Percutaneous tracheostomy: prospective practice.

Foresight specifically instructs users of the CAS cerebral oximeter system to use a light block over the sensor, supposedly in order to prevent disturbance of the readings by the ambient light. Actual clinical use and observation may yield different information from what has appeared from the observations described. Figure 1 shows left (channel 1) and right (channel 2) perioperative cerebral saturation tracings obtained in the same patient during cardiac surgery using both the Foresight and the Equanox 7600 monitoring system. It is apparent that with the Foresight system, a number of drop-outs occurred in the registration of the signals and that the individual values demonstrate a substantial oscillation. Figure 2 shows the tracings obtained in another cardiac surgical case where the left side was monitored using the Invos 5100 system and the right side using the Equanox 7600 system. An important oscillation of data is observed with the Invos system but not with the Equanox system. These examples demonstrate that comparison of devices should not rely only on in vitro observations in specific experimental conditions. Instead, performance of the different monitoring systems should be evaluated in the clinical setting where they are intended to be used. Only in this situation, relevant conclusions on which monitor provides the most reliable information can be made.