Post-intubation tracheal stenosis is the most common cause of an obstructive tracheal lesion in large airways. Usually, the airflow is laminar and the glottic opening, lined by vocal cords on either side, is the narrowest portion of the trachea.
The trachea starts with the vocal folds of the glottic opening and ends with the bifurcation into the right and left bronchi at the carina. The first thing to remember is that the length of the trachea varies from 11-13 cm, 11 cm in women, and 12 cm in men, usually with an average l length of 11.8 cm. There are around 18 to 22 cartilaginous; most are C/D-shaped and deficient posteriorly. There are intervening membranes between the cartilaginous scaffoldings and a trachealis muscle posteriorly. The human trachealis muscle is a thick band that interconnects the deficient cartilaginous structures and also separates the trachea from the posteriorly related oesophagus. This enables flexibility to the trachea with head movements and neck flexion. Also, there is a slight compression of the airway during swallowing.
Almost half the trachea can be excised in complex pathological situations. Age, calcification, and rigidity with age have little or no effect. Extensive dog and rabbit experiments were done and the extent of resection followed by a re-connection was safely done. Supplemental cadaveric experiments also helped without any Incidence of tissue dehiscence or sutures cutting through. The determination of the stress or tension in the anastomotic line also was a consideration. This was not possible during live surgery earlier. Planimetry, later computerized planimetry, in some form was used to find out whether the tension was too much for anastomotic dehiscence. Of late intraoperative suture line tension can be assessed with a Tyrolean tensiometer. The operators remained well within the limits set previously and only in rare, unusual conditions, an adventure beyond was necessary. It was found that –
1. Quite a long length of resection is possible as taught with time and the evolution of surgery.
2. Anastomotic line problems like granulomatous lesions did not occur with absorbable sutures.
3. There was little difference between polyglactone and polydioxanone sutures. Both are delayed absorbable sutures and incite minimal tissue reaction.
4. Anastomotic line stenosis may occur and is of little consequence as a reasonably large diameter for airflow remains.
5. To reduce tension on the suture line certain procedures like the retention sutures, chin-chest apposition with guardian stitches, dissection and release of surrounding tissue, resection of strap muscles with a laryngeal infra-thyroid drop or a supra-hyoid drop, etc.
During live surgery, unless there was a cut-through, the anastomotic tension was considered bearable. It was found that the suture line tension increased with the distance between the anastomotic ends. Initially, there was a proportional rise and later the stress was exponential. A pressure of >1700 gms (based on animal experiments) was considered prohibitive and Grillo suggested a safe margin of around 650 gms. With experience, the length of resection followed by end-to-end re-connection has increased and whether a suture line will hold is determined by the surgeon himself depending upon his knowledge, eye estimation, and skill. So the previous thumb rule of limiting 2 cms to excision and not exceeding the 400 Gms suture line stress was no longer a dictum. As mentioned before, in life the D-shaped trachea is surrounded by the thyroid cartilage, the cricoid cartilage, and several incomplete C/D-shaped cartilaginous rings (16 to 22) downwards up to the carina. Some of these rings may be complete and in the region of the carina, where the trachea divides into the right and left main bronchus, the appearance of the rings is slightly different and will be discussed later. Immediately posterior is the esophagus and the recurrent laryngeal nerves ascend upwards in the tracheo-oesophageal grooves on either side. The right and left recurrent laryngeal nerves have different co-anatomical courses on each side and the relation on the right side is higher. The right-sided nerve loops around the right subclavian artery while the left recurrent laryngeal nerve is branched earlier from the vagus courses around the arch of the aorta and then ascends upwards in the tracheo-oesophageal groove. The right recurrent laryngeal nerve traverses a bit oblique and a bit further away from the left laryngeal nerve in its lower part and both are there in the designated positions at the lower portions. The important consideration to be kept in mind is the fact that ---
1. The left recurrent laryngeal nerve was more proximal to the trachea in its lower part.
2. The recurrent laryngeal nerves, on both sides, traverse between The branches of the inferior thyroid arteries in their course or maybe even above these
3. Both enter the larynx posterolaterally at the level of the ‘Berry ligaments’, which may even pierce and in this region, the right nerve is more vulnerable to injury.
Roughly the trachea can be divided into a cervical and a thoracic part. The recurrent laryngeal nerves or any such major nerves are not in any relation to the thoracic trachea. Understanding the minute points is important. Para-tracheal and circumferential tracheal dissection should be close inside a pre-tracheal fascia and careful. In no circumstance of the nerves lest there be changes in phonation, strength, and ability to speak and bilateral injury may even cause an adductor palsy of the vocal cords thus narrowing further the glottic opening.
Another consideration is the blood supply. Blood supply to cervical and thoracic parts is from different sources. The basic fact is that the cartilages, though hardy, are always compromised when blood supply is considered. From the thyroid cartilage downwards, the blood supply to the trachea is mainly dependent upon an intricate network of anastomoses along the trachea in its submucosa. The superior thyroid artery supplies little to the trachea other than forming a small anastomosis at the superior pole of the thyroid gland. The main supply to the cervical trachea is from the tracheo-oesophageal branches of the inferior thyroid artery. The thoracic trachea has most of its blood from the ascending branches of arterial supply to the main bronchi on either side, i.e. the bronchial arteries.
One has to remember the fact that the recurrent laryngeal nerves and the inferior thyroid arteries are intimately related on either side. In fact, in the majority of cases, the recurrent laryngeal nerve on the right side runs anterior to the inferior thyroid artery and the reverse is true on the left. In some cases, the nerve may even run between the branches of the inferior thyroid artery. Whatever it may be, caution near the tracheal sides, especially near the inferior lobes of the thyroid gland is a must. Additional arterial branches maybe three from the laterally placed major arteries and a dissection close to the tracheal sides and within the pre-tracheal fascia minimize the chance of an injury.
Normally after the narrow space between the vocal folds, the trachea has a spacious airflow cylindrical passage up to the carina. The airflow is mainly laminar, even though there may be changes in the diameter with curvature and flexion of the neck, and is bound by the usual rules of Poiseuille’s equation. Complications start when another area of narrowing appears in the path. Airflow becomes a combination of laminar and turbulent patterns and they are now not governed by straightforward physical laws. There is a critical Reynold’s number after which the symptoms become alarming. However, the physician should always remember that expectoration is a bigger problem as the infection becomes a reality with pent-up mucoid material in the lungs and smaller airways.
The complaint of respiratory distress is always suggestive and when there is a history of prolonged intubation the suspicion becomes stronger. Only relevant investigations should be done and we should always remember that our teachers who successfully did repairs had to depend upon skiagrams, tomograms, and rigid bronchoscopy along with the clinical findings to arrive at a diagnosis. Nowadays together with the skiagrams, we are blessed with CT scans, fibre-optic bronchoscopy, and even a virtual tracheobronchogram for localizing and even having an impression of the nature of the lesion.
A safe dissection for stenotic lesions should be done close to and within the pre-tracheal fascia and never 1-2 cartilaginous segments above or below. The esophagus is to be closely dissected away from the diseased portion of the trachea taking care not to injure the recurrent laryngeal nerves.
The symptoms occur gradually over some time and a positive history of prolonged intubation is necessary. Respiratory distress to effort may happen which initially is attributed to other causes. There has to be a significant diameter reduction of the trachea for symptoms to appear. It is a demonstrable fact that the diameter approximates 8 mm for a stridor to happen. Lumen diameter of 3–6 mm can maintain an oxygen saturation of >90% at an oxygen inhalation rate of 3 L/min while resting. Stridor occurs earlier in patients who hyperventilate and have malatic lesions. In most cases, a gentle placement of an appropriately sized thin endotracheal tube above a post-intubation fibrotic stenotic lesion suffices. Intubation is not a problem in malacia. Cross-table ventilation is required only when after the airway is opened up and the distal tracheal opening is accessed after proper fibrotic excision for ventilation. This allows space for suture placement and a wire-reinforced non-collapsible endotracheal tube is never required. The length of the tube allows additional connection and extension of the tube to an anaesthetic ventilator outside the sterile zone. High-flown jet ventilation may tide over the time required for the re-introduction and re-connection of an endotracheal tube and the anaesthetic ventilator. The presence of such a device in the operation theatre is mandatory.
The length of a stenotic lesion is usually 2-3 cm. Larger cervical lesions may necessitate the division of strap muscles of the neck. Infra-thyroid and supra-hyoid releases may be required for augmentation of tracheal length. The infra-hyoid release is the most effective in the cervical trachea. It should be remembered, however, that the cervical release procedures do not affect increasing the length of the thoracic trachea. Bilateral hilar release is more helpful.
A complex pathological condition consists of the combination of a proximal malatic lesion and distal stenosis. A tracheostoma with unhealthy granulations around the opening and with fibroses may complicate the situation. It is a necessity to clean all the granulomatous tissue and excise the fibrotic zones in totality.
Understanding the pathophysiological process of post-intubation stenosis is important. The first point to know is that the blood supply to the cartilage is always not up to what is expected for a good repair. The majority of blood supply is from the lateral aspect and a close dissection of the pathological area and or, at the most, three cartilaginous segments should be the goal.
The respiratory epithelium lining the trachea is a ciliated columnar epithelium with a wave-like movement of the cilia which helps in the clearance of the particulate material within the respiratory tree. Gentle toilet with isotonic solutions should always be done. Furthermore, the application of lignocaine jelly on the bulb of an endotracheal tube helps in glueing the wall of the bulb to the tracheal mucosa. This may lead to shearing of the tracheal mucosa during the removal of the tube.
As the arterial supplies to the near circumferential cartilaginous segments are compromised, malacia with a loss of structural wall strength during both phases of the respiratory effort is seen. Early stridor may happen as the walls are drawn in paradoxically with inspiration. Focal ulceration at the region of the tip of an endotracheal tube or near a tracheostoma is more likely to cause fibrotic stenoses. Often a combination of complex lesions exists. Total excision of the lesions along with almost all fibrosis followed by re-anastomosis by delayed absorbable suture material gives the best results.
The combination of lesions mainly increases the length of resection. Release and tension-releasing procedures help in reducing the anastomotic stress and allow healing. In addition to the excision of anterior neck strap muscles, supra-hyoid and infra-thyroid release procedures consist of a lengthening of the airway by allowing a drop of the laryngeal box by allowing a stretch of the laryngeal mucosa by removing the superficial muscular restriction. Dedo and Fishman (1969) aggressively excised all anti-flexion neck strap muscles, especially those connected Infra-hyoid to the larynx via the thyroid and cricoid cartilages. This was known as the laryngeal drop and a significant length advantage could be had even allowing slide laryngotracheoplasty just below the vocal folds.
Montgomery (1974) proposed a supra-hyoid release and used this technique primarily to re-appose tracheal ends after the removal of adenoid cystic carcinomas. The muscles resected are the mylohyoid, genioglossal, and geniohyoid. This is a supra-laryngeal release procedure and an advantage of 2-3 cm helps in the reduction of the anastomotic tension. The operation is simple and consists of the separation and identification of the muscles mentioned in the first instance. Then the greater and lesser horns of the hyoid bone are excised from the main body so that the freed hyoid bone along with the larynx is moved inferiorly thus aiding in the anastomotic tension release.
Two additional stress-release steps are taken and these include
a) a couple of tension release sutures between the upper and lower cartilaginous scaffoldings, and
b) chin-chest guardian stitches with non-absorbable material limiting neck extension.
Anaesthesia for tracheal stenosis has distinctive different parts –
a) Quiet sedation,
b) Intubation with a small tube,
c) Gentle placement of the tip of the tube above the area of stenosis not in any way irritating this region,
d) Replacement and advancement of a larger bore endotracheal tube into the distal post-stenotic tracheal lumen or Cross-table ventilation and re-connection with an anaesthetic ventilator followed by re-intubation with a larger bore endotracheal tube.
e) The last step helps in the placement of the posteriorly placed sutures. Almost all the sutures are interrupted sutures.
Careful and quiet extubation should follow with an examination of the vocal cords. Keeping the endotracheal tube in position to stent the anastomotic line is not good for the patient as it has the chance of inviting more infection. Post-intubation and after the spell of anaesthesia, the patients are often restless and need a good deal of analgesia without p respiratory depression of any kind. Gentle and total toilet of the distal respiratory passages is mandatory and there should be no irritants so a coughing bout is initiated. This increases the tension on the anastomosis and may cause a cut-through. A gentle laryngoscopic examination of the vocal cords, their thickness, and their movements is necessary at the end of the procedure to see if there is laryngeal oedema and whether the inadvertent recurrent laryngeal injury had happened during surgery.
The pictures represent actually how it looks during surgery. The main difficulty is when the final sutures are tied. These have to be done while the neck is flexed and little space is available.
Cross-table ventilation is a useful method of the aeration of the airways beyond the stenotic segment. This also allows extra length for connection with an out-of-sterile field anaesthetic ventilator with appropriate length tubing. Posterior placement of sutures, especially of the post-resected distal segment, becomes easier. Normally the usually supplied endotracheal tubes are used and a change to a larger diameter will be required once the stenotic segment is excised.
In unusual cases with a near-total obstruction or pathological deviation of a long segment of the trachea by a space-occupying lesion, extracorporeal circulation with the heart-lung machine becomes a necessity. Usually, femoro-femoral cannulation and connection to a heart-lung machine are done under local anaesthesia, usual general anaesthetic agents are then injected and tracheal dissection is carried out in the prescribed fashion. In cases where the windpipe is only deviated by the tumour mass, a dissection and removal of the mass suffice provided the involved tracheal segment is not malatic. In such a situation bronchoscopic placement of an expandable siliconized metallic stent of appropriate length will be required. We have experience in one such case where thymic mass was removed by this technique.
The incorporation of a tracheostoma is debatable. Some like to have the field cleared of all granulations and fibrotic material before taking sutures. The contention is that the fibrosis is progressive and excision of all fibrotic material is necessary for a good result. Increased length of the excised portion hardly bothers them and with the release procedures, tension stitches, and anti-flexion of the neck on the chin, re-anastomosis is possible in seemingly impossible cases. A few will accept slight stenosis during the end-to-end reconnection with a tracheostoma. The reason behind this is that a small degree of residual stenosis is not going to affect uninterrupted airflow and a 2nd air passage, especially for the distal toilet, is present in case of any emergency. Whatever may be the situation, it is not wise to suture close the tracheostoma. The creation and maintenance of an air passage of a larger diameter lead to spontaneous closure of the tracheostomy.
With the pandemic of the Covid-19 situation, a good number of patients are requiring ventilation with endotracheal intubation. Some of these patients are developing post-intubation tracheal stenosis. Surgery for them follows the same principles.
The mediastinal trachea and the carina get most of their blood supply from the branches of the bronchial vessels. The same rules for dissection are applied here. Access is always difficult and a midline sternotomy is almost always the preferred option.
The carina is more or less a midline structure, slightly inclined to the right with the carinal division opposite the sternal end of the right third costal cartilage.
Anatomically the trachea ends by dividing into the right and left bronchi at the carina. The carinal cartilage is thick and broad with its lower-border curving downwards between the origin of the two bronchi, forming an imperfect ring on each side enclosing the commencement of each bronchus.
Carinal resection is a complex and aggressive procedure and the various reasons are -
1. Complex relationship.
2. Difficulty in access.
3. Precarious blood supply.
4. Complex anesthetic procedures.
Interestingly neoplasms and strictures are common indications and only a limited number of people do airway surgery. Carinal surgery is difficult and reconstruction is always a major issue. In neoplastic lesions, it is often very difficult to leave behind a tumor-free margin and ensure complete resection. Again, thereafter a complex airway reconstruction is involved. The history is replete with names and the following need mention --
Grindley (1949),
Ferguson ( 1950),
Juvenelle and Citret (1951),
Meyer (1951),
Kirkluk & Merendino (1953),
Nicks (1953 ),
Bjork & Rodriguez (1958), and others.
Based on animal work, Barclay resected 5 cm of the lower trachea and anastomosed the left main bronchus to the stem of the right main bronchus below or near the origin of the right upper lobe bronchus.
Strategies in lateralized masses -- Barclay's (Eschapasse) technique.
Strategies in central carinal masses:
The Grillo technique:
Reverse Barclay (or Eschapasse) method:
Care should be taken to minimize anastomotic tension and cervical release procedures do not have any advantages in mediastinal tracheal length. The surgeon should be able to do a mediastinal release by incising the pulmonary ligament and releasing the hilar pericardial fixation wherever necessary.
So tracheal surgery may not appear attractive and a constant stratetisation during operation
is needed. Residual pathological tissue may promote a progression and it is important to correct any stenotic or obstructive lesion.
Comments