Intraventricular pressure dynamics in patients with ventriculopleural shunts: a telemetric study.

Extracranial CSF shunting to the pleural absorptive surface is sometimes used as an alternative to ventriculoperitoneal shunting. The pressure dynamics of this type of shunt would be expected to differ from peritoneal shunting due to active changes in pleural pressures caused by the ventilatory cycle. We have had opportunity to examine the in vivo intraventricular pressure (IVP) dynamics of ventriculopleural shunts utilizing a commercially available implantable telemonitor (Telesensor; Radionics, Burlington, Mass.). Four patients with ventriculopleural shunts were monitored telemetrically while supine and at increments of head elevation to 90 degrees. Two patients with 'medium' grade differential pressure valves exhibited IVPs which were never greater than zero. One patient with an in-line antisiphoning device in the shunt system appeared to have IVPs closely resembling those seen in shunting to the peritoneal space. Another patient with valve opening pressure set at 19 cm of water consistently had supine intraventricular pressures less than 10 cm of water that readily fell to zero with minimal head elevation. We conclude that the negative intrapleural pressures generated by the ventilatory cycle tend to cause IVPs in ventriculopleural shunts to be lower than those expected in peritoneal shunting. This observation suggests that ventriculopleural shunts may be appropriate for patients requiring very low intraventricular pressures in order to resolve their hydrocephalic symptoms.