6.7.1. sensor placement instructions
Assessing the brain4care waveform
The best position for ICP waveform monitoring is a resting supine position at 30 degrees with the chin and sternum aligned (Figure 6.7-1) and the head should not be tilted. The patient must be resting and avoid any movements since that can interfere with the ICP waveform reading.
PRECAUTION - The position, or movement, of the patient and the BcSs-PICNIW-1000 Sensor is known to affect the signal being recorded. As a result, if multiple recording sessions are obtained on the same patient, consistent positioning of the patient and device will lead to more comparable recordings.
A satisfactory waveform reading will present any of the typical shape characteristics (Figure 6.7-2) below, according to the patient’s clinical condition (from normal to pathological)
As a suggestive reference, the waveforms below (Figure 6.7-3.A to 6.7-3.G) are typical non invasive ICP waveforms that are shown with the noninvasive ICP sensor.
WARNING - The appearance of a normal waveform morphology does not eliminate the possibility of elevated intracranial pressure or irregularity in brain compliance.
ATTENTION - The waveforms above are examples of typical noninvasive ICP waveforms in different clinical settings. You may see variations in the ICP waveform, but they should always follow a similar pattern.
The monitoring session should be as long as required to assess the ICP waveform on the monitor. Typical sessions are of 15+ minutes but duration is ultimately defined by trained clinical personnel. The session should be finalized upon patient request due to discomfort or decision by the primary caregiver.
The ICP pulse waveform (Figure 6.7-4) is an alternative to assess certain ICP characteristics, irrespective of the absolute values that are typically captured by an invasive method .
The ICP waveform contains characteristics that can be mathematically analyzed such as:
Wave peaks: P1 (percussion wave, due to arterial pressure being transmitted from the choroid plexus to the brain ventricles), P2 (tidal wave, related to brain compliance) and P3 (dicrotic wave);
Absolute amplitude of wave peaks: dP1 (relative amplitude of percussion wave), dP2 (relative amplitude of tidal wave), dP3 (relative amplitude of dicrotic wave);
Absolute lags in milliseconds of wave peaks: LT (considered the initial timestamp of a pulse), L1 (lag for percussion wave), L2 (lag for tidal wave), L3 (lag for dicrotic wave), Lx (variable lag);
Absolute curvature of wave peaks: Curv1 (percussion wave curvature), Curv2 (tidal wave curvature), Curv3 (dicrotic wave curvature).
Under normal conditions of ICP, the relative amplitudes of the three peaks are related as follows: P1>P2>P3 (Box A in Figure 20 above). In conditions with decreased brain compliance and rising ICP, the pulse waveform morphology gradually changes and certain indicators, such as the P2/P1 amplitude ratio eventually increases.
WARNING - The BcSs-PICNIW-1000 Sensor does not replace a comprehensive clinical evaluation. The waveform output should always be evaluated by the clinician in conjunction with other clinical parameters or analyses.
WARNING - The BcSs-PICNIW-1000 Sensor and waveform output do not substitute ICP monitoring methods when measurement of the absolute value of ICP is required.
WARNING - The medical professional is responsible for determining the additional clinical parameters or analyses required in addition to the BcSs-PICNIW-1000 Sensor waveform to make a clinically informed decision.
WARNING - The appearance of a normal waveform morphology does the eliminate the possibility of elevated intracranial pressure or irregularity in brain compliance.
WARNING - The clinician is reminded to assess the waveform morphology in real-time during a monitoring session. The B4C report is available for the clinician’s convenience to review associated waveform parameter estimates and other clinical observations entered in a past monitoring session
6.7.2 verifying the ni-ICP signal quality in patient monitors using the receiver
After correctly placing the sensor on the patient’s head and pairing with the receiver the waveform should accurately appear on the monitor. Good positioning of the headband and proper placement of the sensor will result in typical waveforms as depicted below (Figure 6.7-5). Note: the figure below is simply an illustration of a sample waveform.
ATTENTION - The waveforms acquired from non-invasive ICP method do NOT represent actual mmHg values on the patient monitor scale.
If the signals shown on the monitor do not present any of the characteristics seen in the depiction above (the signal should at least present identifiable P1 and P2 peaks), modify the position of the sensor on the patient’s head by shifting and/or tightening/ loosening the headband until a satisfactory pulse waveform is obtained. An example of a poor reading is depicted below (Figure 6.7-6).
ATTENTION - Trained Personnel are expected to recognize proper waveform quality.
WARNING - Do NOT attempt to calibrate BcSs-PICNIW-1000 Sensor with your patient monitor. This may result in display of a misleading ICP value shown in the patient monitor that can be misinterpreted when making critical clinical decisions.
WARNING - Make sure NO ICP value is shown in your patient monitor when the BcSs-PICNIW-1000 Sensor is connected. Make sure that the default question marks (? /?) or dashes (- / -) are shown instead.
ATTENTION - Only use with a compatible monitors and DO NOT calibrate the ICP value (mmHg)