The Final Determination of Placement of the Sensors is Up to the Clinician, and What Area is intended to Be Measured.

 

The c-FLOW™ Monitor is based on a combination of a Near-Infrared (NIR) laser, and an ultrasound beam. In conjunction they create Ultrasound Tagged Light (UTL) which is what the c-FLOW™ uses to measure the Cerebral Blood Flow Index (CFI). The combination of Laser and ultrasound allows the monitor to non-invasively track blood flow changes, but does have some possible limitations which should affect placement decisions:

  1. The ultrasound system requires close coupling to the Smart Pad and the tissue to function properly. As such, the Smart Pads should be placed in locations that reduce curvature as much as possible, so as to allow as flat a surface for coupling as possible. Extreme curvature will not offer full coupling and may lead to poor signal or no signal. Coupling is also determined by ensuring sufficient utilization of ultrasound gel – in an extended monitoring situation, ensure gel is replaced every 4-6 hours.
  1. Laser signals are transferred from the c-FLOW™ to the sensors via a fiber optic wire. Although well shielded, the fiber optic wire should be treated carefully when placing the sensors: for best possible signal, ensure that the sensor cables are not under the patient, or become bent or pinched. Furthermore, due to the weight of the sensor cable, when at all possible, the weight of the cable should be off-loaded onto an IV pole, clipped to the bed or any other mechanism that does not allow them to hang loose, as prolonged weight load from the cable may decouple the sensor from the Smart Pad and/or pull the Smart Pad off the patient.
  1. To further off-load weight from the cables, and to help reduce issues caused by patient movement, Smart Pads should be placed, when at all possible, in such a manner as to cause the sensor cables to come off the patient towards the monitor’s location. If, for example, the monitor can be placed to the rear of the patient, the cables should come out towards the top of the head. This positions the cables and sensors in such a manner as to minimize either pulling off the cables when a patient rolls or is rolled, or compression of the end of the sensor cable when the sensor hits the pillow.
  1. The adhesive side of the Smart Pad enables its attachment to the skin. As such, the area should be cleaned with the included alcohol wipe, as demonstrated in the IFU. In addition to this, hair will cause multiple issues: If the area to be used is covered with hair, it should be shaved to allow the adhesive to stick directly to the skin. Furthermore, a heavy density of follicles in the sensing area can cause a reduction in the ability of the ultrasound system to penetrate through to the sensing area, causing some increased noise and reduced signal quality.
  1. Areas with increased skull thickness will cause the ultrasound and laser to not reach as far into tissue as it normally would, causing a decrease in signal quality.
  1. Skin pigmentation may affect NIR laser penetration through the skin.
  1. Sensor should never be placed over wounds, where skin is not intact or on patients with severe edema.
  1. Due to the use of ultrasound and since it does not propagate through air, placement of the sensors over the sinus cavities must be avoided.
  1. Placement of the sensor above large superficial blood vessel might block signals originating from deep tissue. Thus, when obtaining poor signal, repositioning the sensor might help to improve the signal.
  1. Whenever placing the sensor into the Smart Pad, please verify that the silicone cushion is in place.

 

In general, none of the issues in isolation should cause an unusable signal, however, any of them in conjunction can lead to sufficient signals loss to render readings suspect. Ideal placement of the pads is as shown below:

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