Hemorrhage is responsible for more than 35% of pre-hospital deaths and greater than 40% of deaths within the first 24 hours of arrival to a trauma facility. These numbers can reach 90% in the military environment. Traditional vital sign measurements, systolic blood pressure and oxygen saturation, fail to provide sufficient advanced warning of hemorrhage until after the onset of cardiovascular collapse. Clearly earlier recognition of hemorrhage will be beneficial in allowing intervention before the onset of circulatory shock.
Reduction in peripheral tissue oxygenation and increased carbon dioxide is an indicator of reduced central blood volume in the presence of stable vital signs.
Oxyphor-based micro-sensors were designed:
- Based on Pd-tetrabenzoporphyrin modified with generation-3 polyarylglycine dendrons and coated with a layer of polyethylene glycol.
- Teflon AF chambers sequester the Oxyphor solution from contact with the body.
- Provides for measurement of oxygen pressure by phosphorescence quenching.
The sensor’s in vitro measurement response time is less than one minute, readings are stable for greater than 16 hours with less than 2% change, and has a signal to noise ratio of ~40, which declines over 16 hours to ~20.
In vivo experiments in peripheral leg muscle of pigs:
- Insertion via 21 gauge needle
- Signal was stable and without changes in signal-to-noise ratio for up to 6 hours.