A New Tracheostomy Tube

Transcription

1 Kenneth L. Hardy, M.D., Bruce E. Fettel, B.S.M.E., and Donald P. Shiley, B.S.G.E. T remendous advances in our understanding of respiratory physiology and our ability to assist or control respirations over prolonged periods have occurred during the past decade. Through the contributions of engineering and electronics, upgrading of ventilatory assist devices of both the pressure- and volume-controlled variety has been progressive. However, improvements in safety, design, and function of the lowly tracheostomy tube have failed to keep pace with these other outstanding achievements. Mindful of the markedly increased incidence of tracheal stenosis with the recent widespread use of cuffed tubes for prolonged ventilatory support, we should like to introduce a new and unique tube which combines in one unit advantages heretofore not available (Fig. 1). Design, experimental testing, and clinical application of prototype tubes over almost three years have resulted in the unit we are now presenting. We feel that a good tracheostomy tube should incorporate the following features: 1. The outer cannula (Fig. 2, A) is semirigid, neither stiff nor kinkable, and is radiopaque. It is beveled at the distal end so as to be nonirritating. It is slightly shorter than most tubes to prevent riding on the carina, yet it is long enough for the individual with deep neck tissues. Its 70" arc facilitates insertion and adapts to normal anatomy better than most tubes which have a greater arc (up to 90" in some). This has been determined by cadaver studies and x-ray correlations in living patients. 2. An inner cannula (Fig. 2, B) is a must. Its proper use and hourly cleaning assure that the tube will remain patent and free of obstruction. The lack of an inner cannula in most disposable tubes is dangerous. This is one reason for continuing to use the otherwise obsolete heavy metal tubes. Buildup of fibrin, blood clot, and mucoid encrustations can gradually reduce or acutely obstruct an otherwise From the Department of Thoracic and Cardiovascular Surgery, University of California School of Medicine, San Francisco, Calif., the Highland-Alameda County Hospital, Oakland, Calif., and Shiley Laboratories, Inc., Santa Ana, Calif. Presented at the Sixth Annual Meeting of The Society of Thoracic Surgeons, Atlanta, Ga., Jan , Address reprint requests to Dr. Hardy, 3115 Webster Street, Oakland, Calif THE ANNALS OF THORACIC SURGERY

2 FIG. 1. Hardy tracheostomy tube assembled with balloon inflated. good airway when an inner cannula is not used. Nurses then report that it is increasingly difficult to introduce the suction catheter or that only a small catheter can be passed, which is completely ineffective in removing the thick, tenacious secretions present in most of these patients. The inner cannula in our tube is easily inserted, but its tip blends smoothly and snugly with the outer cannula. Its thinness minimizes reduction of inside diameter. Another feature of the inner cannula is that it is transparent, which greatly facilitates thorough cleaning. Encrustations are visible through the wall of the cannula and can be completely removed, which is not always possible when a soft pipe cleaner or brush is passed blindly over them. The cannula locks securely in position, thus preventing the drag of respirator hoses and flex tubes from dislodging it. We are so concerned about the safety features of an inner cannula in keeping the unit clean and patent that we purposely placed the adaptor on the proximal end of the inner cannula. In this way, respirator equipment cannot be attached to the tube if the inner cannula is not in position and locked. 3. The revolutionary neck flange (Fig. 2, C) swivels 45 degrees, thus allowing the basic 70" arc tube to ride free within the tracheal lumen in the widest spectrum of anatomical situations. This lessens VOL. 10, NO. 1, JULY,

3 HARDY, FETTEL, AND SHILEY FIG. 2. Tube disassembled, illustrating component parts: (A) outer cannula; (B) inner cannula; (C) swive2 neck flange; (D) balloon (cufl) deflated; (E) inflation system (inpation line, test balloon, pressure retention clamp); (F) obtzirator; (G) adaptor. impingement of the end of the tube against the mucosa with neck motion, preventing erosion and tracheal injury. It also enhances comfort and early patient acceptance after its introduction. 4. The cuff or balloon (Fig. 2, 0) inflates uniformly and repetitively to a sausage or cylindrical contour. Studies in our laboratory have revealed that existing balloons vary greatly in the pressure they require to achieve minimal occluding volume (MOV) [4, 71, not only from one manufacturer to another but also between tubes of the same brand, and even in the same tube at different times. This is because of variations in thickness and stretch properties and material fatigue inherent in rubber and latex balloons. These cuffs inflate to a round or, more frequently, to an eccentric ball configuration (Fig. 3), and to establish seal they require a high equatorial pressure over a narrow luminal zone. The resulting actual tracheal pressure (ATP) [7] may be excessive, causing localized tracheal wall ischemia, which is a precursor of later cicatricial stenosis [l, 2, 51. Extreme eccentricity in some balloons when inflated actually thrusts the tube tip against the opposite tracheal wall and may at times cause erosion by the end of the tube itself [3]. The uniform cylindrical shape of our balloon when inflated keeps the tube tip in the center of the lumen, preventing it from impinging on the wall. The volume of air necessary to eslablish seal or to prevent leak at 30 cm. positivepressure breathing. Most ventilators are not set at a mask preswre this high. 60 THE ANNALS OF THORACIC SURGERY

4 FIG. 3. Eccentricity of round balloons on inpation. Our studies using various balloon contours inflated within semirigid tubes have shown that a seal is achieved with much less lateral pressure (ATP) when that pressure is exerted uniformly over a longer axial length. In actual clinical practice, cohesion of surfaces over a longer axial length (between the cuff and moist mucosa) aids in establishing seal at even lower pressures than in the experimental model. Our cuff will inflate to 180% volume but exerts approximately one-half the pressure on the tracheal mucosa, as compared with conventional round or eccentric balloons, in achieving MOV. We feel this is another important advantage of this tube in preventing pressure-induced ischemia and subsequent tracheal stenosis. The cuff is extremely durable in order to resist inflation fatigue as well as puncture during insertion. It is made of a flexible polyvinyl chloride material and is integral to the outer cannula. This bond prevents upward migration into the tracheal stoma as a result of insertion or downward displacement over the end of the tube which could cause obstruction. Both of these complications have been seen [6] with the accessory cuffs that one attaches to cuffless tubes. With our tube the operator knows where the cuff is at all times, and he also is spared the travail of making a detachable cuff function properly in an emergency situation. When deflated, the cuff offers minimal resistance to air flow around the tube, so the patient can phonate easily. In this mode, the tube may be used electively for tracheobronchial toilet purposes only, when intermittent positive-pressure breathing (IPPB) is not required. 5. The cuff inflation line (Fig. 2, E> is molded into the wall of the outer cannula itself, thereby eliminating encroachment on the effective lumen, as happens with some tubes. Also, within the trachea VOL. 10, NO. 1, JULY,

5 HARDY, FETTEL, AND SHILEY the inflation line does not lie free to irritate, kink, or become obstructed as a result of pressure between the tube and stomal margin, which is common with free inflation lines (Fig. 3). The inflation system is durable and has a visual external test balloon and a simple integral pressure retention device. This last feature eliminates the need for awkward clamps, hemostats, or plugs to rapidly establish or release the MOV of the system. The line also adapts to either a standard or a disposable syringe for inflation, without the use of needles or special taper syringe adaptors. 6. The insertion obturator (Fig. 2, F) seats positively in position and, because of its chamfered tip, forms a smooth taper with the end of the outer cannula. These features prevent damage to delicate tracheal mucosa during insertion. This advantage is absent in many presently available plastic tubes which lack an obturator for insertion purposes and must be pushed bluntly from the stomal entrance along the mucosa into position. 7. The adaptor (Fig. 2, G) is integral to the inner cannula, requiring that the latter be used at all times for safety, as previously mentioned. It serves as a convenient twist knob to lock the inner cannula in position after insertion (90 clockwise twist) and to remove the inner cannula for cleaning (90 counterclockwise twist). An arrow is embossed on the adaptor to indicate the direction for lock position. The adaptor, a standard 15-mm. taper, fits existing anesthesia and ventilatory equipment or even an Ambu bag directly. This eliminates the frustrations of searching for separate color-coded connectors, T-tubes, flex lines, and other gadgets offered with some tubes. This can be an important consideration in an emergency situation such as might occur in the middle of the night, when personnel may not be familiar with central supply- The entire unit is lightweight and disposable or reusable and is manufactured of a semirigid, medical grade, nontoxic polyvinyl chloride material. It comes sterile in its package, with instructions and neck tietapes included. It is easily cleaned and can be resterilized by gas or chemical means. It has optimal inner-outer diameter ratios when assembled. The unit is competitively priced and is available at present in sizes 6 and 8, with smaller sizes to be marketed shortly. SUMMARY AND CONCLUSION A new tracheostomy tube has been presented which combines safety for the patient and convenience for the surgeon. It is designed to minimize tracheal injury. We believe it will improve the care of the patient requiring tracheostomy for airway toilet only, or for prolonged 62 THE ANNALS OF THORACIC SURGERY

6 respiratory support. It incorporates in one unit many features not previously available. It should be a welcome addition to the armamentarium of the thoracic surgeon. REFERENCES 1. Atkins, J. P. Tracheal reactions following the use of cuffed tracheostomy tubes. Ann. Otol. 73:1125, Fishman, N. H., Dedo, H. H., Hamilton, W. K., Hinchcliffe, W. A., and Roe, B. B. Postintubation tracheal stenosis. Ann. Thorac. Surg. 8:47, Grillo, H. C. The management of tracheal stenosis following assisted respiration. J. Thorac. Cardiouasc. Surg. 57:52, Hardy, K. L. Discussion of Fishman et al. El. 5. Johnston, J. B., Wright, J. S., and Hercus, V. Tracheal stenosis following tracheostomy. J. Thorac. Cardiovasc. Surg. 53:206, Murphy, D. A., MacLean, L. D., and Dobell, A. R. C. Tracheal stenosis as a complication of tracheostomy. Ann. Thorac. Surg. 2:44, Shelly, W. M., Dawson, R. B., and May, I. A. Cuffed tubes as a cause of tracheal stenosis. J. Thorac. Cardiouasc. Surg. 57:623, DISCUSSION DR. PAUL C. SAMSON (Oakland, Calif.): In previous years, when medical meetings were a little smaller and clubbier than they are today, it was not rare for the professor to demonstrate his latest gadget for the edification of the surgeons in the cheaper seats. Recently, this practice has become less frequent, and instruments, valves, and such are described primarily in connection with clinical results. The fact that your Program Committee reverted this once to the earlier practice of pure technical description bespeaks, I think, the value of Dr. Hardy s contribution. My own desultory efforts three or four years ago to design a better mousetrap came to naught; however, I have been privy to the development of the Hardy-Shiley tube and have had the opportunity of making one or two modest suggestions. The Hardy device is everything that present tubes on the market are not, and indeed it may be considered a new tracheostomy tube. The attachment of a rubber cuff to metal tubes is inexact and fraught with the dangers of slippage and obstruction. The plastic tubes presently on the market are clumsy affairs with thick walls and a flat inlet, making them difficult to aspirate. If you gather I admire the new tube, you are entirely correct. To use it is to believe. There are other goodies in the making. It is high time to evolve a uniform receptacle for tracheostomy aspirating tubes, and we must design superior and universal ways to balance and support the tubing of our respirator units. Of these, more anon. DR. NICHOLAS J. DEMOS (Jersey City, N.J.): I am grateful to Drs. Hardy and Shiley for a most welcome improvement in the respiratory care of very ill patients. I would point out one complication which may be immediately fatal. A nicely inflated balloon can become displaced with some motion on the tracheostomy tube or the respirator. Further traction or tripping over the respirator makes the cuff slide in front of the tube. Suction of the gasping patient gives no relief unless the tube is forcibly and immediately removed. The usual tracheostomy cuff may be easily anchored to the tube by wrapping a silk ligature several times around the proximal margin of the cuff. VOL. 10, NO. 1, JULY,

7 HARDY, FETTEL, AND SHILEY DR. HENRY E. MARTINEZ, JR. (Amarillo, Tex.): We, too, have been interested in tracheostomy tubes and six years ago began using a tube of different design. We have used this tube in more than 100 patients and have encountered no difficulty during the active phase of ventilation and no problems, such as stenosis, after treatment. The cuff is inflated through the holes in the tube by the inspiratory gases of the respirator; therefore, the pressure exerted on the tracheal wall is never greater than what the respirator delivers. In addition, the pressure is intermittent, occurring only during inspiration. Some of these tubes may be obtained from the U.S. Catheter and Instrument Corporation. They are made of polyvinyl chloride. We have not found the absence of an inner cannula to be a disadvantage, since the ventilator delivers adequate humidity at all times. Because of the simple design there is no need to inflate and deflate the cuff. This makes nursing care easier. DR. CHARLES P. BAILEY (New York, N.Y.): It sounds as though we really have a superior tube now. However, this problem of tracheal stricture, which is the primary focus of Dr. Hardy s paper, can be solved in certain other ways. One way is to use two balloon cuffs, much as Dr. Hardy showed in one of his tubes. At that point in his presentation I thought it would not be necessary to discuss his paper, but when he did not say much about that tube, I felt I should. We had 7 tracheal strictures over a one-year period. Never having been confronted with such a stricture before in my whole life (and I m as old as Dr. Sarot), I was shocked, as was my anesthesiologist. We solved the problem simply by putting an extra balloon cuff on all our endotracheal tubes and tracheostomy tubes. Today such tubes are manufactured commercially. One cuff is inflated for an hour and then released, and the other cuff is inflated. If your recovery room nurses are any good at all, and if they have a clock, they can do that. Even if they inflate the cuff too much, I don t think it will hurt the trachea as long as they do release it in an hour. We have had no strictures for nearly three years. I suggest that you can use this method no matter what types of tubes are available in your area of the country. DR. HARDY: It is a real pleasure for me to have Dr. Samson discuss this paper. His guidance and inspiration over the years have been most helpful in the evolution of this tube. Dr. Demos mentioned the eccentric expansion of existing balloons. We believe that the cuff we have, which is of a polyvinyl chloride material, does not do this. It has been subjected to repeated test inflations over an extended period of time, and it remains uniform in contour. I am unaware of Dr. Martinez idea. I still do not like the use of a tube without an iper cannula. I appreciate Dr. Bailey s comments. I also showed the double-lumen tube, and I agree with the opinions expressed by Dr. Grillo and Dr. Dobell in their articles. Putting two round balloons on the tube which may be asymmetrical seems to us possibly to double the chances of tracheal stricture. 64 THE ANNALS OF THORACIC SURGERY