uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Brain tissue oxygen monitoring: a study of in vitro accuracy and stability of Neurovent-PTO and Licox sensors
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Neurosurgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Neurosurgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Neurosurgery.
2010 (English)In: Acta Neurochirurgica, ISSN 0001-6268, E-ISSN 0942-0940, Vol. 152, no 4, 681-688 p.Article in journal (Refereed) Published
Abstract [en]

OBJECT: Periods of brain tissue ischemia are common after severe head injury, and their occurrence and duration are negatively correlated with outcome. Accurate and reliable measurement of brain tissue oxygenation (B(ti) pO(2)) may be a key to improve patient outcome after severe head injury. Knowledge of stability and accuracy of the B(ti) pO(2) systems is crucial. We have therefore conducted a bench test study of new Neurovent-PTO(R) (NV) and Licox(R) (LX) oxygen tension catheters to evaluate the sensor accuracy, response time to different oxygen tensions, response to temperature changes and long-term stability. METHODS: For all experiments five new fluorescent NV sensors and five new electrochemical LX sensors were used. The catheter probes were placed into a container filled with a buffer solution. The solution was equilibrated with five high precision calibration gases. The accuracy of the probes was recorded after an equilibration period of 20 min in O(2) concentrations of 5, 10, 20, 30 and 40 mmHg at 37.0 +/- 0.2 degrees C. The probe response to an increase in temperature from 37.0 degrees C to 38.5 degrees C to 40.0 degrees C in two different gases with O(2) concentrations of 10 and 20 mmHg were analysed. We also recorded the time for reaching 90% of a new oxygen concentration level when switching from one concentration to another. Finally, to test if there was a time-dependant drift in pO(2) recordings, all sensors were left in 10 mmHg O(2) solution for 10 days, and recordings were taken every 24 h. RESULTS: In all gas concentrations, NV and LX sensors measured pO(2) with high accuracy and stability in vitro (mean differences from calculated values were for NV 0.76-1.6 mmHg and for LX -0.46-0.26 mmHg). Both sensors showed a shorter response time to pO(2) increase (for NV 56 +/- 22 s and for LX 78 +/- 21 s) compared to pO(2) decrease (for NV 131 +/- 42 s and for LX 215 +/- 63 s). NV pO(2) values were more stable for changes in temperature, while LX sensors showed larger standard deviations with increasing temperature (the difference from the calculated values in 19.7 mmHg O(2) at 40 degrees C were for NV probes between 0.5 and 1.7 mmHg and LX between -2.3 and 1.9 mmHg). Both sensors gave stable results with low standard deviations during long-term (10 days) use, but with a slight elevation of measured pO(2) levels by time. CONCLUSIONS: Both NV and LX were accurate in detecting different oxygen tensions, and they did not deviate over longer recording times. However, LX needed a significantly longer time to detect changes in pO(2) levels compared to NV. Furthermore, LX probes showed an increased standard deviation with higher temperatures.

Place, publisher, year, edition, pages
2010. Vol. 152, no 4, 681-688 p.
Keyword [en]
Licox, Neurovent-PTO, Brain tissue oxygenation, Accuracy, Neurointensive care, Traumatic brain injury
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-110760DOI: 10.1007/s00701-009-0532-xISI: 000275945600017PubMedID: 19826757OAI: oai:DiVA.org:uu-110760DiVA: diva2:278207
Available from: 2009-11-24 Created: 2009-11-24 Last updated: 2013-04-02Bibliographically approved
In thesis
1. Brain Tissue Oxygenation in Traumatic Brain Injury: Experimental and Clinical Studies
Open this publication in new window or tab >>Brain Tissue Oxygenation in Traumatic Brain Injury: Experimental and Clinical Studies
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Traumatic brain injury (TBI) is a major cause of death and disability. TBI is frequently followed by cerebral ischemia which is a great contributor to secondary brain damage. The main causes of cerebral ischemia are pathophysiological changes in cerebral blood flow and metabolism. Treatment of TBI patients is currently based on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) targeted treatment protocols. However, ICP and CPP alone do not provide information of the oxygen availability in the brain. Monitoring of brain tissue oxygenation (BtipO2) may give additional and valuable information about the risk for development of ischemia in TBI patients.

The aims of this thesis were to study BtipO2 monitoring devices in-vitro regarding accuracy and stability, to detect threshold level of cerebral ischemia in-vivo and finally to examine the cerebral oxygen levels and cerebral metabolism in TBI patients.

The BtipO2 probes performed with high accuracy and stability at different clinically relevant oxygen concentrations.

A pig TBI model was developed by step-wise intracranial volume/pressure increase. Volume increase resulted in a gradual increased ICP, decreased CPP, intracranial compliance and BtipO2, respectively. Brain death (BD) was confirmed by negative CPP and negligible amount of previously injected microspheres in the brain tissue. The model simulated the clinical development of BD in humans with a classical pressure-volume response and systemic cardiovascular reactions. The model should be suitable for studies of brain injury mechanisms.

From the same in-vivo model it was also possible to detect the threshold level of cerebral ischemia in the pig, where BtipO2 below 10 mmHg and CPP below 30 mmHg was associated with an impaired cerebral metabolism (microdialysis lactate to pyruvate ratio >30).

BtipO2 together with cerebral microdialysis were studied in 23 severe TBI patients. We observed different patterns of changes in BtipO2 and cerebral microdialysis biomarkers in focal and diffuse TBI.  Increased cerebral microdialysis levels of glutamate, glycerol or the lactate/pyruvate ratio were observed at BtipO2 < 5 mmHg, indicating increased vulnerability of the brain at this critical level of tissue oxygenation in TBI patients.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 74 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 869
Brain tissue oxygenation, Cerebral metabolism, Traumatic brain injury, Cerebral ischemia, Threshold levels, Neurovent-PTO, Microdialysis
National Category
Medical and Health Sciences Anesthesiology and Intensive Care Neurosciences
Research subject
urn:nbn:se:uu:diva-195867 (URN)978-91-554-8607-5 (ISBN)
Public defence
2013-04-19, Grönwallsalen, Akademiska sjukhuset, ingång 70, Uppsala, 09:00 (English)
Available from: 2013-03-27 Created: 2013-02-28 Last updated: 2013-04-02Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed
By organisation
NeurosurgeryClinical Physiology
In the same journal
Acta Neurochirurgica
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 293 hits
ReferencesLink to record
Permanent link

Direct link