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Acs0208 Tracheostomy


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Acs0208 Tracheostomy

  1. 1. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 1 8 TRACHEOSTOMY Ara A. Chalian, M.D., F.A.C.S. Operative Planning Strictly speaking, the term tracheostomy refers to the surgical cre- ation of an opening into the trachea, whereas the term tracheoto- COUNSELING AND INFORMED CONSENT my refers to an incision of the trachea. However, many surgeons use these terms virtually interchangeably; in particular, they com- The patient, the family, or both should receive counseling on monly refer to more temporary openings, in which cutaneous flaps the risks and benefits of the procedure. Commonly discussed are not sutured to the trachea, as tracheotomies. Other surgeons issues include pain, mortality, and the range of possible early and prefer to observe a more formal distinction between the two late complications [see Complications, below]. In my experience, words. In this chapter, I use the term tracheostomy to refer to the many families are intimidated or upset by the consideration of tra- process of creating an opening in the trachea, reserving the term cheostomy.To address their concerns, I offer the option of remov- tracheotomy for the actual tracheal incision. ing the oral or nasal tube from the areas that most affect patient Initially, tracheostomy was performed primarily as a life-saving comfort and ability to interact with the family.When this is done, intervention to secure and establish an airway in patients with life- oral alimentation and mouth care become much more feasible, threatening airway obstruction as a consequence of infection or and the patient’s ability to speak (or at least mouth) words is often neoplastic disease. Currently, it is most commonly done to facili- greatly improved. In patients with significant central nervous sys- tate prolonged ventilator-based respiration in patients with respira- tem injuries or other conditions that alter mental status, it may be tory failure.Tracheostomy has become an integral part of complex advisable to secure the tracheotomy tube to the neck to maintain head and neck tumor resections for cancer involving the larynx, the safety and prevent unintentional extubation. base of the tongue, the pharynx, and, in some cases, the base of the SITE OF PROCEDURE skull. In addition, it is performed to provide airway diversion in patients with laryngeal stenosis or bilateral vocal cord paralysis. A tracheostomy may be performed in an intensive care unit, a shock trauma bay, or an operating room. Emergency tracheosto- mies are often performed in these areas, and thus, the surgical Preoperative Evaluation equipment is most often kept there. In elective situations, howev- Patients scheduled for elective tracheostomy undergo the stan- er, a tracheostomy may be performed virtually anywhere. The dard preoperative assessments. Because the surrounding tissues most commonly required equipment is portable. An electro- are highly vascular, anticoagulants and aspirin should be discon- cautery should be available, and good lighting (whether from over- tinued before operation in nonemergency settings, as should head lights, headlights, or portable OR lights) is critical. OR per- antiplatelet medications. The cervical and tracheal anatomy sonnel usually are more familiar with the procedure than ICU or should be assessed; in rare instances, an extra-long tracheotomy trauma bay personnel; accordingly, many teams request a scrub tube will be required. Any lesions, scars, or masses in the central nurse or a technician, then train team members in the alternative thyrotracheal compartment of the neck should be noted. If there environments. is a mass in the thyroid gland (especially in the isthmus), workup ANESTHESIA or simple resection should be considered. Previous operations on the thyroid, the larynx, the trachea, or the cervical spine can alter The patient’s comfort can be optimized with conscious sedation the anatomy and present additional difficulties to the surgeon. A or, possibly, with local anesthesia alone. Communication and low-lying larynx or cricoid resulting from kyphosis or another cooperation with the anesthesiologist (including specific discus- cause is particularly troublesome. In some patients, the cricoid is sion of the role of sedation and analgesia) can be critical to a suc- at the sternal notch or even lower. cessful outcome and should therefore be key components of In this last situation, if it is determined that a tracheostomy is preparation for emergency tracheostomy. In a decompensating absolutely necessary, the potential problems must be considered. patient, the effect of suppression of the respiratory drive is poten- Although it is logical to assume that the trachea can be pulled tially catastrophic. superiorly, it is important to remember that after the procedure, the position of this structure will tend to drift down toward the mediastinum, presenting the problem of an incorrectly positioned Operative Technique tracheostomy tube that may “kick out” from the anterior tracheal SURGICAL TRACHEOSTOMY wall opening or press against a mucosal surface. Often, this tube will pivot against the anterior wall or the trachea cephalad to the The patient is positioned with a shoulder roll and a foam pad opening, thereby potentially contributing to cartilage injury with (doughnut) under the head. If cervical spine precautions are in subsequent malacia or stenosis. force, the posterior portion of the cervical collar should remain in If the trachea is inferiorly displaced to a substantial degree, place, and the head should be stabilized by a team member. The resection of the manubrium should be considered. This measure procedure may be more difficult to execute in this setting, but oth- very rarely proves necessary, however, and is mentioned only for erwise, the surgical technique is the same. the sake of completeness. The position of the patient can also be optimized by extend-
  2. 2. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 2 ing the headrest of the surgical bed. This measure permits better palpation of landmarks if soft tissues are thick. For patients with cervical stenosis or symptoms related to cervical spine pathology, a larger incision or so-called neutral-position tracheotomy may be considered; such problems do not necessarily preclude the procedure. Step 1: Incision of Skin Before the incision is made, the patient should also be assessed for a high-riding innominate artery or medially placed carotid arteries.These anatomic variants are rare, but when they are pres- ent, additional care may have to be exercised. The cutaneous incision may be made either vertically or hori- zontally. Either incision leaves a well-healed scar once the tra- cheotomy tube is removed. The level and location of the incision may vary, depending on individual surgeons’ preferences. In gen- eral, a good placement is 1 cm below the cricoid or halfway between the cricoid and the sternal notch [see Figure 1]. The size of the incision is also, to an extent, a matter of individual prefer- ence. Given the current emphasis on minimizing scars, I strive to use the smallest possible safe incision. For transverse incisions, 2 to 2.5 cm is often adequate. In an emergency setting, a longer incision—often vertical—may facilitate exposure and help the sur- geon avoid large subplatysmal anterior jugular veins. The skin incision may be accompanied by excision of some of the subcuta- neous fat in the immediate area. Figure 2 Surgical tracheostomy. Retractors are placed, the It should be kept in mind that these recommendations regard- skin is retracted, and the strap muscles are visualized in the ing the size of the incision are only suggestions, not hard-and-fast midline. The muscles are divided along the raphe, then retracted rules. Each case should be considered individually, and each inci- laterally. sion should be designed so as to allow the safest exposure in a given patient. Step 2: Retraction of Strap Muscles The strap muscles are identified, and the midline raphe is divid- ed. The muscles are then retracted laterally by the assistant with Senn or Army-Navy retractors [see Figure 2]. Undermining should be limited to minimize the potential creation of avenues for the pas- sage of air, secretions, or instruments (including the tracheostomy tube).When there is a malignant neoplasm in the soft tissue or the thyroid compartment, anatomic landmarks may be difficult to iden- tify. In such cases, dissection to the notch of the thyroid cartilage helps one identify the midline and work inferiorly [see Step 5, below]. Step 3: Dissection of Thyroid Gland The thyroid isthmus lies in the field of the dissection [see Figure 3]. Its size and thickness may vary greatly.Typically, the isthmus is 5 to 10 mm in its vertical dimension. If the organ is within this size range, one can often mobilize it away from the trachea and retract it superiorly (or inferiorly), then place the tracheal incision in the second or third tracheal interspace [see Figure 4]. If the isthmus is large enough that it may block the tracheostomy site, one may divide it and ligate the edges. In the instance of an isthmus nod- 0.5 –1.0 cm ule, removal of the isthmus and the nodule is reasonable for diag- nostic and therapeutic purposes. Although the recurrent nerves are in the surgical field, they typically are not at great risk for injury during tracheostomy; however, they may be subjected to trauma if dissection or even a retractor extends into the tracheo- esophageal groove. The blood supply to the trachea is laterally based, which is another reason for avoiding significant lateral exposure of the trachea. Figure 1 Surgical tracheostomy. A transverse cutaneous Step 4: Incision of Trachea incision is made that is approximately 2 to 3 cm long (or as long as is necessary for adequate exposure). The extent of flap The tracheotomy should be performed with a knife. If one desires, elevation may be 1 cm or less. the pretracheal tissues may be coagulated with a bipolar (or, cau-
  3. 3. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 3 tiously, with a monopolar) electrocautery.The opening of the airway will bring volatile, flammable gases into the operative field; accord- ingly, the use of a monopolar electrocautery must be limited (or avoided if possible).The choice of a tracheal incision will not make a significant difference to the execution of the procedure. Linear incision A linear incision is probably the simplest choice and the one that is least traumatic to the cartilage.Typically, it is made through either the interspace between the second and third tracheal rings or that between the third and fourth. Tracheal window Instead of a simple incision, one may opt to remove the midportion of the third or fourth tracheal ring to create a window.The theoretical rationale for the tracheal window is that it minimizes trauma to the remaining cartilage resulting from passage of the tracheostomy tube. Bjork flap A Bjork flap is an inferiorly based U-shaped flap that incorporates the ring below the tracheal incision. It is sewn to the skin at the inferior margin of the tracheotomy. The theoretical justification for the use of the Bjork flap is that it helps keep the tra- cheal incision close to the skin edge and facilitates tube replacement if the tube is accidentally dislodged or removed.The flap suture can be released after 3 to 5 days, once the tract has started to mature. Stay sutures Many surgeons place lateral, inferior, or superi- Figure 3 Surgical tracheostomy. With the strap muscles or stay sutures (often, though not always, made of silk) in the tra- retracted, the thyroid isthmus is visualized, and the inferior chea to help stabilize this structure during the procedure. For opti- (or superior) edge of the isthmus is dissected down to the mal stabilization of the exposure during subsequent manipulations trachea. The isthmus is then retracted superiorly (or inferiorly) or possible emergencies, they generally leave the sutures in situ or divided to permit visualization of the trachea before the until the first tracheostomy tube change. These sutures are taped tracheal incision is made. to the patient’s chest and should be labeled for easy identification in emergency situations.The use of stay sutures in tracheostomies is now a well-established (though not universal) practice, particu- larly in children and neonates. Step 5 (optional): Division of Tumor to Facilitate Tube Placement In the case of a neoplasm involving the thyroid, the tumor may have to be resected in the midline to allow placement of the tube. Often, the airway cannot be palpated. To identify the airway, the dissection should begin at the level of the thyroid cartilage—pos- sibly, as high as the thyroid notch—and continue inferiorly until the cricoid and the trachea are identifiable. In these situations, the depth of the wound that must be created before the trachea is Tracheal Ring 1 reached can be a problem. A standard tracheostomy tube may be too short for its intended use, in which case a custom tube will Tracheal Ring 2 have to be ordered. With a custom tube, it is possible to specify both the distance from the tube faceplate to the turn entering the airway and the length of the segment going into the airway. If there is not enough time to order a custom tracheostomy tube, an endo- Tracheal Ring 3 tracheal tube can be placed as a temporizing measure to provide an airway.To help set the length of the tube segment that will enter Tracheal Ring 4 the airway, the endotracheal tube can be bivalved (i.e., split) along its proximal extent. Step 6: Removal or Withdrawal of Endotracheal Tube and Placement of Tracheostomy Tube; Management of Anesthesia and Oxygenation Figure 4 Surgical tracheostomy. A tracheotomy is made either During the transition to tracheostomy tube ventilation, the between the second and third tracheal rings or between the third endotracheal tube either is removed or is withdrawn and kept in and fourth rings. A Bjork flap (inset) may be created by extend- position at the level of the vocal cords until the tracheostomy tube ing the ends of the tracheotomy downward through the next is secured. Preoxygenation is important to allow adequate apnea lower tracheal ring in an inverted U shape. time for incision, withdrawal of the endotracheal tube, and place-
  4. 4. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 4 tracheostomy tube change has been performed and the tract is considered safe. If a patient has excess skin folds in the neck, any collar is likely to irritate the skin, and the application of a semi- permeable membrane dressing, such as Tegaderm (3M, St. Paul, Minnesota), may be advisable to help prevent ulceration. Any local infection that develops should be appropriately treated. Some patients, nurses, and surgeons prefer to use a split gauze swatch placed around the tracheostomy and the tube to help manage the drainage from the site. Care of the patient with a tracheostomy tube Hu- midified air or oxygen should be delivered via a tracheostomy tube collar; the humidification is necessary to prevent tracheal crusts. The inner cannula should be cleaned frequently to remove built- up mucus. The skin and area around the stoma may be cleaned with half-strength hydrogen peroxide and water. A spare inner cannula and a spare tracheostomy tube are often kept at the bed- side. Flexible tracheal suction catheters and suction devices must be readily available. Because patients’ ability to verbalize will be altered (temporarily, at least), they should be given easy access to the call button and be taught its use. First tracheostomy tube change On my service, the first tracheostomy tube change in a patient who requires ventilatory Figure 5 Surgical tracheostomy. The tracheostomy tube is inserted into the tracheal opening from the side, with the face- support is performed approximately 1 week after operation. In a plate rotated 90° so that the tube’s entry into the airway can be patient with a neoplasm who does not need a cuffed tube, the ini- well visualized. tial tube is exchanged for a cuffless tube at an earlier point if pos- sible (i.e., if the anatomy is favorable). I do not use fenestrated tracheostomy tubes. These tubes are ment of the tracheostomy tube. To optimize oxygen tension, more often associated with suprastomal granulation (resulting administration of nitrous oxide is often stopped before the airway from irritation of the mucosa by the fenestrae) and with the devel- is entered. opment of crusting on the fenestrae. Moreover, fenestrated inner Some surgeons prepare and drape the endotracheal tube into cannulae are often difficult to find. the operative field, preferring to withdraw it themselves gradually as the changeover to the tracheostomy tube is occurring. Often, PERCUTANEOUS TRACHEOSTOMY the anesthesiologist or another team member is assigned to man- In certain centers, percutaneous tracheostomy has largely sup- age the release and withdrawal of the endotracheal tube. I prefer planted open tracheostomy. The percutaneous approach involves to advance the endotracheal tube before the tracheal incision is using Seldinger-like techniques to enter the trachea transcuta- made so that the cuff lies deep (distal) to the tracheostomy site. neously with a catheter, then dilating the opening and placing a This measure delays the start of apnea and potentially minimizes tracheostomy tube. A fiberoptic bronchoscope may be used to its duration, permitting ventilation to continue even though the confirm entry into the airway and facilitate the procedure. airway has been entered. Delivery of the volatile anesthetic, venti- The suitability of this procedure for a given patient is deter- lation, and oxygenation can be performed actively during the first mined primarily by the patient’s stability or lack thereof, the anato- step of entry into the airway and preparation for tube changeover. my of the neck, and the skills of the team. For example, a patient The size of the tracheostomy tube is chosen on the basis of the with a thick neck and unclear anatomic landmarks is not a suitable length and diameter required to achieve adequate respiration and candidate, whereas a patient with a thin neck and good range of correct positioning in a given patient. A No. 6 tube is appropriate motion is an ideal candidate. for most adults. If frequent suction bronchoscopy is required, many intensivists will request a larger tube, such as a No. 8; the AWAKE TRACHEOSTOMY No. 8 tube allows passage of a standard suction bronchoscope and permits ventilation to continue. Anesthetic Considerations The placement of the tracheostomy tube [see Figure 5] should For an awake tracheostomy, the patient should be placed in a be confirmed with auscultation or, in cases where capnography is semi-Fowler position to give the anesthesiologist ready access to unavailable, with visualization of chest movement; alternatively, in the airway, to optimize his or her own comfort, and, most impor- cases involving end-tidal CO2 monitoring, it may be confirmed tant, to enhance primary and accessory respiratory muscle func- visually with the capnograph. tion. Every effort should be made to keep the patient comfortable The fresh tracheostomy tube should be secured with sutures and to minimize (or, if possible, eliminate) environmental stimuli, from the faceplate to the skin and with tracheostomy ties. (If the especially the work noise generated by the surgical team. Generally, patient has had a microvascular flap and the tracheostomy tube sedatives are contraindicated, because they can diminish or even was placed concurrently, the ties are not used, so as to ensure that abolish respiratory drive and protective mechanisms. the veins providing outflow are not compressed.) If the patient has Clear communication with the anesthesiologist must be ensured a long-term need for a tracheostomy, the use of a soft foam collar before the patient even enters the room; life-threatening emergen- band with hook-and-loop fasteners is recommended, once the first cies may arise that necessitate close collaboration.The same is true
  5. 5. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 5 for the scrub and circulating nurses and technicians. Their instru- Infection ment tray should contain the most essential equipment, along with Impaired handling of tracheal secretions may facilitate the an appropriate selection of tracheostomy tubes prepared for use. development of local site infection. Such infection can generally be Tracheal Stents and T Tubes treated with antibiotics and local wound care. As tracheobronchial airway stenting becomes more common, Crusting or Mucous Plug tracheostomy tubes may be increasingly required for definitive or Mucus and blood, individually or in combination, can create end-of-life care. The position of the airway stent must be known difficult management problems. Accordingly, a fresh tracheostomy with some precision because the tracheostomy tube may have to should be carefully supported with humidified oxygen or air. interface exactly with the end of the stent. Alternatively, the stent Tracheal suction should be available, and the nurses caring for the may have to be incised to afford entry into the airway. If the stent patient should be comfortable with using it. The patient and the is metal, incision may not be possible. family should also learn how to employ tracheal suction. With some mucous plugs, suction bronchoscopes may be required for Complications removal. Negative Pressure Pulmonary Edema EARLY This complication may develop when an awake tracheostomy is Soft Tissue Placement (False Passage) of Tracheostomy Tube done in the setting of significant airway obstruction. The patient’s Adjacent to Trachea negative inspiratory pressures and effort are initially high, then suddenly drop to normal after the trachea is incised. A frothy pul- If the tracheostomy tube is inadvertently misplaced in soft tis- monary edema will be apparent. The standard treatment is posi- sue during the procedure, the endotracheal tube should be tive pressure ventilatory support, often including positive end- advanced from its intermediate position in the larynx back into the expiratory pressure (PEEP). airway. The patient should undergo ventilation, and when oxy- genation and ventilation are adequate, the endotracheal tube LATE should be withdrawn and the tracheostomy tube replaced. If the tracheostomy tube cannot be placed directly, a guide tube may be Granulation employed (via the Seldinger technique) to help guide the tube into Granulation tissue may develop at the suprastomal region as a the airway; alternatively, a flexible bronchoscope may be used for consequence of irritation by the tracheostomy tube. Symptoms this purpose. If the tracheostomy tube cannot be properly or effec- related to speech or airway function may be seen when the tra- tively placed, transoral intubation is the safest way of resecuring cheostomy tube is capped or fitted with Passy-Muir valves, which the airway. allow inspiration via the tube and exhalation via the native airway. In some cases, granulation at the tip of the tracheostomy tube may Decannulation lead to bleeding or airway symptoms (e.g., dyspnea). When these If the tracheostomy tube becomes decannulated on an acute accumulations of granulation tissue give rise to symptoms, basis, the protocol for reestablishing the airway is to intubate the removal should be considered. patient via standard transoral approaches. Although it is theoreti- cally possible to replace the tracheostomy tube directly into the Tracheomalacia tracheostomy site, it is safer to take an endolaryngeal approach, Tracheomalacia, defined as the loss of cartilage structure in the which allows the tube to be replaced into the tracheostomy site trachea, can cause a dynamic collapse with partial or complete with good lighting and retraction and with the patient stable. blockade of the trachea during inspiration. Fortunately, it is a rare complication; typically, it is manifested as inspiratory noise and, Pneumomediastinum potentially, as dyspnea after decannulation. It may be related less Pneumomediastinum is a potential complication if the tube is to the placement or presence of the tracheostomy tube than to placed in a false passage or if the patient requires ventilation with the loss of tracheal cartilage at the site of the endotracheal tube the trachea incised. balloon as a result of previous intubation, infection, or even pres- sure (e.g., the pressure that can be generated by large thyroid Pneumothorax goiters). Pneumothorax is an uncommon complication of tracheosto- my—so uncommon that most protocols do not require chest x- Stenosis rays after routine tracheostomies. Tracheal stenosis may be seen at the site of the tracheostomy or at any site along the trachea where trauma caused by cuffs or tubes Bleeding has occurred. Laryngeal stenosis, though rare, may develop after Bleeding may occur after tracheostomy, usually related either to placement of the tracheostomy tube or after decannulation. Like the vasculature in the field (in particular, the thyroid vessels) or to tracheal stenosis, laryngeal stenosis is most often related to endola- the gland itself. If the bleeding is minor, it can generally be treated ryngeal or endotracheal intubation, infection, or neoplastic dis- by applying absorptive gauze or a collagen-type dressing to the site; ease. In rare instances, stenosis can be a manifestation of condi- if it is coming from vessels of significant size, exploration and liga- tions such as gastroesophageal reflux disease or sarcoidosis. tion or cauterization may be required. In rare cases, early bleeding from a major vessel may become apparent through the tracheosto- Tracheoinnominate or Tracheoesophageal Fistula my site. When this occurs, it is managed with the techniques used Moderate to heavy bleeding, though uncommon, sometimes to treat tracheoinnominate or tracheoesopahgeal fistula [see Late, develops. It may herald an erosion of the anterior tracheal wall into Tracheoinnominate or Tracheoesophageal Fistula, below]. the innominate artery and may be fatal if this vessel ruptures. Such
  6. 6. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 2 HEAD AND NECK 8 TRACHEOSTOMY — 6 bleeding is a result either of injury caused by the tip of the tra- Tracheocutaneous Fistula cheostomy tube or of other types of injuries associated with endo- Tracheocutaneous fistula is not a common side effect of tra- tracheal intubation. Diagnostic assessment should include partial cheostomy. If a cutaneous-lined tract persists, repair is indicated or total withdrawal of the tube to allow flexible assessment of the (see below). The key differential point to consider when a fistula anterior tracheal wall for erosions, clot, or cartilage breakdown and persists is whether there is a stenosis in the endolaryngeal or endo- defects and to permit visualization of the mediastinal tissues. tracheal airway that is causing the condition. Supportive management includes preparation for transfusion if the patient is anemic and formulation of a plan to manage the air- Planned Decannulation Protocols way if hemorrhage is occurring. In the event of hemorrhage, the If there is any doubt about the patient’s respiratory drive, level tracheostomy tube usually will have to be removed, and an endo- of consciousness, or airway protective mechanisms, the airway may tracheal tube will have to be placed through the tracheostomy and be sequentially downsized. If there is no real doubt, flexible laryn- advanced deeper so that the inflated cuff is distal to the bleeding goscopy and tracheoscopy may be done to confirm the presence site.To tamponade the bleeding, one should try to place the tip of of an intact airway. If the airway is adequate, the tracheostomy a finger into the tracheostomy site and compress the trachea tube may be withdrawn and the wound managed with local clean- against the manubrium; this must be done with the tube in the air- ing and dry compressive dressings.The wound should heal by sec- way as well. Alternatively, one may pass a rigid bronchoscope into ondary intention. If a fistula forms, the cutaneous tract should be the tracheostomy, provide ventilation through the scope, and then freshened or excised, after which the wound typically heals by sec- press the scope anteriorly against the manubrium to achieve ondary intention. Some surgeons prefer to close the wound in hemostasis. For salvage in cases where the bleeding is immediate- three layers, including the trachea. If this approach is followed, ly life-threatening, emergency operative intervention with the there is a potential for cervical emphysema or for dissection into appropriate cardiovascular or vascular teams is required. the chest and pneumomediastinum. Recommended Reading Goldenberg D, Ari EG, Golz A, et al: Tracheotomy cheostomy in the intensive care unit: a prospective ran- Walts PA, Murth SC, DeCamp MM: Techniques of complications: a retrospective study of 1130 cases. domized trial comparing open surgical tracheostomy surgical tracheostomy. Clin Chest Med 24:413, 2003 Otolaryngol Head Neck Surg 123:495, 2000 with endoscopically guided percutaneous dilational Gysin C, Dugluerov P, Guyot JP, et al: Percutaneous tracheotomy. Laryngoscope 111:494, 2001 versus surgical tracheostomy: a double blind random- Pryor JP, Reilly PM, Shapiro MB: Surgical airway Acknowledgment ized trial. Ann Surg 230:708, 1999 management in the intensive care unit. Crit Care Clin Massick DD, Yao S, Powell DM, et al: Bedside tra- 16:473, 2000 Figures 1 through 5 Thom Graves.