Biomedical subjects

Wolfram Miekisch

Publications and source records attributed to Wolfram Miekisch.

6 recordsLinked to original sources

PubMed2006

A novel visually CO2 controlled alveolar breath sampling technique.

BACKGROUND: A crucial issue in the analysis of exhaled breath is the collection of gaseous samples. The analysis of pure alveolar gas is the method of choice if contamination of samples is to be minimized. Monitoring of expired CO2 can be used to identify alveolar gas. The purpose of this study was to evaluate a bed side version of this technique using visual CO2 control by means of a capnometer. METHODS: 22 mechanically ventilated patients of an ICU were enrolled into the study. Alveolar and mixed expiratory gas, and arterial blood were sampled. PCO2 in blood and gas was determined in a blood gas analyzer. End tidal PCO2 was monitored in all patients by a fast responding main stream capnometry. Taking the gaseous samples was visually synchronized with the expired CO2. RESULTS: Alveolar CO2 contents measured during two different respiratory cycles were identical (p 0.86). The variation of the CO2 content during 10 measurements in one patient was lower than 4%. Arterial PCO2, PCO2 in alveolar gas and end tidal PCO2 showed positive correlation. CONCLUSIONS: The visually CO2-controlled sampling technique of alveolar gas is a reliable and reproducible method. It represents an important step in simplifying and standardizing breath analysis.

Aged↗

PubMed2005

The extent of induction of CYP3A by St. John's wort varies among products and is linked to hyperforin dose.

OBJECTIVE: Induction of CYP3A by St. John's wort (SJW) extracts with high hyperforin (HYF) content is well described. Since SJW products vary in the amount of HYF and other main constituents, the aim of the study was to evaluate the effect on CYP3A function of SJW preparations with a range from very low to high HYF content. METHODS: Forty-two male, healthy volunteers were randomized into six parallel SJW medication groups with varying composition especially with regard to HYF content. Midazolam plasma concentration profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication. RESULTS: All SJW preparations tested resulted in a decrease in midazolam AUC, although the extent of the effect differed. The extract LI 160 (HYF 41 mg/day) decreased midazolam AUC0-12h by 79.4% (95% CI -88.6; -70.1), which was significantly greater than the effect by any other medication (p<0.05). SJW powder tablets 2.7 g/day (HYF 12 mg/day) resulted in a midazolam AUC0-12h decrease of 47.9% (95% CI -59.7;-36.2), while 2.7 g/day SJW powder tablets that were almost devoid of HYF (0.13 mg/day) reduced midazolam AUC0-12h by only 21.1% (95% CI -33.9; -8.3). Considering all six SJW medications tested, the extent of midazolam AUC decrease correlated significantly with increasing HYF dose (r=-0.765, p<0.001), but not with hypericin dose (r=-0.067; p=0.673). CONCLUSION: The extent of induction of CYP3A varies among St. John's wort products and depends on hyperforin dose.

Adult↗

PubMed2004

Diagnostic potential of breath analysis--focus on volatile organic compounds.

Breath analysis has attracted a considerable amount of scientific and clinical interest during the last decade. In contrast to NO, which is predominantly generated in the bronchial system, volatile organic compounds (VOCs) are mainly blood borne and therefore enable monitoring of different processes in the body. Exhaled ethane and pentane concentrations were elevated in inflammatory diseases. Acetone was linked to dextrose metabolism and lipolysis. Exhaled isoprene concentrations showed correlations with cholesterol biosynthesis. Exhaled levels of sulphur-containing compounds were elevated in liver failure and allograft rejection. Looking at a set of volatile markers may enable recognition and diagnosis of complex diseases such as lung or breast cancer. Due to technical problems of sampling and analysis and a lack of normalization and standardization, huge variations exist between results of different studies. This is among the main reasons why breath analysis could not yet been introduced into clinical practice. This review addresses the basic principles of breath analysis and the diagnostic potential of different volatile breath markers. Analytical procedures, issues concerning biochemistry and exhalation mechanisms of volatile substances, and future developments will be discussed.

Air↗

PubMed2004

Lipid peroxidation early after brain injury.

The role of lipid peroxidation after brain injury is still not completely understood, and results of different studies have been equivocal. In this study, three proposed peroxidation markers were determined in patients early after isolated head injury and results compared to healthy controls. Malondialdehyde (MDA) and thiobarbituric acid-reactive substances (TBARS) were measured in plasma, and n-pentane was determined in patients' exhaled air. For MDA and TBARS no significant differences could be shown (0.267 vs. 0.358 ng/mL, and 0.896 vs. 0.814 ng/mL in patients vs. healthy volunteers, respectively). n-Pentane, however, was significantly increased in the expired air of patients (0.471 vs. 0.118 nmol/L in healthy volunteers). Similar results for n-pentane were obtained when only male patients and volunteers were considered (0.510 vs. 0.113 nmol/L). Stratification according to clinical outcome showed significantly higher values for n-pentane in male patients with poor outcome (0.656 nmol/L) in comparison with healthy male volunteers (0.113 nmol/L). No difference was found when patients were stratified according to the presence or absence of subarachnoid hemorrhage. It is concluded that, only in a sub-population of patients with brain injury, lipid-peroxidation is a crucial mechanism. n-Pentane seems to be a valuable marker to detect lipid peroxidation early after brain trauma. Malondialdehyde may be of value only later in the course of the disease. TBARS are not a specific marker and should therefore not be used.

Acute-Phase Reaction↗

PubMed2004

Breath analysis in critically ill patients: potential and limitations.

Breath tests are attractive since they are noninvasive and can be repeated frequently in the dynamically changing state of critically ill patients. Volatile organic compounds can be produced anywhere in the body and are transported via the bloodstream and exhaled through the lung. They can reflect physiologic or pathologic biochemical processes such as lipid peroxidation, liver disease, renal failure, allograft rejection, and dextrose or cholesterol metabolism. This review describes the diagnostic potential of endogenous organic volatile substances in the breath of critically ill patients. Since many of these patients require ventilatory support, aspects of breath analysis under mechanical ventilation will be addressed. Analytical procedures, problems concerning the physiologic meaning of breath markers and future developments will be discussed.

Biomarkers↗

PubMed2002

Breath markers and soluble lipid peroxidation markers in critically ill patients.

Free radical-mediated inflammatory processes account for a great portion of morbidity and mortality in critically ill patients. The purpose of this study was to determine two plasma peroxidation markers and three volatile markers related to lipid peroxidation, metabolic activity and cholesterol metabolism, and to explore relationships between the different markers and patients' clinical status. Substances were analyzed in whole blood and in exhaled air in patients with head injury, acute respiratory distress syndrome (ARDS) and in those being at risk of developing ARDS. These results were compared with the baseline measurements in healthy individuals. Additionally, patients were assessed according to their inflammatory status. Concentrations of malondialdehyde and thiobarbituric acid-reactive substances in plasma as well as pentane concentrations in breath increased with increasing inflammatory status. Although these compounds are generated through peroxidation of fatty acids, concentrations of these markers were significantly different in patient groups. Isoprene concentrations were lowest in the ARDS group. Acetone concentrations were not different between patient groups. We conclude that for the assessment of lipid peroxidation and other inflammatory reactions a set of parameters has to be defined. More detailed insights into inflammatory processes can be obtained when the volatile markers and the serum markers are considered together.

Acetone↗