Tracheobronchomalacia in a patient on invasive mechanical ventilation: the role of electrical impedance tomography in its detection and positive end-expiratory pressure titration

1 Attending Physician, Department of Cardiorespiratory Diseases, Heart Institute, University of Sao Paulo School of Medicine Hospital das Clinicas, Sao Paulo, Brazil 2 Attending Physician, Respiratory Intensive Care Unit, University of Sao Paulo School of Medicine Hospital das Clinicas, Sao Paulo, Brazil 3 Attending Physician, Department of Cardiorespiratory Diseases, Heart Institute, University of Sao Paulo School of Medicine Hospital das Clinicas, Sao Paulo, Brazil Tracheobronchomalacia (TBM) is a disorder caused by weakness of the tracheal and bronchial walls, together with softening of the supporting cartilage, resulting in excessive expiratory collapse. (1) Although some individuals with TBM are asymptomatic, others present with symptoms such as dyspnea, hemoptysis, wheezing, and chronic cough.(1-3) Because the symptoms are nonspecific, TBM can be easily overlooked or misdiagnosed as other obstructive airway diseases, including asthma and COPD.(4) In TBM patients with acute respiratory failure, noninvasive ventilation is a therapeutic option, because positive end-expiratory pressure (PEEP) can prevent airway collapse.(5-7) Kandaswamy et al.(8) reported that, among patients with respiratory distress who failed weaning from mechanical ventilation or required reintubation in the ICU, the prevalence of TBM, identified on CT scans of the chest acquired only days before intubation, was 1.6%. However, to our knowledge, there have been no reports of TBM being diagnosed during invasive mechanical ventilation. Electrical impedance tomography (EIT) is a noninvasive, radiation-free monitoring tool that provides real-time imaging of ventilation at the bedside. Here, we report a case in which the combination of CT and EIT scans of the chest allowed us to make the diagnosis of TBM and to determine the best PEEP titration for preventing airway collapse in an intubated patient. A 66-year-old female was admitted to the emergency room complaining of breathlessness. She had a history of recurrent episodes of wheezing and dry cough, both of which partially improved after treatment with aminophylline and inhaled short-acting bronchodilators. Her past medical history included orotracheal intubation, for severe bronchospasm, five years prior. She reported no fever, sputum production, or other symptoms. She stated that she had not been exposed to any inhaled allergens, had no known allergies, and had no family history of asthma. She reported that she was not a tobacco user but had long been exposed to biomass smoke from cooking. On physical examination, she was in respiratory distress, presenting with accessory muscle use, her RR was 28 breaths/min, and her SpO2 was 96% while breathing room air. Examination of the lungs revealed prolonged expiration and diffuse wheezing. The results of the radiographic assessment and laboratory exams were unremarkable. Partial symptomatic relief was achieved after inhalation therapy with ipratropium bromide and fenoterol, together with intravenous hydrocortisone. She was discharged home but returned to the emergency room with bronchospasm minutes later. Although she was then treated with additional doses of inhaled bronchodilators, as well as intravenous magnesium sulfate, her dyspnea worsened. A few hours later, she became comatose, requiring orotracheal intubation and admission to the ICU. At ICU admission, the patient was deeply sedated with fentanyl and midazolam, was started on inhaled albuterol (400 μg/h), received

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