Acute complications of artificial airways David Feller-Kopman, MD Medical Procedure Service, Interventional Pulmonology, Division of Pulmonary and Critical Care Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA There are reports dating back to Galen (129��� 210 AD) of using bellows to ventilate animals during vivisection with some form of tracheal tube [1]. Although tracheotomy has likely been performed for more than 3000 years [2���4], the Italian physician Antonio Musa Brasavola is credited with the first description of a successful tracheotomy in 1546 [5,6]. Sanctorio Sanctorius, an Italian surgeon, provided the first description of percutaneous tracheotomy in 1626, when he used a ������ripping needle������ to introduce a silver cannula into the tracheal lumen [5]. In the mid-1700s, artificial ventilation was encouraged as a method of resuscitating drowning victims, and in 1776, Cullen recommended endotracheal intubation as an adjunct to bellows ventilation [1,3]. MacEwen later described the successful use of translaryngeal endotracheal intubation to relieve upper airway ob- struction during the diphtheria outbreak in 1858, as well as in a patient undergoing oropharyngeal sur- gery [3]. In 1869, Trendelenberg developed the first cuffed tracheostomy tube [7], yet it wasn���t until early 20th Century that tracheotomy became a popular procedure, due to the standardization of open surgical tracheotomy by the famous American surgeon Cheva- lier Jackson. Jackson is credited with reducing the operative mortality associated with tracheotomy from 25% to 1% [6]. Though the first negative-pressure ventilator was developed in 1832 [3], the Drinker- Shaw ������iron-lung������ described in 1929, did not enter widespread clinical practice until the polio epidemic in the 1940s and 1950s. Lassen was the first to report an improvement in mortality in patients with ventilatory failure from polio by the use of tracheostomy, positive pressure ventilation and pH monitoring [8]. This epidemic also spurred the idea of using positive pressure ventilators, previously only used in the oper- ating room, to be used for other causes of ventila- tory failure. There has since been an exponential use of mechanical ventilation as well as translaryngeal endotracheal tubes (ETT) and tracheotomy tubes (TT). Other types of artificial airways include the laryngeal mask airway, and cricothyroidotomy and transtracheal oxygen catheters. The use of all of these devices is associated with both physiologic and as physical complications, in addition to the complica- tions associated with the use of anesthesia and positive pressure ventilation. There are a variety of ways to categorize the complications of tracheal intubation, some of which include chronologic, anatomic, and etiologic. Blanc and Tremblay suggest a classification scheme based on chronology, both in terms of duration of tracheal intubation and when the injury occurs: during the act of intubation, while the tube is in place, and during the act of extubation [9]. They further divide these three time periods into complications associated with mechanical complications, neurogenic or reflex com- plications, and pharmacologic complications. Early or immediate complications were defined as those that occurred in the first 24 hours [9]. Although the actual incidence of airway injury from endotracheal intubation has probably declined, the prevalence is likely increasing, solely due to the increased use of artificial airways in the era of high- technology medicine. Because traumatic airway injury is relatively uncommon, the diagnosis, evalua- tion, and management of these patients are often delayed. This article reviews the acute complications associated with artificial airways, with a focus on the complications associated with endotracheal intuba- 0272-5231/03/$ ��� see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0272-5231(03)00047-9 E-mail address: dfellerk@caregroup.harvard.edu Clin Chest Med 24 (2003) 445���455

tion (ETI), ETTs and TTs, and stays relatively true to the classification scheme suggested by Blanc and Tremblay (Table 1)[9]. The late complications asso- ciated with artificial airways are reviewed elsewhere in this issue. Timing of tracheotomy Though there are many similarities in the pattern of injury induced by both ETTs and TTs, each is associated with its own set of complications as well. Tracheostomy tubes, for example, can induce stenosis at the level of the stoma, whereas ETTs may result in glottic and subglottic injury. The incidence of clini- cally significant stenosis at the stoma is estimated at 3% to 12% [10,11]. Nasotracheal intubation, though potentially associated with a reduced incidence of tracheal injury at the tube tip by being less mobile than an oral ETT [12], significantly increases the risk of sinusitis [13,14]. These differences in complication rates are a major factor influencing the decision to convert an ETT to a TT, as stenosis at the level of the stoma is more easily repaired than stenosis at the level of the glottis or immediate subglottic space [12]. Immediate and severe procedural complications are more com- mon with tracheotomy, however [16]. The timing of tracheotomy is subject to much debate, and a review of the relevant data is the scope of another article. A complicating factor in this debate stems from the fact that almost all patients who receive TTs have also had ETTs for some time. Additionally, there are few data examining the long-term effects of brief ( 24 hours) intubation with an ETT. Clearly, it is not ideal to subject the patient to the complications of both ETTs and TTs [17]. In 1989, the American College of Chest Physicians published its Consensus Conference on Artificial Airways in Patients Receiving Mechanical Ventilation [18] and recommended tracheotomy when the anticipated need for an artificial airway was more than 21 days. Additionally, it noted that the procedure should be done ������as early as possible,������ and that ������once the decision is made, the procedure should be done without undue delay������ [18]. Physiologic considerations The lower respiratory tract is protected by reflex arcs from both the upper and lower airways. The afferent pathways are comprised of the glosso- pharyngeal nerves in the oropharynx superior to the anterior surface of the glottis, and the superior and recurrent laryngeal nerves for the posterior and in- ferior glottis, whereas the efferent pathway is con- trolled by the vagus [19]. Afferent stimuli can therefore trigger cardiac, airway, cerebral, neuromus- cular, and adrenal responses. Although bradycardia can develop in up to 10% of patients undergoing endotracheal intubation, the typi- cal result, even under general anesthesia, is one of hypertension and tachycardia, resulting in an increase in myocardial oxygen consumption [19]. Furthermore, many of the medications used for endotracheal intu- bation have direct and indirect cardiovascular effects. It has been shown that up to 15% of patients under- going endotracheal intubation under general anesthe- sia will have ventricular arrhythmias, with the majority of events occurring at the time of tube insertion, as opposed to at the time of laryngoscopy [20]. Table 1 Acute complications of artificial airways Physiologic/Pharmacologic Anatomic/Mechanical Hypertension Fracture/subluxation of the cervical spine Hypotension Injury to the nasal mucosa/septum, epistaxis Tachycardia Dental trauma Bradycardia Injury to the lip, tongue and buccal mucosa Glottic closure Oropharyngeal/retropharyngeal injury Increased intracranial and intraocular pressure Laryngeal injury Bronchospasm Subglottic injury Barotrauma: pneumothorax, pneumomediastinum, subcutaneous emphysema Tracheal injury Injury to the lingual, hypoglossal and recurrent laryngeal nerves Bronchial intubation Esophageal intubation/injury Aspiration: blood, tooth, gastric contents Failed intubation Equipment failure: cuff rupture, tube obstruction or dislocation D. Feller-Kopman / Clin Chest Med 24 (2003) 445���455 446