Complications Following Long-Term Intubation
Intubation of patients in an intensive care setting is very common. Tracheal intubation involves passing a tube down the trachea in order to maintain an open airway. This may also be achieved by performing a tracheostomy, in which a tube is inserted through an incision in the neck, made below the vocal cords. Prolonged intubation is generally defined as intubation lasting for longer than seven days. Many complications have been reported following prolonged intubation but it is outside the scope of this short article to discuss them all. Therefore, attention is limited to the most serious complications, from which legal claims are more likely to arise. These include ulceration, formation of granulation tissue and tracheal and laryngeal stenosis.
Before the use of low-pressure high-volume cuffs, post-intubation tracheal stenosis (PITS) was estimated to occur in 1% of intubated patients, but the incidence is now considerably lower. PITS occurs when excessive cuff pressure leads to a mucosal ischemic injury. Necrosis of the tracheal mucosa leads to sloughing and ulceration of the mucosal layer and the tracheal cartilage becomes exposed. This may lead to partial or complete destruction of the cartilaginous tracheal rings and loss of the structural integrity of the affected segment. The body’s attempt to heal this damage can result in a tight fibrous stricture, or stenosis, which may restrict the airway. Although PITS has been noted in patients who have been intubated for less than 24h, it is predominately seen after prolonged intubation. PITS is not easily diagnosed, and it has been estimated that nearly half of all cases of PITS are not initially diagnosed as such. This is partly because the expiratory wheeze which is a feature of the disease can be confused with asthma. Furthermore, symptoms may not be seen until several weeks after extubation. Therefore, the disease may not be identified until it reaches an advanced stage, at which point the trachea may have lost up to 70% of its diameter.
Occasionally, the fibrinous material forms a membrane across the trachea, and this condition is known as obstructive fibrinous tracheal pseudomembrane (OFTP). OFTP is an extremely rare complication, but one that can prove fatal and around one-third of cases develop respiratory failure. Spontaneous expulsion of the fibrinous material is uncommon and it is usually removed using bronchoscopy, particular in paediatric patients.
The pathogenesis of tracheomalacia (TM) is very similar to that of PITS and OFTP, in that cuff pressure causes airway ischemia, resulting in necrosis and softening of the trachea. However, in TM the trachea then collapses. If TM occurs below the thoracic inlet collapse of the trachea occurs during expiration; above this level and the collapse occurs during inspiration. In severe cases TM can lead to hypercapnic respiratory failure. Although the incidence is unclear, intubation is a known risk factor for the disease. If the tracheal narrowing is mild, TM is easily missed although it can often be diagnosed early in patients who are difficult to wean from mechanical ventilation. Intubation itself can also pose problems in diagnosing the condition, as the tube keeps the trachea patent and prevents its collapse. As with PITS, there is also an overlap with the symptoms of asthma. In particular, recurrent episodes of bronchitis caused by the retained secretions in TM are easily confused with exacerbations of an existing asthmatic disorder.
Cuff pressure can also cause the formation of fistulae, where erosion of the posterior membranous part of the trachea forms a communicating tract with either the oesophagus or surrounding blood vessels, most commonly the innominate artery, due to its anatomical proximity to the trachea. The presentation of this condition is variable and depends on the size of the fistula. In tracheoesophageal fistula, food material may be aspirated and the abdomen becomes distended with air. In addition, coughing and choking after extubation are common and aspiration pneumonia may also develop. Signs of involvement of blood vessels include bleeding, aspiration of blood during suctioning and pulsation of the breathing tube. If an artery is involved, bleeding can be significant and the condition is often fatal. Spontaneous resolution of either type of fistula is rare and surgical intervention is often necessary.
As well as direct injury to the larynx, tracheal intubation can also result in ulceration in this area. While these injuries often heal spontaneously, sometimes granulomata may form. This inflammation can lead to fixation of the cricoarytenoid joint, which causes compression on the recurrent laryngeal nerve. The resulting nerve palsy presents as vocal cord paralysis. Alternatively, the granuloma may directly affect the vocal cord. In unilateral paralysis, intervention is not generally required, as the condition usually spontaneously resolves over the course of a few weeks or months. However, if the condition has not resolved after 12 months, then recovery is unlikely. Bilateral paralysis is very rare, but can result in airway obstruction for which tracheostomy may be required.
As advances have been made in critical care medicine, the necessity of prolonged intubation has increased and it is now possible to maintain mechanical ventilation longterm. However, prolonged intubation carries a risk of complications. While minor complications are relatively common, the incidence of serious complications is rare. Many of these major complications are due to high pressure being exerted by the cuff of the endotracheal tube. Fortunately, their incidence has dropped significantly since using low-pressure high-volume cuffs. However, it is still important to closely monitor cuff pressure to prevent any unwanted side-effects from occurring.
About Dr Martin Stotz
Dr Martin Stotz is an expert witness specialising in Intensive care medicine and Anaesthesia. If you have a clinical negligence or personal injury claim acting either for the claimant and defendant and would like advice please don’t hesitate to call Medicolegal Partners on 020 7118 0650.
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