Apnea Tests as the Methods of Brain Death Diagnosis.

Overview

Apnea test (AT) is the most important clinical test performed usually at the end of brain death (BD) diagnosis procedure. Traditional insufflation apnea test (I-AT) cannot be completed in patients with extremely compromised lung function due to rapid blood desaturation and circulatory disturbances. Therefore the investigators decided to verify alternative AT options such as continuous positive airway pressure apnea test (CPAP-AT) in patients with good and poor baseline oxygenation, before implementing them in currently reviewed Polish BD criteria.

Apnea test (AT) is one of the most important examination during the diagnosis of brain death. It is usually performed at the end of each series of clinical examinations during diagnostic process. The most popular standard insufflation apnea test (I-AT) may be potentially harmful. It may cause some serious complications including pneumothorax, severe hypoxemia, hemodynamic instability and even cardiac arrest. Therefore, the investigators decided to analyze apnea test in CPAP option (CPAP-AT) as a new tool. For safety of the study the investigators analyzed a method after BD diagnosis. Methods: I-AT and hypoventilation with 100 % oxygen (if needed) were performed according to Polish guidelines. Two hours after BD diagnosis was performed extra apnea test in CPAP option (CPAP-AT). Before CPAP-AT the patients were ventilated 100% oxygen. After then the ventilator settings were changed to CPAP mode with PEEP 10 cm H2O, PS 0 cm H2O, FiO2 1,0, flow 6L/min. Emergency apnea ventilation was turned off. At the beginning of CPAP mode and 10 minutes after, blood samples for arterial blood gases (ABG) were collected. If were observed rapid desaturation defined as a decline in O2 saturation below 85%, CPAP-AT was aborted and study was finished. During routine diagnosis of brain death, pupillary dilation after a neck flexion was observed in one case. Therefore, the investigators decided to use a pupillometer during brain death examination to find out how pupils react after a neck flexion and how often it happens. Pupil measurements were taken immediately after the diagnosis of brain death. The measurements of pupil diameter were taken twice: A - before neck flexion; B - after neck flexion. We used pupillometer: AlgiScan (Equip Medkey BV).