EVD Drainage Data and Intracranial Pressure (ICP) Measurements

"Patients will have one or more existing external ventricular drains (EVDs). Phase B patients will additionally have an accessible (shaved) region of skin \>3 cm x 3 cm overlaying the EVD tubing.~Clinical data to be collected include: 1) total drainage volume1 over the 20-minute measurement period; 2) handheld ultrasound measurement of skin thickness2 over the EVD; and 3) an ICP waveform from a standard-of-care transducer, 4) dimensions (inner diameter and outer diameter) of tunneled catheter. Single patients may be measured multiple times during their admission; each measurement will be considered independent for analysis."