Cardiogenic oscillation and ventilator autotriggering in brain-dead patients: a case series

Brain death is manifested by a flaccid, areflexic patient on assessment of brain function with fixed and dilated pupils at midpoint, loss of consciousness, no response to stimulation, loss of brainstem reflexes, and apnea. A lesion or clinical state responsible for the loss of consciousness must be found. An integral part of clinical evaluation of brain death is apnea testing, which indicates complete loss of brainstem function and respiratory drive. Ventilator triggering or overbreathing the ventilator's set rate may be considered consistent with intrinsic respiratory drive consequent to residual brainstem function. Ventilator autotriggering, however, may potentially occur in a brain-dead patient as a result of interaction between the hyperdynamic cardiovascular system and compliant lung tissue altering airway pressure and flow patterns. Also, chest wall and precordial movements may mimic intrinsic respiratory drive. Ventilator autotriggering may delay determination of brain death, prolong the intensive care unit experience for patients and their families, increase costs, risk loss of donor organs, and confuse staff and family members. A detailed literature review and 3 cases of cardiogenic ventilator autotriggering are presented as examples of this phenomenon and highlight the value of close multidisciplinary clinical evaluation and examination of ventilator pressure and flow waveforms.