Multi-parametric optical sensing for monitoring haemodynamic shock

The primary function of blood circulation is to provide oxygen and substrates to the tissues. Failure to do this results in a clinical condition known as shock. Up to one-third of patients admitted to intensive care units (ICUs) are in circulatory shock, and early recognition of the condition is vital in order to avoid subsequent tissue injuries.

The level of lactate in blood is an important indicator when assessing response to therapy and guiding treatment in patients with life-threatening shock. For this reason, lactate measurements are routinely carried out in critically ill patients. Patients with elevated lactate concentration have a higher mortality rate and are at greater risk of developing multiple organ failure.

At present, lactate measurements are performed using invasive techniques where blood sample are needed in order to perform each measurement. These invasive procedures are time consuming and inhibit continuous monitoring of lactate. There is demand for a rapid use non-invasive medical device that allows continuous measurements of blood lactate levels in real time. Such a device is currently unavailable.
In addition, many experimental studies have confirmed the relationship between inadequate tissue oxygenation and blood lactate. Increased blood lactate levels have also been linked to metabolic processes not related to tissue oxygenation. This complexity makes it difficult to interpret lactate readings directly. A better understanding of the link between tissue oxygenation and blood lactate levels is necessary to improve the use of important lactate data and enable better interpretation and diagnosis.

The aim of this project is to address this demand by developing a novel non-invasive sensor that can continuously monitor blood lactate levels in real time. The device will be based on light sensing technology, consisting of a light source and a processing system that contains smart data analysis software to process light reflected from the skin. In principal, this is possible because the lactate chemical is sensitive to near infrared light, and together with the appropriate analysis, this property can be used to measure lactate levels from light reflected from the body.

It is also the aim of this project to conduct rigorous research and acquire new understanding of the relationship between tissue oxygenation and blood lactate levels in extreme conditions involving short term episodes of hyperlactamia (elevated lactate levels)
The project will address these aspects through a combined experimental and mathematical modelling approach using state of the art facilities. The successful development of the sensor will allow effective use of lactate as a basis for treatment of patients in critical care units, emergency departments and pre-hospital environments, where the availability of simple, rapid use monitoring technology is a key limitation to life saving treatments.

Economic: The NHS (including patients), and the UK healthcare technology sector will be the principal beneficiaries. Around a third of patients admitted into ICU are in shock. Alone, haemorrhagic shock accounts for four out of every five deaths during surgery, whilst septic type shocks are associated with hospital mortality rates greater than 40%, and 5-9% of hospitalised patients with acute myocardial infarction would experience a cardiogenic shock. Patients admitted into ICUs have a higher mortality rate and longer hospitalisation periods. National figures indicate that each additional day spent in an ICU bed costs more than £1200. Occupation of these beds also further denies access of an already scarce resource to other patients in need. This places a significant strain on already tight healthcare budgets.
The proposed disruptive non-invasive sensor technology is part of the vibrant market for patient monitoring which is currently witnessing significant growth, as such devices can provide safe and continuous monitoring without imposing staff intervention time (and cost), and resulting in improved patient outcomes and reduced hospitalisation times. This is particularly important in critically ill patients where continuous monitoring can allow adverse changes to be detected early and would have direct impact on timeliness of subsequent interventions, minimising harm to the patients and saving cost to the NHS.

Scientific: The scientific impact consists of five components: (i) new sensor based on optical spectroscopy for multi-parametric monitoring of blood lactate levels non-invasively and in real time; (ii) multivariate models that can predict lactate concentrations and haemodynamic response to hyperlactatemia; (iii) new insight into relationship between tissue perfusion and lactate concentrations, and how they relate to shock; (iv) detailed experimental and computational results from exercise induced hyperlactatemia, perfectly suited to validate generated models (v) new sensing strategy for continuous spectroscopic acquisition and analysis for studying dynamic chemical and physical processes in the body.

People: Both of the PDRAs will directly benefit from the opportunity of being involved in an interesting and novel collaborative project with great potential for impact and publications. In particular they will get to work alongside our collaborative partners, both PerkinElmer Corp and Edward Lifesciences, as well as two expert academics in the fields of clinical biochemistry and critical care.

Further: In the long term, the sensing technology that would be developed in this project can readily be modified and have significant impact on other medical fields and beyond, and will not be limited to lactate, emphasizing a wider potential application of the device as well as research beyond the scope of the current proposal. There is therefore the possibility of further grants and research, with associated impact.