Anatomic and functional lesions resulting in partial or complete upper airway obstruction

Planning human upper airway surgery using computational fluid dynamics

The study advances the idea of using computational fluid dynamics in the process of planning surgical treatment modalities for patients with obstructive airway disorders. It is hypothesized that the a priori knowledge of the functional outcome of surgical intervention on the flow and airway resistance can guide the surgeon in choosing an effective surgical strategy. Computed tomography images spanning the respiratory tract of an adult patient with a combined glottic and subglottic stenosis are used to reconstruct three-dimensional geometrical models of the airway. Computational fluid dynamics is used to obtain airway flow patterns during inspiration and expiration in these models. Numerical predictions about flow velocity, pressure distribution on the airway lumen, wall shear stress, and airway resistance are obtained so that the relevance of each individual stenotic level is quantified. Four different virtual surgeries in different combinations are assessed in order to remedy the constricted airway. The virtual surgery based airway models are evaluated by comparisons with the pre-treatment flow modeling results. The predicted numerical data revealed that the removal of the constriction at the level of the vocal folds will have the most significant effect on the airway resistance. The flow simulations offer a quantitative method of evaluating the airway resistance in patients with combined glottic and subglottic stenoses. Predictions of airway resistances and other numerical calculations from different virtual surgeries give additional inputs for the surgeon, in deciding the most appropriate surgery on a case-by-case basis.

Immediate postoperative airway obstruction secondary to airway edema following tumor excision from the neck

A 46-year-old woman was scheduled for excision of a malignant peripheral nerve sheath tumor from the neck. The tumor had caused deviation of the trachea to the left and partial obstruction of the superior vena cava. Her upper airway at laryngoscopy after induction of anesthesia was normal. During tumor resection there were transient phases characterized by the complete disappearance of the peripheral oxygen saturation (Sp(O2)) and radial artery tracings. At the end of the operation, the trachea was extubated after ensuring adequate antagonization of neuromuscular blockade. However, immediately post-extubation, she showed signs of acute airway obstruction that necessitated reintubation of the trachea. Laryngoscopy revealed significant edema of the upper airway and vocal cords, requiring a smaller size tracheal tube. Many reports suggest the development of significant airway edema 24 h after such surgery. Our report highlights the fact that this can happen in the immediate postoperative period also. Some authors suggest that, in such surgery, extubation should routinely be done over pediatric tube exchangers. Routine leak testing and direct laryngoscopic/fiberoptic evaluation of the upper airway prior to extubation may also help. While our report reaffirms these points, it also stresses the importance of intraoperative monitoring for the compression of the great vessels, which may serve as a useful indicator of the early development of airway edema.

Asphyxia by Tracheobronchial Thrombus

Asphyxia secondary to airway obstruction has numerous underlying causes, both acute and chronic. Causes of chronic airway obstruction, such as neoplasms and tracheal scarring, are often clinically apparent well prior to asphyxia. Causes of acute airway obstruction may not be as obvious to clinicians or investigators. These include infections, anaphylactic reactions, status asthmaticus, inhalational injuries, and aspirations, which may result in acute obstruction and sudden death. We report the deaths of 2 individuals, a 43-year-old female and a 78-year-old female, both with adenocarcinoma. The 43-year-old was hospitalized with a stage III, poorly differentiated infiltrating ductal carcinoma of the breast metastatic to the lymph nodes. She was intubated to treat poor respiratory function and acidosis. A bronchoalveolar lavage was consistent with alveolar hemorrhage; no organisms were identified. Blood and "clot" were in her endotracheal tube, so the endotracheal tube was replaced. She became comatose and life support was withdrawn. At autopsy, a large red-gray thrombus obstructed the trachea and extended into the right bronchus. Microscopically, the entire clot was composed of fibrin, red blood cells, and some mucus. Findings of acute respiratory distress syndrome with hyaline membranes were identified. The cause of death was listed as acute respiratory distress syndrome with tracheobronchial thrombus. Experiencing a decline in mental status, the 78-year-old had metastatic adenocarcinoma of unknown primary. She developed sudden respiratory distress and an airway obstruction was discovered. After failure to relieve the obstruction, she decompensated and died. At autopsy, a large, red-gray thrombus obstructed the distal trachea and both bronchi. Microscopically, the thrombus was composed of fibrin, platelets, and red blood cells. The cause of death was asphyxia secondary to airway obstruction by thrombus. We present these 2 unusual cases of asphyxia and review of the literature focusing on asphyxia and the etiology of airway thrombi.