Virtual bronchoscopy and 3D reconstruction in the critical care setting

Background: Airway management of the critically ill patient is challenging. An audit of airway management in the UK reported higher incidence of significant airway complications (death and hypoxic brain damage) in the Intensive Care Unit (ICU) compared to regular anesthetic practice in the operating theatre.(1) Virtual bronchoscopy (VB) can be valuable in airway management in the ICU. Methods: Virtual reality (VR) emerged in the clinical field 20 years ago(2,3) utilizing graphics, high-end information technology, advanced sensors, and human-computer interfaces to create an immersive and interactive artificial environment. Conversion of standard radiological Computer Tomography (CT) images as computer-generated simulation of airway anatomy is referred to as VB or virtual endoscopy (VE).(2,3) VB allows the display of high-resolution airway images down to 6/7th bronchial subdivisions and simulates findings of traditional fiberoptic bronchoscopy (FOB)(3) (Figures 1 and 2). The indications of VB in ICU include evaluation and management of tracheobronchial stenosis, airway trauma, inhalation injury, foreign body aspiration, tracheostomy tracheoesophageal fistula (TOF) (3), and bronchopleural fistula (BPF)(2). Results: VB has several advantages including non-invasiveness, non interruption of mechanical ventilation or potential loss of airway, and no need for specific patient preparation. In addition, there is no exposure to contrast and it can be accomplished within a minute. VB allows airway evaluation of intra- and extra-luminal airway structure from all angles in isolation from its surroundings. Being operator-independent is a major advantage of VB.(4) FOB has significant limitations and potential complications. These include limited access via severe stenosis, inability to evaluate caliber and morphology of post-stenotic airway, limited information about airway surrounding structures in addition to risk of hypoxia, hypercarbia, and de-recruitment. Notably there is absence of bronchial colour or texture information, no endobronchial gesture such as bacterial sampling is possible, there are many false negatives and false positives, and the reproducibility of the measurements is still mediocre. Adequate sedation is needed during FOB with associated hazards. Moreover, risks of airway trauma, bleeding, pneumothorax, infection, and increased airway pressure with FOB have been observed.(2–4) In tracheobronchial stenosis, VB showed sensitivity of 63–100% and specificity of 61–99%, allows examination of the post-stenotic section of tracheobronchial tree and provides information about extra-luminal pathology.(3) VB is safe and well-tolerated by critically ill patients and does not pose a risk of contamination or infection of critically ill immunocompromised patients.(3) 3D reconstruction and VB can be performed either by the radiologist, anesthetist or surgeon on an appropriate workstation utilizing widely available software to generate an internal simulated view of the airway or the pathology. This can be utilized to formulate an airway management plan in critical and challenging situations.(4,5) However, retained mucus or blood mimic tracheobronchial stenosis. VB cannot be utilized for evaluation of pulmonary mucosa, biopsy, or pulmonary lavage. Dynamic changes, such as vocal cord palsy can be challenging to appreciate using VB. In addition, VB mandates transfer of critically ill patients to the radiology department and exposure to radiation.(3) Conclusion: 3D and VB volume rendering of CT images of the airway can provide anesthetists and intensivists with an alternative view of the airway in ICU settings. This can be utilized to formulate an airway management plan in the most demanding conditions.