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Introduction to Mechanical Debridement
Mechanical debridement of the airways is the method of using tools to manually remove benign or malignant obstructive lesions. In principle, mechanical debridement of endotracheal or endobronchial lesions is one step in a very complex and intricate approach to the management of central airway obstruction ( Fig. 7.1 ). The characteristics of the patient, the lesion, and the tools must be considered when choosing one method or modality of debulking over another. Additionally, what may be considered a basic bronchoscopic procedure can have significant risks if there is inadequate preparation or access to the equipment and skill sets needed to manage complications.
There are two major advantages of mechanical debulking. First, some of these tools (rigid coring, rigid dilatation, microdebrider) provide the ability to rapidly debulk tumors. This is important in lesions that are causing critical stenosis, especially in the trachea. Second, all these tools can be used in patients who have high oxygen requirements, whereas thermal tools are contraindicated due to the risk of fire. Still, it is important to remember that coagulation of a tumor prior to mechanical debulking remains a foundational principle of endobronchial therapeutic interventions.
Role of Instrument
Rigid coring can be used in the management of endobronchial obstruction from benign or malignant disorders. Typically, mechanical coring is used to debulk endobronchial obstructive tumors following devascularization with thermal therapies. Its unique benefit, however, is in the situation of life-threatening obstruction when rapid tumor removal is necessary to avoid asphyxiation, when there is insufficient time to use other modalities. The severe, life-threatening obstruction necessitating this technique is usually apparent at presentation, but occasionally an unexpected degree of obstruction and hypoxia will follow anesthetic induction and muscle relaxation. As such, it is an important skill that the proceduralist should be prepared to rapidly employ.
As discussed in other sections of this book, the rigid scope is a hollow metal tube with a beveled distal tip. Rigid coring is the technique of using the beveled tip of a rigid ventilating bronchoscope or tracheoscope to debulk an exophytic endotracheal or endobronchial tumor. It is most useful to remove exophytic lesions that are pedunculated with a narrow-based stalk. It can also be used to debulk sessile tumors in pieces. This method allows resection of the tumor from the airway, but removal of the resected tumor requires the use of other equipment.
Method of Use
The beveled tip of the rigid scope is maneuvered gently to the proximal base of the exophytic lesion under direct visualization with a 0-degree rigid telescope. The plane of dissection is along the tract between the lesion and the mucosal wall of the airway. The rigid scope is corkscrewed gently across the entire base of the tumor while applying pressure along the plane of dissection toward the distal end of the tumor. Alternatively, rigid forceps can be used to stabilize the exophytic lesion while using the rigid scope to dissect it under direct visualization. The airway axis needs to be defined prior to coring, and the bronchoscope should remain parallel to the longitudinal axis of the airway to avoid accidental airway perforation. The use of tactile feedback is valuable to inform the physician as dissection occurs, ensuring that the airway wall and airway cartilage are not being perforated. This can help confirm that indeed the longitudinal axis of the airway is being followed when visualization is compromised. The use of in-line large-volume suction catheters (rigid or flexible) is extremely helpful during coring to aspirate blood that can obstruct viewing and to collect detached tumor. Additionally, as there can be temporary worsening of obstruction during coring and tumor removal, using suction to remove as much of the secretions, debris, and mucus surrounding the tumor as possible prior to coring will improve visualization and respiratory reserve during the intervention. Use of thermal therapies to devascularize the lesion prior to coring is strongly suggested to reduce the likelihood of bleeding. If devascularization is not possible or if there is significant bleeding, the rigid bronchoscope should be slightly advanced to cover and tampon the base for at least 3 min before evaluating the resection base for evidence of hemostatic control.
While this technique is useful for debulking central airway tumors, it is also one of the most dangerous in inexperienced hands, especially in the setting of active clinical deterioration requiring rapid tumor removal or during active bleeding that compromises visualization. While the beveled tip feels blunt, one must always remember that when excessive force is used or airway planes are not respected, collateral damage such as mucosal tears, full-thickness perforation, and catastrophic injury to vascular structures can occur.
Airway Dilatation (Balloon or Rigid)
Role of Instrument
Airway dilatation can be performed for both benign strictures as well as malignant obstruction and can be accomplished with airway balloons or serial rigid bronchoscopes, as well as serial insertion of tapered bougies. In malignant obstruction, the effects of airway dilatation are typically temporary, and it is typically used to expand the airway to allow for stent implantation or passage of other debulking instruments. Dilatation can occasionally be used alone in malignant disease, as a sizable minority of patients can have more than a transient effect, with one study showing short-term benefit with 43% of patients having sustained response at 7 days postdilatation. Thus, when no other options are available, balloon dilatation can be occasionally used alone to briefly palliate symptoms or to facilitate extubation.
Dilatation can have long-lasting effects for benign strictures that are secondary to fibrotic weblike stenotic lesions. However, complicated stenosis with cartilage involvement or in the setting of inflammation or calcified lesions (such as in fibrosing mediastinitis) usually does not respond to balloon dilatation alone. The use of laser or electrocautery knife to create radial incisions into stenotic webs is advocated, prior to dilatation, to reduce the amount of uncontrolled mucosal tearing by generating controlled points for tearing and hence reducing local injury that can contribute to recurrence of stenosis.
When choosing between balloon dilatation and rigid bronchoscopic dilatation, generally balloons are preferable, as they do not cause longitudinal sheering, which increases the degree of mucosal injury and risk of fibrosis and restenosis, since the balloon is expanded after insertion through the stenotic segment. In contrast, longitudinal mucosal injury is unavoidable with the forward insertion of rigid bronchoscopes or bougie dilators. One advantage of the rigid dilatational method over balloon dilatation is that the tactile feedback provided by the rigid scope facilitates assessment of airway stiffness and resistance to dilatation, possibly reducing the risk of perforation when used by experienced operators. Another advantage of the rigid system is in patients with tracheal obstruction who have minimal respiratory reserve and cannot tolerate complete airway occlusion for the appropriate amount of time necessary to dilate with a balloon. In this situation the rigid dilatational method allows constant ventilation during the procedure. By contrast, balloon dilatation requires 30–60-s periods of airway obstruction while the balloon is inflated. Jackson dilators are tapered bougies that can be serially inserted through an airway obstruction to dilate the airway lumen. They have been largely replaced by balloon dilatation systems, as they work similarly but require rigid bronchoscopy for insertion, obscure the distal view during insertion, and are difficult to use in the distal trachea, as the distal tip will angulate to either the left or right as it passes the carina.
Dilatational bronchoplasty balloons are designed to pass through the working channel of the therapeutic bronchoscope and are composed of high-pressure, low-compliance inflatable thermoplastic polymers that, when expanded by injection through a pressure-regulated water system filled with either saline or occasionally radiopaque contrast medium, inflate in a uniform manner to a specified diameter. There are a variety of disposable and reusable inflation devices available. Balloons come as either single-phase dilatational balloons that expand to one specific diameter or multiphase balloons that expand to multiple different diameters depending on the specific manometrically monitored expansible pressure induced when fluid is injected. Originally airway dilatation was performed with 5.5-cm long balloons designed for esophageal dilatation; however, shorter balloons are now available that have been specifically designed for the airway. Typically, the balloons can be wire-guided, but this is usually only necessary in rare cases where balloon dilatation is performed using fluoroscopy without bronchoscopic guidance.
Vascular cutting balloons work in a similar fashion to standard dilatational balloons; however, they have three to four longitudinally oriented microsurgical blades attached that, during dilatation, produce incisions that reduce uncontrolled mucosal tears. Cutting balloons have traditionally only been placed over a guidewire using fluoroscopic guidance, due to the high risk of bronchoscope damage. This has made them a generally unattractive option for bronchoscopic dilatation; however, reports of these balloons being used in the management of airway obstruction do exist, and there are few situations where cutting balloons might have unique advantages over other dilatational methods. The first is in extremely tight long-segment stenosis or when hypoxia exists that precludes safe usage of the electrocautery knife or laser for creation of mucosal incisions, and the second is in children where only small-caliber bronchoscopes, which do not allow the insertion of cutting instruments, are required. Although rarely used in the airways, the role of cutting balloons might gain new attention, since bronchoscopic insertion could be performed through disposable bronchoscopes that are now widely available. Malleable, high-volume, low-pressure, vascular latex Fogarty balloons are traditionally considered an emergency tool to rapidly occlude a hemorrhagic airway, but they also can have an occasional role in dilatation, which we will discuss further within this section.
Serial insertion of standard rigid bronchoscopes of increasing size is also an effective tool for airway dilatation. The ability to perform rigid dilatation, however, does depend on the rigid system that is being used. The Jackson rigid bronchoscope, which is no longer produced, was considered ideal for airway dilatation due to the presence of a blunt and more rounded tip that allowed for safer passage through the obstruction when compared with the modern rigid bronchoscopes. Serial rigid dilatation is much more practical with modular rigid bronchoscopic systems with detachable universal bases than systems where the base is fused to the barrel of the bronchoscope. By first inserting a large-caliber tracheoscope, detaching the base, and then inserting smaller-diameter but longer-ventilating rigid bronchoscopes, serial dilatation can be achieved without the need to reintubate the patient every time.
Methods of Use
Rigid bronchoscopic dilatation requires general anesthesia, whereas balloon dilatation with conscious sedation is an option for disease distal to the main carina. Some patients can tolerate tracheal dilatation under moderate sedation; however, often general anesthesia may be necessary with prolonged dilatation, as a sense of asphyxiation may result in considerable distress to the patient.
As mentioned previously, radial incisions with either the electrocautery knife or with laser can reduce the amount of uncontrolled tearing and fibrin production, hence decreasing the likelihood of restenosis. The electrocautery knife is a reusable instrument that is employed through the working channel of a flexible bronchoscope. Selection of a laser with cutting properties (carbon dioxide, holmium:yttrium aluminum garnet, or diode) provides the best option to produce precise radial incisions without inciting an inflammatory response or deeper tissue damage. Three 1–2-mm incisions mimicking the Mercedes emblem (12, 4, 8 o’clock) are made along the stenosis. Following radial incision, balloon broncho-plasty is typically performed.
For balloon bronchoplasty, the size of the balloon selected depends on consideration of the size of the stenotic airway as well as consideration of the normal adjacent airways that are contiguous with the lesion. When balloons are oversized relative to the stenosis, the improvement of diameter will be greater, but the risk of airway perforation will also be higher. Small incremental dilatations should be performed beginning with a balloon that only slightly expands the airway. Dilatation is continued serially with balloons of increasing size until target dilatation is achieved. The literature varies in regard to the optimal inflation time and repetitions, but typically two to three dilatations with inflation periods of 30 to 90 s per dilatational stage are sufficient.
The specifications of balloon and inflation device preparation vary based on manufacturer. It is important to refer to the user manual, as an in-depth description of each of these devices is beyond the scope of this chapter. There is a tag on each balloon that correlates specific manometric pressures to balloon inflation diameter. Lubricating the tip of the deflated balloon can help pass the instrument more easily through the working channel of a flexible bronchoscope. The balloon must be completely out of the working channel prior to inflation to prevent scope damage. The uninflated balloon should be passed into the stenotic segment with at least 0.5 cm of the balloon proximal to the level of the stenosis, as it can easily slide out of place if too proximal or distal. Retraction of the balloon to make contact with the tip of the flexible bronchoscope while simultaneously inflating it can fix the balloon in place across the stenosis. A 360-degree view through the balloon can be obtained by applying suction to the fluid-filled balloon, which allows the operator to visualize developing airway tears, indicating potential for perforation (see Fig. 7.2 ). Once the dilatation cycles are complete, the balloon can be deflated and removed from the working channel. Repeated reinsertion results in reduced catheter tip strength, which can make it impossible to reinsert the balloon. This is less of a problem with some of the newer inflation balloons that are designed to allow multiple passes through the working channel of the scope.
Wire-guided balloon dilatation with fluoroscopy without bronchoscopic visualization is an alternative method to direct bronchoscopic visualization of balloon dilatation, which is performed in a similar manner to fluoroscopic-guided insertion of self-expandable metallic stents. This method might be considered in children or patients intubated with smaller endotracheal tubes that cannot accommodate the therapeutic bronchoscope. The major disadvantage of this technique is the inability to visually monitor for complications such as evidence of impending airway rupture or hemorrhage. For this procedure the balloon is filled with a nonionic water-soluble contrast material such as iohexol diluted at least 50% in case of accidental balloon rupture, as hypertonic solutions can result in serious bronchospasm.
Fogarty balloons can be useful adjuncts to standard balloon dilatation, especially in the smaller airways. When the larger, more rigid dilating balloons cannot safely pass an obstruction, the soft malleable Fogarty catheter can be extended beyond the obstruction prior to inflating, and then the catheter can be withdrawn in a retrograde fashion. This technique can be used to compress an obstructive tumor against the airway walls or for extraction of debris, clots, or foreign bodies. The major risk of inflating a balloon catheter beyond the visible field is airway injury or rupture; however, this is much less likely with the soft malleable Fogarty balloon. This technique is useful in segmental airways, at acute angles where stiffer flexible instruments such as the cryoprobe or forceps prevent adequate scope flexion required to engage the target tissue.
For rigid bronchoscopic dilatation, it is ideal to insert a large tracheoscope and detach the universal base, which will allow insertion of smaller rigid bronchoscopes in a serial fashion without requiring repeated reintubations. In tight stenosis the use of neonatal/pediatric bronchoscopes during the initial phases of dilatation is sometimes necessary. The rigid bronchoscopes are inserted through the stenotic lesion using a twisting motion similar to the apple-coring motion used for mechanically debulking tumors. As ventilation can be maintained with this technique, dilatation can be performed for longer periods than with balloon dilatation.
It is important to consider the patient’s ability to tolerate periods of hypoxia and hypoventilation during dilatation, especially with tracheal involvement or in patients with contralateral disease when dilatation is performed beyond the main carina. In addition to inability to tolerate long tracheal dilatation periods, symptoms consistent with negative pressure pulmonary edema have also been reported following long periods of tracheal dilatation in the spontaneously breathing patient. Barotrauma resulting in pneumothorax or pneumomediastinum can theoretically occur when jet ventilation is used beyond a tight stenosis, especially with higher respiratory rates or with accidental occlusion of the proximal ports. If the patient can tolerate it, holding ventilation during balloon inflation periods is reasonable. To minimize the risk of accidental expiratory occlusion, caution should be used if instrumentation is performed through the rigid bronchoscope during dilatation, and simultaneous insertion of multiple instruments should be avoided.
Overinflation of dilatational balloons can result in airway lacerations, bleeding, and perforation. It is important to vigilantly monitor the airway mucosa through the inflated balloon for signs of developing airway tears and to use gentle incremental dilatations instead of dilating to a maximum or near-maximum diameter immediately. A potential source for accidental overinflation is related to miscommunications between bronchoscopist and technician, as the pressure in standard atmospheres (atm) required to inflate the balloon to a specific diameter in millimeters falls in similar ranges. For example, a balloon might require 8 atm to inflate to 12 mm. If the technician interprets the instruction of “inflate to 12” to mean atm, balloon rupture could occur. Closed-loop communication can help mitigate this risk.
Aggressive dilatation of highly vascular lesions, mixed obstructive tumors involving vasculature adjacent to the airway, or those with fragile mucosa or ulceration can lead to significant hemorrhage. Balloon dilatation should usually be avoided when visualization is impaired beyond the stenosis, but very gentle dilatation with the tip of the balloon is safe even in tight stenosis to allow distal visualization.
Role of Instrument
The rigid forceps are indispensable and possibly the most useful instruments available to the rigid bronchoscopist. Competence with the forceps is a mandatory skill for anyone who performs rigid bronchoscopic procedures. They are the primary modality for removing detached tissue, foreign bodies, and stents from the airways but also play an important role in the debulking of endobronchial obstructive lesions.
The rigid forceps are available in several different configurations similar to the flexible forceps: cupped, alligator, pointed serrated, and peanut grasping. Forceps are broadly classified as either single action or double action based on whether only one jaw or both move with opening (see Fig. 7.3 ). Typical rigid forceps open in a superior and inferior orientation; however, forceps are available that allow rotation of the tip while the operator maintains the hand in a neutral position, as well as backward grasping forceps which open proximally. While most forcep handles are nonratcheting, allowing for free opening and closing, ratcheted forceps are also available that allow the operator freedom to release the handle grip. The rigid cupped forceps have a smooth tip and are appropriate for obtaining biopsies. They produce minimal trauma to the mucosa and surrounding normal tissue. The rigid alligator forceps have a sharp tip and serrated teeth, making them appropriate for grasping large tumors, foreign bodies, and stents for removal through the rigid bronchoscope. The rigid optical forceps are forceps that are coupled with a channel through which the telescope is secured. They are available in several configurations as well.