Evaluation of Electrical Impedance Tomography for the Diagnosis of Chronic Rejection in Lung Transplants Recipients
Condition: Transplantation, Heart-Lung; Chronic Lung Allograft Dysfunction; Bronchiolitis Obliterans Syndrome
MeSH terms: Bronchiolitis; Bronchiolitis Obliterans; Bronchiolitis Obliterans Syndrome
Study type: Interventional

Summary: 
      Electrical impedance tomography (EIT) is non-invasive and provides functional imaging of the
      lung and it could be a useful tool to diagnose chronic lung allograft dysfunction (CLAD) and
      specially Bronchiolitis Obliterans Syndrome (BOS). Hence, for this study, the investigators
      aim to show that EIT would provide an accurate diagnostic CLAD with an ability to to
      distinguish BOS from Restrictive Allograft Syndrome (RAS) and to stage BOS accurately when
      compared to FEV1 the current gold standard. The investigators are also aiming to provide
      physiological data in lung transplant recipients with chronic rejection.
    

Detailed description: 
      Lung transplantation is the only treatment option available for patients affected by
      end-stage lung diseases such as chronic obstructive pulmonary disease (COPD), cystic fibrosis
      or idiopathic pulmonary fibrosis, not responding to maximal medical therapy. Despite the
      advance in the surgical techniques, immunosuppression treatment and prevention of acute
      cellular rejection episodes as well as opportunistic infections, the long terms outcomes
      following lung transplant remain unsatisfactory. Chronic lung allograft dysfunction (CLAD) is
      the first cause of long term mortality in lung transplant recipients responsible of 5 years
      mortality post-surgery of 50%. CLAD can lead to chronic respiratory failure and can presents
      in two different phenotypes: Restrictive forms of CLAD were all lung volumes are decreased
      (commonly called RAS, Restrictive Allograft Syndrome) that has been recently associated with
      antibodies mediated rejection. A more common form of obstructive CLAD has been identified as
      the well-known and defined Bronchiolitis Obliterans Syndrome (BOS). In patients with BOS, the
      progressive obliteration and a narrowing of the distal airways result in breathlessness,
      airflow obstruction and air trapping.

      Currently, Forced Expiratory Volume at 1 second (FEV1) measurement is the gold standard to
      assess BOS severity. This test is non invasive and easily performed at bedside. Thus, it only
      gives a broad idea of the regional consequences of BOS as may be influenced by large airway
      obstructions. Chest computed tomography (CT) gives more detailed imaging of the regional
      consequences of BOS but is time-consuming and expose patients to radiations. Others imaging
      techniques such as ventilation/perfusion scintigraphy have been studied but cannot be
      performed at bedside.

      As to date there is no curative treatment for BOS, preventive treatments such as long term
      azithromycin, bronchodilators, inhaled steroids or plasmapheresis have to be started at early
      stage of the disease to improve outcomes for the recipients Electrical impedance tomography
      (EIT) is a new technology that involves wearing a belt of sensors around the chest that
      provides information on how well the lungs are being filled with air by the ventilator. It
      allows the assessment of these differences, which previously required the use of invasive
      equipment to obtain. Information is gained by repeatedly injecting small alternating electric
      currents (usually 5 mA) at high frequency of 50 - 80 kHz through a system of skin electrodes
      (usually 16) applied circumferentially around the thorax in a single plane between the 4th
      and 6th intercostal space. While an adjacent pair of electrodes 'injects' the current
      ('adjacent drive configuration'), all the remaining adjacent passive electrode pairs measure
      the differences in electric potential. A resistivity (impedance) image is reconstructed from
      this data by a mathematical algorithm using a two dimensional model and a simplified shape to
      represent the thoracic cross-section.

      The resulting image possesses a high temporal and functional resolution making it possible to
      monitor dynamic physiological phenomena (e.g. delay in regional inflation or recruitment) on
      a breath by breath basis. It is important to realize that the EIT images are based on image
      reconstruction techniques that require at least one measurement on a well-defined reference
      state. All quantitative data are related to this reference and can only indirectly quantify
      (relative) changes in local lung impedance (but not absolute).

      EIT can be used in mechanically ventilated patients to assess recruitment and to optimise
      ventilator settings to reduce risk of iatrogenic ventilator associated lung injury. To date,
      EIT has never been used in lung transplant recipients.
    

Intervention name(s): EIT; Salbutamol nebulisation and with CPAP
Intervention type(s): Other; Other
Intervention description(s): All participants will have continuous monitoring of EIT whilst self venting; All participants will have continuous monitoring - salbutamol nebulisation will be given during 15 minutes using 5mg of salbutamol. Assessments on CPAP will be performed at 3 different level of pressure during this time.
Intervention MeSH terms: Albuterol
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic