Validation of Brain Oxygenation Monitor
Condition: Healthy
Study type: Interventional

Summary: 
      A cerebral oximeter is a device that uses light to measure the amount of oxygen within the
      brain. It is similar to the device that measures the level of oxygen in the tip of the
      finger, known as a pulse oximeter. The cerebral oximeter consists of a sensor placed on the
      forehead that both emits and detects the amount of light absorbed. This study will determine
      how accurate the device is by comparing the displayed value on the monitor with blood samples
      taken simultaneously from the arterial blood in the wrist and venous blood in the neck. In
      order to test the device over a suitable range, the level of oxygen within the blood will be
      reduced in a controlled manner by reduction of the inspired oxygen concentration. This is the
      equivalent of ascending to an altitude of 16,000 feet. The study will be conducted in healthy
      volunteers.
    

Detailed description: 
      This is a calibration and validation study of a near-infrared spectroscopy (NIRS) device
      designed to measure the cerebral tissue oxygen saturation non-invasively. This is achieved by
      comparing NIRS-derived cerebral tissue oxygen saturation with a calculated value derived from
      simultaneous arterial and jugular venous blood samples.

      At present the FDA have adopted the standards published in 2005 by the International
      Organization for Standardization (ISO), entitled ISO 9919. This is a set of technical
      specifications and guidelines for pulse oximeters, which share certain technical similarities
      to cerebral oximeters. In particular, Annex EE details the conduct of a controlled
      desaturation study for the calibration of pulse oximeter equipment. Specifically, the
      fraction of inspired oxygen delivered to test subjects is varied to achieve a series of
      targeted steady state saturation periods over a range of arterial oxygen saturation of 70 -
      100%.

      While cerebral oximeters differ from pulse oximeters in terms of the what is being measured
      (brain tissue v arterial blood) the FDA have maintained the requirement to examine data from
      human volunteer studies in which the arterial oxygen saturation ranges from 70 - 100%. Two
      FDA-approved cerebral oximeters were validated in a similar manner.

      The device controlling the inspired gas concentration is the RespirAct, which permits precise
      reduction in the arterial oxygen saturation while maintaining the arterial carbon dioxide
      level at 40 mmHg.

      The study consists of 3 sequences:

        -  First sequence: reduction in arterial oxygen saturation in approximately 5% increments
           from 100 to 70% followed by return to room air and then a period of supplemental oxygen.

        -  Second sequence: reduction in arterial oxygen saturation in a single drop from 100 to
           70% followed by return to room air and then a period of supplemental oxygen.

        -  Third sequence: reduction in arterial oxygen saturation in approximately 10% increments
           from 100 to 70% with alteration of carbon dioxide level from 35 to 45 mmHg at each
           interval followed by return to room air.
    

Intervention name(s): Desaturation
Intervention type(s): Device
Intervention description(s): Reduction in blood oxygen saturation by sequential reduction in inspired gas composition. Steps are of 6 minutes duration with reduction in pulse oximeter oxygen saturation from 100 to 70%.
Other intervention name(s): Nonin cerebral oximeter
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Spectroscopy, near infrared; Oximetry; Hypoxemia; Tissue oxygenation