The monitoring of blood gases is often essential in evaluating patients in surgery, critical care or in emergency rooms. Measuring arterial or venous values involves either puncture of a vessel and blood removal for intermittent testing, or the insertion of an intravascular sensor. For newborns in critical care, and particularly the premature infant requiring supplemental oxygen, blood and tissue gas levels are crucial. If the oxygen is insufficient, the infant may develop cerebral palsy or expire, while too much oxygen may cause blindness from retinopathy. The patient's carbon dioxide level is important to indicate pulmonary and metabolic status, as is the pH value. The removal of blood for testing, however, represents a considerable risk for the fragile infant, and does not measure the perfusion of vital organs such as the brain. To solve this problem, Intelligent Optical Systems (IOS), in collaboration with the Los Angeles Biomedical Institute at Harbor-UCLA Medical Center, proposes to develop a minimally invasive, continuous blood and tissue gas monitoring system for infants and critical care patients. The setup will be based on a thin, flexible, non-irritant fiberoptic probe placed on the conjunctiva of the patient's eye. Four optical sensors embedded in the probe will determine the pH, carbon dioxide, and oxygen tension of the gas diffusing through the conjunctiva, together with the temperature. An electrooptic readout unit will interrogate the fiberoptic system, and continuously display and monitor the patient's conjunctival or blood gases. Based on IOS'distributed fiber sensor technology, the system will be insensitive to the patient's head or ocular movements. Preliminary studies performed by our collaborators have validated this innovative detection approach. The proposed system fills an important gap in critical care for infants, making continuous blood and tissue gas monitoring available to fragile premature infants and newborns in intensive care, as well as for critically ill children and adults requiring intensive care or undergoing major surgery. Given both the minimal invasive nature of conjunctival monitoring and the importance of blood gas analysis, this system could become a standard tool in critical care, during surgery, and in the emergency room.
