the cuff has emerged from the endotracheal tube tip. At this point (Fig 2B) both channels are fully patent and the tubes can be connected to a respirator while the last phase of the bronchial intubation is completed with the patient being ventilated. The bronchial tube, properly oriented, is pushed a few centimeters until its advancement is stopped by the engagement of the lateral arm into the upper lobar bronchus (Fig 2C and D), indicating that the correct position has been reached.
RESULTS
Right bronchial intubation was successful in all cases. In all but one case, the bronchial intubation was carried out with the patient in the supine position, immediately after having positioned the endotracbeal tube. One bronchial intubation was carried out during surgery with
i
Fig 2. (A, B) The new rightsided bronchial tube is put in place by passing it through a standard andotracheal tube. (C) The lateral branch is engaged into the right upper lobar bronchus and stops the tube advancement when the proper position has been reached. (D) Thus, upper lobar bronchial cuff obstruction is prevented, and ventilation is possible from the distal lumen.
NEW RIGHT-SIDED ENDOBRONCHIAL TUBE
the patient in the lateral decubitus position. Standard endotracheal tubes from different companies were used for endotracheal intubation provided that they did not have a Murphy eye lateral opening. It was sometimes useful to shorten the tracheal tube by cutting off 3 to 5 cm of the outer end; this allows a deeper insertion of the bronchial tube when required. In 120 patients (81%) the sizes in set 2 (Table 1) were used, in 25 (16.8%) set 3 was used, and in 3 patients (2%) set 1 was needed. In 32 patients (21%), the first trial of right bronchial intubation was unsuccessful. Chest auscultation gave doubtful or completely unsatisfactory results. The bronchial tube was then removed, and intubation was repeated. In these cases, pulling back the endotracheal tube often led to successful intubation of the right mainstem bronchus. In all but three cases proper bronchial tube position was achieved after this procedure. In the remaining three cases, the bronchial tube was positioned under bronchoscopic control, with a pediatric bronchoscope being inserted through the bronchial tube during intubationY When pneumonectomy was performed, the bronchial tube tip was inspected at the carinal area before suturing the bronchial stump at its origin. The cuff was found to be properly placed in all cases. In a few cases it was necessary to correct the bronchial tube position during surgery because of subsequent displacement and incomplete separation. This did not present special difficulties, and cooperation between the anesthesiologist and surgeon resulted in proper tube placement in all cases. In no patients, including those intubated with the ll-mm endotracheal tube, was postoperative laryngeal stridor or any other clinical sign of laryngotracheal injury due to the tracheal tube evident. The airway pressure and blood gas analysis during one-lung anesthesia showed similar values to those recorded using standard double-lumen tubes (Table 2). DISCUSSION
Right-sided one-lung anesthesia is still a problem in clinical practice. Although experienced anesthesiologists are usually able to safely and reliably position the Carlens or Robertshaw left-sided double-lumen tubes, there is much
463
Table 2. Peak Pressures in Bronchial Channel and Blood Gases During One-Lung Anesthesia Set 2 (n = 8)
Tidal volume delivered (mL) Peak pressure (cm H20)
300 -
15
Set 3 (n = 2) 2 8 0 _+ 10
35 + 5
4 5 _+ 6
7 . 3 2 _+ 0.01
7 , 3 0 _+ 0.01
130 _+ 2 0
110 _+ 18
Blood gases (arterial) pH PO z (mmHg) PCOz (mmHg) Hb saturation (%)
4 5 _+ 6 99
4 8 _+ 7 99
more difficulty with the right-sided tubes (White, Robertshaw). Good results with a new type of bronchial blocker whose position is facilitated by placement of the blocker in a special channel of an endotracheal tube have been reported. 8 However, it should be emphasized that all blockers must be positioned in the main bronchus of the "surgical lung ''9 and can be used only when lobectomy is planned. Pneumonectomy or main bronchus plastic procedures cannot be carried out with a bronchial blocker because it is in the operative field at the time of the main bronchial surgical repair. The new right-sided tube described in this report seems to offer many advantages over the other methods used to isolate the lungs. The bifurcated tip of the tube ensures both proper right upper lobe ventilation and airtight lung separation no matter how long the right bronchus may be (Fig 3). The importance of these anatomical variations has been recently described and their impact on right bronchial intubation emphasized. 10 In difficult cases (eg, tracheobronchial displacement by tumors) endobronchial intubation can be carried out under direct vision with the new system. A fiberoptic bronchoscope can be passed through the bronchial tube during insertion.7 The bronchial tube tip can be guided and properly positioned in the right main bronchus, and proper hooking of the bifurcation of the tube onto the upper lobe bronchus can be verified. Additional advantages of this new doubletube system include the possibility of removing the bronchial tube when one-lung anesthesia is no longer needed. The patient can then be ventilated through the tracheal tube at the end of
464
TRAZZl AND NAZARI
~-4J --..j
/f
\ A
B
C
surgery and postoperatively if required (ie, aortic surgery, lung transplant). The bronchial tube can also be positioned during surgery while the patient is in the lateral decubitus position. This
Fig 3. When variations in the length of the right main bronchus are present (B,C), the new tube allows proper ventilation of the upper lobe as well as airtight lung separation (n, normal right bronchus length in A).
allows unexpected clinical problems to be resolved. In addition, all problems related to the passage through the larynx of bulky, traumatic double-lumen tube tips are virtually avoided.
REFERENCES 1. Wilson RS: Endobronchial intubation, in Kaplan JA (ed): Thoracic Anesthesia. New York, Churchill Livingstone, 1983, pp 389-402 2. Carlens E: A new flexible double-lumen catheter for bronchospirometry. J Thorac Surg 18:742-746, 1949 3. White GMJ: A new double-lumen tube. Br J Anaesth 32:232-234, 1960 4. Pappin JC: Current practice of endobronchial intubation. Anaesthesia 34:57-64, 1979 5. Alfery DD, Benumof JL, Spragg RR: Anesthesia for bronchopulmonary lavage, in Kaplan JA (ed): Thoracic Anesthesia. New York, Churchill Livingstone, 1983, pp 409-410 6. Nazari S, Trazzi R, Moncalvo F, et al: Selective
bronchial intubation for one-lung anaesthesia in thoracic surgery. A new method. Anaesthesia 41:519-526, 1986 7. Nazari S, Trazzi R, Moncalvo F, et al: A new method for separate lung ventilation. J Thorac Cardiovasc Surg 95:133-138, 1988 8. Inoue H, Shotsu A, Ogawa J, et al: New device for one-lung anesthesia: Endotracheal tube with movable blocker. J Thorac Cardiovasc Surg 83:940-941, 1982 (letter) 9. Ginsberg R J: New technique for one-lung anesthesia using an endobronchial blocker. J Thorac Cardiovasc Surg 82:542-546, 1981 10. Benumof J, Partridge BL, Salvatierra C, et al: Margin of safety in positioning modern double-lumen endotracheal tubes. Anesthesiology 67:729-738, 1987
bronchus. The intubation technique was greatly simplified when compared with commercially available double-lumen tubes. Airway pressures and arterial blood gases were similar to those obtained with standard double-lumen tubes during one-lung ventilation. There w e r e no complications due to the new tube system. © 1989 by W.B. Saunders Company.
NE-LUNG ANESTHESIA is commonly used during thoracic surgery. Its major aims are to prevent down-lung flooding by blood or secretions from the upper lung; to guarantee proper ventilation when the bronchus is open; and to make the surgical procedure easier by collapsing or inflating the lung in the operative field. 1 Although many methods for one-lung anesthesia have been used in the past, 1-3 doublelumen endobronchial tubes are now most frequently used in clinical practice. 4 However, use of these tubes is quite complex; the major problem is proper tube positioning. The left-sided tubes, Carlens (Rusch, Waiblingen, FRG) and Robertshaw (Hallinckrodt GmbH, Hennef/Sieg 1, FRG), 2 are routinely used in most centers. 4 Fiberoptic bronchoscopy is usually used to obtain the proper position. 5 However, major problems still arise with intubation of the right mainstem bronchus, which is often used when left-sided surgery is planned. 1 The right main bronchus is shorter than the left, and right upper lobar bronchial obstruction by the tube or cuff and/or incomplete lung separation often result. 1 Right-sided double-lumen tubes fitted with a lateral opening in the cuff have been used to try to prevent these complications (Fig 1). Nevertheless, extreme precision in positioning these tubes is required in order to achieve correct alignment of the upper lobar bronchus with the lateral opening of the tube. This problem is worse in cases with abnormalities in the length of the right main bronchus. In these cases, the presence of the carinal hook on a White tube (Rusch) may stop the tube tip in an incorrect position, and incomplete separation of the lungs may result
(Fig 1). Thus, although this and other techniques (ie, Robertshaw) enable right bronchus intubation, the anatomy of the right mainstem bronchus and its variations frequently limit their practical clinical use. The purpose of this article is to report on a large clinical experience using a new right-sided endobronchial tube.
O
MATERIALS A N D METHODS
The right-sided single-lumen endobronchial tube used in this series of patients consisted of a longer-than-normal (5to 6-mm inner diameter) cuffed tube. At its distal end, the tube is fitted with a side branch arm originating immediately after the cuff, which forms a 45 ° angle with the major axis (Fig 2). Separate lung ventilation is achieved by positioning the tip of the endobronchial tube into the right main bronchus after passing through a standard endotracheal tube (Fig 2). The two tubes assembled in this way define two independent channels, each in communication with one lung. Coupling the endobronchial tube size with the suitable size of the endotraeheal tube (Table 1), the two resulting channels have similar air resistances allowing similar tidal volumes to the two lungs when both lumens are ventilated.7 The endobronchial tube can be positioned in several ways, even during surgery in the lateral decubitus position. However, the following technique is recommended. A standard endotracheal tube is positioned with the usual technique at 20 to 22 cm from the dental arch and the patient is ventilated. The inner surface of the endotracheal tube as well
From the Department of Surgery, Division Patologia Chirurgica, University of Pavia, Pavia, Italy, and H Cattedra di Anestesia e Rianimazione, Universita di Milano, Milan, Italy. Address reprint requests to Professor Rinaldo Trazzi, Direttore della II Cattedra di Anestesia e Rianimazione dell'Universita di Milano, Padiglione Zonda, Via Francesco Sforza, Milan, Italy. © 1989 by W..B. Saunders Company. 0888-6296/89/0304-0013503.00/0
Journal of Cardiothoracic Anesthesia, Vol 3, No 4 (August), 1989: pp 461-464
461
462
TRAZZl AND NAZARI Table 1. Possible Combinations of Trachael and Bronchial Tubes
Tracheal tube (mm) Inner diameter Outer diameter Bronchial tube (mm) Inner diameter Outer diameter Cross-sectional area (mm 2) Bronchial channel Tracheal channel
A
Set1
~t2
~t3
11 15
10 13.6
9 12.2
6 6.2
5.5 7.4
5 6.8
28.3 42.2
23.7 35.5
19.6 27.3
The bronchial tubes are available upon special request from Portex, Ltd.
Fig 1. The right-sided double-lumen tubes commercially available (White and Robertshaw} are fitted with a lateral opening in order to prevent right upper lobar bronchus obstruction by the cuff. (A) However, extreme accuracy is required in positioning these tubes to obtain proper alignment of the lateral opening of the tube with the upper lobar bronchus origin. (B) In cases of even minor variation of the length of the right main bronchus, the proper alignment of the lateral opening with the upper lobar bronchus may not be achievable; this may result in incomplete lung separation (arrow).
As a general rule, the largest possible endotracheal tube is inserted, coupled with the corresponding bronchial tube size (Table 1) to obtain two lumens with minimal resistance. However, when exact division of the tidal volume between the two lungs is not mandatory, ie, one-lung anesthesia, any combination of the tracheal and bronchial tubes can be used. From January 1985 through August 1987, 148 patients (122 men, 26 women; mean age, 54 _+9 years) underwent one-lung anesthesia with the new right-sided endobronchial tube for left lung cancer surgery. Thirty-five patients underwent pneumonectomy, 102 upper or lower lobectomy, and 11 left main bronchus plastic procedures, alone or in association with upper lobectomy and/or sleeve resections. In 10 patients, airway pressure andblood gases during one-lung anesthesia were recorded.
as the outer surface of the bronchial tube must be lubricated before insertion with suitable material (Silkospray, Rusch). Then the right bronchial tube is inserted and pushed down into the endotracheal tube. A longitudinal blue line on the anterior surface of the tube provides a reference for proper orientation during insertion. An external mark on the bronchial tube indicates when the distal end of the tube with the cuff has emerged from the endotracheal tube tip. At this point (Fig 2B) both channels are fully patent and the tubes can be connected to a respirator while the last phase of the bronchial intubation is completed with the patient being ventilated. The bronchial tube, properly oriented, is pushed a few centimeters until its advancement is stopped by the engagement of the lateral arm into the upper lobar bronchus (Fig 2C and D), indicating that the correct position has been reached.
RESULTS
Right bronchial intubation was successful in all cases. In all but one case, the bronchial intubation was carried out with the patient in the supine position, immediately after having positioned the endotracbeal tube. One bronchial intubation was carried out during surgery with
i
Fig 2. (A, B) The new rightsided bronchial tube is put in place by passing it through a standard andotracheal tube. (C) The lateral branch is engaged into the right upper lobar bronchus and stops the tube advancement when the proper position has been reached. (D) Thus, upper lobar bronchial cuff obstruction is prevented, and ventilation is possible from the distal lumen.
NEW RIGHT-SIDED ENDOBRONCHIAL TUBE
the patient in the lateral decubitus position. Standard endotracheal tubes from different companies were used for endotracheal intubation provided that they did not have a Murphy eye lateral opening. It was sometimes useful to shorten the tracheal tube by cutting off 3 to 5 cm of the outer end; this allows a deeper insertion of the bronchial tube when required. In 120 patients (81%) the sizes in set 2 (Table 1) were used, in 25 (16.8%) set 3 was used, and in 3 patients (2%) set 1 was needed. In 32 patients (21%), the first trial of right bronchial intubation was unsuccessful. Chest auscultation gave doubtful or completely unsatisfactory results. The bronchial tube was then removed, and intubation was repeated. In these cases, pulling back the endotracheal tube often led to successful intubation of the right mainstem bronchus. In all but three cases proper bronchial tube position was achieved after this procedure. In the remaining three cases, the bronchial tube was positioned under bronchoscopic control, with a pediatric bronchoscope being inserted through the bronchial tube during intubationY When pneumonectomy was performed, the bronchial tube tip was inspected at the carinal area before suturing the bronchial stump at its origin. The cuff was found to be properly placed in all cases. In a few cases it was necessary to correct the bronchial tube position during surgery because of subsequent displacement and incomplete separation. This did not present special difficulties, and cooperation between the anesthesiologist and surgeon resulted in proper tube placement in all cases. In no patients, including those intubated with the ll-mm endotracheal tube, was postoperative laryngeal stridor or any other clinical sign of laryngotracheal injury due to the tracheal tube evident. The airway pressure and blood gas analysis during one-lung anesthesia showed similar values to those recorded using standard double-lumen tubes (Table 2). DISCUSSION
Right-sided one-lung anesthesia is still a problem in clinical practice. Although experienced anesthesiologists are usually able to safely and reliably position the Carlens or Robertshaw left-sided double-lumen tubes, there is much
463
Table 2. Peak Pressures in Bronchial Channel and Blood Gases During One-Lung Anesthesia Set 2 (n = 8)
Tidal volume delivered (mL) Peak pressure (cm H20)
300 -
15
Set 3 (n = 2) 2 8 0 _+ 10
35 + 5
4 5 _+ 6
7 . 3 2 _+ 0.01
7 , 3 0 _+ 0.01
130 _+ 2 0
110 _+ 18
Blood gases (arterial) pH PO z (mmHg) PCOz (mmHg) Hb saturation (%)
4 5 _+ 6 99
4 8 _+ 7 99
more difficulty with the right-sided tubes (White, Robertshaw). Good results with a new type of bronchial blocker whose position is facilitated by placement of the blocker in a special channel of an endotracheal tube have been reported. 8 However, it should be emphasized that all blockers must be positioned in the main bronchus of the "surgical lung ''9 and can be used only when lobectomy is planned. Pneumonectomy or main bronchus plastic procedures cannot be carried out with a bronchial blocker because it is in the operative field at the time of the main bronchial surgical repair. The new right-sided tube described in this report seems to offer many advantages over the other methods used to isolate the lungs. The bifurcated tip of the tube ensures both proper right upper lobe ventilation and airtight lung separation no matter how long the right bronchus may be (Fig 3). The importance of these anatomical variations has been recently described and their impact on right bronchial intubation emphasized. 10 In difficult cases (eg, tracheobronchial displacement by tumors) endobronchial intubation can be carried out under direct vision with the new system. A fiberoptic bronchoscope can be passed through the bronchial tube during insertion.7 The bronchial tube tip can be guided and properly positioned in the right main bronchus, and proper hooking of the bifurcation of the tube onto the upper lobe bronchus can be verified. Additional advantages of this new doubletube system include the possibility of removing the bronchial tube when one-lung anesthesia is no longer needed. The patient can then be ventilated through the tracheal tube at the end of
464
TRAZZl AND NAZARI
~-4J --..j
/f
\ A
B
C
surgery and postoperatively if required (ie, aortic surgery, lung transplant). The bronchial tube can also be positioned during surgery while the patient is in the lateral decubitus position. This
Fig 3. When variations in the length of the right main bronchus are present (B,C), the new tube allows proper ventilation of the upper lobe as well as airtight lung separation (n, normal right bronchus length in A).
allows unexpected clinical problems to be resolved. In addition, all problems related to the passage through the larynx of bulky, traumatic double-lumen tube tips are virtually avoided.
REFERENCES 1. Wilson RS: Endobronchial intubation, in Kaplan JA (ed): Thoracic Anesthesia. New York, Churchill Livingstone, 1983, pp 389-402 2. Carlens E: A new flexible double-lumen catheter for bronchospirometry. J Thorac Surg 18:742-746, 1949 3. White GMJ: A new double-lumen tube. Br J Anaesth 32:232-234, 1960 4. Pappin JC: Current practice of endobronchial intubation. Anaesthesia 34:57-64, 1979 5. Alfery DD, Benumof JL, Spragg RR: Anesthesia for bronchopulmonary lavage, in Kaplan JA (ed): Thoracic Anesthesia. New York, Churchill Livingstone, 1983, pp 409-410 6. Nazari S, Trazzi R, Moncalvo F, et al: Selective
bronchial intubation for one-lung anaesthesia in thoracic surgery. A new method. Anaesthesia 41:519-526, 1986 7. Nazari S, Trazzi R, Moncalvo F, et al: A new method for separate lung ventilation. J Thorac Cardiovasc Surg 95:133-138, 1988 8. Inoue H, Shotsu A, Ogawa J, et al: New device for one-lung anesthesia: Endotracheal tube with movable blocker. J Thorac Cardiovasc Surg 83:940-941, 1982 (letter) 9. Ginsberg R J: New technique for one-lung anesthesia using an endobronchial blocker. J Thorac Cardiovasc Surg 82:542-546, 1981 10. Benumof J, Partridge BL, Salvatierra C, et al: Margin of safety in positioning modern double-lumen endotracheal tubes. Anesthesiology 67:729-738, 1987