The apnea test is a component in the determination of brain death. One technique used to evaluate the absence of breathing drive is to perform the "Apneic Oxygenation Diffusion Technique" also know as a "CO2 Challenge". In 1995 the American Academy of Neurology published prerequisites and parameters to perform this clinical assessment[1].
In his recent journal article "A Critique of the Apneic Oxygenation Test for the Diagnosis of Brain Death"[2], Dr. James Tibballs provides a strong argument against the utility and questions the safety of the apnea test.
The author proposes four areas of concern to fortify his disagreement:
- The reliability of apnea with a rise in PaCO2 as a neurological diagnostic of brain death.
- The potential for injury due to the unpredictable rise in PaCO2.
- The large amount of variability, in regards to performance of the technique.
- There are other tests which can be performed, which are superior.
Safety of techniques for determining apnea is a foremost concern for all health care providers and the Academy of Neurology has readdressed this apprehension. In their current evidence-based guideline update[3] , the academy reviewed over 367 articles which 38 met inclusion criteria. On the topic of "what is the comparative safety techniques for determining apnea?" the academy based their conclusion on four published, class IV studies. The guideline stated "apneic oxygenation diffusion to determine apnea is safe.
The test requires five perquisites to be met before application. The procedure itself is approximately 13 steps, in which the first few steps assure that the patient is hemodynamically stable and well oxygenated with pulse oximetry saturations > 95%. The steps are easy to follow and well defined.
For more information on methods of ancillary testing and checklist determination of brain death click on the following link:
[1] The Quality Standards Subcommittee of the American Academy of Neurology. Practice Parameters for Determining Brain Death in Adults. Neurology. 1995; 45: 1012-1014.
[2] Tibballs, J. A Critique of the Apneic Oxygenation Test for the Diagnosis of Brain Death. Pediatric Critical Care Medicine. 2010; 4: 475-477.
[3] Wijdicks E, Varelas P, Gronseth G, and Greer D: Evidence-Based Guideline Update: Determining Brain Death in Adults: Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2010; 74: 1911-1918.