Patient Studies

Our patient studies involve patients with head injury [1-3], primary autonomic failure [4-6], sleep apnoea [7] and stroke [8].

Figure 1. Optical data from a sleep apnoea patient.

Recently, using a UCL-developed multi-wavelength (or broadband) NIRS system we investigated the importance of the CCO measurement in patients with traumatic brain injury [1-3]. These were the first studies looking at the relationship of oxygen delivery and oxygen utilisation with broadband NIRS on the injured human adult brain. We demonstrated that hyperoxia has potentially beneficial effects on the injured brain and that it is possible to use CCO as a surrogate marker of cellular oxygen metabolism which may be used to identify treatment strategies.

More information about these studies can be found in the MD thesis of Dr Martin Tisdall: Non-invasive near infrared spectroscopy: a tool for measuring cerebral oxygenation and metabolism in patients with traumatic brain injury).

Figure 2. Head injury study with optical instrumentation and microdialysis.

More studies in traumatic brain injury patients are currently carried out with the Hybrid Spectrometer during hyperoxia and hypercapnia.

Figure 3. The hybrid spectrometer in use on a traumatic brain injured patient.

We are also interested in the role of NIRS in continuous monitoring of cerebral autoregulation (CA) This type of monitoring might identify therapeutic windows and novel treatment targets, potentially improving outcome in brain injury. Near infrared spectroscopy has become increasingly investigated within this role as it may reflect cerebral haemodynamics and is easily delivered in the clinical environment. We compare NIRS indices of vasoreactivity with established indices using a variety of novel techniques [9].

References

1. Tisdall M., Tachtsidis I., Leung T.S., Elwell C., Smith M., "Normobaric hyperoxia increases cerebral aerobic metabolism after traumatic brain injury." Journal of Neurosurgical Anesthesiology (2007) 19(3):218 [URL]
2. Tisdall M., Tachtsidis I., Leung T.S., Elwell C., & Smith M., "Increase in cerebral aerobic metabolism by normobaric hyperoxia after traumatic brain injury." Journal of Neurosurgery(2008) 109(3):424-432 [URL] [PDF]
3. Tachtsidis I., Pritchard C., Tisdall M.M., Leung T.S., Elwell C.E., Smith, M., "Hypercapnea does not consistently increase the oxidation of cytochrome c oxidase in traumatic brain injury." Journal of Cerebral Blood Flow and Metabolism (2009) 29:S197 [URL] [Poster]
4. Tisdall M. Tachtsidis I., Bleasdale-Barr K., Mathias C.J., Delpy D.T., Elwell C.E., Smith M., "Investigation of the cerebral haemoglobin and cytochrome signals using near infrared spectroscopy during head up tilt in patients with orthostatic hypotension."Journal of Cerebral Blood Flow and Metabolism (2005) 25:S571 [URL] [PDF] [Poster]
5. Tachtsidis I., Elwell C.E., Leung T.S., Bleasdale-Barr K., Hunt K., Toms N., Smith M., Mathias C.J., Delpy D.T., "Rate of change in cerebral oxygenation and blood pressure in response to passive changes in posture: a comparison between pure autonomic failure patients and controls." Advances in Experimental Medicine and Biology (2005) 566:187-193 [URL] [PDF] 
6. Hunt K., Tachtsidis I., Bleasdale-Barr K., Elwell C., Mathias C., Smith M., "Changes in cerebral oxygenation and haemodynamics during postural blood pressure changes in patients with autonomic failure." Physiological Measurement (2006) 27(9):777-785 [URL]
7. Tachtsidis I., Cooper C.E., McGown A.D., Makker H., Delpy D.T., Elwell C.E., "Changes in cerebral total haemoglobin volume and cytochrome oxidase redox state during deep apnoeas in patients with obstructive sleep apnoea." in Biomedical Optics OSA Technical Digest (CD) (Optical Society of America, 2004) paper: WF6 [URL] [Poster]
8. Taylor C., Coward L., Tachtsidis I., Tisdall M., Elwell C.E., Brown M., Smith M., "Measurement of cerebral tissue oxygenation using near infrared spectroscopy (NIRS) in stroke patients."Journal of Neurosurgical Anaesthesiology. (2005) 17(3):157-158 [URL]
9. Highton D.T., Ghosh A., Tachisidis I., Kolyva C., Elwell C.E., Smith M., "A comparison between pressure reactivity index, mean velocity index and near infrared spectroscopy in brain injury." inAnnual Meeting of the Society for Neuroscience in Anesthesiology and Critical Care (October 2010) [Poster]