Novel noninvasive intracranial pressure monitoring device comparable to invasive method
A new noninvasive intracranial pressure monitoring device (HS-1000) produces comparable results and may protect patients from the risks associated with the invasive monitoring method, according to preliminary findings of a German study.
“The findings of this study highlight the capability of the HS-1000 to provide information about normal and elevated [intracranial pressure] levels in a clinical setting,” said the researchers led by Dr Oliver Ganslandt from the Department of Neurosurgery, Klinikum Stuttgart, Stuttgart, Germany.
“The HS-1000 could be extremely beneficial as an adjunct modality by assisting clinicians in deciding if a patient requires an [invasive intracranial pressure] monitor,” they said.
The HS-1000 device emits 6-second-long beeps (66 dB) from the ipsilateral ear which are propagated through the cranium and detected by a receiving sensor placed in the contralateral ear. The signal modulations are evaluated with advanced signal analysis algorithms with data derived displayed on the device monitor.
In this study, the intracranial pressure of 14 patients (aged ≥18 years) with traumatic brain injury or subarachnoid haemorrhage receiving treatment in an intensive care unit (ICU) was measured using the invasive method (external ventricular drainage or intraparenchymal monitoring, n=12 and 2, respectively) as well as noninvasively with the HS-1000 device. Data was collected for 30 minutes to 1 hour. A total of 2,543 data points of continuous parallel recording were accrued from both methods and compared.
Differential pressures between the invasive and noninvasive methods were within ± 3 mm Hg in 63 percent of readings and within ± 5 mm Hg in 85 percent of readings. Mean intracranial pressure measurements were 10 and 9.5 mm Hg for the invasive and noninvasive methods, respectively. [J Neurosurg 2017;doi:10.3171/2016.11.JNS152268]
The differential pressures between the invasive and noninvasive methods were similar to that between the intraventricular and intraparenchymal invasive monitoring methods observed in several studies, said the researchers.
Sensitivity and specificity for noninvasive intracranial pressure monitoring at ≥17 mm Hg cutoff were 0.7541 and 0.8887, respectively. Linear regression analysis indicated a positive relationship between the measurements obtained using both methods (r=0.82; p<0.0001).
The researchers acknowledged that data could not be compared between the two techniques when the patient’s condition did not enable continuous recording.
In the currently used invasive procedure, a burr hole is drilled into the patient’s skull, through which a transducer-coupled probe is inserted into the brain parenchyma or ventricles, while an external extraventricular drain is used to monitor pressure and extract excess cerebrospinal fluid from the brain. Aside from being a technically demanding procedure, invasive intracranial pressure monitoring is associated with risks such as infection, postoperative haemorrhage, and inaccurate recordings, said the researchers.
To counter these drawbacks, noninvasive methods such as transcranial Doppler ultrasonography, tympanic membrane displacement, and optic nerve sheath diameter have been tested, though none have proven accurate enough to replace the invasive method, they said.
“The use of [the HS-1000] monitoring device may help avoid the immediate risk of infection and/or haemorrhage … and reduce the morbidity and mortality rates in neurocritical ICUs,” said the researchers.
However, the algorithms would require further refinement before the device is ready for clinical use, said Ganslandt.