Czosnyka M, Czosnyka Z, Whitehouse H, Pickard J D
MRC Cambridge Centre for Brain Repair, Addenbrooke's Hospital, UK.
J Neurol Neurosurg Psychiatry. 1997 Jan;62(1):43-50. doi: 10.1136/jnnp.62.1.43.
Although about 80% of properly diagnosed patients with hydrocephalus improve after implantation of any model of shunt, the remaining 20% may develop further complications because of inadequate shunt performance. Therefore, hydrocephalus shunts require careful independent laboratory evaluation.
Computer supported shunt testing, based on the new International Standard Organisation directives, characterises various aspects of pressure-flow performance of shunts such as variability with time, susceptibility to reflux, siphoning, temperature related behaviour, external pressure, the influence of a strong magnetic field (for example, MRI), presence of pulsation in differential pressure, particles in drained fluid, etc.
Seven different models of valves, representing most common constructions, have been tested so far. Most contemporary valves have a hydrodynamic resistance which is too low. This may result in overdrainage both related to posture and during nocturnal cerebral vasogenic waves. A long distal catheter increases the resistance of these valves by 100%-200%. Most shunts are very sensitive to the presence of air bubbles and small particles in drained fluid. Few shunt models offer reasonable resistance to negative outlet pressure, preventing complications related to overdrainage. Valves with an antisiphon device may be blocked by raised subcutaneous pressure. All programmable valves are susceptible to overdrainage in an upright position.
The behaviour of a valve during such testing is of immediate relevance to the surgeon and may not be adequately described in the manufacturer's product information.
尽管约80%诊断正确的脑积水患者在植入任何型号的分流器后病情有所改善，但其余20%的患者可能因分流器性能不佳而出现进一步的并发症。因此，脑积水分流器需要进行仔细的独立实验室评估。
基于新的国际标准化组织指令的计算机辅助分流器测试，可对分流器压力-流量性能的各个方面进行表征，如随时间的变化、对反流的敏感性、虹吸作用、温度相关行为、外部压力、强磁场（如磁共振成像）的影响、压差中的脉动情况、引流液中的颗粒等。
到目前为止，已经测试了代表最常见结构的七种不同型号的阀门。大多数现代阀门的流体动力阻力过低。这可能导致与体位相关的过度引流以及夜间脑血管源性波动期间的过度引流。较长的远端导管会使这些阀门的阻力增加100%-200%。大多数分流器对引流液中气泡和小颗粒的存在非常敏感。很少有分流器型号能对出口负压提供合理的阻力，从而预防与过度引流相关的并发症。带有抗虹吸装置的阀门可能会因皮下压力升高而堵塞。所有可编程阀门在直立位置时都容易出现过度引流。
在这种测试过程中阀门的行为与外科医生密切相关，而制造商的产品信息中可能并未充分描述。
