Ann Otol 84: 1975
SPECIAL NEW LOW RESISTANCE TO FLOW TUBE AND ENDOTRACHEAL TUBE ADAPTER FOR USE DURING FIBEROPTIC BRONCHOSCOPY EDWARD CARDEN, FRCP(C) PHULCHAND P. RAJ, M.D. Los
ANGELES, CALIFORNIA
SUMMARY - This paper describes endotracheal tubes and adapters which are designed specially for fiberoptic bronchoscopy; the tubes are designed in such a way that they are wide at the upper part but are narrow and thin walled in the part of the tube which goes through and below the cords. By designing tubes in this manner, the resistance to How of gas through the tube when the fiberoptic bronchoscope is in place is very much reduced and the safety of the whole precedure is enhanced. A special adapter for use under these circumstances is also described which utilizes a commercially available swivel tracheostomy adapter with a special silicone diaphragm fitted onto the top to enable the fiberoptic bronchoscope to be placed through the diaphragm and keep a sealed system. A plug is available for the hole in the diaphragm when the fiberoptic bronchoscope is not being used. Clinical and laboratory data show that these pieces of equipment perform the function for which they were designed.
Fiberoptic bronchoscopy is a relatively new art which has gained much prominence over the last two or three years. With the advent of the fiberoptic bronchoscope, peripheral regions of the lungs can be viewed and previously undiagnosable conditions seen, biopsied, and diagnosed. There are, however, problems in the use of the fiberoptic bronchoscope when it is utilized during general anesthesia or during local anesthesia if an endotracheal tube is used as a sheath down which to slide the bronchoscope. The two problems which are the most prominent are the fact that, firstly, with the fiberoptic bronchoscope inside an endotracheal tube, the resistance to £low of gas through the tube rises very significantly and may be high enough to impair the respirations of the patient being bronchoscoped; 1 secondly, when the patient is being ventilated with positive pressure ventilation during the bronchoscopy, an adapter through which to slide the fiberoptic bronchoscope is needed which will seal
the bronchoscope and not allow anesthetic gases to leak out into the atmosphere. The purpose of this paper is to describe a new endotracheal tube for use during fiberoptic bronchoscopy and a special adapter to go with the tube to simplify the management of patients under general anesthesia. TUBE DESIGN
Adult endotracheal tubes (Fig. 1) were made in the same design as the Cole tube" used in infant anesthesia in that the upper section of the tube was made with a large diameter but the section of the tube which goes through the cords was of a smaller diameter. Tubes were manufactured from silicone elastomer, the narrow section of the tube being specially thin-walled with the external diameter equivalent to that of a normal 8.0, 8.5 or 9.0 silicone endotracheal tube but being 8.75, 9.25 and 9.5 mm in internal diameter respectively. In the narrow section of the tube a Murphy eye was present, as was a
Presented at the meeting of the American Broncho-Esophagological Association Atlanta Georgia, April 7-8, 1975. ' , 631
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
632
CARDEN-RAJ
Fig. 2. A) Diaphragm with attached plug. B) Swivel tracheostomy adaptor. C) A and B assembled, end on view. D) Portex endotracheal tube anchoring device.
Fig. 1. A) Standard 8.0 mm endotracheal tube. B) Special endotracheal tube. C) Special adaptor ( plug out) . D ) Special adaptor connected to tube (plug in place).
short cuff only approximately one inch long as opposed to the normal H to 2 inches long. The upper parts of the tubes were manufactured with tubing of 11 mm internal diameter and into the top of these tubes an endotracheal tube adapter was fitted with a conventional 15 mm male taper for connection to anesthesia apparatus. At the point where the wide section of the tube and the narrow section of the tube meet, the internal parts of the tube were streamlined to minimize turbulence. The outside parts of the tube were also smoothed, so that when resting against the cords, trauma would not occur. SPECIAL ADAPTER DESIGN
A commercially available, swivel, tracheostomy adapter" was obtained
and a special silicone elastomer diaphragm made to slip over the end of it (Fig. 2). The diaphragm has a hole in the center of it which is approximately 3 mm in diameter but which will stretch to accommodate anything from a 3 to a 6.5 mm rod placed through it. A special plug was also made to fit into this hole in the diaphragm. The plug was attached to the cap by a 1" length of 16 gauge Silastic®oo tubing. The intention was that general anesthesia would be maintained with the plug in place, and when fiberoptic bronchoscopy is going to be carried out the plug is removed and the bronchoscope inserted. The connection to the endotracheal tube is of a conventional 15 mm female type and the connection to the anesthesia machine is of the conventional15 mm male type. EXPERIMENTAL DATA
Tubes from the same manufacturer of 8, 8.5 and 9 mm internal diameter were obtained, and the resistance to flow through these tubes compared to the new tubes of equivalent external diameter in the distal portion with the fiberoptic bronchoscope inside them. In order to do this a flow rate of 20, 30 and 40 l.jmin was used through the endo-
.. Harris Lake, Inc . .." Dow Coming Corp., Midland, Mich.
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
FIBEROPTlC BRONCHOSCOPY
~4°1 ~
~ 20 '" o ._
.-----~
,_______
(i;
•
o
.
l--:::::;;. t f
20
• STAN'O 8.5 mm
..-----
~
iX!
_.--
~. STAN'O 8mm
:
' • STAN 0
9,Omm
:}
gg ~
- - - - - - - - - . STAN'O
30
I
SPEC'l
9.5 mm
9.0mm
40
LITERS IMIN
Fig. 3. Resistance to How through standard and special endotrach~al tubes with fiberoptic bronchoscope In place.
tracheal tube. Utilizing the special adapter described abov~, a 5.7 mm external diameter fiberoptic bronchoscope was placed inside these endotracheal tubes and the resistance to flow of gas through these tubes measured on a manometer. These results can be seen in Figure 3. CLINICAL STUDIES
633
out with the upward and downward movement of the bronchoscope? 3) Did the patient suffer any ~auma ~o the vocal cords with the wide section ?f the tube resting upon them? 4) DId anesthetic gases leak from around the diaphragm whilst the fiberoptic bronchoscope was being used? 5) Would the bronchoscope slide in and ~)Ut through the diaphragm and tube WIthout undue friction? 6) Could the anesthesia equipment be easily hooked up to this apparatus? RESULTS
The results of the laboratory studies (Fig. 3) confirm that the resistance to flow through these tubes is significantly less than an equivalent sized endotracheal tube. As noted earlier, rises of pC0 2 did not ocC?r. during bro~cho scopy. Further clinical observations: 1) The tubes were found to be easy to insert. 2) The tendency to come back out through the cords was minimal despite the use of a shorter than normal cuff length. 3) Careful viewing of the vocal cords following the endoscopy showed no evidence of trauma to the vocal cords from the shoulder of the tube resting upon them. 4) Provided the bronchoscope was lubricated with a water soluble gel, there was little tendency for gas to leak from around the diaphragm during the bronchoscopy procedure unless excessively high v~n tilation pressures were needed ( t.e., over 40 em H 20). 5) Provided that lubrication of the bronchoscope was carried out, there was very little friction noticed by the operator either from the inside of the tube or the diaphragm. 6) The tube was very simple to hook up to the standard anesthetic equipment and its use was made even easier by the fad that the adapter would swivel around its base.
Patients who were to have fiberoptic bronchoscopy under general anesthesia were anesthetized utilizing a conventional anesthetic technique with Pentothal,®O Anectine;®u this was follow~d by intubation with the special tube, mflation of the cuff, and ventilation ~ith nitrous oxide/oxygen mixtures usmg a Monaghan volume-cycled ventilator. n 0 The tube was anchored in the mouth with tape or a Portex tube a.nchorinz device (Fig. 2) and artenal blood b gas samples were obtained in heparinized syringes and. analyzed ~or oxygen, CO 2 and pH pnor to the msertion of the fiberoptic bronchoscope and ten minutes after beginning the fiberoptic bronchoscopy. No increas~s in arterial pC0 2 levels were found m the 15 cases studied all using the smallest diameter tube. The following clinical questions and DISCUSSION observations were made. 1) Was the tube as easy to insert through the cords The principle used in the design of as a normal endotracheal tube? 2) Was the tube is that embodied in the Cole there any tendency for the tube to come tube used in infants. The resistance to ---- .. Abbott Laboratories, North Chicago, Ill. 00 Burroughs Wellcome Co., Research Tria~gle Park, NC ...... Monaghan, Div, Sandoz-Wander, Inc., Littleton, CO
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
634
CARDEN-RAJ
flow down the upper part of the tube is negligible. The high resistance to flow occurs in the narrow section of the tube; and since the narrow section of the tube is approximately one fourth of the total length of the tube, the total resistance to flow through this endotracheal tube would be expected to be approximately one fourth the resistance to flow through a tube of equivalent internal diameter, but of normal configuration ( i.e., the same diameter throughout the whole length). In order to enhance the effectiveness of the tube, the terminal section was made with special thinwall tubing, thereby increasing the effective internal diameter and hence reducing the resistance to flow even more. To eliminate the possibility of the cuff overriding the end of the tube, the cuff has been made shorter and slightly stiffer than the normal silicone elastomer cuff. Its wall pressure in the trachea is still very much less than conventional smooth cuffed endotracheal tubes, but
its sealing is just as adequate. In carrying out the procedure of fiberoptic bronchoscopy, really critical resistance to flows occur when the difference between the external diameter of the fiberoptic bronchoscope and the internal diameter of the tube in which it is placed becomes less than 3~ mm.! and very small changes in this difference can make large changes in resistance to flow. Should the resistance to flow become too high, then we would expect to be able to blow a gas into the patient's lungs utilizing a ventilator. However, the patient may not have time to exhale, which may lead initially to an increase in arterial CO 2 levels, an increase in mean intrathoracic pressure with a fall off of cardiac output, and possibly to the development of a pneumothorax. It is therefore critical that resistance to flow of gases through these endotracheal tubes be as low as possible to minimize the occurrence of these complications. These tubes accomplish this.
Requests for reprints should be sent to Edward Carden, FRCP(C), VA Wadsworth Hospital Center, Anesthesiology Section, Wilshire and Sawtelle Blvd., Los Angeles CA 90073. REFERENCES 1. Lindholm CE: Flexible fiberoptic bronchoscopy in the critically ill patient. Ann Otol Rhinol Laryngol 83:786-794, 1974
2. Cole F: A New Endotracheal Tuhe for Infants. Anesthesiology 6:87-88, 1945
AMERICAN BOARD OF OTOLARYNGOLOGY The American Board of Otolaryngology will hold its next certifying examination Novemher 15-21, 1975, at the Palmer House, Chicago, Illinois. The deadline for applying for the 1975 examination is May 1, 1975.
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
SPECIAL NEW LOW RESISTANCE TO FLOW TUBE AND ENDOTRACHEAL TUBE ADAPTER FOR USE DURING FIBEROPTIC BRONCHOSCOPY EDWARD CARDEN, FRCP(C) PHULCHAND P. RAJ, M.D. Los
ANGELES, CALIFORNIA
SUMMARY - This paper describes endotracheal tubes and adapters which are designed specially for fiberoptic bronchoscopy; the tubes are designed in such a way that they are wide at the upper part but are narrow and thin walled in the part of the tube which goes through and below the cords. By designing tubes in this manner, the resistance to How of gas through the tube when the fiberoptic bronchoscope is in place is very much reduced and the safety of the whole precedure is enhanced. A special adapter for use under these circumstances is also described which utilizes a commercially available swivel tracheostomy adapter with a special silicone diaphragm fitted onto the top to enable the fiberoptic bronchoscope to be placed through the diaphragm and keep a sealed system. A plug is available for the hole in the diaphragm when the fiberoptic bronchoscope is not being used. Clinical and laboratory data show that these pieces of equipment perform the function for which they were designed.
Fiberoptic bronchoscopy is a relatively new art which has gained much prominence over the last two or three years. With the advent of the fiberoptic bronchoscope, peripheral regions of the lungs can be viewed and previously undiagnosable conditions seen, biopsied, and diagnosed. There are, however, problems in the use of the fiberoptic bronchoscope when it is utilized during general anesthesia or during local anesthesia if an endotracheal tube is used as a sheath down which to slide the bronchoscope. The two problems which are the most prominent are the fact that, firstly, with the fiberoptic bronchoscope inside an endotracheal tube, the resistance to £low of gas through the tube rises very significantly and may be high enough to impair the respirations of the patient being bronchoscoped; 1 secondly, when the patient is being ventilated with positive pressure ventilation during the bronchoscopy, an adapter through which to slide the fiberoptic bronchoscope is needed which will seal
the bronchoscope and not allow anesthetic gases to leak out into the atmosphere. The purpose of this paper is to describe a new endotracheal tube for use during fiberoptic bronchoscopy and a special adapter to go with the tube to simplify the management of patients under general anesthesia. TUBE DESIGN
Adult endotracheal tubes (Fig. 1) were made in the same design as the Cole tube" used in infant anesthesia in that the upper section of the tube was made with a large diameter but the section of the tube which goes through the cords was of a smaller diameter. Tubes were manufactured from silicone elastomer, the narrow section of the tube being specially thin-walled with the external diameter equivalent to that of a normal 8.0, 8.5 or 9.0 silicone endotracheal tube but being 8.75, 9.25 and 9.5 mm in internal diameter respectively. In the narrow section of the tube a Murphy eye was present, as was a
Presented at the meeting of the American Broncho-Esophagological Association Atlanta Georgia, April 7-8, 1975. ' , 631
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
632
CARDEN-RAJ
Fig. 2. A) Diaphragm with attached plug. B) Swivel tracheostomy adaptor. C) A and B assembled, end on view. D) Portex endotracheal tube anchoring device.
Fig. 1. A) Standard 8.0 mm endotracheal tube. B) Special endotracheal tube. C) Special adaptor ( plug out) . D ) Special adaptor connected to tube (plug in place).
short cuff only approximately one inch long as opposed to the normal H to 2 inches long. The upper parts of the tubes were manufactured with tubing of 11 mm internal diameter and into the top of these tubes an endotracheal tube adapter was fitted with a conventional 15 mm male taper for connection to anesthesia apparatus. At the point where the wide section of the tube and the narrow section of the tube meet, the internal parts of the tube were streamlined to minimize turbulence. The outside parts of the tube were also smoothed, so that when resting against the cords, trauma would not occur. SPECIAL ADAPTER DESIGN
A commercially available, swivel, tracheostomy adapter" was obtained
and a special silicone elastomer diaphragm made to slip over the end of it (Fig. 2). The diaphragm has a hole in the center of it which is approximately 3 mm in diameter but which will stretch to accommodate anything from a 3 to a 6.5 mm rod placed through it. A special plug was also made to fit into this hole in the diaphragm. The plug was attached to the cap by a 1" length of 16 gauge Silastic®oo tubing. The intention was that general anesthesia would be maintained with the plug in place, and when fiberoptic bronchoscopy is going to be carried out the plug is removed and the bronchoscope inserted. The connection to the endotracheal tube is of a conventional 15 mm female type and the connection to the anesthesia machine is of the conventional15 mm male type. EXPERIMENTAL DATA
Tubes from the same manufacturer of 8, 8.5 and 9 mm internal diameter were obtained, and the resistance to flow through these tubes compared to the new tubes of equivalent external diameter in the distal portion with the fiberoptic bronchoscope inside them. In order to do this a flow rate of 20, 30 and 40 l.jmin was used through the endo-
.. Harris Lake, Inc . .." Dow Coming Corp., Midland, Mich.
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
FIBEROPTlC BRONCHOSCOPY
~4°1 ~
~ 20 '" o ._
.-----~
,_______
(i;
•
o
.
l--:::::;;. t f
20
• STAN'O 8.5 mm
..-----
~
iX!
_.--
~. STAN'O 8mm
:
' • STAN 0
9,Omm
:}
gg ~
- - - - - - - - - . STAN'O
30
I
SPEC'l
9.5 mm
9.0mm
40
LITERS IMIN
Fig. 3. Resistance to How through standard and special endotrach~al tubes with fiberoptic bronchoscope In place.
tracheal tube. Utilizing the special adapter described abov~, a 5.7 mm external diameter fiberoptic bronchoscope was placed inside these endotracheal tubes and the resistance to flow of gas through these tubes measured on a manometer. These results can be seen in Figure 3. CLINICAL STUDIES
633
out with the upward and downward movement of the bronchoscope? 3) Did the patient suffer any ~auma ~o the vocal cords with the wide section ?f the tube resting upon them? 4) DId anesthetic gases leak from around the diaphragm whilst the fiberoptic bronchoscope was being used? 5) Would the bronchoscope slide in and ~)Ut through the diaphragm and tube WIthout undue friction? 6) Could the anesthesia equipment be easily hooked up to this apparatus? RESULTS
The results of the laboratory studies (Fig. 3) confirm that the resistance to flow through these tubes is significantly less than an equivalent sized endotracheal tube. As noted earlier, rises of pC0 2 did not ocC?r. during bro~cho scopy. Further clinical observations: 1) The tubes were found to be easy to insert. 2) The tendency to come back out through the cords was minimal despite the use of a shorter than normal cuff length. 3) Careful viewing of the vocal cords following the endoscopy showed no evidence of trauma to the vocal cords from the shoulder of the tube resting upon them. 4) Provided the bronchoscope was lubricated with a water soluble gel, there was little tendency for gas to leak from around the diaphragm during the bronchoscopy procedure unless excessively high v~n tilation pressures were needed ( t.e., over 40 em H 20). 5) Provided that lubrication of the bronchoscope was carried out, there was very little friction noticed by the operator either from the inside of the tube or the diaphragm. 6) The tube was very simple to hook up to the standard anesthetic equipment and its use was made even easier by the fad that the adapter would swivel around its base.
Patients who were to have fiberoptic bronchoscopy under general anesthesia were anesthetized utilizing a conventional anesthetic technique with Pentothal,®O Anectine;®u this was follow~d by intubation with the special tube, mflation of the cuff, and ventilation ~ith nitrous oxide/oxygen mixtures usmg a Monaghan volume-cycled ventilator. n 0 The tube was anchored in the mouth with tape or a Portex tube a.nchorinz device (Fig. 2) and artenal blood b gas samples were obtained in heparinized syringes and. analyzed ~or oxygen, CO 2 and pH pnor to the msertion of the fiberoptic bronchoscope and ten minutes after beginning the fiberoptic bronchoscopy. No increas~s in arterial pC0 2 levels were found m the 15 cases studied all using the smallest diameter tube. The following clinical questions and DISCUSSION observations were made. 1) Was the tube as easy to insert through the cords The principle used in the design of as a normal endotracheal tube? 2) Was the tube is that embodied in the Cole there any tendency for the tube to come tube used in infants. The resistance to ---- .. Abbott Laboratories, North Chicago, Ill. 00 Burroughs Wellcome Co., Research Tria~gle Park, NC ...... Monaghan, Div, Sandoz-Wander, Inc., Littleton, CO
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
634
CARDEN-RAJ
flow down the upper part of the tube is negligible. The high resistance to flow occurs in the narrow section of the tube; and since the narrow section of the tube is approximately one fourth of the total length of the tube, the total resistance to flow through this endotracheal tube would be expected to be approximately one fourth the resistance to flow through a tube of equivalent internal diameter, but of normal configuration ( i.e., the same diameter throughout the whole length). In order to enhance the effectiveness of the tube, the terminal section was made with special thinwall tubing, thereby increasing the effective internal diameter and hence reducing the resistance to flow even more. To eliminate the possibility of the cuff overriding the end of the tube, the cuff has been made shorter and slightly stiffer than the normal silicone elastomer cuff. Its wall pressure in the trachea is still very much less than conventional smooth cuffed endotracheal tubes, but
its sealing is just as adequate. In carrying out the procedure of fiberoptic bronchoscopy, really critical resistance to flows occur when the difference between the external diameter of the fiberoptic bronchoscope and the internal diameter of the tube in which it is placed becomes less than 3~ mm.! and very small changes in this difference can make large changes in resistance to flow. Should the resistance to flow become too high, then we would expect to be able to blow a gas into the patient's lungs utilizing a ventilator. However, the patient may not have time to exhale, which may lead initially to an increase in arterial CO 2 levels, an increase in mean intrathoracic pressure with a fall off of cardiac output, and possibly to the development of a pneumothorax. It is therefore critical that resistance to flow of gases through these endotracheal tubes be as low as possible to minimize the occurrence of these complications. These tubes accomplish this.
Requests for reprints should be sent to Edward Carden, FRCP(C), VA Wadsworth Hospital Center, Anesthesiology Section, Wilshire and Sawtelle Blvd., Los Angeles CA 90073. REFERENCES 1. Lindholm CE: Flexible fiberoptic bronchoscopy in the critically ill patient. Ann Otol Rhinol Laryngol 83:786-794, 1974
2. Cole F: A New Endotracheal Tuhe for Infants. Anesthesiology 6:87-88, 1945
AMERICAN BOARD OF OTOLARYNGOLOGY The American Board of Otolaryngology will hold its next certifying examination Novemher 15-21, 1975, at the Palmer House, Chicago, Illinois. The deadline for applying for the 1975 examination is May 1, 1975.
Downloaded from aor.sagepub.com at MICHIGAN STATE UNIV LIBRARIES on June 17, 2015
