Respirator triggering of electron beam computed tomography (EBCT): Research on vital capacities

In this project we evaluate the dynamic changes during expiration at differ ent levels of positive-end-expiratory pressure (PEEP) in ventilated patient s. We wanted to discriminate between normal lung function and acute respira tory distress syndrome (ARDS). After approval by the local Ethic Committee we studied two ventilated patients: (one with normal lung function and one with ARDS) We used the 50 ms scan, mode of the EBCT. The beam was positione d 1 cm above the diaphragm while the table position remained unchanged. We developed an electronic trigger that utilizes the respirator's synchronizin g signal to start the EBCT at the onset of expiration. During controlled me chanical expiration at two levels of PEEP (0 and 15 cm H2O), pulmonary aera tion was rated as: well-aerated (-900HU to -500HU) poorly aerated (-500HU t o -100HU) and non-aerated (-100HU to +100HU). Pathological and normal lung functions showed different dynamic changes. Th e different PEEP levels resulted in a significant change of pulmonary aerat ion in the same patient. Although rue studied only two patients, respirator triggered EBCT may be accurate in discriminating pathological changes due to the abnormal Lung function in a mechanically ventilated patient.