Apnea testing for the diagnosis of brain death

Objectives –  A review is given on various methods, preconditions and pitfalls of apnea testing for the diagnosis of brain death. Materials and methods –  An extensive medical data base search was implemented by information gathered from books and our own experience with more than 2000 apnea tests. Results –  While testing for apnea (AT) is considered indispensable worldwide, recommendations and handling differ. Rather than relying on elapsed time, a specific target value for the partial arterial pressure of carbon dioxide (PaCO 2 ) should be aimed at being the maximum physiological stimulus for respiration. Methodological points are elaborated upon in detail for apneic oxygenation and hypoventilation. Conclusion –  AT is an indispensable element of diagnosing brain death. Although with proper handling and adequate precautions AT is safe, it should be performed as a last resort. An international agreement on target values for the PaCO 2 is desirable.